JP5238772B2 - Power converter - Google Patents

Description

  The present invention relates to a power conversion device.

  In an electric railway DC feeding system, a system in which three-phase AC power is converted into DC power by a power diode rectifier connected in a three-phase bridge is often employed. This method has the advantage that the overload capability is excellent and the converter cost can be reduced. However, there was a problem that when the train applied the regenerative brake, the power could not be regenerated to the AC power source side, and the regeneration was often invalidated. In addition, there is a load current dependency, and there is a drawback that the DC feeding voltage varies greatly depending on the load.

  Therefore, a power conversion device having a mechanism capable of regenerating power has been developed. FIG. 25 shows a configuration of a conventional PWM converter CNV (pulse width modulation control converter) capable of power regeneration. In the figure, R, S, and T are terminals of a three-phase AC power supply SUP, Ls is an AC reactor, CNV is a PWM converter, Cd is a DC smoothing capacitor, VDT is a voltage detector that detects the voltage of the smoothing capacitor Cd, and INV is A three-phase output VVVF (variable voltage variable frequency) inverter, M represents an AC motor.

  As the control circuit CNTL, comparators C1 and C2, a voltage control compensator GV (S), a multiplier ML, a current control compensator Gi (S), and a pulse width modulation control circuit PWMC are prepared. A portion surrounded by a broken line is prepared for three phases, and only the R phase is shown in detail, but the S phase and the T phase are similarly configured.

  The PWM converter CNV controls the input currents Ir, Is, It so that the voltage Vd applied to the DC smoothing capacitor Cd matches the voltage command value Vd *.

In the control circuit CNTL, the deviation between the voltage command value Vd * and the voltage detection value Vd is amplified by the control compensator GV (S) to obtain the amplitude command value Ism * of the input current. The multiplier ML multiplies the unit sine wave sinωt synchronized with the R-phase voltage by the amplitude command value Ism * of the input current, and sets it as the R-phase current command value Ir *. That is,

It becomes.

  The R-phase current command value Ir * and the R-phase current detection value Ir are compared, and the deviation is inverted and amplified by the current control compensator Gi (S). Normally proportional amplification is used, Gi (S) = − Ki. Ki is a proportionality constant. The voltage command value er * = − Ki × (Ir * −Ir), which is the output of Gi (S), is input to the PWM control circuit PWMC, and the gate signals g1 of the R-phase self-extinguishing elements S1 and S4 of the converter CNV Make g4. The PWM control circuit PWMC compares the voltage command value er * with the carrier signal X (for example, a 1 kHz triangular wave). When er *> X, the element S1 is turned on (S4 is off), and er * <X If so, the element S4 is turned on (S1 is turned off). As a result, the R-phase voltage Vr of the converter CNV generates a voltage proportional to the voltage command value er *.

  When Ir *> Ir, the voltage command value er * becomes a negative value, and Ir is increased. Conversely, when Ir * <Ir, the voltage command value er * becomes a positive value, and Ir is decreased. Therefore, it is controlled so that Ir * = Ir. The S-phase and T-phase currents are similarly controlled.

  The voltage Vd applied to the DC smoothing capacitor is controlled as follows.

  When Vd *> Vd, the amplitude command value Ism * of the input current increases. The current command value of each phase is in phase with the power supply voltage, and the active power Ps proportional to the amplitude command value Ism * is supplied from the AC power supply SUP to the DC smoothing capacitor Cd. As a result, the direct-current voltage Vd is increased and controlled so that Vd * = Vd.

  Conversely, when Vd * <Vd, the amplitude command value Ism of the input current becomes a negative value, and the power Ps is regenerated to the AC power supply side. Therefore, the stored energy of the DC smoothing capacitor Cd is decreased, Vd is decreased, and the control is performed so that Vd * = Vd.

  The VVVF inverter INV and the AC motor M are loads using the DC smoothing capacitor Cd as a voltage source, and consume power of the capacitor Cd and reduce Vd during powering operation. Further, during the regenerative operation, the regenerative energy is returned to the smoothing capacitor Cd, so that it works in the direction of increasing Vd. Since the DC voltage Vd is controlled to be constant by the PWM converter CNV as described above, the effective power corresponding to the regenerative energy is automatically supplied during the regenerative operation. Will be regenerated to the AC power supply side. Thus, according to the conventional PWM converter CNV, the DC voltage can be stabilized, power regeneration is possible, and the problem of regeneration invalidation in the DC power feeding system of the electric railway is solved.

  However, the PWM converter CNV has a drawback in that switching loss increases because switching is performed at a high frequency. Further, the switching element needs to be capable of cutting the maximum value of the AC input current as a cutoff current. Therefore, it must be designed to withstand the breaking current even for a short time overload (for example, 300% of the rated current), and a self-extinguishing element constituting the power converter must have a large breaking current. There is a problem that it becomes an uneconomical system.

  On the other hand, in electric railways, power diode rectifiers are often installed, and when a new PWM converter CNV is installed there, it is necessary to operate the existing power diode rectifier and the new PWM converter CNV in parallel. It becomes.

  The existing power diode rectifier has a regulation of the DC voltage Vd depending on the load current. For example, in the case of a rectifier having a voltage regulation of 8% at a rated load of Vd = 1500V, Vd = 1260V at 300% overload operation. To fall.

  The DC voltage Vd of the PWM converter CNV that operates in parallel is restricted to be the same as the rectified voltage of the power diode rectifier, and cannot operate when Vd = 1500V is constant. As a result, during overload operation, the DC voltage of the PWM converter CNV becomes Vd = 1260 V, and the input current Is supplied from the AC power supply must be controlled with the voltage value. When operating with an input power factor of 1, assuming that the power supply voltage is Vs and the voltage drop of the AC reactor Ls is jωLs · Is, the AC voltage Vc of the PWM converter CNV is Vc = √ {Vs2 + (ωLs · Is) 2} The size of is required. The maximum value of the AC voltage Vc of the PWM converter CNV is proportional to the DC voltage Vd. If Vd decreases, the maximum value of the AC voltage Vc that can be output by the PWM converter CNV also decreases. In general, considering the voltage utilization factor of the PWM converter CNV, the effective value of the AC voltage Vc (secondary voltage V2 of the transformer) is designed to be about (1/2) of the DC voltage Vd.

  That is, when the DC voltage Vd = 1500V, the secondary voltage of the transformer is V2 = 750V. However, when the voltage decreases to Vd = 1260V, the operation with the input power factor = 1 cannot be performed unless the voltage V2 = 630V. It will be. In other words, in the PWM converter CNV operating in parallel with the existing rectifier, the secondary voltage of the transformer of the converter CNV must be designed to V2 = 630V from the beginning. Then, in the converter with the same output, the secondary current of the transformer increases, and naturally, the input current of the PWM converter CNV also increases, and the current capacity of the self-extinguishing element constituting the converter CNV is required to be large. As a result, there is a drawback that the device is expensive.

  As described above, there is a self-excited power converter (referred to as a PWM converter) based on pulse width modulation control as a power converter capable of power regeneration. However, the cost is higher than that of a diode rectifier and the overload capability can be increased. There are no difficulties. In addition, there is a problem that switching loss accompanying PWM control becomes large and converter efficiency is poor. Furthermore, when operating in parallel with an existing diode rectifier, the AC voltage Vc of the PWM converter CNV decreases due to voltage regulation of the rectifier, the input current increases, and the current capacity of the self-extinguishing elements constituting the converter increases. There was a drawback that would be an uneconomical system.

Japanese Patent Publication No. 5-7950

  The present invention has been made to solve the above-described conventional technical problems, and is suitable for parallel operation with an existing diode rectifier, has excellent overload capability, is capable of power regeneration, has high converter efficiency, and is economical. An object is to provide a typical power conversion device.

One feature of the present invention is that an AC power source, a power diode rectifier having an AC terminal connected to the AC power source via a first transformer, and a second transformer connected to the AC power source. A voltage-type self-excited power converter in which an AC terminal is connected to the secondary winding of the second transformer via a third transformer, and the voltage-type self-excited power converter. A DC smoothing capacitor connected between DC terminals and the voltage-type self-excited power converter are operated in a constant pulse pattern, and the phase of the AC-side terminal voltage of the voltage-type self-excited power converter with respect to the voltage of the AC power supply Input current control means for controlling the input current of the voltage source self-excited power converter by adjusting the angle, and connected between the DC common terminals of the voltage source self-excited power converter and the power diode rectifier Power to the DC load A power converter supplied.

Another feature of the present invention is that an AC power source, a power diode rectifier having an AC terminal connected to the AC power source via a first transformer, and a second transformer connected to the AC power source. An AC load, a voltage-type self-excited power converter having an AC terminal connected to the secondary winding of the second transformer via a third transformer, and a DC of the voltage-type self-excited power converter A series circuit of a DC smoothing capacitor and a resistor connected between terminals and the voltage source self-excited power converter are operated with a constant pulse pattern, and the AC of the voltage source self-excited power converter with respect to the voltage of the AC power supply Input current control means for controlling the input current of the voltage source self-excited power converter by adjusting the phase angle of the side terminal voltage, and the direct current of the voltage source self-excited power converter and the power diode rectifier Connected between common terminals A power converter for supplying power to the DC load.

  Still another feature of the present invention is that an AC power source, a power diode rectifier having an AC terminal connected to the AC power source via a first transformer, and a second transformer connected to the AC power source. A voltage-type self-excited power converter in which an AC terminal is connected to the secondary winding of the second transformer via a third transformer, and the voltage-type self-excited power converter. A series circuit of a DC smoothing capacitor and a resistor connected between DC terminals, a diode for bypassing the one-way current of the resistor, and the voltage-type self-excited power converter are operated in a constant pulse pattern, and the AC An input current control means for controlling an input current of the voltage type self-excited power converter by adjusting a phase angle of an AC side terminal voltage of the voltage type self-excited power converter with respect to a voltage of a power source; Self-excited power variation To a DC load connected between the vessel and the DC common terminal of the power diode rectifier is a power converter for supplying power.

  According to the power conversion device of the present invention, an economical power conversion device that is suitable for parallel operation with an existing power diode rectifier, has excellent overload capability, is capable of power regeneration, has high converter efficiency, and is economical. be able to.

The block diagram of the power converter device of the 1st Embodiment of this invention. The block diagram of the specific structural example of the self-excited power converter in the power converter device of FIG. The AC side equivalent circuit for demonstrating control operation of the power converter device of the said embodiment. The voltage / current vector diagram for demonstrating control operation of the power converter device of the said embodiment. The block diagram of the phase control circuit in the control circuit in the power converter device of FIG. 6 is a waveform example diagram during one-pulse operation of the phase control circuit of FIG. The operation waveform figure of each part at the time of carrying out the power running operation by 1 pulse of the self-excitation power converter of the power converter device of this Embodiment. The operation | movement waveform diagram of each part at the time of carrying out the regenerative operation by 1 pulse of the self-excitation power converter of the power converter device of this Embodiment. The operation waveform figure of each part at the time of carrying out the power running operation by 3 pulses of the self-excited power converter of the power converter device of this Embodiment. The driving | operation characteristic figure of the self-excitation type power converter by the power converter device of the 2nd Embodiment of this invention. The driving | operation characteristic figure of the self-excited power converter by the power converter device of the 3rd Embodiment of this invention. The block diagram of the control circuit in the power converter device of the 4th Embodiment of this invention. FIG. 13 is a calculation characteristic diagram of a voltage command calculation circuit in the control circuit of FIG. 12. The block diagram of the power converter device of the 5th Embodiment of this invention. The block diagram of the power converter device of the 6th Embodiment of this invention. The block diagram of the control circuit in the power converter device of the 7th Embodiment of this invention. The alternating current side voltage and electric current vector diagram of the self-excitation type power converter at the time of power running overload operation by the power converter of the 8th embodiment of the present invention. AC side voltage / current vector diagram of a self-excited power converter during overload operation by the power converter of the embodiment. The block diagram of the power converter device of the 9th Embodiment of this invention. The block diagram of the power converter device of the 10th Embodiment of this invention. The block diagram of the power converter device of the 11th Embodiment of this invention. The block diagram of the control circuit in the power converter device of the 12th Embodiment of this invention. The characteristic example figure of the electric current command generator in the said embodiment. The block diagram of the power converter device of the 13th Embodiment of this invention. The block diagram of the power converter device of a prior art example.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  (First Embodiment) FIG. 1 is a block diagram showing a power conversion apparatus according to a first embodiment of the present invention. In the figure, SUP is a three-phase AC power source, MCB is an AC main circuit breaker, TR1 and TR2 are three-phase transformers, REC is a power diode rectifier, CNV is a voltage-type self-excited power converter, Cd is a DC smoothing capacitor, and VDT is DC voltage detector, DCDT is a DC current detector, and Load is a load device.

  On the other hand, as the control circuit CNTL, comparators C1 and C2, adder AD, voltage control compensation circuit Gv (S), current control compensation circuit Gi (S), current command generator F (x), switch SW, level detection LBL, limiter circuit LIM, feedforward compensator FF, coordinate conversion circuit Z, power supply synchronous phase detection circuit PLL, and phase control circuit PHC are prepared.

  The power conversion device according to the present embodiment includes an AC power supply SUP, a power diode rectifier REC having an AC terminal connected to the AC power supply SUP via a first transformer TR1, and a second transformer for the AC power supply SUP. Voltage-type self-excited power converter CNV having an AC terminal connected thereto via a transformer TR2, a DC smoothing capacitor Cd connected between DC terminals of the voltage-type self-excited power converter CNV, and voltage-type self-excited power conversion Control the input current of the voltage-type self-excited power converter by adjusting the phase angle of the AC-side terminal voltage of the voltage-type self-excited power converter CNV with respect to the voltage Vs of the AC power supply. And a control circuit CNTL for supplying power to a load device connected between the DC common terminals of the voltage-type self-excited power converter and the power diode rectifier. The control circuit CNTL controls the effective amount of the input current of the voltage type self-excited power converter CNV according to the current supplied to the load device Load or the active power during the power running operation, and is applied to the DC smoothing capacitor Cd during the regenerative operation. The input current is controlled so that the applied voltage matches the voltage command value.

  In the power converter of the present embodiment, the power diode rectifier REC and the voltage source self-excited power converter CNV are operated in parallel. In the power running operation (electric power is supplied from the power supply SUP to the load Load), the load sharing is adjusted by controlling the effective amount of the input current Ic of the self-excited power converter CNV. In regenerative operation (electric power is regenerated from load Load to power supply SUP), input current Ic of self-excited power converter CNV is controlled so that DC voltage Vd matches command value Vd *.

  FIG. 2 shows a specific configuration example of the self-excited power converter CNV of the apparatus of FIG. 1, wherein R, S, and T are three-phase AC power terminals, TR2 is a transformer, and Ls is an AC reactor (transformer (TR2 leakage inductance), CNV is a converter body, S1 to S6 are self-extinguishing elements, D1 to D6 are high-speed diodes, Cd is a DC smoothing capacitor, and Load is a load device. Hereinafter, the control operation of the self-excited power converter CNV will be described with reference to this main circuit configuration example.

  In the control circuit CNTL in FIG. 1, the voltage Vd applied to the DC smoothing capacitor Cd is detected and compared with the voltage command value Vd * by the comparator C1. The deviation εv is integrated or proportionally amplified by the voltage control compensation circuit Gv (S) and input to the adder AD. The DC current IL consumed by the load LOAD is detected and input to the adder AD via the feedforward compensator FF. The output Iq1 * of the adder AD becomes a command value for the effective current supplied from the power supply SUP. The level detector LBL of the control circuit CNTL outputs a switching signal CL when the direct current IL becomes larger than a set value (for example, ILo = 0), and switches the switch SW to the current control side. That is, when IL> ILo, current control is performed using the output signal Iq2 * from the current command generator F (x) as an effective current command value. The actual effective current command value Iq * is given through the limiter circuit LIM as the current command value Iq1 * or Iq2 *.

  The coordinate converter Z of the control circuit CNTL converts the detected values of the three-phase input currents Icr, Ics, Ict supplied from the AC power supply SUP into dq axes (DC amount). The coordinate-converted q-axis current Iq represents an effective current detection value, and the d-axis current Id represents a reactive current detection value. The comparator C2 compares the effective current command value Iq * and the effective current detection value Iq, and a deviation εi thereof is amplified by the current control compensation circuit Gi (S) to obtain a phase angle command value φ *. The power supply synchronization phase detection circuit PLL generates phase signals θr, θs, θt synchronized with the three-phase AC power supply voltage and inputs the phase signals to the phase control circuit PHC. The phase control circuit PHC generates the gate signals g1 to g6 of the self-extinguishing elements S1 to S6 of the self-excited power converter CNV using the phase angle command value φ * and the phase signals θr, θs, and θt.

  The voltage type self-excited power converter CNV controls the input current Ic by controlling the phase angle φ with respect to the power supply voltage with a constant pulse pattern (1 pulse, 3 pulses, 5 pulses, etc.) synchronized with the power supply voltage.

  FIG. 3 shows an AC side equivalent circuit for explaining the control operation of the power conversion device of the present embodiment. FIG. 4 shows the voltage / current vector diagram. In the figure, Ls is an AC reactor (generally substituted for the leakage inductance of the transformer TR2), Vs is a power supply voltage, Vc is an AC output voltage of the self-excited power converter CNV, Ic is an input current, and jωLs · Ic is This represents a voltage drop due to the AC reactor Ls (however, the resistance of the reactor Ls is ignored as being sufficiently small). As a vector, there is a relationship of Vs = Vc + jωLs · Ic.

  The peak value of the power supply voltage Vs is matched with the fundamental peak value of the AC output voltage Vc of the self-excited power converter. The DC voltage Vd is often determined by a request from the load side, and when the pulse pattern is determined, the fundamental wave peak value of the AC output voltage Vc is determined. Therefore, a transformer is installed on the power supply side, and the peak value is adjusted with the secondary voltage as Vs.

  The input current Ic can be controlled by adjusting the phase angle φ of the AC output voltage Vc of the self-excited power converter with respect to the power supply voltage Vs. That is, when the phase angle φ = 0, the voltage jωLs · Ic applied to the AC reactor Ls becomes zero, and the input current Ic also becomes zero. As the phase angle (delay) φ increases, the voltage of jωLs · Ic increases and the input current Ic also increases in proportion to the value. The input current vector Ic is delayed by 90 ° with respect to the voltage jωLs · Ic, and is a vector delayed by φ / 2 with respect to the power supply voltage Vs. Therefore, the input power factor viewed from the power supply side is cos (φ / 2).

  On the other hand, when the AC output voltage of the self-excited power converter CNV is increased in the advance direction by the phase angle φ like Vc ′, the voltage jωLs · Ic applied to the AC reactor Ls becomes negative, and the input current is Ic ′. Thus, the phase angle is (π−φ / 2) with respect to the power supply voltage Vs. That is, the electric power Ps = Vs · Ic becomes negative, and the electric power can be regenerated to the power source. When the AC output voltage Vc is rotated in the direction of Vc ′ along the broken line in the figure with the power supply voltage Vs as a reference, the input current vector Ic changes in the direction of Ic ′ along the broken line.

  In FIG. 1, the effective current Iq is controlled as follows. When Iq *> Iq, the output φ * of the current control compensation circuit Gi (S) increases, and the input currents Icr, Ics, and Ict are increased. Since the input power factor≈1, the effective current Iq increases and eventually settles as Iq * = Iq. Conversely, when Iq * <Iq, the output φ * of the current control compensation circuit Gi (S) decreases or becomes a negative value, and the input currents Icr, Ics, Ict are decreased. Since the input power factor≈1, the effective current Iq is decreased, and Iq * = Iq is also settled.

  The voltage Vd applied to the DC smoothing capacitor Cd is controlled as follows. When Vd *> Vd, the output Iq1 * of the voltage control compensation circuit Gv (S) increases and is controlled to Iq1 * = Iq as described above, so that the active power is supplied from the AC power supply SUP to the DC smoothing capacitor Cd. To be supplied. As a result, the direct-current voltage Vd increases and is controlled so that Vd * = Vd. Conversely, when Vd * <Vd, the output Iq1 * of the voltage control compensation circuit Gv (S) decreases or becomes a negative value, and the active power is regenerated from the DC smoothing capacitor Cd to the AC power supply SUP side. As a result, the direct-current voltage Vd is decreased and is controlled so that Vd * = Vd.

  In the apparatus of FIG. 1, a DC current IL taken by a load is detected, a compensation amount IqFF = kL · IL is calculated by a feedforward compensator FF so as to supply an effective current corresponding to the amount, and input to an adder AD. doing. As a result, when the load suddenly changes, an input current (effective current) Iq corresponding to the load is supplied, and fluctuations in the applied voltage Vd of the DC smoothing capacitor Cd are suppressed.

  FIG. 5 shows a specific example of the phase control circuit PHC of the self-excited power converter CNV of the apparatus of FIG. In the figure, ADr and ADsaDt are adders / subtracters, and PTN1 to PTN3 are pulse pattern generators. The adders / subtractors ADr, ADsaDt subtract the phase angle command value φ * from the phase signals θr, θs, θt to generate new phase signals θcr, θcs, θct. The new phase signals θcr, θcs, θct change in synchronization with the power supply frequency by a periodic function of 0 to 2π. The pulse pattern generators PTN1 to PTN3 generate gate signals g1 to g6 so as to obtain a constant pulse pattern with respect to the new phase signals θcr, θcs, and θct. The pulse pattern generator PTN1 stores the pulse pattern of the R-phase elements S1 and S4 with respect to the phase signal θcr as a table function, and FIG. 6 shows a waveform during one-pulse operation.

In FIG. 6, Vr is an R-phase power supply voltage, θr is a phase signal synchronized with the power supply voltage Vr, and is a periodic function that varies between 0 and 2π. The new phase signal θcr = θr−φ * is a periodic function that changes between 0 and 2π, and is given as a signal delayed by φ * with respect to the θr signal. That is, the following gate signal g1 (or g4) is output with respect to the input θcr.

The AC side output voltage (R phase) Vcr of the self-excited power converter CNV is:

It becomes. If the DC voltage Vd is constant, the amplitude value of the AC output voltage Vcr is constant. The phase of the fundamental wave Vcr * of Vcr is delayed by the phase angle φ with respect to the power supply voltage Vr. The S phase and the T phase are given in the same manner.

  FIG. 7 shows an operation waveform of each part of the R phase during power running when the self-excited power converter CNV is operated with the pulse pattern of FIG. For convenience of explanation, the input current Icr is drawn as a sine wave with the ripples omitted. The fundamental wave of the AC output voltage Vcr of the self-excited power converter CNV is delayed by the phase angle φ with respect to the power supply voltage Vr. The input current Icr flows with a phase angle (φ / 2) behind the power supply voltage Vr. At this time, IS1 and IS4 represent currents of R-phase self-extinguishing elements S1 and S4, and ID1 and ID4 represent currents of high-speed diodes D1 and D4, respectively. The operation at that time will be described below using the apparatus of FIG. 1 and the main circuit of FIG.

  Until the input current Icr changes from negative to positive, a current flows through the high speed diode D4. When the direction of the current Icr is changed from this state, the element S4 is in the ON state, so that the input current Icr flows through the self-extinguishing element S4. Next, when the element S4 is turned off, the current Icr flows through the high speed diode D1. The current flows through the high speed diode D1 until the input current Icr is inverted again. After the input current Icr is inverted again, the same operation as described above is performed between the element S1 and the high speed diode D4.

  The maximum current Imax cut off by the self-extinguishing elements S1 to S6 is Imax = Icm × sin (φ / 2), where Icm is the peak value of the input current. For example, when φ = 20 °, Imax = 0.174 × Icm. That is, it is only necessary to prepare a self-extinguishing element with a small cutoff current, and a low-cost power conversion device can be provided.

  FIG. 8 shows operation waveforms during regenerative operation. IS1 and IS4 represent currents of R-phase self-extinguishing elements S1 and S4, and ID1 and ID4 represent currents of high-speed diodes D1 and D4, respectively. The fundamental wave of the AC output voltage Vcr of the converter is advanced by the phase angle φ with respect to the power supply voltage Vr. Further, the input current Icr flows with a phase angle (φ / 2) with respect to the inversion value −Vr of the power supply voltage. When the input current Icr is negative and the self-extinguishing element S1 is on (S4 is off), the input current Icr flows through the element S1. When the element S1 is turned off (S4 is turned on), the current Icr flows through the high speed diode D4. When the input current Icr is inverted, a current flows in the self-extinguishing element S4, and the element S4 is turned off in the same manner as described above, whereby the current moves to the high speed diode D1. During regenerative operation, the maximum current Imax that is interrupted by the self-extinguishing elements S1 to S6 is Imax = Icm × sin (φ / 2), where Icm is the peak value of the input current. For example, when φ = 20 °, Imax = 0.174 × Icm.

  As described above, most of the input current Icr during the regenerative operation flows to the self-extinguishing element, but the cut-off current of the elements S1 to S6 is small, and a low-cost power converter can be realized. Here, by operating the self-excited power converter CNV with a fixed pulse, the number of times of switching is minimized, and the converter efficiency is further improved. Moreover, the fundamental wave component of the AC side output voltage Vc is increased, and the voltage utilization factor of the self-excited power converter is improved. In addition, since the converter is operated with a power factor of approximately 1, switching is performed near the zero point of the input current Is, and the cut-off current of the self-extinguishing element is extremely small during power running and regenerative operation. . As a result, a highly efficient and low cost power conversion device can be realized. Moreover, not interrupting a large current is close to soft switching, EMI noise is reduced, and an environment-friendly power converter can be realized.

  In the above description, the operation when the self-excited power converter CNV is operated with one pulse has been described. However, as a matter of course, the harmonics of the input current Ic can be increased by increasing the number of pulses to 3, 5, and 7 pulses. Waves can be reduced, and adverse effects on the power supply system can be reduced. FIG. 9 shows an operation waveform of each part when the self-excited power converter CNV is operated with 3 pulses, and depicts the R phase during the power running operation. In order to simplify the description, the input current Icr is drawn as a sine wave with the ripples omitted.

The pulse pattern of the R phase elements S1 and S4 of the self-excited power converter CNV with respect to the phase signal θcr = θr−φ * is as follows.

At this time, the AC side output voltage (R phase) Vcr of the self-excited power converter CNV is

It becomes. The phase of the fundamental wave Vcr * of the output voltage Vcr is delayed by the phase angle φ with respect to the power supply voltage Vr. The S phase and the T phase are given in the same manner. This pulse pattern is fixed, and when the DC voltage Vd is constant, the fundamental wave peak value of the AC output voltage of the self-excited power converter CNV is constant.

  The fundamental wave of AC output voltage Vcr of power converter CNV is delayed by phase angle φ with respect to power supply voltage Vr. The input current Icr flows with a phase angle (φ / 2) behind the power supply voltage Vr. At this time, IS1 and IS4 represent currents of the R-phase self-extinguishing elements S1 and S4, and ID1 and ID4 represent currents of the R-phase fast diodes D1 and D4, respectively. The operation at that time will be described below.

  Until the input current Icr changes from negative to positive, a current flows through the high speed diode D4. When the direction of the current Icr is changed from this state, the element S4 is in the ON state, so that the input current Icr flows through the element S4. Next, when the element S4 is turned off, the current Icr flows through the high speed diode D1. Next, when the self-extinguishing element S4 is turned on again at the zero cross point of the fundamental wave of the AC output voltage Vcr, the input current Icr flows through the element S4, and the current of the high speed diode D1 becomes zero. Further, when the element S4 is turned off at θ1 in FIG. 9, a current flows through the high speed diode D1 as described above, and the current flows through the high speed diode D1 until the input current Icr is inverted again. After the input current Icr is inverted, the same operation as described above is performed between the element S1 and the high-speed diode D4.

  In the case of the three-pulse operation, the maximum current Imax that is interrupted by the self-extinguishing elements S1 to S6 is Imax = Icm × sin (φ / 2 + θ1), where the peak value of the input current is Icm. For example, when φ = 20 ° and θ1 = 10 °, Imax = 0.342 × Icm. Thus, even when operated with three pulses, the maximum cutoff current Imax of the self-extinguishing elements S1 to S6 can be suppressed to about 1/3 of the input current peak value Icm, and the cost of the apparatus can be greatly reduced. Furthermore, even when the number of pulses is increased to 5 pulses or 7 pulses in order to reduce the harmonics of the input current Ic, the switching of the self-extinguishing element is performed in the vicinity of the zero cross point of the current. It is also a feature of the power conversion device of the present embodiment that is not so large.

  The operation of the voltage-type self-excited power converter CNV alone connected to the three-phase bridge shown in FIG. 2 has been described above. However, a plurality of such self-excited power converters CNV are prepared and operated in parallel or in series. By doing so, it is possible to further reduce the harmonics of the input current Ic.

 In this embodiment, the power diode rectifier REC and the fixed pulse phase control self-excited power converter CNV are operated in parallel. When assuming the ground facilities of an electric railway, there is an existing power diode rectifier REC, and a self-excited power converter CNV may be newly installed to add a power regeneration function.

  Since the power diode rectifier REC cannot perform power regeneration, the regenerative side performs the DC voltage Vd = constant control as described above by the self-excited power converter CNV. The DC voltage command value Vd * at that time is set higher than the no-load rectified voltage of the power diode rectifier REC, so that a wasteful circulating current flows between the power diode rectifier REC and the self-excited power converter CNV. I am trying not to.

  In the power running operation, the power diode rectifier REC and the self-excited power converter CNV are operated in parallel, and how to adjust the load sharing becomes important. Therefore, in the apparatus of FIG. 1, the effective amount Iq of the input current of the self-excited power converter CNV is controlled in accordance with the current IL or power PL = Vd × IL supplied to the load Load. That is, in the apparatus of FIG. 1, the level detector LBL operates the switch SW by the load current IL, and when the load current IL <0 (regeneration), the switch SW is output from the adder AD (Iq1 *). When the load current IL> 0 (power running), the switch SW is connected to the output (Iq2 *) of the current command generator F (x). That is, in the regenerative operation, the effective amount Iq of the input current is controlled so that the DC voltage Vd matches the command value Vd *. In the power running operation, the current command generator F (x) generates an effective current command value Iq2 * proportional to the load current IL so that the effective current command value Iq2 * matches the effective portion Iq of the input current. Control.

  During powering operation, the DC output current of the power converter CNV is limited to Idc = KIq2 * by controlling the effective amount Iq of the input current of the self-excited power converter CNV so as to coincide with the command value Iq2 *. . As a result, the DC output current Idd of the power diode rectifier REC is Idd = IL−Idc. This DC output current ratio Idc / Idd can be determined according to the output capacity of the voltage source self-excited power converter CNV and the output capacity of the power diode rectifier REC.

  The DC voltage Vd of the power diode rectifier REC gradually decreases as the DC output current Idd increases. That is, the DC voltage of the voltage source self-excited power converter CNV that has voltage regulation and is operated in parallel is also constrained thereto. Is done. However, unlike the conventional PWM converter, the voltage-type self-excited power converter CNV with fixed pulse phase control can control the input current Ic even if the DC voltage Vd slightly decreases, and the influence of the voltage regulation of the rectifier REC. Is small. In other words, it is not necessary to reduce the secondary voltage V2 of the transformer TR2 in anticipation of DC voltage regulation at the design stage, and a self-excited power converter with a small current capacity can be used, and an economical power converter can be realized. .

  For example, in the power conversion device of the present embodiment, even if it is assumed that the DC voltage Vd changes from 1620V to 1260V, the secondary voltage design value of the transformer TR2 is about V2 = 1200V. In the conventional PWM converter, V2 is about 630 V, but the voltage is about twice as much, and the input current Ic of the self-excited power converter CNV is reduced accordingly, and the self-extinguishing that constitutes the converter CNV is performed. The current capacity of the element is reduced to about half, and the size and cost of the device can be reduced.

  Further, during the regenerative operation, the voltage type self-excited power converter CNV controls the input current Ic supplied from the AC power supply SUP so that the voltage Vd applied to the DC smoothing capacitor Cd matches the command value Vd *. By controlling the DC voltage Vd to be constant, the DC feeding voltage is stabilized and functions as an ideal voltage source for the load device Load.

  As described above, in the power conversion device of the present embodiment, the parallel operation of the power diode rectifier REC and the voltage type self-excited power converter CNV is smoothly performed, and in particular, the self-excited power converter CNV in the power running operation. The load sharing control according to the output capacity can be performed while preventing the power factor from decreasing. In regenerative operation, the DC voltage can be kept constant, and the DC feeding voltage in the electric railway can be stabilized.

  (Second Embodiment) The circuit configuration of the power conversion device of the second embodiment is the same as that of the first embodiment of FIG. 1, but the operation characteristics of the self-excited power converter CNV are different.

  FIG. 10 shows an example of operation characteristics of the self-excited power converter CNV in the power conversion device of the second embodiment. The DC voltage Vd control and the effective current Iq are controlled according to the load power PL = Vd × IL. Control is in progress. That is, when PL <0 (regenerative operation), control is performed so that the DC voltage Vd matches the command value Vd * = constant, and when PL> 0 (power running operation), load sharing with the power diode rectifier REC is performed. Considering this, the effective amount Iq of the input current of the self-excited power converter CNV is controlled.

  Here, during power running, the power diode rectifier REC shares three quarters of the total output, and the self-excited power converter CNV bears the other one-fourth. The input current is controlled. That is, when operating at a rated load of 4 MW, the self-excited power converter CNV outputs 1 MW, and the remaining 3 MW is output by the power diode rectifier REC. At this time, the DC voltage Vd is determined by the regulation of the power diode rectifier REC, and Vd = 1500V. When operating at an overload of 300% (output: 12 MW), the self-excited power converter CNV outputs 3 MW, and the remaining 9 MW is output by the power diode rectifier REC. At this time, the DC voltage Vd drops to Vd = 1260V when the regulation of the power diode rectifier REC is 8%. Conversely, the no-load rectified voltage is Vd = 1620V. Therefore, Vd * = 1650V is set in the DC voltage control during the regenerative operation.

  In electric railways, a power running vehicle and a regenerative vehicle coexist, so that a large output capacity is required on the power running side, and a large capacity is generally not required on the regeneration side. For example, as the power diode rectifier REC, a device having a rated output of 3000 kW (DC 1500 V × 2000 A) and an overload output of 300% (9000 kW, 1 minute) is prepared. Further, as the self-excited power converter CNV, a device having a rated output: ± 1000 kW (DC 1500 V × 667 A) and an overload output: 300% (3000 kW, 1 minute) is prepared. As a whole apparatus, power running rated output: 4000 kW (overload 12 MW, 1 minute), regenerative rated output: 1000 kW (overload 3 MW, 1 minute).

  In the power conversion device according to the second embodiment, during power running, the self-excited power converter CNV controls the effective amount of the input current Ic according to the load current IL or the active power PL = Vd · IL. That is, the DC output current is limited to Idc = Kic by controlling the effective part of the input current Ic of the voltage source self-excited power converter CNV so as to coincide with the command value. As a result, the DC output current Idd of the power diode rectifier REC is Idd = IL−Idc. The DC output current ratio Idc / Idd is determined in accordance with the output capacity of the voltage source self-excited power converter CNV and the output capacity of the power diode rectifier REC.

  For example, when the rated output of the power diode rectifier REC is 3000 kW and the rated output of the self-excited power converter CNV is 1000 kW, the DC output current of the self-excited power converter CNV is Idc = (1/4) IL. , The direct current output current of the power diode rectifier REC becomes Idd = IL−Idc = (3/4) IL, and the ratio of the output current becomes Idc / Idd = 1/3, and the load Sharing can be proportional to the rated capacity of each converter.

  (Third Embodiment) The circuit configuration of the power converter of the third embodiment is the same as that of the first embodiment of FIG. 1, but the operation characteristics of the self-excited power converter CNV are different. This embodiment is the voltage type self-excited power conversion in the power conversion device of the first embodiment until the input current control means reaches a certain set value during the power running operation. The effective portion of the input current Ic of the capacitor is controlled to be zero or a sufficiently small value. In addition, during the power running overload operation, the input current control means has an effective portion of the input current of the voltage type self-excited power converter CNV until the current supplied to the load device reaches a certain overload current set value. Control is performed so as to be equal to or less than the value.

  During power running, the voltage type self-excited power converter CNV controls the effective amount of the input current Ic according to the load current IL or the active power PL = Vd · IL. That is, the DC output current is limited to Idc = Kic by controlling the effective part of the input current Ic of the voltage source self-excited power converter CNV so as to coincide with the command value. As a result, the DC output current Idd of the power diode rectifier REC is Idd = IL−Idc.

  Here, when the effective amount of the input current Ic of the voltage type self-excited power converter CNV is controlled so that Idc = 0 until the load current IL reaches the set value IL0, the DC output current of the power diode rectifier REC is , Idd = IL. On the other hand, when the load current IL exceeds the set value IL0, a direct current of Idc = IL−IL0 is output from the self-excited power converter CNV. As a result, the direct-current output current of the power diode rectifier becomes Idd = IL0 = constant. When the output current Idc of the self-excited power converter eventually reaches the rated value Idco, the output current is limited there, and Idd = IL−Idco is output from the power diode rectifier at a load current IL higher than that.

  In electric railways, the load current IL changes from moment to moment and sometimes exceeds the set value IL0. However, since it takes a long time to operate at IL <IL0, self-excited power conversion is performed by controlling as described above. The device does not need to output current until the load current IL reaches IL0, and the thermal burden can be reduced. As a result, the cooling facility for the self-excited power converter can be reduced, and an economical system as a whole can be realized.

  In electric railways, it may be required to operate for 1 minute at an overload current of 300%. For example, when a power diode rectifier with a rating of 3000 kW (DC 1500 V × 2000 A) and a voltage-type self-excited power converter with a rating of 1000 kW (DC 1500 V × 667 A) are operated in parallel, the rated output is 4000 kW (DC 1500 V × 2667 A), which is an overload. The output current at the time of 300% operation is Idd + Idc = 2667A × 3 = 8000A.

  Until the load current reaches IL = 6667A (= 2000A × 3 + 667A) in the overload operation region, the DC output current of the self-excited power converter is controlled so as not to exceed the rated current Idc = 667A. As a result, the power diode rectifier outputs Idd = IL−667A. When IL = 6667A or less, the self-excited power converter does not need to flow an overload current. Further, only when the load current IL increases (6667A <IL <8000A), the self-excited power converter causes the overload current (Idc = 667A to 2000A) to flow, so that the overload output current 8000A of the entire apparatus is reduced. Secure.

  Overload operation on electric railways is a short time, and the time tends to be shorter as the output current of the overload increases. As a result, the time for which the self-excited power converter is overloaded is negligible, and the thermal burden is greatly reduced. As a result, the cooling facility for the self-excited power converter can be reduced, and an economical system as a whole can be realized.

  FIG. 11 shows an example of operation characteristics of the self-excited power converter CNV in the power conversion device of the third embodiment. Example when the rated output of the power diode rectifier REC is 3 MW (DC 1500 V × 2 kA), overload 300% -1 min, the rated output of the self-excited power converter CNV is ± 1 MW, overload 300% -1 min Show.

  During regenerative operation, DC voltage Vd * = 1650 V = constant control is performed. In power running operation, the power diode rectifier REC and the self-excited power converter CNV are operated in parallel.

  Until the power running load reaches PL = 3 MW, the effective amount Iq of the input current is controlled so that the output Pcnv of the self-excited power converter CNV becomes zero. As a result, all the load power PL is supplied from the power diode rectifier REC. At this time, the DC voltage Vd, which was 1620 V during no-load operation, becomes Vd = 1500 V with a PL = 3 MW load.

  When the power running load is between PL = 3 MW and 4 MW, the effective amount Iq of the input current is controlled so that the output of the self-excited power converter CNV becomes Pcnv = PL-3 MW. As a result, the output of the power diode rectifier REC becomes Prec = 3 MW = constant. At this time, the DC voltage Vd is Vd = 1500 V = constant.

  Further, the load PL increases, and the effective amount Iq of the input current is controlled so that the output of the self-excited power converter CNV becomes Pcnv = 3 MW = constant between PL = 4 MW and 10 MW. As a result, the output of the power diode rectifier REC increases as Prec = PL-3MW. At this time, the DC voltage Vd, which was Vd = 1500 V when PL = 4 MW, decreases to Vd = 1260 V at a PL = 10 MW load.

  Further, the load PL increases, and the effective amount Iq of the input current is controlled so that the output of the self-excited power converter CNV becomes Pcnv = PL-9 MW when PL = 10 MW to 12 MW. As a result, the output of the power diode rectifier REC becomes Prec = 9 MW = constant. At this time, the DC voltage Vd is Vd = 1260 V = constant.

  By controlling as described above, the following advantages can be obtained. In an electric railway, the load PL changes every moment with respect to the rated value of 4 MW for the entire device, and sometimes exceeds the first set value PLO = 3 MW, but in terms of time, it takes a long time to operate at PL <3 MW. By controlling as described above, the self-excited power converter CNV does not need to output current until the load PL reaches 3 MW, and the thermal burden can be reduced. Further, the overload operation in which the load PL exceeds 4 MW is originally a short time (within 1 minute), and the overload time in which the load PL exceeds 10 MW is extremely short. As a result, the time during which the self-excited power converter CNV is overloaded is very short, and the thermal burden is greatly reduced. As a result, the cooling equipment for the self-excited power converter CNV can be reduced, and an economical system as a whole can be realized.

  (Fourth Embodiment) In the power conversion device of the present embodiment, when the effective value of the voltage of the AC power supply changes, the input current control means changes the DC voltage command value according to the change. It is characterized by doing.

  FIG. 12 shows a block diagram of the control circuit CNTL in the power conversion device of the fourth embodiment, in which CAL is a voltage command calculation circuit, C1 and C2 are comparators, AD is an adder, and Gv ( S) is a voltage control compensation circuit, Gi (S) is a current control compensation circuit, FF is a feedforward compensator, Z is a coordinate conversion circuit, PLL is a power supply synchronous phase detection circuit, and PHC is a phase control circuit.

FIG. 13 shows an example of calculation characteristics of the voltage command calculation circuit CAL of FIG. 12, and shows characteristics of the DC voltage command Vd * with respect to the magnitude | Vs | of the power supply voltage Vs. That is, when Vsa>Vso> Vsb, ΔVs = | Vs | −Vso and k is a proportional constant with respect to the rated value Vso of the power supply voltage,

It is said.

  When the DC voltage command value Vd * is operated with Vdo * constant regardless of fluctuations in the power supply voltage Vs, there are the following problems. That is, when the power supply voltage Vs becomes higher than the rated value Vso, the DC voltage of the power diode rectifier REC operating in parallel increases and becomes higher than the control voltage Vdo * of the self-excited power converter CNV. Then, self-excited power converter CNV regenerates power in an attempt to match DC voltage Vd with command value Vdo *. On the other hand, the power diode rectifier REC supplies power from the power source when the DC voltage drops. In this way, a circulating current flows between the two, and accordingly, the current of the elements constituting the converter is increased, leading to an increase in loss.

  On the contrary, when the power supply voltage Vs becomes lower than the rated value Vso, if the DC voltage Vd is controlled to be constant, the AC side voltage Vc of the self-excited power converter CNV becomes a constant value, and Vc> Vs. As a result, a reactive current flows from the power supply SUP and the input current of the self-excited power converter CNV increases, leading to an increase in element loss and an increase in element cutoff current. In particular, when a voltage drop is large but an instantaneous drop (instantaneous voltage drop) occurs in a short time, the reactive current value is large, and the apparatus may be shut down due to overcurrent.

  In this embodiment, when the power supply voltage Vs changes as Vd * = Vdo * + k · ΔVs in the range of Vsb <| Vs | <Vsa, the change ΔVs = | Vs | −Vso The DC voltage command value Vd * is changed. That is, when Vs increases, the DC voltage Vd is increased in proportion to the increase, thereby suppressing an increase in circulating current. Further, when Vs decreases, the direct current voltage Vd is decreased in proportion to the decrease, thereby suppressing the reactive current from flowing from the power supply SUP. As a result, it is possible to prevent an increase in element current due to power supply voltage fluctuations, and it is possible to continue operation without stopping the apparatus even if a voltage sag occurs.

  When the power supply voltage becomes | Vs | ≧ Vsa, Vd * = Vdmax * is set so that the DC voltage Vd is not further increased. In general, the fluctuation of the power supply voltage Vs is about ± 5% at most. However, when the power supply voltage further increases due to a lightning surge or the like, the entire apparatus is set without Vdc * = Vdmax * and increasing the DC voltage Vd unnecessarily. Is consistent. This prevents an excessive voltage from being applied to the load device Load.

  Conversely, when | Vs | ≦ Vsb, Vd * = Vdmin * is set so that the DC voltage Vd is not lowered below that. However, it is appropriate that the set value Vsb is set to about 0.9 to 0.6 times the rated value Vso in consideration of the continuation of operation at the time of a momentary drop.

  Thus, according to the present embodiment, it is possible to prevent an increase in useless circulating current and reactive current even when the power supply voltage Vs fluctuates, and the current capacity of elements constituting the device is reduced. An economical power converter can be realized. In addition, a highly reliable system can be realized without stopping the apparatus even if an instantaneous voltage drop occurs.

  (Fifth Embodiment) FIG. 14 is a block diagram of a power conversion apparatus according to a fifth embodiment. In the figure, SUP is a three-phase AC power source, MCB is an AC main circuit breaker, TR1 and TR2 are three-phase transformers, REC is a power diode rectifier, CNV is a voltage-type self-excited power converter, Cd is a DC smoothing capacitor, and VDT is DC voltage detector, DCDT is a DC current detector, Rd is a resistor, Lf is an inductance of a DC feeder, and Load is a load device.

  On the other hand, as the control circuit CNTL, a voltage command calculation circuit CAL, comparators C1 and C2, an adder AD, a voltage control compensation circuit Gv (S), a current control compensation circuit Gi (S), a current command generator F (x), A switch SW, a level detector LBL, a limiter circuit LIM, a feedforward compensator FF, a coordinate conversion circuit Z, a power supply synchronous phase detection circuit PLL, and a phase control circuit PHC are prepared.

  The power conversion device according to the present embodiment includes an AC power supply SUP, a power diode rectifier REC having an AC terminal connected to the AC power supply SUP via a first transformer TR1, and a second transformer for the AC power supply SUP. A voltage-type self-excited power converter CNV having an AC terminal connected via a transformer TR2, and a series circuit of a DC smoothing capacitor Cd and a resistor Rd connected between the DC terminals of the voltage-type self-excited power converter CNV The voltage type self-excited power converter CNV is operated with a constant pulse pattern, and the voltage type self-excited power converter is adjusted by adjusting the phase angle of the AC side terminal voltage of the voltage type self-excited power converter CNV with respect to the voltage of the AC power supply. And a control circuit CNTL for controlling the input current of the capacitor, and is connected between the DC common terminals of the voltage source self-excited power converter CNV and the power diode rectifier REC. And supplying power to the device Load.

  In the power converter of the present embodiment, the power diode rectifier REC and the voltage source self-excited power converter CNV are operated in parallel. During power running, the power diode rectifier REC and the voltage type self-excited power converter CNV supply power to the load device Load while adjusting the load sharing. In the regenerative operation, the voltage type self-excited power converter CNV regenerates the electric power generated by the load device Load to the AC power supply SUP while performing voltage control so that the DC voltage Vd matches the command value Vd *.

  The voltage type self-excited power converter CNV is a constant pulse pattern (1 pulse, 3 pulses, 5 pulses, etc.) synchronized with the power supply voltage, and the AC side terminal voltage Vc of the voltage type self-excited power converter CNV with respect to the power supply voltage Vs. By controlling the phase angle φ, the input current Ic is controlled, and it is always operated near the input power factor = 1. In addition, switching of the self-extinguishing element constituting the self-excited power converter CNV is performed near the zero point of the input current Ic, so that the cutoff current of the self-extinguishing element can be reduced and the harmonics of the input current Ic are reduced. There are advantages you can do.

  In an electric railway, electric power is supplied to a train load Load via a DC feeder. A resonance circuit is constituted by the inductance Lf of the DC feeder and the DC smoothing capacitor Cd of the voltage type self-excited power converter CNV, which affects the DC voltage control by the self-excited power converter CNV. In particular, when the load current IL changes suddenly, a voltage oscillation occurs due to a transient phenomenon and does not easily attenuate, and in some cases, the control system may become unstable. Further, the vibration of the DC voltage Vd affects the train load Load, and also causes pulsation of train generated torque and vibration of the vehicle body.

  Therefore, in the present embodiment, the resistor Rd is connected in series with the DC smoothing capacitor Cd. The resistance value of the resistor Rd may be about 0.1Ω with respect to the DC smoothing capacitor Cd having a capacity of about 10 mF, and serves to attenuate the vibration phenomenon caused by the inductance Lf and the capacitor Cd. This makes it possible to stabilize the DC voltage control by the self-excited power converter CNV.

  In the power conversion device of the present embodiment, the effective amount Iq of the input current of the self-excited power converter CNV is controlled as follows in accordance with the current IL or power PL = Vd × IL supplied to the load Load. In the control circuit CNTL, the level detector LBL operates the switch SW by the load current IL. When the load current IL <0 (regeneration), the switch SW is connected to the output (Iq1 *) of the adder AD. When the load current IL> 0 (powering), the switch SW is connected to the output (Iq2 *) of the current command generator F (x). That is, in the regenerative operation, the effective amount Iq of the input current is controlled so that the DC voltage Vd matches the command value Vd *. In the power running operation, the current command generator F (x) generates an effective current command value Iq2 * proportional to the load current IL so that the effective current command value Iq2 * matches the effective portion Iq of the input current. Control.

  During powering operation, the DC output current of the power converter CNV is limited to Idc = KIq2 * by controlling the effective amount Iq of the input current of the self-excited power converter CNV so as to coincide with the command value Iq2 *. . As a result, the DC output current Idd of the power diode rectifier REC is Idd = IL−Idc. This DC output current ratio Idc / Idd can be determined according to the output capacity of the voltage source self-excited power converter CNV and the output capacity of the power diode rectifier REC.

  The DC voltage Vd of the power diode rectifier REC gradually decreases as the DC output current Idd increases. That is, the DC voltage of the voltage source self-excited power converter CNV that has voltage regulation and is operated in parallel is also constrained thereto. Is done. However, unlike the conventional PWM converter, the voltage-type self-excited power converter CNV with fixed pulse phase control can control the input current Ic even if the DC voltage Vd slightly decreases, and the influence of the voltage regulation of the rectifier REC. Is small. In other words, it is not necessary to reduce the secondary voltage V2 of the transformer TR2 in anticipation of DC voltage regulation at the design stage, and a self-excited power converter with a small current capacity can be used, and an economical power converter can be realized. .

  For example, in the apparatus of the present embodiment, even if it is assumed that the DC voltage Vd changes from 1620V to 1260V, the secondary voltage design value of the transformer TR2 is about V2 = 1200V. In the conventional PWM converter, V2 is about 630 V, but the voltage is about twice as much, and the input current Ic of the self-excited power converter CNV is reduced accordingly, and the self-extinguishing that constitutes the converter CNV is performed. The current capacity of the element is reduced to about half, and the size and cost of the device can be reduced.

  Further, during the regenerative operation, the voltage type self-excited power converter CNV controls the input current Ic supplied from the AC power supply SUP so that the voltage Vd applied to the DC smoothing capacitor Cd matches the command value Vd *. By controlling the DC voltage Vd to be constant, the DC feeding voltage is stabilized and functions as an ideal voltage source for the load device Load.

  As described above, in the power conversion device of the present embodiment, the parallel operation of the power diode rectifier REC and the voltage type self-excited power converter CNV is smoothly performed, and in particular, the self-excited power converter CNV in the power running operation. The load sharing control according to the output capacity can be performed while preventing the power factor from decreasing. In regenerative operation, the DC voltage can be kept constant, and the DC feeding voltage in the electric railway can be stabilized.

  The control circuit CNTL controls the effective amount of the input current of the voltage type self-excited power converter CNV according to the current supplied to the load device Load or the active power during the power running operation, and the DC smoothing capacitor Cd during the regenerative operation. The input current can be controlled so that the voltage applied to the voltage coincides with the voltage command value.

  During power running, the voltage-type self-excited power converter CNV controls the effective amount of the input current Ic according to the current IL supplied to the load device Load or the active power PL = Vd · IL. That is, the DC output current is limited to Idc = Kic by controlling the effective part of the input current Ic of the voltage source self-excited power converter so as to coincide with the command value. As a result, the DC output current Idd of the power diode rectifier is Idd = IL−Idc. This DC output current ratio Idc / Idd can be determined in accordance with the output capacity of the voltage-type self-excited power converter and the output capacity of the power diode rectifier.

  In the regenerative operation, the voltage type self-excited power converter controls the input current Ic supplied from the AC power supply so that the voltage Vd applied to the DC smoothing capacitor matches the command value Vd *. For example, when Vd <Vd *, the phase angle φ of the output voltage Vc of the power converter with respect to the power supply voltage Vs is delayed, and the effective component of the input current Ic is increased. As a result, the active power is supplied from the power source to the DC smoothing capacitor, and the DC voltage Vd is increased and controlled so that Vd = Vd *. Conversely, when Vd> Vd *, the phase angle φ of the output voltage Vc of the power converter with respect to the power supply voltage Vs is advanced, and the effective component of the input current Ic is set to a negative value. As a result, the active power is regenerated from the DC smoothing capacitor to the power source, and the DC voltage Vd is lowered so that Vd = Vd *. As described above, during the regenerative operation, the DC voltage Vd is controlled to be constant, so that the DC feeding voltage is stabilized and functions as an ideal voltage source for the load device.

  In the above, when the effective value of the voltage of the AC power supply SUP changes, the control circuit CNTL can be controlled by changing the DC voltage command value according to the change.

  If the voltage Vs of the AC power supply system drops instantaneously (so-called instantaneous drop), it may be possible to stop the apparatus. However, if the voltage drops to some extent, it is desirable to continue the operation as it is. In that case, in this power converter, | Vc |> | Vs | is satisfied, and a large advance current flows from the power source to the self-excited power converter. Conversely, when the power supply voltage Vs becomes high, | Vc | <| Vs | is satisfied, and a delayed current flows from the power supply to the self-excited power converter. As a result, in any case, the input power factor is decreased, the input current Is is increased, the cutoff current of the self-extinguishing element constituting the self-excited power converter is increased, and in some cases, the element is broken. Sometimes.

  Further, when the DC voltage Vd of the self-excited power converter is regeneratively operated and the effective value of the power supply voltage Vs increases, the rectified voltage of the power diode rectifier becomes the DC voltage Vd of the self-excited power converter. The power becomes larger and power is supplied from the power diode rectifier to the DC side, and the self-excited power converter maintains the DC voltage Vd, so that the power is regenerated. That is, a circulating current flows between the power diode rectifier and the self-excited power converter. As a result, the current flowing through the self-extinguishing element constituting the self-excited power converter is increased, and the capacity of the transformer TR2 is increased.

  Therefore, when the effective value of the voltage Vs of the AC power supply SUP changes, the DC voltage command value Vd * is changed and controlled in proportion to the change. As a result, the magnitude of the AC voltage | Vc | of the self-excited power converter CNV is proportional to the DC voltage Vd = Vd *, so that | Vc | ≈ | Vs | is maintained even if the power supply voltage changes. This eliminates the problem of a decrease in input power factor of the self-excited power converter CNV and an increase in circulating current during regenerative operation. At the same time, it is possible to continue the operation of the device even when a voltage sag occurs, and a more reliable system can be realized.

This embodiment will be described more specifically. The control circuit CNTL uses the voltage command calculation circuit CAL to set the DC voltage command value Vd * to the rated value Vso of the power supply voltage.

It is said. However, Vsa> Vso> Vsb, ΔVs = | Vs | −Vso, k is a proportionality constant.

  When the DC voltage command value Vd * is operated with Vdo * constant regardless of fluctuations in the power supply voltage Vs, there are the following problems. That is, when the power supply voltage Vs becomes higher than the rated value Vso, the DC voltage of the power diode rectifier REC operating in parallel increases and becomes higher than the control voltage Vdo * of the self-excited power converter CNV. Then, self-excited power converter CNV regenerates power in an attempt to match DC voltage Vd with command value Vdo *. On the other hand, the power diode rectifier REC supplies power from the power source when the DC voltage drops. In this way, a circulating current flows between the two, and accordingly, the current of the elements constituting the converter is increased, leading to an increase in loss.

  On the contrary, when the power supply voltage Vs becomes lower than the rated value Vso, if the DC voltage Vd is controlled to be constant, the AC side voltage Vc of the self-excited power converter CNV becomes a constant value, and Vc> Vs. As a result, a reactive current flows from the power supply SUP and the input current of the self-excited power converter CNV increases, leading to an increase in element loss and an increase in element cutoff current. In particular, when a voltage drop is large but an instantaneous drop (instantaneous voltage drop) occurs in a short time, the reactive current value is large, and the apparatus may be shut down due to overcurrent.

  Therefore, in the control circuit CNTL in the present embodiment, when the power supply voltage Vs changes as Vd * = Vdo * + k · ΔVs in the range of Vsb <| Vs | <Vsa, the change ΔVs = | Vs | −Vso. The DC voltage command value Vd * is changed in proportion to. That is, when Vs increases, the DC voltage Vd is increased in proportion to the increase, thereby suppressing an increase in circulating current. Further, when Vs decreases, the direct current voltage Vd is decreased in proportion to the decrease, thereby suppressing the reactive current from flowing from the power supply SUP. As a result, it is possible to prevent an increase in element current due to power supply voltage fluctuations, and it is possible to continue operation without stopping the apparatus even if a voltage sag occurs.

  When the power supply voltage is | Vs | ≧ Vsa, Vd * = Vdmax * is set so that the DC voltage is not further increased. In general, the fluctuation of the power supply voltage Vs is about ± 5% at most. However, when the power supply voltage further increases due to a lightning surge or the like, the entire apparatus is set without Vdc * = Vdmax * and increasing the DC voltage Vd unnecessarily. Is consistent. This prevents an excessive voltage from being applied to the load device Load.

  Conversely, when | Vs | ≦ Vsb, Vd * = Vdmin * is set so that the DC voltage Vd is not lowered below that. However, it is appropriate that the set value Vsb is set to about 0.9 to 0.6 times the rated value Vso in consideration of the continuation of operation at the time of a momentary drop.

  As described above, according to the power conversion device of the present embodiment, it is possible to prevent an increase in useless circulating current and reactive current even when the power supply voltage Vs fluctuates, and the current capacity of elements constituting the device. Therefore, an economical power conversion device can be realized. In addition, a highly reliable system can be realized without stopping the apparatus even if an instantaneous voltage drop occurs.

  (Sixth Embodiment) FIG. 15 is a block diagram of a power converter according to a sixth embodiment of the present invention. In the figure, SUP is a three-phase AC power source, MCB is an AC main circuit breaker, TR1 and TR2 are three-phase transformers, REC is a power diode rectifier, CNV is a voltage-type self-excited power converter, Cd is a DC smoothing capacitor, Rd is A resistor, Dd is a bypass diode, Lf is an inductance of a DC feeder, and Load is a load device.

  On the other hand, as the control circuit CNTL, a voltage command calculation circuit CAL, comparators C1 and C2, an adder AD, a voltage control compensation circuit Gv (S), a current control compensation circuit Gi (S), a current command generator F (x), A switch SW, a level detector LBL, a limiter circuit LIM, a feedforward compensator FF, a coordinate conversion circuit Z, a power supply synchronous phase detection circuit PLL, and a phase control circuit PHC are prepared.

  The power conversion device according to the present embodiment includes an AC power supply SUP, a power diode rectifier REC having an AC terminal connected to the AC power supply SUP via a first transformer TR1, and a second transformer for the AC power supply SUP. A voltage-type self-excited power converter CNV having an AC terminal connected via a transformer TR2, and a series circuit of a DC smoothing capacitor Cd and a resistor Rd connected between the DC terminals of the voltage-type self-excited power converter CNV The diode Dd for bypassing the one-way current of the resistor Rd and the voltage-type self-excited power converter CNV are operated with a constant pulse pattern, and the AC side terminal voltage of the voltage-type self-excited power converter with respect to the voltage of the AC power supply And a control circuit CNTL for controlling the input current of the voltage-type self-excited power converter CNV by adjusting the phase angle of the voltage-type self-excited power converter CNV and And supplies power to a load device Load connected between the DC common terminal of the power diode rectifier Dd.

  The inventive device of the present embodiment performs parallel operation of the power diode rectifier REC and the voltage type self-excited power converter CNV, and the power diode rectifier REC and the voltage type self-excited power converter CNV are loaded during powering operation. Electric power is supplied to the load device Load while adjusting the sharing. In the regenerative operation, the voltage type self-excited power converter CNV regenerates the electric power generated by the load device Load to the AC power supply SUP while performing voltage control so that the DC voltage Vd matches the command value Vd *.

  The voltage type self-excited power converter CNV is a constant pulse pattern (1 pulse, 3 pulses, 5 pulses, etc.) synchronized with the power supply voltage, and the AC side terminal voltage Vc of the voltage type self-excited power converter CNV with respect to the power supply voltage Vs. By controlling the phase angle φ, the input current Ic is controlled, and it is always operated near the input power factor = 1. In addition, switching of the self-extinguishing element constituting the self-excited power converter CNV is performed near the zero point of the input current Ic, so that the cutoff current of the self-extinguishing element can be reduced and the harmonics of the input current Ic are reduced. There are advantages you can do.

  In an electric railway, electric power is supplied to a train load Load via a DC feeder. A resonance circuit is constituted by the inductance Lf of the DC feeder and the DC smoothing capacitor Cd of the voltage type self-excited power converter CNV, which affects the DC voltage control by the self-excited power converter CNV. In particular, when the load current IL changes suddenly, voltage oscillation occurs due to a transient phenomenon, and it takes time to attenuate, and in some cases, the control system may become unstable. Further, the vibration of the DC voltage Vd affects the train load Load, and also causes pulsation of train generated torque and vibration of the vehicle body.

  In the power changing device of the present embodiment, a resistor Rd is connected in series with the DC smoothing capacitor Cd. The resistance value of the resistor Rd may be about 0.1Ω with respect to the DC smoothing capacitor Cd having a capacity of about 10 mF, and serves to attenuate the vibration phenomenon caused by the inductance Lf and the capacitor Cd. This makes it possible to stabilize the DC voltage control by the self-excited power converter CNV.

  As described above, the resistor Rd serves to attenuate the vibration phenomenon generated by the DC smoothing capacitor Cd and the inductance Lf of the DC feeder and stabilize the DC voltage control by the self-excited power converter CNV. A loss of Icap2 × Rd occurs due to the current Icap flowing through the DC smoothing capacitor Cd. The diode Dd bypasses the one-way current flowing through the resistor Rd, and the loss can be reduced by half. Even if the bypass diode Dd is inserted, the effect of suppressing the resonance phenomenon is almost the same.

  Also in the present embodiment, the control circuit CNTL is one that controls the input current in the same manner as the control circuit CNTL in the fifth embodiment.

  (Seventh Embodiment) In the present embodiment, the control circuit CNTL gates all self-extinguishing elements constituting the self-excited power converter CNV when the powering load current exceeds a certain set value. It controls to do. That is, the voltage-type self-excited power converter CNV is operated mainly utilizing the regenerative function, and the self-extinguishing element is gate-blocked in a region exceeding the set load current ILo on the power running side, thereby A parallel operation of the rectifier REC and a rectifier using a high-speed diode of the self-excited power converter CNV is performed. In this case, the load sharing between them depends on the% impedance of the first and second transformers TR1 and TR2. If% ZI1 and% ZI2 are the same, load sharing is achieved in proportion to the capacities of the two transformers TR1 and TR2. For example, when the rated current is selected as the set load current ILo, the normal operation, that is, the parallel operation of the self-excited power converter and the power diode rectifier is performed up to the rated load current, and the rated current is exceeded. In the area, the high-speed diode rectifier and the power diode rectifier are switched to parallel operation. As a result, even if the DC voltage Vd drops due to the regulation characteristics of the power diode rectifier in the overload region, the self-excited power converter operates as a simple high-speed diode rectifier because of the gate block, and the input power factor decreases. No problem. Moreover, by gate-blocking the self-excited power converter in the overload region, the loss of the self-excited power converter can be reduced, the operation efficiency can be improved, and the cooling equipment of the apparatus can be reduced.

  FIG. 16 is a block diagram of the control circuit CNTL in the power conversion device according to the seventh embodiment of the present invention, in which C1 and C2 are comparators, AD is an adder, SW is a switcher, and LIM is Limiter circuit, LBL1 and LBL2 are level detectors, Gv (S) is a voltage control compensation circuit, Gi (S) is a current control compensation circuit, F (x) is a current command generator, FF is a feedforward compensator, and Z is A coordinate conversion circuit, PLL is a power supply synchronous phase detection circuit, and PHC is a phase control circuit.

  The first level detector LBL1 generates a signal CL = “1” when the load current IL becomes larger than the set value ILo1, and connects the switch SW to the output Iq2 * of the current command generator F (x). To do. Conversely, if IL <ILo1, the signal CL = "0" is generated, and the switch SW is connected to the output Iq1 * of the adder AD. For example, when ILo1 = 0, when IL <0 (regenerative operation), the effective amount Iq of the input current of the self-excited power converter CNV is controlled so that the DC voltage Vd matches the command value Vd *. Further, when IL> 0 (powering operation), the current command generator F (x) calculates an effective current command Iq2 * corresponding to the load power PL, and the current command value Iq2 * is input to the self-excited power converter CNV. Is controlled so that the effective amount Iq matches.

  The coordinate conversion circuit Z converts the three-phase input currents Icr, Ics, and Ict of the self-excited power converter CNV into dq coordinate values, where Iq is an active current component and Id is a reactive current component. The comparator C2 compares the current command value Iq * output from the limiter circuit LIM with the effective current Iq, amplifies the deviation by the current control compensation circuit Gi (S), and self-excited power converter CNV with respect to the power supply voltage Vs. The phase difference command value φ * of the AC output voltage Vc is input to the phase control circuit PHC. At this time, the phase control circuit PHC is operated with reference to the reference signals θr, θs, and θt from the power supply synchronous phase detection circuit PLL.

  The second level detector LBL2 generates a gate block signal GB when the load current IL becomes larger than the set value ILo2, and turns off all the self-extinguishing elements constituting the self-excited power converter CNV. At this time, the self-excited power converter CNV operates as a high-speed diode rectifier, and the power diode rectifier REC and the high-speed diode rectifier are operated in parallel. The load sharing of the two rectifiers is determined by the% impedance (% ZI) of each of the transformers TR1 and TR2. If the% ZI of both is the same, the load sharing is proportional to the output capacity of each.

  The setting value ILo2 of the second level detector LBL2 is set to ILo1 ≦ ILo2 with respect to the setting value ILo1 of the first level detector LBL1. Thereby, it is possible to prevent the gate from being blocked when the DC voltage control is performed.

  For example, when a rated current is selected as the set load current ILo2, the normal operation, that is, the parallel operation of the self-excited power converter CNV and the power diode rectifier REC is performed up to the rated load current. In the exceeding region, the high-speed diode rectifier and the power diode rectifier REC are switched to parallel operation. As a result, even if the DC voltage Vd is reduced due to the regulation characteristics of the power diode rectifier REC in the overload region, the self-excited power converter CNV is gate-blocked, and thus operates as a simple high-speed diode rectifier. The problem of lowering is eliminated. Further, by gate-blocking the self-excited power converter CNV in the overload region, the loss of the self-excited power converter CNV can be reduced, the operation efficiency can be improved, and the cooling equipment of the apparatus can be reduced. .

  (Eighth Embodiment) A power conversion apparatus according to an eighth embodiment of the present invention will be described. The eighth embodiment is characterized in that, in the first embodiment shown in FIG. 1, the impedances of the transformers TR1 and TR2 of the power diode rectifier REC and the voltmeter diode rectifier CNV are optimally designed.

  As described above, in the power converter that operates the power diode rectifier REC and the voltage source self-excited power converter CNV in parallel, the DC voltage Vd becomes the rectified voltage of the power diode rectifier REC in the power running operation. The rectified voltage of the power diode rectifier REC decreases at a constant rate as the DC output current Idd increases. For example, in the case of a power diode rectifier having a regulation of 8%, the no-load DC voltage is 1620V with respect to the rated DC voltage 1500V, and is reduced to 1260V in 300% overload operation. At this time, the DC voltage Vd of the self-excited power converter CNV operating in parallel is also restricted to the above value.

  The magnitude of the AC side voltage Vc of the self-excited power converter CNV is determined by the value of the DC voltage Vd. When the DC voltage Vd decreases, the AC voltage Vc also decreases.

  FIG. 17 shows an AC side voltage / current vector diagram of the self-excited power converter CNV during powering overload operation. As the load current IL increases, the regulation of the power diode rectifier REC operated in parallel decreases the DC voltage Vd, and the AC output voltage Vc = k · Vd of the converter CNV becomes smaller than the power supply voltage Vs. As a result, the phase of the vector of the voltage jωLs · Ic applied to the AC reactor Ls approaches the power supply voltage Vs vector. Then, the phase difference θ between the input current Ic vector of the self-excited power converter CNV and the power supply voltage Vs vector becomes large, and the self-excited power converter CNV is forced to operate with a low power factor. When the same active power is supplied, the input current Ic of the self-excited power converter CNV increases due to the power factor reduction, and the current capacity of the elements constituting the converter CNV must be increased.

  On the other hand, in the power conversion device of the present embodiment, the% impedance (% ZI2) of the transformer TR2 of the self-excited power converter CNV is larger than the% impedance (% ZI1) of the transformer TR1 of the power diode rectifier REC. It is designed to be. As a result, the AC side voltage / current vector diagram of the self-excited power converter CNV during overload operation is as shown in FIG. That is, by increasing% ZI2, the value of AC reactor Ls becomes the same, and even when the same current Ic is passed, voltage jωLs · Ic applied to reactor Ls increases, and the power supply voltage The phase difference φ between the Vs vector and the AC voltage Vc vector of the converter CNV increases. Therefore, the phase of the voltage jωLs · Ic applied to the reactor Ls with respect to the power supply voltage Vs spreads in the 90 ° direction, the phase angle θ of the input current Ic vector with respect to the power supply voltage Vs becomes small, and the input of the self-excited power converter CNV Power factor can be improved. Thereby, the current capacity of the elements constituting the self-excited power converter CNV is reduced, and an economical device can be realized. The impedance design of the transformers TR1 and TR2 can be equally applied to the other embodiments.

  (Ninth Embodiment) The power converter of this embodiment is the same as the power converter of each of the embodiments described above, except that the DC reactor DCL and the high-speed circuit breaker are on the path from the DC smoothing capacitor Cd to the load device Load. It is characterized by inserting HSCB. FIG. 19 is a block diagram of a power conversion device according to the ninth embodiment of this invention. In the figure, SUP is a three-phase AC power source, MCB is an AC main circuit breaker, TR1 and TR2 are three-phase transformers, REC is a power diode rectifier, CNV is a voltage-type self-excited power converter, and Rf and Cf are harmonic filter circuits. Resistors and capacitors, Cd is a DC smoothing capacitor, VDT is a DC voltage detector, DCDT is a DC current detector, Rd is a resistor, Dd is a bypass diode, DCL is a DC reactor, HSCB is a high-speed circuit breaker, and Load is a load device Is shown.

  In the power converter of the present embodiment, the power diode rectifier REC and the voltage source self-excited power converter CNV are operated in parallel. During power running, the power diode rectifier REC and the voltage type self-excited power converter CNV supply power to the load device Load while adjusting the load sharing. In the regenerative operation, the voltage type self-excited power converter CNV regenerates the electric power generated by the load device Load to the AC power supply SUP while performing voltage control so that the DC voltage Vd matches the command value Vd *.

  The voltage type self-excited power converter CNV is a constant pulse pattern (1 pulse, 3 pulses, 5 pulses, etc.) synchronized with the power supply voltage, and the AC side terminal voltage Vc of the voltage type self-excited power converter CNV with respect to the power supply voltage Vs. By controlling the phase angle φ, the input current Ic is controlled, and it is always operated near the input power factor = 1. In addition, switching of the self-extinguishing element constituting the self-excited power converter CNV is performed near the zero point of the input current Ic, so that the cutoff current of the self-extinguishing element can be reduced and the harmonics of the input current Ic are reduced. There are advantages you can do.

  The high-speed circuit breaker HSCB serves to quickly disconnect the circuit when an excessive current flows due to a ground fault of a DC feeder, and prevents the accident from expanding. However, when the DC smoothing capacitor Cd is a voltage source and a ground fault occurs at the closest end, the fault current rises quickly and may not be disconnected even by the high-speed circuit breaker HSCB. The DC reactor DCL suppresses the rising of the accident current, and can reliably operate the high-speed circuit breaker HSCB at the time of the accident. That is, when the DC voltage is Vd, the inductance value of the DC reactor DCL is Ldc, and a ground fault occurs at the closest end, the rise of the fault current is (dIdt) = Vd / Ldc. For example, when Vd = 1500V and Ldc = 1mH, the rise of the fault current at the near end is (dIdt) = 1500 A / msec, and the circuit can be disconnected by the high-speed circuit breaker HSCB operating at several msec. It becomes possible to prevent the spread of accidents.

  In an electric railway, electric power is supplied to a train load Load via a DC feeder. A resonance circuit is constituted by the inductance Lf of the DC feeder and the DC smoothing capacitor Cd of the voltage type self-excited power converter CNV, which affects the DC voltage control by the self-excited power converter CNV. In particular, when the load current IL changes suddenly, a voltage oscillation occurs due to a transient phenomenon and does not easily attenuate, and in some cases, the control system may become unstable. Further, the vibration of the DC voltage Vd affects the train load Load, and also causes pulsation of train generated torque and vibration of the vehicle body.

  Therefore, in the power conversion device of the present embodiment, the resistor Rd is connected in series with the DC smoothing capacitor Cd. The resistor Rd serves to attenuate the vibration phenomenon, and can stabilize the DC voltage control by the self-excited power converter CNV. The resistor Rd serves to attenuate the vibration phenomenon generated by the DC smoothing capacitor Cd and the inductance Lf of the DC feeder and stabilize the DC voltage control by the self-excited power converter CNV. A loss of Icap2 × Rd occurs due to the current Icap flowing through. The diode Dd bypasses the one-way current flowing through the resistor Rd, and the loss can be reduced by half. Even if the bypass diode Dd is inserted, the effect of suppressing the resonance phenomenon is almost the same.

  (Tenth Embodiment) FIG. 20 is a block diagram of a power conversion apparatus according to a tenth embodiment of the present invention. In the figure, SUP is a three-phase AC power source, MCB is an AC main circuit breaker, ACCB1 and ACCB2 are AC circuit breakers, DCCB1 and DCCB2 are DC circuit breakers, TR1, TR2 and TR3 are three-phase transformers, and AC-Load is an AC load. REC is a power diode rectifier, Cf and Rf are harmonic filter circuit capacitors and resistors, CNV is a voltage-type self-excited power converter, Cd is a DC smoothing capacitor, VDT is a DC voltage detector, and DCDT is a DC current detector. , Load indicates a load device.

  On the other hand, as the control circuit CNTL, comparators C1 and C2, adder AD, voltage control compensation circuit Gv (S), current control compensation circuit Gi (S), current command generator F (x), switch SW, level detection LBL, limiter circuit LIM, feedforward compensator FF, coordinate conversion circuit Z, power supply synchronous phase detection circuit PLL, and phase control circuit PHC are prepared.

  The power conversion device according to the present embodiment includes an AC power supply SUP, a power diode rectifier REC having an AC terminal connected to the AC power supply SUP via a first transformer TR1, and a second transformer for the AC power supply SUP. AC-load AC-Load connected via the transformer TR2, and a voltage-type self-excited power converter CNV having an AC terminal connected to the secondary winding of the second transformer TR2 via the third transformer TR3 And the DC smoothing capacitor Cd connected between the DC terminals of the voltage type self-excited power converter CNV and the voltage type self-excited power converter CNV are operated in a constant pulse pattern, and the voltage type for the voltage of the AC power supply SUP A control circuit CNTL for controlling the input current of the voltage-type self-excited power converter CNV by adjusting the phase angle of the AC-side terminal voltage of the self-excited power converter CNV. And supplying power to the DC load Load connected between the DC common terminal of the converter CNV and power diode rectifier REC.

  The AC load AC-Load connected via the second transformer TR2 is a load such as lighting or air conditioning equipment of a substation where the power converter is installed, and generally receives power supply from an AC power supply SUP. The power diode rectifier REC is connected to the AC power supply SUP via the AC circuit breaker ACCB1 and the first transformer TR1. Harmonic filter circuits Cf and Rf are connected to the DC side terminal of the rectifier REC. On the other hand, voltage-type self-excited power converter CNV is connected to the AC side terminal from the secondary winding of second transformer TR2 via AC circuit breaker ACCB2 and third transformer TR3. A DC smoothing capacitor Cd is connected to the DC side terminal of the self-excited power converter CNV.

  The power diode rectifier REC and the self-excited power converter CNV are connected in parallel via the DC circuit breakers DCCB1 and DCCB2, respectively, and the power diode rectifier REC and the voltage-type self-excited power converter CNV share the load during powering operation. Electric power is supplied to the load device Load while adjusting. In the regenerative operation, the voltage type self-excited power converter CNV regenerates the electric power generated by the load device Load to the AC power supply SUP while performing voltage control so that the DC voltage Vd matches the command value Vd *.

  The level detector LBL of the control circuit CNTL generates the signal CL = “1” when the load current IL becomes larger than the set value ILo, and the switch SW is set to the output Iq2 * of the current command generator F (x). Connecting. On the other hand, when IL <ILo, the signal CL = "0" is generated, and the switch SW is connected to the output Iq1 * of the adder AD. For example, when ILo = 0, when IL <0 (regenerative operation), the effective amount Iq of the input current of the self-excited power converter CNV is controlled so that the DC voltage Vd matches the command value Vd *. Further, when IL> 0 (powering operation), the current command generator F (x) calculates an effective current command Iq2 * corresponding to the load power PL, and the current command value Iq2 * is input to the self-excited power converter CNV. Is controlled so that the effective amount Iq matches.

  The coordinate conversion circuit Z of the control circuit CNTL converts the three-phase input currents Icr, Ics, Ict of the self-excited power converter CNV into dq coordinate values, where Iq is an effective current component and Id is a reactive current component. . The comparator C2 compares the current command value Iq * output from the limiter circuit LIM with the effective current Iq, amplifies the deviation by the current control compensation circuit Gi (S), and self-excited power converter CNV with respect to the power supply voltage Vs. The phase difference command value φ * of the AC output voltage Vc is input to the phase control circuit PHC. At this time, the phase control circuit PHC is operated with reference to the reference signals θr, θs, and θt from the power supply synchronous phase detection circuit PLL.

  The voltage type self-excited power converter CNV is a voltage type with respect to the power supply voltage Vs in a constant pulse pattern (1 pulse, 3 pulses, 5 pulses, etc.) synchronized with the power supply voltage (secondary voltage of the second transformer TR2). By controlling the phase angle φ of the AC side terminal voltage Vc of the self-excited power converter CNV, the input current Ic is controlled and is always operated near the input power factor = 1. In addition, switching of the self-extinguishing element constituting the self-excited power converter CNV is performed near the zero point of the input current Ic, so that the cutoff current of the self-extinguishing element can be reduced and the harmonics of the input current Ic are reduced. There are advantages you can do.

  The power diode rectifier REC is a rectifier that converts AC power into DC power, and supplies DC power to the load device Load during powering operation. When power is regenerated from a load device Load such as a train, the voltage-type self-excited power converter CNV performs reverse conversion operation, converts DC power to AC power, and regenerates power to the AC power supply SUP. At the same time, the regenerative power is also supplied to the AC load device AC-Load, so that the power can be effectively used. As a result, the electricity bill can be saved and the operating cost of the electric railway can be reduced. Further, in the power conversion device of the present embodiment, most of the power regenerated by the self-excited power converter CNV is consumed by the AC load AC-Load in the substation, but at that time, the self-excited power converter CNV Since the harmonics of the input current Ic can be reduced, the AC-side filter equipment required conventionally can be omitted, and an economical system can be realized.

  The voltage-type self-excited power converter CNV operates even during powering operation, and can supply power to the load device Load while adjusting the load sharing with the power diode rectifier. The voltage type self-excited power converter CNV performs switching in synchronization with the voltage Vs of the AC power supply with a constant pulse pattern. If the DC voltage Vd is constant, the amplitude value of the voltage Vc is constant. In this state, by changing the phase angle φ of the output voltage Vc with respect to the power supply voltage Vs, the voltage (Vs−Vc) applied to the AC reactor Ls (or the leakage inductance of the transformer TR3) changes, and the input current Ic = (Vs−Vc) / (jω · Ls) can be adjusted.

  Increasing the phase angle φ of the output voltage Vc with respect to the power supply voltage Vs in the delay direction increases the effective power supplied from the AC power supply. Conversely, when the phase angle φ is increased in the advance direction, the active power is regenerated to the AC power source. For example, at the phase angle φ = 0, no active power is transferred. The phase angle of the input current Ic is φ / 2 or π−φ / 2 with respect to the power supply voltage Vs, and the input power factor is cos (φ / 2). Moreover, the phase difference between the input current Is and the AC output voltage Vc of the self-excited power converter CNV is −φ / 2 or π + φ / 2, and the converter power factor is cos (φ / 2). The phase angle φ is at most about φ = 30 ° even during overload operation, and the power factor is cos 15 ° = 0.966.

  When the self-excited power converter CNV is controlled with a constant pulse pattern, the switching pattern is determined so that the harmonic component of the input current Ic becomes small. However, since the converter power factor is close to 1 as described above, the current Ic Switching is performed in the vicinity of the zero point of the self-extinguishing power converter CNV, and the self-extinguishing element of the self-extinguishing power converter CNV can be cut off. Thereby, electric power regeneration is possible, and a power converter with high power factor, high efficiency, and low cost can be realized.

  In regenerative operation, most of the current flows to the self-extinguishing element, but the power factor is controlled to approximately 1 even during regenerative operation, and switching of the self-extinguishing element is performed near the current zero point. The cut-off current of the element can be kept small. Therefore, the switching loss is greatly reduced, and the self-excited power converter CNV can be configured with a self-extinguishing element having a small breaking current, thereby realizing an economical device.

  (Eleventh Embodiment) FIG. 21 is a block diagram of a power converter according to an eleventh embodiment of the present invention. In the figure, SUP is a three-phase AC power source, MCB is an AC main circuit breaker, ACCB1 and ACCB2 are AC circuit breakers, DCCB1 and DCCB2 are DC circuit breakers, TR1, TR2 and TR3 are three-phase transformers, and AC-Load is an AC load. REC is a power diode rectifier, Cf and Rf are capacitors and resistors of a harmonic filter circuit, CNV is a voltage type self-excited power converter, Cd is a DC smoothing capacitor, Rd is a resistor, VDT is a DC voltage detector, DCDT Is a DC current detector, Dd is a diode, Lf is an inductance of a DC feeder, and Load is a load device. The control circuit CNTL is configured similarly to that shown in FIG.

  The power conversion device according to the present embodiment includes an AC power supply SUP, a power diode rectifier REC having an AC terminal connected to the AC power supply SUP via a first transformer TR1, and a second transformer for the AC power supply SUP. AC-load AC-Load connected via the transformer TR2, and a voltage-type self-excited power converter CNV having an AC terminal connected to the secondary winding of the second transformer TR2 via the third transformer TR3 And a series circuit of a DC smoothing capacitor Cd and a resistor Rd connected between the DC terminals of the voltage type self-excited power converter CNV, and bypass the unidirectional current of the resistor Rd inserted as necessary The phase angle of the AC side terminal voltage of the voltage type self-excited power converter CNV with respect to the voltage of the AC power supply SUP is caused to operate the diode Dd and the voltage type self-excited power converter CNV with a constant pulse pattern. And a control circuit CNTL for controlling the input current Ic of the voltage-type self-excited power converter CNV, and is connected between the DC common terminals of the voltage-type self-excited power converter CNV and the power diode rectifier REC. Power is supplied to the DC load Load.

  In the power converter of the present embodiment, the power diode rectifier REC and the voltage source self-excited power converter CNV are operated in parallel. During power running, the power diode rectifier REC and the voltage type self-excited power converter CNV supply power to the load device Load while adjusting the load sharing. Further, during regenerative operation, the voltage type self-excited power converter CNV controls the voltage so that the DC voltage Vd matches the command value Vd *, and supplies the power generated by the load device Load (such as a train) to the AC power supply SUP. Regenerative power is also supplied to the AC load AC-Load for effective use.

  The voltage type self-excited power converter CNV is a constant pulse pattern (1 pulse, 3 pulses, 5 pulses, etc.) synchronized with the power supply voltage, and the AC side terminal voltage Vc of the voltage type self-excited power converter CNV with respect to the power supply voltage Vs The input current Ic is controlled by controlling the phase angle φ and is always operated near the input power factor = 1. In addition, switching of the self-extinguishing element constituting the self-excited power converter CNV is performed near the zero point of the input current Ic, so that the cutoff current of the self-extinguishing element can be reduced and the harmonics of the input current Ic are reduced. There are advantages you can do.

  In the power conversion device of the present embodiment, most of the power regenerated by the self-excited power converter CNV is consumed by the AC load AC-Load in the substation, but at that time, the input of the self-excited power converter CNV Since the harmonics of the current Ic can be reduced, it is possible to omit the AC side filter equipment that has been required in the past, and to realize an economical system.

  In an electric railway, a train load is connected via a DC feeder, a resonance phenomenon occurs due to the DC smoothing capacitor Cd and the inductance Lf of the DC feeder, and the DC voltage control may become unstable. In order to prevent this, in the power conversion device of the present embodiment, a resistor Rd is connected in series with the DC smoothing capacitor Cd. The resistor Rd serves to attenuate the vibration phenomenon, and can stabilize the DC voltage control by the self-excited power converter CNV. However, the resistor Rd serves to attenuate a vibration phenomenon generated by the DC smoothing capacitor Cd and the inductance Lf of the DC feeder and stabilize the DC voltage control by the self-excited power converter CNV. A loss of Icap2 × Rd occurs due to the current Icap flowing through the capacitor Cd. Therefore, a diode Dd is inserted when necessary. The diode Dd bypasses the one-way current flowing through the resistor Rd, and the loss can be reduced by half. Even if the bypass diode Dd is inserted, the effect of suppressing the resonance phenomenon is almost the same.

  Also in the present embodiment, the control circuit CNTL controls in the same manner as the control circuit CNTL in the tenth embodiment.

  (Twelfth Embodiment) FIG. 22 shows a block diagram of another control circuit CNTL in the power converters of the eleventh and twelfth embodiments of FIGS. 20 and 21, in which CAL is a direct current. Voltage command calculator, C1 and C2 are comparators, SW is a switcher, LIM is a limiter circuit, LBL1 and LBL2 are level detectors, Gv (S) is a voltage control compensation circuit, Gi (S) is a current control compensation circuit, F (x) is a current command generator, Z is a coordinate conversion circuit, PLL is a power supply synchronous phase detection circuit, and PHC is a phase control circuit.

  In this embodiment, in the power converters of the eleventh and twelfth embodiments, the voltage source self-excited power converter CNV is controlled by the control circuit CNTL according to the magnitude of the current supplied to the AC load AC-Load. The effective amount of the input current is controlled.

  The AC load is connected to an AC power supply via the second transformer TR2. The voltage source self-excited power converter is connected to the AC power supply via the second transformer and the third transformer. For this reason, during powering operation, the sum of the power supplied to the AC load and the power output from the voltage source self-excited power converter is supplied via the second transformer. The second transformer is originally prepared with a capacity corresponding to the power consumed by the AC load, and there is not much room for it.

  In the power conversion device of the present embodiment, by controlling the effective amount of the input current of the voltage type self-excited power converter CNV according to the magnitude of the current supplied to the AC load AC-Load, during power running operation, When the power supplied to the AC load AC-Load is small, the power Pcnv output from the voltage-type self-excited power converter CNV is increased. Conversely, when the power supplied to the AC load is large, the voltage-type self-excited power converter Reduce the power output from the CNV. As a result, the capacity of the apparatus during power running is increased without increasing the capacity of the second transformer TR2.

  On the other hand, when the current supplied to the AC load AC-Load is increased, the effective current command value Iq * <0, that is, the regeneration command is controlled when the load current is small. As a result, the self-excited power converter CNV performs power regeneration (Pcnv <0) during powering operation, and the power diode rectifier REC outputs the sum of load power and AC load power. Thereby, the electric power exceeding the capacity | capacitance of 2nd transformer TR2 can be supplied to alternating current load.

  In the present embodiment, the control circuit CNTL also controls to block all the self-extinguishing elements constituting the self-excited power converter CNV when the power running load current exceeds a certain set value. Features.

  The voltage-type self-excited power converter CNV operates mainly utilizing the regenerative function, and all the self-extinguishing elements are gate-blocked in a region that exceeds the set load current on the power running side. The self-excited power converter CNV is operated in parallel with a rectifier using a high-speed diode. For example, when a rated current is selected as the set load current, normal operation, that is, a parallel operation of a self-excited power converter and a power diode rectifier is performed up to the rated load current, and the region where the rated current is exceeded. Then, it switches to the parallel operation of the high-speed diode rectifier and the power diode rectifier. As a result, even if the DC voltage drops due to the regulation characteristics of the power diode rectifier in the overload region, the self-excited power converter operates as a simple high-speed diode rectifier because the gate block is used, and the input power factor decreases. The problem disappears. Moreover, by gate-blocking the self-excited power converter in the overload region, the loss of the self-excited power converter can be reduced, the operation efficiency can be improved, and the cooling equipment of the apparatus can be reduced.

  The present embodiment is further characterized in that the percentage impedance of the third transformer TR3 is made larger than the percentage impedance of the first transformer TR1.

  During power running, the voltage type self-excited power converter CNV controls the effective portion of the input current according to the load current IL. The DC output current is limited to Idc = k · Ic by controlling the effective amount of the input current Ic of the voltage type self-excited power converter CNV so as to coincide with the command value. As a result, the DC output current Idd of the power diode rectifier is Idd = IL−Idc. This DC output current ratio Idc / Idd is determined in accordance with the output capacity of the voltage source self-excited power converter and the output capacity of the power diode rectifier.

  In the power diode rectifier REC, the DC voltage Vd decreases as the DC current increases. For example, in a rectifier having a regulation of a DC voltage of 8% in an electric railway, the voltage drops to Vd = 1260V during a 300% overload operation with respect to the rated voltage Vd = 1500V. At this time, the direct-current voltage Vd of the voltage source self-excited power converter CNV performing the parallel operation also decreases to the same value. Then, the AC voltage | Vc | = k · Vd of the self-excited power converter becomes smaller than the power supply voltage Vs, and | Vs |> | Vc |. This differential voltage (Vs−Vc) is applied to the leakage inductance of the second transformer TR2, a large delayed reactive current flows, and the voltage-type self-excited power converter is forced to operate with a low power factor.

  The regulation of the DC voltage of the power diode rectifier is determined by the percentage impedance% IZ1 of the first transformer TR1. When the magnitude of the AC voltage of the converter | Vc | = k · Vd is smaller than the magnitude of the power supply voltage | Vs |, the magnitude of the delayed reactive current of the voltage-type self-excited power converter is It is determined by the percent impedance% IZ3 (that is, leakage inductance) of the second transformer TR3.

  Therefore, by making the percentage impedance% IZ3 of the third transformer TR3 larger than the percentage impedance% IZ1 of the first transformer TR1, the voltage type is regulated with respect to the regulation of the DC voltage of the power diode rectifier during overload operation. The rate of increase of the delayed reactive current of the self-excited power converter can be reduced, and as a result, it is possible to suppress a decrease in the input power factor of the voltage type self-excited power converter.

  This embodiment will be described in more detail. The first level detector LBL1 generates a signal CL = “1” when the load current IL becomes larger than the set value ILo1, and connects the switch SW to the output Iq2 * of the current command generator F (x). To do. Conversely, if IL <ILo1, the signal CL = "0" is generated, and the switch SW is connected to the output Iq1 * of the adder AD. For example, when ILo1 = 0, when IL <0 (regenerative operation), the effective amount Iq of the input current of the self-excited power converter CNV is controlled so that the DC voltage Vd matches the command value Vd *. Further, when IL> 0 (powering operation), the current command generator F (x) calculates an effective current command Iq2 * corresponding to the load power PL, and the current command value Iq2 * is input to the self-excited power converter CNV. Is controlled so that the effective amount Iq matches.

  The coordinate conversion circuit Z converts the three-phase input currents Icr, Ics, and Ict of the self-excited power converter CNV into dq coordinate values, where Iq is an active current component and Id is a reactive current component. The comparator C2 compares the current command value Iq * output from the limiter circuit LIM with the effective current Iq, amplifies the deviation by the current control compensation circuit Gi (S), and self-excited power converter CNV with respect to the power supply voltage Vs. The phase difference command value φ * of the AC output voltage Vc is input to the phase control circuit PHC. At this time, the phase control circuit PHC is operated with reference to the reference signals θr, θs, and θt from the power supply synchronous phase detection circuit PLL.

  20 and 21, the effective amount Iq of the input current of the self-excited power converter CNV is set as follows according to the current IL or power PL = Vd × IL supplied to the load Load as follows. Control. In the control circuit CNTL, the level detector LBL operates the switch SW by the load current IL. When the load current IL <0 (regeneration), the switch SW is connected to the output (Iq1 *) of the adder AD. When the load current IL> 0 (powering), the switch SW is connected to the output (Iq2 *) of the current command generator F (x). That is, in the regenerative operation, the effective amount Iq of the input current is controlled so that the DC voltage Vd matches the command value Vd *. In the power running operation, the current command generator F (x) generates an effective current command value Iq2 * proportional to the load current IL so that the effective current command value Iq2 * matches the effective portion Iq of the input current. Control.

  During powering operation, the DC output current of the power converter CNV is limited to Idc = KIq2 * by controlling the effective amount Iq of the input current of the self-excited power converter CNV so as to coincide with the command value Iq2 *. . As a result, the DC output current Idd of the power diode rectifier REC is Idd = IL−Idc. This DC output current ratio Idc / Idd can be determined according to the output capacity of the voltage source self-excited power converter CNV and the output capacity of the power diode rectifier REC.

  The DC voltage Vd of the power diode rectifier REC gradually decreases as the DC output current Idd increases. That is, the DC voltage of the voltage source self-excited power converter CNV that has voltage regulation and is operated in parallel is also constrained thereto. Is done. However, unlike the conventional PWM converter, the voltage-type self-excited power converter CNV with fixed pulse phase control can control the input current Ic even if the DC voltage Vd slightly decreases, and the influence of the voltage regulation of the rectifier REC. Is small. In other words, it is not necessary to reduce the secondary voltage V2 of the transformer TR2 in anticipation of DC voltage regulation at the design stage, and a self-excited power converter with a small current capacity can be used, and an economical power converter can be realized. .

  For example, in the apparatus of the present embodiment, even if it is assumed that the DC voltage Vd changes from 1620V to 1260V, the secondary voltage design value of the transformer TR2 is about V2 = 1200V. In the conventional PWM converter, V2 is about 630 V, but the voltage is about twice as much, and the input current Ic of the self-excited power converter CNV is reduced accordingly, and the self-extinguishing that constitutes the converter CNV is performed. The current capacity of the element is reduced to about half, and the size and cost of the device can be reduced.

  Further, during the regenerative operation, the voltage type self-excited power converter CNV controls the input current Ic supplied from the AC power supply SUP so that the voltage Vd applied to the DC smoothing capacitor Cd matches the command value Vd *. By controlling the DC voltage Vd to be constant, the DC feeding voltage is stabilized and functions as an ideal voltage source for the load device Load.

  As described above, in the power conversion device of the present embodiment, the parallel operation of the power diode rectifier REC and the voltage type self-excited power converter CNV is smoothly performed, and in particular, the self-excited power converter CNV in the power running operation. The load sharing control according to the output capacity can be performed while preventing the power factor from decreasing. In regenerative operation, the DC voltage can be kept constant, and the DC feeding voltage in the electric railway can be stabilized.

In the control circuit CNTL shown in FIG. 22, the voltage command calculation circuit CAL converts the DC voltage command value Vd * to the rated value Vso of the power supply voltage.

It is said. However, Vsa> Vso> Vsb, ΔVs = | Vs | −Vso, k is a proportionality constant.

  When the DC voltage command value Vd * is operated with Vdo * constant regardless of fluctuations in the power supply voltage Vs, there are the following problems. That is, when the power supply voltage Vs becomes higher than the rated value Vso, the DC voltage of the power diode rectifier REC operating in parallel increases and becomes higher than the control voltage Vdo * of the self-excited power converter CNV. Then, self-excited power converter CNV regenerates power in an attempt to match DC voltage Vd with command value Vdo *. On the other hand, the power diode rectifier REC supplies power from the power source when the DC voltage drops. In this way, a circulating current flows between the two, and accordingly, the current of the elements constituting the converter is increased, leading to an increase in loss.

  On the contrary, when the power supply voltage Vs becomes lower than the rated value Vso, if the DC voltage Vd is controlled to be constant, the AC side voltage Vc of the self-excited power converter CNV becomes a constant value, and Vc> Vs. As a result, a reactive current flows from the power supply SUP and the input current of the self-excited power converter CNV increases, leading to an increase in element loss and an increase in element cutoff current. In particular, when a voltage drop is large but an instantaneous drop (instantaneous voltage drop) occurs in a short time, the reactive current value is large, and the apparatus may be shut down due to overcurrent.

  Therefore, in the control circuit CNTL in the present embodiment, when the power supply voltage Vs changes as Vd * = Vdo * + k · ΔVs in the range of Vsb <| Vs | <Vsa, the change ΔVs = | Vs | −Vso. The DC voltage command value Vd * is changed in proportion to. That is, when Vs increases, the DC voltage Vd is increased in proportion to the increase, thereby suppressing an increase in circulating current. Further, when Vs decreases, the direct current voltage Vd is decreased in proportion to the decrease, thereby suppressing the reactive current from flowing from the power supply SUP. As a result, it is possible to prevent an increase in element current due to power supply voltage fluctuations, and it is possible to continue operation without stopping the apparatus even if a voltage sag occurs.

  When the power supply voltage is | Vs | ≧ Vsa, Vd * = Vdmax * is set so that the DC voltage is not further increased. In general, the fluctuation of the power supply voltage Vs is about ± 5% at most. However, when the power supply voltage further increases due to a lightning surge or the like, the entire apparatus is set without Vdc * = Vdmax * and increasing the DC voltage Vd unnecessarily. Is consistent. This prevents an excessive voltage from being applied to the load device Load.

  Conversely, when | Vs | ≦ Vsb, Vd * = Vdmin * is set so that the DC voltage Vd is not lowered below that. However, it is appropriate that the set value Vsb is set to about 0.9 to 0.6 times the rated value Vso in consideration of the continuation of operation at the time of a momentary drop.

  As described above, according to the power conversion device of the present embodiment, it is possible to prevent an increase in useless circulating current and reactive current even when the power supply voltage Vs fluctuates, and the current capacity of elements constituting the device. Therefore, an economical power conversion device can be realized. In addition, a highly reliable system can be realized without stopping the apparatus even if an instantaneous voltage drop occurs.

  20 and FIG. 21, the voltage type self-excited power converter CNV of the main circuit is the same as that of the voltage type self-excited power converter CNV according to the magnitude of the current IacL supplied to the AC load AC-Load. The effective amount of the input current Ic is controlled. This control is performed by the control circuit CNTL.

  As described above, the current command generator F (x) of the control circuit CNTL in FIG. 22 determines the input current of the self-excited power converter CNV according to the current IL supplied to the load Load or the power PL = Vd × IL. An effective command value Iq * is given, and the command value Iq * is changed by the effective value of the current IacL supplied to the AC load AC-Load.

FIG. 23 shows an example of the characteristics. When the current supplied to the load Load is IL, the effective value of the current supplied to the AC load AC-Load is IacL, and the proportionality constants are k1 and k2, self-excited power The effective current command value Iq * of the converter CNV is

As given. As a result, when IacL = 0, Iq * = k1 · IL and, as usual, the current Idc which is a fraction of the load current IL is output from the self-excited power converter CNV, and the rest is used for power It is operated to output Idd = IL−Idc from the diode rectifier REC. Further, when the current IacL supplied to the AC load AC-Load increases, as shown in FIG. 23, the characteristic curve of the active current command value Iq * shifts downward.

  As illustrated in FIGS. 20 and 21, the AC load AC-Load is connected to the AC power supply SUP via the second transformer TR2. The voltage source self-excited power converter CNV is connected to the AC power supply SUP via the second transformer TR2 and the third transformer TR3. For this reason, during powering operation, the sum of the electric power Pac to the AC load AC-Load and the electric power Pcnv output from the voltage source self-excited power converter CNV is supplied via the second transformer TR2. The second transformer TR2 is originally provided with a capacity corresponding to the power consumed by the AC load AC-Load, and there is not much room.

  By controlling as described above, the power Pcnv output from the voltage-type self-excited power converter CNV is increased when the power supply Pac to the AC load AC-Load is small during powering operation, and conversely, the AC load AC -When the supply power Pac to the load is large, the power Pcnv output from the voltage source self-excited power converter CNV is reduced. As a result, it is possible to increase the device capacity during powering operation without increasing the capacity of the second transformer TR2.

  On the other hand, when the current IacL supplied to the AC load AC-Load increases, the characteristic curve of the effective current command value Iq * shifts downward, and when IL = 0, Iq * <0, that is, a regeneration command is given. It becomes like this. As a result, in the apparatus of FIG. 20 or FIG. 21, the self-excited power converter CNV performs power regeneration (Pcnv <0) during powering operation, and the power diode rectifier REC has the load power PL and the AC load power Pac. Is output as a power Prec. Thereby, the electric power exceeding the capacity | capacitance of 2nd transformer TR2 can be supplied to AC load AC-Load.

  For example, when the capacity of TR2 is 1000 kW and the capacity of TR3 is 1000 kW, the AC load AC-Load can consume up to 2000 kW. That is, when the power consumed by the load device Load is PL, PL + 1000 kW is supplied through the transformer TR1 and the power diode rectifier REC, and 1000 kW is regenerated by the self-excited power converter CNV. The AC load AC-Load is supplied with 1000 kW of power through the transformer TR2 and 1000 kW of power through the transformer TR3. As a result, even when there is no power regeneration from the load device Load, more power can be supplied to the AC load AC-Load without increasing the capacity of the second transformer TR2.

  In the control circuit CNTL of FIG. 22, the second level detector LBL2 generates the gate block signal GB when the load current IL becomes larger than the set value ILo2, and self-extinguishes constituting the self-excited power converter CNV. Turn off all of the elements. At this time, the self-excited power converter CNV operates as a high-speed diode rectifier, and the power diode rectifier REC and the high-speed diode rectifier are operated in parallel. The load sharing of the two rectifiers is determined by the% impedance (% ZI) of each of the transformers TR1 and TR2. If the% ZI of both is the same, the load sharing is proportional to the output capacity of each.

  The setting value ILo2 of the second level detector LBL2 is set to ILo1 ≦ ILo2 with respect to the setting value ILo1 of the first level detector LBL1. Thereby, it is possible to prevent the gate from being blocked when the DC voltage control is performed.

  For example, when a rated current is selected as the set load current ILo2, the normal operation, that is, the parallel operation of the self-excited power converter CNV and the power diode rectifier REC is performed up to the rated load current. In the exceeding region, the high-speed diode rectifier and the power diode rectifier REC are switched to parallel operation. As a result, even if the DC voltage Vd is reduced due to the regulation characteristics of the power diode rectifier REC in the overload region, the self-excited power converter CNV is gate-blocked, and thus operates as a simple high-speed diode rectifier. The problem of lowering is eliminated. Further, by gate-blocking the self-excited power converter CNV in the overload region, the loss of the self-excited power converter CNV can be reduced, the operation efficiency can be improved, and the cooling equipment of the apparatus can be reduced. .

  In the power converter of the present embodiment in which the power diode rectifier REC and the voltage source self-excited power converter CNV are operated in parallel, the DC voltage Vd becomes the rectified voltage of the power diode rectifier REC in the power running operation. The rectified voltage of the power diode rectifier REC decreases at a constant rate as the DC output current Idd increases. For example, in the case of a power diode rectifier having a regulation of 8%, the no-load DC voltage is 1620V with respect to the rated DC voltage 1500V, and is reduced to 1260V in 300% overload operation. At this time, the DC voltage Vd of the self-excited power converter CNV operating in parallel is also restricted to the above value.

  The magnitude of the AC side voltage Vc of the self-excited power converter CNV is determined by the value of the DC voltage Vd. When the DC voltage Vd decreases, the AC voltage Vc also decreases.

  As the load current IL increases, the regulation of the power diode rectifier REC operated in parallel decreases the DC voltage Vd, and the AC output voltage Vc = k · Vd of the converter CNV becomes smaller than the power supply voltage Vs. As a result, the phase of the vector of the voltage jωLs · Ic applied to the AC reactor Ls approaches the power supply voltage Vs vector. Then, the phase difference θ between the input current Ic vector of the self-excited power converter CNV and the power supply voltage Vs vector becomes large, and the self-excited power converter CNV is forced to operate with a low power factor. When the same active power is supplied, the input current Ic of the self-excited power converter CNV increases due to the power factor reduction, and the current capacity of the elements constituting the converter CNV must be increased.

  Therefore, in the present embodiment, in the apparatus of FIG. 20 and FIG. 21, the% impedance (% ZI3) of the transformer TR3 of the self-excited power converter CNV is higher than the% impedance (% ZI1) of the transformer TR1 of the power diode rectifier REC. Designed to be large. As a result, by increasing% ZI3, the value of AC reactor Ls becomes the same, and even when the same current Ic is passed, voltage jωLs · Ic applied to reactor Ls increases, The phase difference φ between the voltage Vs vector and the AC voltage Vc vector of the converter CNV increases. Therefore, the phase of the voltage jωLs · Ic applied to the reactor Ls with respect to the power supply voltage Vs spreads in the 90 ° direction, the phase angle θ of the input current Ic vector with respect to the power supply voltage Vs becomes small, and the input of the self-excited power converter CNV Power factor can be improved. Thereby, the current capacity of the elements constituting the self-excited power converter CNV is reduced, and an economical device can be realized.

  (Thirteenth Embodiment) FIG. 24 is a block diagram of a power converter according to a thirteenth embodiment of the present invention. In the figure, SUP is a three-phase AC power source, MCB is an AC main circuit breaker, ACCB1 and ACCB2 are AC circuit breakers, DCCB1 and DCCB2 are DC circuit breakers, TR1, TR2 and TR3 are three-phase transformers, and AC-Load is an AC load. REC is a power diode rectifier, Cf and Rf are harmonic filter circuit capacitors and resistors, CNV is a voltage-type self-excited power converter, Cd is a DC smoothing capacitor, VDT is a DC voltage detector, and DCDT is a DC current detector. , DCL indicates a DC reactor, HSCB indicates a DC high-speed circuit breaker, and Load indicates a load device. The control circuit CNTL is configured similarly to that shown in FIG. 20 or FIG.

  The power conversion device according to the present embodiment is characterized in that a DC reactor DCL and a high-speed circuit breaker HSCB are inserted between a DC smoothing capacitor Cd and a DC load Load.

  In the power converter of the present embodiment, the power diode rectifier REC and the voltage source self-excited power converter CNV are operated in parallel. During power running, the power diode rectifier REC and the voltage type self-excited power converter CNV supply power to the load device Load while adjusting the load sharing. Further, during regenerative operation, the voltage type self-excited power converter CNV controls the voltage so that the DC voltage Vd matches the command value Vd *, and supplies the power generated by the load device Load (such as a train) to the AC power supply SUP. Regenerative power is also supplied to the AC load AC-Load for effective use.

  The voltage type self-excited power converter CNV is a constant pulse pattern (1 pulse, 3 pulses, 5 pulses, etc.) synchronized with the power supply voltage, and the AC side terminal voltage Vc of the voltage type self-excited power converter CNV with respect to the power supply voltage Vs. By controlling the phase angle φ, the input current Ic is controlled, and it is always operated near the input power factor = 1. In addition, switching of the self-extinguishing element constituting the self-excited power converter CNV is performed near the zero point of the input current Ic, so that the cutoff current of the self-extinguishing element can be reduced and the harmonics of the input current Ic are reduced. it can.

  In the power conversion device of the present embodiment, most of the power regenerated by the self-excited power converter CNV is consumed by the AC load AC-Load in the substation, but at that time, the input of the self-excited power converter CNV Since the harmonics of the current Ic can be reduced, it is possible to omit the AC side filter equipment that has been required in the past, and to realize an economical system.

  In the apparatus of FIG. 24, a DC reactor DCL and a high-speed circuit breaker HSCB are inserted between the DC smoothing capacitor Cd and the load device Load. The high-speed circuit breaker HSCB serves to quickly disconnect the circuit when an excessive current flows due to a ground fault of a DC feeder, and prevents the accident from expanding.

  However, when the DC smoothing capacitor Cd is a voltage source and a ground fault occurs at the closest end, the fault current rises quickly and may not be disconnected even by the high-speed circuit breaker HSCB. The DC reactor DCL suppresses the rising of the accident current, and can reliably operate the high-speed circuit breaker HSCB at the time of the accident. That is, when the DC voltage is Vd, the inductance value of the DC reactor DCL is Ldc, and a ground fault occurs at the closest end, the rise of the fault current is (dIdt) = Vd / Ldc. For example, when Vd = 1500V and Ldc = 1 mH, the rise of the fault current at the closest end is (dIdt) = 1500 A / msec, and the circuit can be disconnected by the high-speed circuit breaker HSCB operating at several msec. It becomes possible to prevent the spread of accidents.

SUP 3-phase AC power supply MCB AC main circuit breaker TR1, TR2, TR3 3-phase transformer Ls AC reactor REC Power diode rectifier CNV Voltage-type self-excited power converter S1-S6 Self-extinguishing element D1-D6 High-speed diode Cd DC smoothing capacitor Rd Resistor Dd Bypass diode Cf, Rf Harmonic filter capacitor and resistor DCL DC reactor HSCB DC high-speed circuit breaker ACCB1, ACCB2 AC circuit breaker DCCB1, DCCB2 DC circuit breaker AC-Load AC load (in-house load)
Load load device CAL DC voltage command calculator C1, C2 Comparator AD Adder F (x) Current command generator Gv (S) Voltage control compensation circuit Gi (S) Current control compensation circuit SW Switch LBL, LBL1, LBL2 Level Detector LIM Limiter circuit FF Feedforward compensator Z Coordinate conversion circuit PLL Power supply synchronous phase detection circuit PHC Phase control circuit CNTL Control circuit PWMC PWM control circuit

Claims (5)

AC power supply,
A power diode rectifier having an AC terminal connected to the AC power source via a first transformer;
An AC load connected to the AC power source via a second transformer ;
A voltage-type self-excited power converter having an AC terminal connected to the secondary winding of the second transformer via a third transformer ;
A DC smoothing capacitor that connected between the DC terminals of the voltage type self-commutated power converter,
The voltage-type self-excited power converter is operated with a constant pulse pattern, and the voltage-type self-excited power is adjusted by adjusting the phase angle of the AC side terminal voltage of the voltage-type self-excited power converter with respect to the voltage of the AC power supply. Input current control means for controlling the input current of the converter,
A power conversion apparatus for supplying power to a DC load connected between DC common terminals of the voltage-type self-excited power converter and the power diode rectifier. AC power supply,
A power diode rectifier having an AC terminal connected to the AC power source via a first transformer;
An AC load connected to the AC power source via a second transformer ;
A voltage-type self-excited power converter having an AC terminal connected to the secondary winding of the second transformer via a third transformer ;
A series circuit of a DC smoothing capacitor and a resistor connected between DC terminals of the voltage type self-excited power converter ;
Operating the pre SL voltage type self-commutated power converter at a fixed pulse pattern, the voltage type self-commutated by adjusting the phase angle of the AC side terminal voltage of the voltage type self-commutated power converter for the voltage of the AC power source An input current control means for controlling the input current of the power converter,
A power conversion apparatus for supplying power to a DC load connected between DC common terminals of the voltage-type self-excited power converter and the power diode rectifier. AC power supply,
A power diode rectifier having an AC terminal connected to the AC power source via a first transformer;
An AC load connected to the AC power source via a second transformer;
A voltage-type self-excited power converter having an AC terminal connected to the secondary winding of the second transformer via a third transformer;
A series circuit of a DC smoothing capacitor and a resistor connected between DC terminals of the voltage type self-excited power converter;
A diode that bypasses the one-way current of the resistor;
The voltage-type self-excited power converter is operated with a constant pulse pattern, and the voltage-type self-excited power is adjusted by adjusting the phase angle of the AC side terminal voltage of the voltage-type self-excited power converter with respect to the voltage of the AC power supply. Input current control means for controlling the input current of the converter,
A power conversion apparatus for supplying power to a DC load connected between DC common terminals of the voltage-type self-excited power converter and the power diode rectifier . 2. The input current control means controls to gate block all self-extinguishing elements constituting the self-excited power converter when a power running load current exceeds a certain set value. The power converter device in any one of -3. 5. The power conversion device according to claim 1, wherein a percentage impedance of the third transformer is larger than a percentage impedance of the first transformer .