JP5428744B2 - Power converter control method - Google Patents

Description

  The present invention relates to pulse width modulation (PWM) control in a power converter that performs AC / DC conversion or DC / AC conversion.

  FIG. 3 is a circuit configuration diagram showing an example of a three-phase voltage source PWM inverter. This three-phase voltage type PWM inverter is a power converter that converts DC power into AC power by turning on and off the semiconductor switches Q1, Q2, Q3, Q4, Q5, and Q6. The semiconductor switches Q1, Q2, Q3, Q4, Q5, and Q6 are turned on and off by gate signals Gu, Gv, Gw, Gx, Gy, and Gz, and mainly applied with pulse width modulation (PWM) control. Has been.

  As a modulation method of PWM control, there are a most basic three-arm modulation method and a two-arm modulation method capable of reducing switching loss. The main PWM modulation method will be described below.

(1) Three-arm Modulation Method FIG. 4 is a diagram illustrating an example of a phase voltage waveform and a gate signal in a PWM-controlled triangular wave-sine wave comparison method (hereinafter referred to as a three-arm modulation method). In the three-arm modulation method, the phase voltage waveforms V ^* _U , V ^* _V , and V ^* _W of the inverter are used as command values (hereinafter referred to as voltage command values), which are compared with a triangular wave carrier carrier to generate a gate signal. . Gate signals input to the semiconductor switches Q1, Q2, Q3, Q4, Q5, and Q6 are generated according to the rules of the following formulas (1) to (6). FIG. 4 shows a PWM pattern of the gate signal Gu as an example. Here, carrier: triangular wave carrier, V ^* _U : U-phase voltage command value, V ^* _V : V-phase voltage command value, V ^* _W : W-phase voltage command value.

  However, if the gate signals Gu, Gv, Gw, Gx, Gy, Gz are given to the semiconductor switches Q1, Q2, Q3, Q4, Q5, Q6 as in the above formulas (1) to (6), the semiconductors of the upper and lower arms A period in which the switches (for example, Q1 and Q2) are turned on at the same time occurs, resulting in a DC short circuit. Therefore, the gate signals Gu, Gv, Gw, Gx, Gy, Gz are given to the semiconductor switches Q1, Q2, Q3, Q4, Q5, Q6 by delaying the turn-on timing in practice by the dead time td.

(2) Two-arm modulation method The main loss of the power converter is classified into conduction loss and switching loss. FIG. 5 is an explanatory diagram of the switching loss. Furthermore, loss w _sw per switching to following equation (7) shows the switching loss W _sw per unit time in the following equation (8). Here, for easy understanding, it is assumed that the voltage v and the current i change linearly as shown in FIG.

In this case, the energy w _sw for losses during the switching time T _sw is the equation (7). Further, as expressed by the above equation (8), the switching loss W _sw per unit time is proportional to the switching frequency f _sw , so in order to reduce the switching loss W _sw , the switching frequency f _sw is set low. It is preferable to do. However, if the switching frequency f _sw is low, the waveform control performance is degraded. Therefore, a two-arm modulation method has been devised as a method of reducing the number of switching times (frequency) while maintaining the waveform control performance.

FIG. 6 shows an example of a voltage command value and a gate signal in the PWM control two-arm modulation method. During the period when the voltage command values V ^* _U , V ^* _V , V ^* _W are 1 or −1, the absolute values of the voltage command values V ^* _U , V ^* _V , V ^* _W are larger than the triangular wave carrier carrier. Therefore, the semiconductor switches Q1, Q2, Q3, Q4, Q5, and Q6 do not perform switching. As a result, in the two-arm modulation method, the average switching frequency f _sw is lowered and the switching loss W _sw is reduced (Patent Document 1, Non-Patent Document 1).

(3) M-arm modulation method FIG. 7 is an explanatory diagram of the modulation method disclosed in Patent Document 2 (hereinafter referred to as the M-arm modulation method). In the 2-arm modulation method, since the average switching frequency f _sw is low, the switching loss W _sw per unit time can be reduced, but there is a period in which the voltage command values V ^* _U , V ^* _V , and V ^* _W change sharply. Therefore, there is a problem that noise increases. The M-arm modulation method is a modulation method that suppresses an increase in noise by reducing the switching loss W _sw by providing an inclination in the period in which the voltage command values V ^* _U , V ^* _V , and V ^* _W change sharply. is there.

JP 59-139871 A Japanese Patent Application No. 2009-99491 (paragraphs [0025] to (0068), FIGS. 1 to 3)

IEEJ Technical Report, No.635 “Latest Technical Trend of PWM Inverter Control”

  A comparison of the three modulation schemes described in the prior art is shown below. However, the control method and parameters are all the same conditions.

(1) Three-arm modulation method The three-arm modulation method is most advantageous from the viewpoint of reducing harmonics because the voltage command values V ^* _U , V ^* _V , and V ^* _W are sinusoidal. However, since the number of times of switching per unit time is large, this is a disadvantageous modulation method from the viewpoint of switching loss.

(2) Two-arm modulation method The two-arm modulation method has an advantage that the switching loss W _sw per unit time can be reduced because the average switching frequency f _sw is lowered. However, there is a problem that a period in which the waveforms of the voltage command values V ^* _U , V ^* _V , and V ^* _W change sharply is generated, and noise increases. In addition, since the waveforms of the voltage command values V ^* _U , V ^* _V , and V ^* _W are not sinusoidal, there is a problem that many harmonic components are included.

(3) M-arm modulation method The M-arm modulation method can suppress noise while reducing switching loss. However, the voltage command value _V ^* _U, V ^* V, although abrupt change in the waveform of V ^* _W can be suppressed, the voltage command value V ^* _U, because _V ^* V, V ^* _W is not a sinusoidal waveform, There is a problem of containing many harmonic components.

  As described above, in the power conversion device, it is an object to reduce switching loss and improve control performance.

One aspect of the method for controlling the power conversion device of the present invention is that a gate signal obtained by PWM modulating the voltage command value is output to a semiconductor switch, and the semiconductor switch is provided for AC / DC conversion or DC / AC. A method for controlling a power conversion device that performs conversion, wherein a change in load current detected during voltage control operation is extracted by a high-pass filter in a switch switching unit, and the output signal of the high-pass filter and a preset switching level The changeover signal is generated, and the changeover switch outputs the correction amount of the 2-arm modulation method or M-arm modulation method in the normal state, the load current changes suddenly, and the output of the high-pass filter exceeds the switching level. In this case, the 3-arm modulation method is switched to output the correction amount of the 3-arm modulation method, and the 2-arm modulation method or the M-arm It switched to scheme and outputs the correction amount of two-arm modulation scheme or M-arm modulation method, a voltage command value corrected by the correction amount by PWM modulation, and outputs a gate signal to the semiconductor switch.

  In addition, you may use the control method of the said power converter device for an uninterruptible power supply device, a sag compensation device, etc.

In another aspect of the power conversion device of the present invention, a gate signal obtained by PWM-modulating a voltage command value is output to a semiconductor switch, and this semiconductor switch is provided for AC / DC conversion or DC / AC. A method for controlling a power conversion device that performs conversion, wherein a switch switching unit extracts a change in a current control amplifier detected during current control operation by a high-pass filter, and outputs a high-pass filter output signal and a preset switching Compares the level and outputs the change signal. At the changeover switch, the correction amount of the 2-arm modulation method or M-arm modulation method is output during normal operation, the output of the current control amplifier changes suddenly, and the output of the high-pass filter changes. When the value exceeds the value, it switches to the 3-arm modulation method and outputs the correction amount of the 3-arm modulation method. And outputs the correction amount of two-arm modulation scheme or M-arm modulation method switches to M-arm modulation scheme, a voltage command value corrected by the correction amount by PWM modulation, to output the gate signal to the semiconductor switch Features.

  In addition, you may use the control method of the said power converter device for a rectifier and a grid connection apparatus.

  As is apparent from the above description, according to the present invention, it is possible to reduce switching loss and improve control performance in the power converter.

The block diagram of the gate signal generation part in the modulation system of this invention. The figure which shows an example of each part waveform of the power converter device of this invention. The circuit block diagram which shows an example of a three-phase voltage form PWM inverter. The figure which shows an example of the phase voltage waveform and gate signal in a 3 arm modulation system. An explanatory view of switching loss. The figure which shows an example of the phase voltage waveform in a 2 arm modulation system, and a gate signal. The figure which shows an example of the phase voltage waveform in a M arm modulation system, and a gate signal.

In the present invention, in a power converter provided in a UPS (uninterruptible power supply), a voltage sag compensator, etc. that perform voltage control operation, or a rectifier or grid interconnection device, etc. that performs current control operation, normally, two-arm modulation is used. When the power converter is operated by the M-arm modulation method or the M-arm modulation method and the load changes suddenly during voltage control operation, or when the load changes suddenly during current control operation and the current control amplifier outputs a large command value, three arms are instantaneously generated. The control performance is improved by switching to the modulation method and raising the switching frequency f _sw equivalently.

[Embodiment 1]
FIG. 1 shows a block diagram of a gate signal generator in the modulation system of the present invention. The method for controlling the power conversion apparatus according to the first embodiment is applied to a power conversion apparatus that performs a voltage-controlled operation, such as a UPS (uninterruptible power supply) or a voltage sag compensator. In the modulation method of the first embodiment, the correction voltage command value E ^* _U + γ, E ^* _{V is} obtained by adding the correction amount γ to the sinusoidal voltage command values E ^* _U , E ^* _V , E ^* _W of each phase. + Γ, E ^* _W + γ is generated.

  The correction amount γ is generated by switching the addition term α of the 3-arm modulation method and the addition term β of the 2-arm modulation method or the M-arm modulation method with the changeover switch sw.

In the addition term α of the three-arm modulation system, correction values necessary for the voltage command values E ^* _U , E ^* _V , and E ^* _W are set. If the voltage command values E ^* _U , E ^* _V , E ^* _W are used as they are as the voltage command values V ^* _U , V ^* _V , V ^* _W when operating in the three-arm modulation system, this addition term α Should be set to 0.

Moreover, two-arm modulation scheme or M arm addition term β of the modulation scheme is a sinusoidal voltage command value E ^* _U, E ^* _V, the voltage command value of E ^* _W a two-arm modulation scheme or M-arm modulation scheme V ^* It is a correction term for correcting to _U , V ^* _V , and V ^* _W. Since the addition term β of the two-arm modulation method or the M-arm modulation method is disclosed in Patent Documents 1 and 2 in the prior art, description thereof is omitted here.

  The switch switching unit 1 includes a high-pass filter HPF, a comparator 2, and an off-delay timer T. When the load current is input to the high-pass filter HPF, the switch switching unit 1 extracts the change in the load current, and the output of the high-pass filter HPF is input to the input terminal A of the comparator 2. The comparator 2 also receives a switching level set to a predetermined value in advance at the input terminal B, and compares the output level of the high-pass filter HPF with the switching level. This switching level is set according to the specifications of the inverter and load used in the power converter.

  The comparator 2 outputs a “1” level signal if the output signal of the high-pass filter HPF is greater than the switching level, and “0” if the switching level is greater than the output signal of the high-pass filter HPF. A level signal is output.

  The signal output from the comparator 2 is input to the off-delay timer T. The off-delay timer T receives a “0” signal from the “1” level signal during the period when the “1” level signal is input. A switch signal “0” is output for a predetermined period after switching to the level signal. In addition, during the period in which other “0” level signals are input, a “1” level switching signal is output to the changeover switch sw.

  The change-over switch sw to which the switching signal from the off-delay timer T is input has a three-arm modulation type addition term α during the period when the input switching signal is “0” level and the input switching signal is at “1” level. During the period, the addition term β of the 2-arm modulation system or the M-arm modulation system is output as the correction amount γ to the adders 3a, 3b, 3c.

Then, in the adders 3a, 3b, 3c, the correction amount γ is added to the sinusoidal voltage command values E ^* _U , E ^* _V , E ^* _W , respectively, and the correction voltage command values E ^* _U + γ, E ^* _V + γ. , E ^* _W + γ.

  By configuring the switch switching unit 1 as described above, the period during which the output signal of the high-pass filter HPF exceeds a predetermined switching level, and the predetermined period after the output signal of the high-pass filter HPF falls below the predetermined switching level. Is added to the adders 3a, 3b, 3c as a correction amount γ, and the adder 3b of the 2-arm modulation method or the M-arm modulation method is added to the adders 3a, 3b, Is output to 3c. As a result, the 3-arm modulation method can be used only when the load current changes suddenly, and the 2-arm modulation method or the M-arm modulation method can be used during other periods.

FIG. 2 shows an example of the waveform of each part of the power conversion device according to the first embodiment. Fig. 2 (1) shows waveforms of sinusoidal voltage command values E ^* _U , E ^* _V , E ^* _W , Fig. 2 (2) shows waveforms of load current, high-pass filter output and switching level, and Fig. 2 (3) shows. The output waveform (switching signal) of the off-delay timer T, FIG. 2 (4) shows the waveform of the correction amount γ output from the selector switch sw, and FIG. 2 (5) shows the correction voltage command values E ^* _U + γ, E ^* _V + γ. , E ^* _W + γ waveform. Here, as an example, it is assumed that the normal operation is performed by the M-arm modulation method.

  As shown in FIG. 2 (2), the output signal of the high pass filter HPF rises in response to the steep rise of the load current. The output signal of the high-pass filter HPF initially becomes a large value in response to the steep rise of the load current, and thereafter the value becomes small. The output signal of the high-pass filter HPF and the switching level are compared by the comparator 2. When the output signal of the high-pass filter HPF is larger, a “1” level signal is output, and when the switching level is larger, “0” is output. ”Level signal is output.

  The signal output from the comparator 2 is input to the off-delay timer T. As shown in FIG. 2 (3), the off-delay timer T has a signal period in which the input signal is “1” level and the input signal is After switching from the “1” level to the “0” level, a “0” level switching signal is output for a period preset in the off-delay timer T. In addition, during the period in which other “0” level signals are input, a “1” level switching signal is output.

  The switching signal output from the off-delay timer T is input to the switching switch sw. From the switching switch sw, a switching signal of “1” level is input from the off-delay timer T as shown in FIG. The addition term β of the M-arm modulation method is used during the period during which the switching signal of “0” level is output from the off-delay timer T (0 in the first embodiment). Is output as a correction amount γ.

The correction amount γ output from the changeover switch sw is output to the adding units 3a, 3b, and 3c, and added to the sinusoidal voltage command values E ^* _U , E ^* _V , and E ^* _W shown in FIG. Is done. As shown in FIG. 2 (5), the signals added by the adders 3a, 3b, and 3c are in the M-arm modulation method during the period when the “1” level switching signal is output from the off-delay timer T. The correction voltage command values E ^* _U + γ, E ^* _V + γ, E ^* _W + γ are output as waveforms, and during the period when the “0” level switching signal is output from the off-delay timer T, the three-arm modulation type correction voltage The waveforms of command values E ^* _U + γ, E ^* _V + γ, E ^* _W + γ are output.

  As described above, during normal operation, operation is performed using the M-arm modulation method, and when the load current changes suddenly (increases) and the output of the high-pass filter HPF exceeds the switching level, the change-over switch sw is switched to the three-arm modulation method. Then, the load current is settled and the M-arm modulation method is switched after a certain time.

  Therefore, in the first embodiment, even when the load suddenly changes during the voltage control operation, the mode is instantaneously switched to the three-arm modulation method, and the switching frequency is equivalently increased. As a result, it is possible to improve the control performance by improving the responsiveness by increasing the switching frequency, increasing the voltage response speed, and preventing distortion of the voltage waveform.

  Further, since the normal operation is performed by the 2-arm modulation method or the M-arm modulation method, the switching loss can be reduced as compared with the case where the operation is always performed by the 3-arm modulation method.

  Furthermore, if the M-arm modulation method is applied in normal times, noise can be suppressed.

  In the present invention, the 2-arm modulation method or the M-arm modulation method is operated in the normal state, and the 3-arm modulation method is operated only for a short time (when the load suddenly changes). There is an advantage that it is not necessary to change the correspondingly designed main circuit.

[Embodiment 2]
In the first embodiment, the detected load current is input to the high-pass filter HPF and the change in the load current is extracted, but in the second embodiment, the sudden change of the inverter is detected by inputting the output of the current control amplifier to the high-pass filter HPF. Thus, the changeover switch sw is switched. Since other configurations are the same as those of the first embodiment, description thereof is omitted. In addition, the control method of the power converter device of this Embodiment 2 is applied to the power converter device which performs an electric current control driving | operation like a rectifier and a grid connection apparatus.

  By configuring as in the second embodiment, the power converter is operated in the normal mode by the 2-arm modulation method or the M-arm modulation method, the current command value changes suddenly during the current control operation, and the current control amplifier has a large command value. Is immediately switched to 3-arm modulation. Therefore, when switching to the three-arm modulation system, the switching frequency is equivalently increased. As a result, it is possible to improve the control performance by improving the responsiveness by increasing the switching frequency, and by preventing the current waveform from being distorted by increasing the current response speed. In addition, the same effects as those of the first embodiment are obtained.

  Although the present invention has been described in detail only for the specific examples described above, it is obvious to those skilled in the art that various changes and modifications are possible within the scope of the technical idea of the present invention. Such variations and modifications are naturally within the scope of the claims.

  For example, a UPS or a sag compensator in the first embodiment is applied to the power converter, and a rectifier or a grid interconnection device is applied in the second embodiment. However, the power converter is applicable to any power converter that performs voltage control operation or current control operation. Is possible.

  In the first and second embodiments, the switch switching unit 1 having a specific configuration has been described. However, any configuration may be used as long as it can output a switching signal that can switch the switching switch sw when the load current or the current control amplifier suddenly changes.

^{_{E * U, E * V,}} E * W ... sinusoidal voltage command value ^{_{E * U + γ, E *}} V + γ, E * W + γ ... correction voltage command value _{G U, G V, G W} , G X, G Y , G _Z ... gate signals Q _{1 to} Q ₆ ... semiconductor switches V ^* _U , V ^* _V , V ^* _W ... voltage command values sw ... changeover switch 1 ... switch changeover part 2 ... comparators 3a, 3b, 3c ... addition part

Claims (6)

A control method of a power conversion device that outputs a gate signal obtained by PWM modulating a voltage command value to a semiconductor switch, and includes the semiconductor switch, and performs AC / DC conversion or DC / AC conversion,
In the switch switching unit, a change in the load current detected during the voltage control operation is extracted by a high pass filter, and the output signal of the high pass filter is compared with a preset switching level to generate a switching signal,
When the change-over switch is in normal operation, it outputs a correction amount of the 2-arm modulation method or M-arm modulation method, and when the load current changes suddenly and the output of the high-pass filter exceeds the switching level, it switches to the 3-arm modulation method. Output the correction amount of the system, switch to the 2-arm modulation system or the M-arm modulation system after a certain time, and output the correction amount of the 2-arm modulation system or the M-arm modulation system,
A method for controlling a power converter, comprising: PWM-modulating a voltage command value corrected by the correction amount and outputting a gate signal to a semiconductor switch.   The method for controlling a power converter according to claim 1, wherein the power converter is provided in an uninterruptible power supply.   The method for controlling a power conversion device according to claim 1, wherein the power conversion device is provided in a sag compensation device. A control method of a power conversion device that outputs a gate signal obtained by PWM modulating a voltage command value to a semiconductor switch, and includes the semiconductor switch, and performs AC / DC conversion or DC / AC conversion,
In the switch switching unit, the change amount of the current control amplifier detected during the current control operation is extracted by the high pass filter, and the output signal of the high pass filter is compared with a preset switching level to output the switching signal,
When the changeover switch is in normal condition, it outputs the correction amount of 2-arm modulation method or M-arm modulation method, and when the output of the current control amplifier changes suddenly and the output of the high-pass filter exceeds the switching level, it switches to the 3-arm modulation method. Outputs the correction amount of the 3-arm modulation method, switches to the 2-arm modulation method or the M-arm modulation method after a certain time, and outputs the correction amount of the 2-arm modulation method or the M-arm modulation method,
A method for controlling a power converter, comprising: PWM-modulating a voltage command value corrected by the correction amount and outputting a gate signal to a semiconductor switch.   5. The method of controlling a power converter according to claim 4, wherein the power converter comprises a rectifier.   The method according to claim 4, wherein the power conversion device is provided in a grid interconnection device.

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