JP2010114969A - Power conversion device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power conversion device wherein it is possible to reduce the capacitance of a capacitor located between a power converter and a switch means more than before, suppress fluctuation in the voltage of the capacitor, and reduce the size and weight of the power conversion device. <P>SOLUTION: The power conversion device includes: a first capacitor 5 connected in parallel with a direct-current power supply 6; the power converter 2 that drives a synchronous machine 1; a second capacitor 3 connected in parallel with the direct current side of the power converter 2; the switch means 4 placed in the first capacitor 5 and the second capacitor 3; and a controlling means 9 that controls the power converter 2 based on the respective pieces of detection information from a speed detecting means 7 for detecting the speed of the synchronous machine 1 and a second voltage detecting means 8 for detecting the voltage of the second capacitor 3. The controlling means 9 keeps the switch means 4 off when the power converter 2 is at a stop. When the operation of the power converter 2 is started, it turns on the switch means 4 and simultaneously starts the power converter 2 and thereby controls an exciting current so that the terminal voltage of the synchronous machine 1 becomes equal to a predetermined value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power conversion device for driving a synchronous machine used in an electric vehicle such as a railway vehicle or an electric vehicle. In particular, the no-load induced voltage of the synchronous machine is a DC power source during high-speed operation. The present invention relates to a power converter that can cope with a case where the voltage is higher than a DC voltage.

  In drive systems for electric vehicles such as electric cars and trains, DC power is converted into AC power of required variable voltage and variable frequency by a power converter (inverter) and supplied to a permanent magnet type synchronous machine. Is driven at variable speed. Further, in this type of electric vehicle, so-called coasting operation is frequently performed in which the vehicle travels by inertia without being accelerated or decelerated by the drive system. In this coasting operation, in a drive system using a synchronous machine, a no-load induced voltage is generated, and this no-load induced voltage is all transmitted via a diode connected in reverse parallel to the switching elements constituting the power converter. The power is regenerated on the power source side by the wave rectification, and the regenerative energy causes a problem that the brake operation is performed instead of coasting.

  In order to prevent such a phenomenon, in a conventional power conversion device, a unidirectional conducting means such as a diode and a switching means such as a switch for performing a mechanical opening and closing operation are connected in parallel between the power source and the power converter. A drive device that inserts a circuit in series and drives a permanent magnet synchronous machine via a power converter, and when the power converter is stopped, opens a switching means to prevent regeneration of no-load induced voltage, When the operation of the power converter is started, the switching means is kept open and the excitation current is controlled so that the terminal voltage of the synchronous machine becomes a predetermined value. When the terminal voltage of the synchronous machine reaches the predetermined value, the switching means is closed. In this state, when controlling the torque current of the synchronous machine and accelerating / decelerating the synchronous machine and stopping the operating power converter, the excitation current remains controlled so that the terminal voltage of the synchronous machine becomes a predetermined value. After reducing the torque current to zero with Open, then a technique of decreasing the excitation current and so as to stop the power converter has been proposed (e.g., see Patent Document 1 below).

JP 2000-308388 A (Claim 1, FIG. 1)

  In the conventional power conversion device described in Patent Document 1, the open / close means constituting the parallel connection circuit inserted in series between the power source and the power converter includes a relay switch that performs a mechanical open / close operation. Is used, the on (closing) operation of the switching means is slower than the operation of the switching elements constituting the power converter. For this reason, it was necessary to start the power converter first with the opening / closing means opened at the start of operation. That is, at the start of operation, the power converter could not be started simultaneously with closing the opening / closing means.

  Therefore, for example, when the operation command at the start of operation is a brake and the synchronous machine performs regeneration, the power cannot be returned to the power source side even if the power converter is activated because the opening / closing means is open. Therefore, the voltage of the capacitor between the power converter and the switching means may increase excessively. Further, in order to eliminate such fluctuations in the voltage of the capacitor between the power converter and the switching means, the capacitance of the capacitor is considerably increased (specifically, the filter capacitor between the power source and the switching means). It was necessary to make it equal to or greater than the capacity of

  Thus, in the prior art, since the closing operation of the mechanical opening / closing means constituted by a relay switch or the like is slow, the power converter and the opening / closing means cannot be turned on at the same time. There is a problem that the fluctuation of the capacitor between and the capacitor becomes larger or the capacitance of the capacitor becomes larger.

  The present invention has been made to solve the above-described problems, and can reduce the capacitance of the capacitor between the power converter and the switch means, and can suppress fluctuations in the voltage of the capacitor. Thus, it is possible to obtain a power conversion device that can be reduced in size, weight and cost, and can improve responsiveness at the start of operation.

  The power converter of the present invention includes a first capacitor connected in parallel to a DC power source, a power converter that drives the synchronous machine, and a second capacitor connected in parallel to the DC side of the power converter. A switching means composed of a semiconductor element inserted in a DC power supply path between the second capacitor and the first capacitor to turn on / off the supply path, and a speed for detecting the speed of the synchronous machine The power based on the detection means, the second voltage detection means for detecting the voltage of the second capacitor, the speed information detected by the speed detection means and the voltage information detected by the second voltage detection means. Control means for controlling the converter, and when the power converter is stopped from the operating state, the control means maintains the excitation current so that the terminal voltage of the synchronous machine becomes a predetermined value. Torque current After that, the switch means is turned off to stop the operation of the power converter, the switch means is kept off while the power converter is stopped, and the switch means is turned off when the power converter starts operation. At the same time as turning on, the excitation current is controlled so that the terminal voltage of the synchronous machine becomes a predetermined value. After the terminal voltage of the synchronous machine reaches the predetermined value, the torque current of the synchronous machine is controlled. The synchronous machine is characterized by performing acceleration / deceleration operation.

  According to the present invention, since the capacity of the second capacitor between the power converter and the switch means can be reduced, the power converter can be reduced in size, weight, and cost. Moreover, since the power converter can be activated immediately when an operation command such as a power running command or a brake command is input, the responsiveness to the operation command can be enhanced.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram illustrating a power conversion device according to Embodiment 1 of the present invention.
The power conversion device according to the first embodiment includes a first capacitor 5 connected in parallel to a DC power source 6, a power converter (inverter) 2 that drives the synchronous machine 1, and a DC side of the power converter 2. The second capacitor 3 connected in parallel, the switch means 4 inserted in series in the DC power supply path between the first and second capacitors 5 and 3, and the speed of the synchronous machine 1 (here, rotational speed ω) Speed detecting means 7 for detecting the voltage, second voltage detecting means 8 for detecting the voltage of the second capacitor 3, speed information detected by the speed detecting means 7, and voltage information detected by the second voltage detecting means 8. And control means 9 for controlling the power converter 2 based on the above.

  The above-described synchronous machine 1 includes a permanent magnet type synchronous machine (hereinafter simply referred to as a synchronous machine) that generates a magnetic field by a permanent magnet attached to a rotor. The power converter 2 has switching means Gu, Gv, Gw, Gx, Gy, Gz comprising switching elements such as IGBTs and diodes connected in antiparallel thereto. The switch means 4 located between the first and second capacitors 5 and 3 is composed of a diode 4a and a switching element 4b made of a semiconductor element such as an IGBT or a power MOSFET connected in antiparallel to the diode 4a. ing. In this case, if the same switch means 4 as each of the switch means Gu, Gv, Gw, Gx, Gy, Gz constituting the power converter 2 is used, there is an advantage that the entire apparatus can be realized in a small size and at low cost. Further, the speed detecting means 7 detects the rotational speed ω of the synchronous machine 1 and outputs the speed information to the control means 9 here. For example, a resolver or a rotary encoder is applied.

  The control means 9 is constituted by, for example, a microcomputer, and a switch opening / closing command means 12, a dq-axis current command calculation means 10, and a voltage command calculation means 11 are configured by installing a predetermined calculation program. ing.

  Here, the switch opening / closing command means 12 outputs a signal for turning on / off the switching element 4b of the switch means 4 in response to the operation command when the operation command (power running command or brake command) is input from the outside. It is. The dq-axis current command calculation means 10 is based on the value of the rotation speed ω detected by the speed detection means 7 and the voltage Vc of the second capacitor 3 detected by the second voltage detection means 8. It calculates dq-axis current commands id * and iq * for controlling the excitation current (hereinafter, those added with * are meanings of command values). The voltage command calculation means 11 includes a dq-axis current command id *, iq * calculated by the dq-axis current command calculation means 10, a rotation speed ω detected by the speed detection means 7, and a second voltage detection means 8. Based on each value of the detected voltage Vc, voltage commands Vu *, Vv *, Vw * for three phases for controlling the power converter 2 are calculated, and further based on each voltage command Vu *, Vv *, Vw *. Thus, a gate pulse signal for controlling each switch means Gu, Gv, Gw, Gx, Gy, Gz of the power converter 4 is output.

  As shown in FIG. 3, the no-load induced voltage of the synchronous machine 1 is a function of the rotational speed ω, and increases in proportion to the rotational speed ω as shown by the broken line in the figure. There is a risk of generating a no-load induced voltage exceeding the voltage Vdc of the power supply 6. On the other hand, since the power converter 2 cannot generate a voltage higher than the DC voltage of the input DC power source 6, the region where the no-load induced voltage exceeds the maximum output voltage of the power converter (in the figure) In a region where the rotational speed is equal to or higher than ωsh), field weakening control is performed by the power converter 2 so that a magnetic flux that cancels the magnetic flux generated by the permanent magnet is generated by the armature winding, thereby enabling control in a high speed range.

  This is also necessary when the synchronous machine 1 restarts the power converter 2 from the coasting operation in the high speed range, or when the power converter 2 is stopped and shifted to the coasting operation. It is necessary to perform field-weakening control immediately after starting the power converter 2 or before stopping so that the regenerative energy does not flow backward from the synchronous machine 1 to the power converter 2 side.

  Therefore, the principle of field weakening control by the dq-axis current command calculation means 10 and the voltage command calculation means 11 will be described below.

  The voltage equation and the torque T expressed on the dq coordinate in the synchronous machine 1 are given by the following equations (1) and (2), respectively.

  Here, id and iq are armature current d and q-axis components, vd and vq are armature voltage d and q-axis components, φa = √ {(3/2) φf}, and φf is a permanent magnet armature. The maximum value of the flux linkage, R is the armature resistance, Ld and Lq are d-axis and q-axis inductance, p = d / dtf, Pn is the number of pole pairs, and ω is the rotational speed (electrical angular speed).

The terminal voltage that can be supplied to the synchronous machine 1 is given by | Vm | = √ (vd ² + vq ² ). In this case, | Vm | corresponds to the effective value of the line voltage. When the voltage of the second capacitor 3 is Vc, the power conversion from the synchronous machine 1 is performed when the power converter 2 is restarted (or stopped). In order to prevent the current from flowing into the capacitor 2, the line voltage effective value | Vm | is limited as shown in the following equation (3).

  Note that the following relationship holds between the peak value Vmp of the line voltage and the voltage Vc of the second capacitor 3.

  As described above, the synchronous machine 1 performs equivalent field-weakening control using a demagnetization action due to the d-axis armature reaction by flowing a d-axis current in the high speed range, but similarly, the power converter 2 is operated in the high speed range. Similarly, when restarting (or stopping), it is necessary to perform field-weakening control immediately after starting or immediately before stopping the power converter 2. For this reason, the d-axis current command id * is calculated by the following procedure using the voltage limiting condition of the above equation (3).

  First, when the above equation (3) is simplified, the following equation (5) is obtained.

However, vd ₀ and vq ₀ are considered to have a sufficiently large ωL because the differential term is ignored from the equation (1) and the field weakening control is performed to restart (or stop) in the high speed range. Therefore, if the drop of the armature resistance is ignored, the equation (1) is simplified as the following equation.

When √ (v _d0 ² + v _q0 ² ) = Vc / √2 in equation (5), the condition of d-axis current id for field weakening control is expressed by the following equation from equation (6).

In order to suppress the generation of torque T so that the vehicle speed or the like does not cause a shock when the power converter 2 is restarted (or stopped), T = 0 in equation (2). Good. For this _purpose , i _q = 0 may be set. Therefore, when i _q = 0 is input to the equation (7), the following equation is obtained.

  If the d-axis current id of field weakening control is determined so as to satisfy this equation (8), the effective value of the line voltage | Vm shown in the above equation (3) when the power converter 2 is restarted (or stopped). The voltage limiting condition (| Vm | ≦ Vc / √2) for | can be satisfied, and torque can be prevented from being generated (T = 0).

  That is, as can be seen from the equation (8), Ld can be obtained from φf using a relational equation of d-axis inductance, φa is φa = √ {(3/2) φf}, and φf is an armature made of a permanent magnet. Since the maximum value of the linkage flux is a constant value determined by the characteristics of the synchronous machine 1, the d-axis current id in the equation (8) is eventually synchronized with the charging voltage Vc of the second capacitor 3. It is a function of the rotational speed ω of the machine 1. Therefore, if Vc and ω can be given in the equation (8), the peak value Vmp of the line voltage (see the above equation (4)) is equal to or lower than the charging voltage Vc of the second capacitor 3 (Vmp ≦ Vc). It is possible to calculate the d-axis current command id * necessary for instant control and to prevent the generation of torque.

  Therefore, in the first embodiment, in order to perform field-weakening control, the dq-axis current command calculation means 10 includes the motor speed ω detected by the speed detection means 7 and the second speed detected by the second voltage detection means 8. The voltage Vc of the capacitor 3 is input, the q-axis current command iq * is set to zero, and the id obtained by the equation (8) is obtained as the d-axis current command id * for satisfying the condition of the equation (3).

  The voltage command calculation means 11 in the next stage is detected by the q-axis current command iq * (= 0) and the d-axis current command id * calculated by the dq-axis current command calculation means 10 and the speed detection means 7. The following processing is performed using the value of the rotational speed ω.

  That is, as is well known, when the coordinate transformation of the three-phase voltage or the three-phase current to the rotation orthogonal two axes is necessary, the control coordinate axis is necessary, so the voltage command calculation means 11 is detected by the speed detection means 7. Using the value of the rotational speed ω, the phase θ of the control coordinate axis, which is a rotational biaxial coordinate, is calculated by the following equation (9).

  Further, the dq axis voltage commands vd * and vq * are calculated from the following equations (10), respectively. In equation (10), iq * is a zero value so that torque is not generated.

  Subsequently, the voltage command calculation unit 11 calculates the voltage phase θv of the three-phase voltage command based on the dq-axis voltage commands vd * and vq *, and sets the phase angle of the dq-axis voltage command to the phase angle obtained by the equation (9). In addition, the calculation is performed by the following equation (11).

  Further, the modulation factor PMF is calculated by the following equation (12) based on the voltage of the capacitor 3.

  The three-phase voltage commands Vu *, Vv *, Vw * are calculated by the following formula (13) from the formulas (9), (11), and (12).

  The voltage command calculation means 11 is configured by each switch constituting the power converter 2 so as to perform switching by a general PWM (Pulse Width Modulation) based on the three-phase voltage commands Vu *, Vv *, and Vw *. A gate pulse signal is output to the means Gu, Gv, Gw, Gx, Gy, Gz.

  When the field weakening control is performed as described above, when the power converter 2 is restarted (or stopped), the voltage limiting condition of the expression (3) can be satisfied, and the peak value Vmp of the line voltage is the first value. The charging voltage Vc of the second capacitor 3 can be instantaneously controlled so as not to exceed (Vmp ≦ Vc), and torque can be prevented from being generated (T = 0).

  Next, an overall control operation when the power conversion device having the above-described configuration is mounted on, for example, an electric vehicle will be described with reference to a timing chart shown in FIG.

  In a state where the operation command before time t0 is input (turned on), the switching element 4b of the switch device 4 is turned on by the switch opening / closing command device 12. When accelerating operation is performed, power is supplied from the DC power source 6 to the power converter 2 via the diode 4a of the switch means 4, and is converted into AC power having a predetermined frequency by the power converter 2 to be synchronized with the synchronous machine 1. Given to. At this time, when the rotation speed of the synchronous machine 1 is higher than ωsh shown in FIG. 3, field weakening control based on the equation (10) by the control means 9 is performed. Therefore, the line voltage peak value Vmp of the synchronous machine 1 is substantially equal to the voltage Vc of the second capacitor 3. Further, the charging voltage Efc1 of the first capacitor 5 is also substantially equal to the voltage Vc of the second capacitor 3. Further, when performing the deceleration operation, the regenerative power from the synchronous machine 1 is regenerated to the DC power supply 6 side via the power converter 2 and the switching element 4b of the switch means 4.

  Next, when the operation command is stopped (turned off) at time t0, the coasting operation is started. In this case, the dq-axis current command calculation unit 10 of the control unit 9 first starts the synchronous machine 1 The field weakening control is performed to control the excitation current based on the equation (10) so that the line voltage peak value Vmp of the current becomes a predetermined value. That is, in order to control the exciting current of the synchronous machine 1, first, the d-axis current command id * is controlled and the q-axis current command iq * is set to zero (that is, the torque current is set to zero). Then, the switch opening / closing command means 12 turns off the switching element 4b when time t1 is reached. Subsequently, even after the switching element 4b is turned off, the control means 9 continues the field weakening control for the synchronous machine 1 for a period of several milliseconds until the time t2. The time from time t1 to t2 may be about several milliseconds to several μsec. This is to suppress the voltage increase of the first capacitor 5 due to the no-load induced voltage. Then, at time t2, the operation of the power converter 2 is stopped.

  No load generated in the synchronous machine 1 when the no-load induced voltage generated by the synchronous machine 1 is larger than the charging voltage Vc of the second capacitor 3 when the power converter 2 is stopped (off) and shifted to coasting operation. Since the energy of the induced voltage is absorbed by the second capacitor 3 via the diode of the switch means constituting the power converter 2, the voltage of the second capacitor 3 rises and the line voltage of the synchronous machine 2 increases. The peak value Vmp and the voltage Vc of the second capacitor 3 are balanced. At that time, the capacitor is immediately charged by appropriately selecting the capacity of the second capacitor 3 and does not cause a brake operation. In addition, since the peak value Vmp of the line voltage of the synchronous machine 1 is lowered to a predetermined value by field weakening control before the power converter 2 is stopped (turned off), the second capacitor 3 The voltage rise of is kept low. Note that the voltage of the first capacitor 5 does not rise above the voltage Vdc of the normal DC power supply 6 because the switching element 4b of the switch means 4 is off.

  Further, during the coasting operation, the operation of the power converter 2 is stopped and the field-weakening control is not performed. Therefore, the copper loss and the energy loss of the power converter 2 caused by flowing the winding current of the synchronous machine 1 are eliminated. Can do. Further, the no-load induced voltage generated in the synchronous machine 1 is cut off from the DC power source 6 side because the switching element 4b of the switch means 4 is turned off. Therefore, the no-load induced voltage is regenerated to the DC power source 6 side. As a result, generation of unnecessary braking force caused by the operation is eliminated, and power loss can be prevented accordingly.

  Next, when an operation command (power running command or brake command) is input (turned on) at time t3, the switch opening / closing command means 12 immediately turns on the switching element 4b of the switch means 4 in response to this, At the same time, the dq-axis current command calculation means 10 is also activated and the power converter 2 starts operating. At this time, if the rotational speed ω of the synchronous machine 1 detected by the speed detecting means 7 is equal to or higher than ωsh in FIG. 3, field weakening control for the synchronous machine 1 is immediately started, so the voltage Vc of the second capacitor 3, In addition, the peak value Vmp of the line voltage of the synchronous machine 1 can be instantaneously controlled to a desired value.

  Thus, at time t3, the power converter 2 is activated at the same time as the switching element 4b is turned on to perform voltage control (field weakening control) of the synchronous machine 1, and therefore the terminal voltage peak value Vmp of the synchronous machine 1 Can be prevented from exceeding the charging voltage Vc of the second capacitor 3 and the voltage Vdc of the DC power supply 6, and no brake torque can be generated.

  As described above, when the coasting operation is started after the operation command is turned off, the switching element 4b of the switch unit 4 is turned off. At this time, the energy of the no-load induced voltage generated in the synchronous machine 1 is the second value. The peak value Vmp of the line voltage of the synchronous machine 1 and the voltage of the second capacitor 3 are balanced by being absorbed by the capacitor 3. The capacity of the second capacitor 3 in this case can be determined as follows.

  Now, since the no-load induced voltage of the synchronous machine 1 is 1800 V at the maximum and the initial voltage of the second capacitor 3 immediately after coasting is 1500 V (in the case of a domestic train overhead wire DC voltage), the voltage increase is 300 V. . The voltage increase of the second capacitor 3 can be expressed by the following equation, where idc is the current flowing into the capacitor 3. The relationship between the voltages Vc and idc of the second capacitor 3 is as shown in FIG. 1, and the capacitance of the capacitor 3 is C.

  The current idc flowing into the second capacitor 3 from the equation (14) can be expressed by the following equation.

  Further, when the average torque generated when the no-load induced voltage of the synchronous machine 1 and the voltage of the second capacitor 3 are balanced is T, the energy by the torque is P, and the rotational angular frequency (mechanical angle) is ω. , (16).

  The energy P can be expressed by the following equation (17) from the voltage Vc of the second capacitor 3 and the current id flowing into the capacitor 3.

  From the equations (15), (16), and (17), the torque T generated when the no-load induced voltage of the synchronous machine 1 and the voltage of the second capacitor 3 are balanced can be expressed by the following equation.

  Therefore, from the equation (18), the capacitance C of the second capacitor 3 can be expressed as the equation (19).

  The capacitance C of the second capacitor 3 can be determined by substituting specific values for the respective parameters in the equation (19). Here, a specific capacitance C of the second capacitor 3 will be considered using a typical constant such as an electric vehicle. For example, ω = 270 × 2π / 3 [rad / sec], Vc = 1800 [V], and T is considered to be allowable generated torque during dt = 0.1 [sec], and T = −0.1. [Nm] or less and the time is dt = 0.1 [sec]. Substituting the above parameters into equation (19) yields the following.

  From the above, it can be understood that the capacitance C of the second capacitor 3 may be 10.471 μF or more. The capacity of the first capacitor 5 is about 1500 μF to 3000 μF in the case of an electric vehicle.

  Thus, the capacity of the second capacitor 3 only needs to be smaller than that of the first capacitor 5, and is 1/100 or more and 1/10 or less of the capacity of the first capacitor 5. I just need it. That is, the following relationship holds for the capacitance of the second capacitor 3.

  As described above, the capacity of the second capacitor 3 can be made equal to or less than the capacity of the first capacitor 5 × (1/10), and as a result, the power converter can be reduced in size and cost. Can do.

  FIG. 4 shows an example of a simulation result in the case where the operation command is restarted from the start-up through the stop at the motor speed of 270 Hz using the electric motor constant in the power conversion device of the first embodiment.

  The simulation result of FIG. 4 shows that the power converter 2 is started from 0.1 sec on the horizontal axis, and the switching element 4b of the switch means 4 is turned off at 0.14 sec (corresponding to time t1 in FIG. 2). Yes. FIG. 4 (a) shows the voltage Vc of the second capacitor 3 and the line voltage peak value Vmp waveform of the synchronous machine 1, and the power converter 2 is gated off from 0.15 sec (corresponding to time t2 in FIG. 2). Thus, the voltage Vc of the second capacitor 3 rises to 3650 V so as to coincide with the no-load induced voltage of the synchronous machine 1. When the operation command is turned on from OFF at 0.24 sec (corresponding to time t3 in FIG. 2), the power converter 2 is gated on at the same time as the switching element 4b is turned on to start the operation. At this time, it can be seen that the line voltage peak value Vmp of the synchronous machine 1 and the voltage Vc of the second capacitor 3 can be controlled to the desired 3000V. FIG. 4B shows the motor current of the synchronous machine 1 (here, U-phase current as an example). FIG. 4 (c) shows the torque generated in the synchronous machine 1, but it can be confirmed that the torque is transiently generated immediately after the power converter 2 is stopped and started, but at an acceptable level.

  As described above, in the first embodiment, when the operation command is stopped (off), the peak value Vmp of the line voltage of the synchronous machine 1 is set to a predetermined value by field weakening control in advance before the power converter 2 is stopped. Since the voltage is lowered to a value, the voltage increase of the second capacitor 3 after shifting to coasting operation can be kept low. Further, when an operation command (power running command or brake command) is input during coasting operation, the power converter 2 is activated simultaneously with the switching element 4b being turned on in response to this, and the voltage control of the synchronous machine 1 ( Field weakening control), the peak value Vmp of the terminal voltage of the synchronous machine 1 is immediately controlled so as not to exceed the charging voltage Vc of the second capacitor 3 and the voltage Vdc of the DC power supply 6, and the second capacitor 3 The voltage rise is kept low. As described above, the voltage fluctuation of the second capacitor 3 can be suppressed as compared with the conventional case, and the voltage increase can be suppressed low, so that the capacity of the second capacitor 3 can be set small. Thereby, size reduction and weight reduction of a power converter device can be implement | achieved compared with the past. Furthermore, since the power converter 2 can be started at the same time as the switching element 4b is turned on when an operation command (power running command or brake command) is input, the responsiveness of the device is improved as compared with the prior art.

Embodiment 2. FIG.
FIG. 5 is a block diagram showing a configuration of the power conversion device according to the second embodiment of the present invention, and components corresponding to or corresponding to those of the first embodiment shown in FIG.

The feature of the second embodiment is that the configuration of the dq-axis current command calculating means 10 in the control means 9 is slightly different from that of the first embodiment.
That is, in the first embodiment, when the operation command is stopped, the field weakening control of the synchronous machine 1 is performed in advance by the power converter 2 before the operation of the power converter 2 is stopped, and the peak value Vmp of the line voltage Is controlled so as not to exceed the charging voltage Vc of the second capacitor 3, and a dq-axis current command is generated so as not to generate brake torque. Even when an operation command is input, the switching element 4b is turned on, and at the same time, the operation of the power converter 2 is started to perform field weakening control, and the peak value Vmp of the line voltage of the synchronous machine 1 becomes the second value. The dq axis current command is generated so as not to exceed the charging voltage Vc of the capacitor 3 and to prevent the brake torque from being generated.

  On the other hand, in the second embodiment, when the operation command is stopped or when the operation command is input, the dq-axis current command calculation means is used so that the voltage Vc of the second capacitor 3 does not increase excessively. 10 generates dq axis current commands id * and iq *. At this time, the brake torque is not generated at all. Generation is allowed.

  That is, the d-axis current command id * is not given based on the above-described equation (8), but based on the equation (7), that is, when the expression is rewritten, it is given as in the equation (22). This indicates that the q-axis current command iq * is not zero.

  At this time, the q-axis current command iq * is set as in the following equation so as to give a predetermined positive value so that electric power is not regenerated.

  However, K is a predetermined value of K> 0.

  Specifically, from equation (2), the second term on the right side can be assumed to be a value smaller than the first term. Therefore, in order to make the generated torque acceptable, T = 0.1 Nm or less. The following equation (24) may be used.

As described above, in the second embodiment, when the operation command is stopped or when the operation command is input, the dq-axis current command calculation means 10 causes the voltage Vc of the second capacitor 3 to increase excessively. Since the dq axis current command is generated so as not to increase, the increase in the voltage Vc of the second capacitor 3 can be suppressed, and at that time, the brake torque is not generated at all, and the driving speed is not shocked. If it is within the range, the generation of the brake torque is allowed, so that the allowable range of control is widened and the control of the power converter 2 is facilitated.
Other configurations and operational effects are the same as those of the first embodiment, and thus detailed description thereof is omitted here.

Embodiment 3 FIG.
FIG. 6 is a block diagram showing the configuration of the power conversion device according to the third embodiment of the present invention, and components corresponding to or corresponding to those of the first embodiment shown in FIG.

  The feature of the third embodiment is that the first voltage detecting means 16 for detecting the voltage of the first capacitor 5 is provided in order to reduce the number of operations of the switching element 4b constituting the switch means 4 and extend the life, The configuration of the switch opening / closing command means 12 of the control means 9 is partially changed.

  That is, in the first embodiment, when the operation command is stopped (turned off), the switching element 4b of the switch means 4 is always turned off. For this reason, there is a possibility that the number of on / off operations of the switching element 4b increases and the operating life is shortened. Therefore, in the third embodiment, the first voltage detecting means 16 detects the voltage Efc1 of the first capacitor 5, and the switch opening / closing command means 12 determines the detected value of the voltage Efc1 of the first capacitor 5 and the detected voltage Efc1. Based on the value of the rotational speed ω detected by the speed detection means 7, when the operation command is stopped, the operation of whether or not to turn off the switching element 4b of the switch means 4 is determined. .

  That is, the switch opening / closing command means 12 first uses the following equation using the rotation speed ω of the synchronous machine 1 and the maximum value of the armature linkage magnetic flux by the permanent magnet, which is a predetermined constant determined from the characteristics of the synchronous machine 1. The peak value Vmp1 of the no-load induced voltage of the synchronous machine 1 when the power converter 2 is stopped is calculated.

  Here, when the peak value Vmp1 of the no-load induced voltage calculated by the equation (25) is larger than the voltage Efc1 of the first capacitor 5 detected by the first voltage detecting means 16 (Efc1 ≦ Vmp1), A current based on the no-load induced voltage of the synchronous machine 1 flows backward to the DC power supply 6 side, and the voltage Vc of the second capacitor 3 may be excessively increased or an element of the power converter 2 may be damaged. Therefore, when the operation command is stopped, if Efc1 ≦ Vmp1, the switch opening / closing command means 12 controls the timing for turning on / off the switching element 4b in the same manner as in the first embodiment. Since details in that case are the same as those in the first embodiment, the description thereof is omitted here.

  On the other hand, as shown in the timing chart of FIG. 7, when the operation command is stopped at time t0, the peak value Vmp1 of the no-load induced voltage calculated by the equation (25) is obtained by the first voltage detecting means 16. When the detected voltage Efc1 of the first capacitor 5 is smaller (Efc1> Vmp1), there is no possibility that the current based on the no-load induced voltage of the synchronous machine 1 flows backward to the DC power supply 6 side. The switch opening / closing command means 12 continues the on state without turning off the switching element 4b. At the same time, the control means 9 stops the operation of the power converter 2. Further, when an operation command (power running command or brake command) is input at time t3, the switching device 4b has already been turned on by the switch opening / closing command means 12, so that the control means 9 starts the operation of the power converter 2. Command only.

As described above, in the third embodiment, when the operation command is stopped and the operation of the power converter 2 is stopped, the voltage Efc1 of the first capacitor 5 and the power converter 2 are stopped. The peak value Vmp1 of the no-load induced voltage of the synchronous machine 1 is compared, and the switching element 4b of the switch means 4 is turned off only when Efc1 ≦ Vmp1, and when the Efc1> Vmp1, the switching element 4b is kept on. Therefore, as a result, the number of times the switching element 4b is turned on / off can be reduced, and the life of the switch means 4 can be extended.
Other configurations and operational effects are the same as those of the first embodiment, and thus detailed description thereof is omitted here.

Embodiment 4 FIG.
FIG. 8 is a block diagram showing a configuration of the power conversion device according to the fourth embodiment of the present invention, and the same reference numerals are given to components corresponding to or corresponding to those of the third embodiment shown in FIG.

In the fourth embodiment, the configuration of the dq-axis current command calculation means 10 of the control means 9 is slightly different from the configuration in the third embodiment.
That is, when the peak value Vmp1 of the no-load induced voltage is larger than the voltage Efc1 of the first capacitor 5 detected by the first voltage detecting means 16 when the operation command is stopped (off) (Efc1 ≦ Vmp1). The dq-axis current command calculation means 10 calculates the d-axis current command so that the charging voltage Vc of the second capacitor 3 matches the voltage Efc1 of the first capacitor 5, performs field-weakening control, and then The switching element 4b is turned off. When the operation command is input (turned on), the control means 9 activates the power converter 2 at the same time as turning on the switching element 4b. At that time, the dq-axis current command calculation means 10 The d-axis current command is calculated and field weakening control is performed so that the voltage Vc of the second capacitor 3 matches the voltage Efc1 of the capacitor 5, so that the line voltage of the synchronous machine 1 becomes a desired value.
At that time, the q-axis current command iq * may be controlled to be zero as in the first embodiment, or may be set to a predetermined positive value as in the second embodiment. good.

  Specifically, the d-axis current command id * is calculated from the equation (26), so that the voltage Vc of the second capacitor 3 is controlled to coincide with the voltage Efc1 of the capacitor 5.

  Note that kp and ωp are set as in the following equation (27), where the maximum speed of the synchronous machine 1 is ωmax.

As described above, in the fourth embodiment, the voltage Vc of the second capacitor 3 is the voltage of the first capacitor 5 regardless of whether the operation command is stopped or the operation command is input. It can be controlled to match Efc1. Then, by using the first voltage detecting means 16 for detecting the voltage Efc1 of the first capacitor 5, the d-axis current command id * can be calculated relatively easily as shown in the equation (26). Compared to the first to third embodiments, it is possible to eliminate the calculation of a complicated route by the dq-axis current command calculation means 10, and the configuration is simplified. For this reason, an inexpensive microcomputer can be used as the microcomputer for realizing the control means 9.
Other configurations and operational effects are the same as those of the third embodiment, and thus detailed description thereof is omitted here.

Embodiment 5 FIG.
FIG. 9 is a block diagram showing a configuration of the power conversion device according to the fifth embodiment of the present invention, and portions corresponding to or corresponding to those of the first embodiment shown in FIG.

  The feature of the fifth embodiment is that, compared with the configuration of the first embodiment, the switch means 4 is constituted by a bidirectional switch including two switching elements 4b and 4c made of semiconductor elements such as IGBT and power MOSFET. It is that you are.

  That is, as shown in FIG. 10, when the operation command is a powering command, the switching element 4 c on the upper side of the switch unit 4 is turned on and power is supplied from the DC power source 6 to the synchronous machine 1 via the power converter 2. To be supplied. When the operation command is a brake command, the lower switching element 4b of the switch means 4 is turned on so that regenerative power is supplied from the synchronous machine 1 to the DC power supply 6 via the power converter 2. To.

As described above, in the fifth embodiment, since the switch means 4 is constituted by a bidirectional switch including two switching elements 4b and 4c, the operation command is turned on / off according to the power running command and the brake command. The path through which the current flows can be determined by selecting the switching elements 4b and 4c. Thereby, compared with the case of Embodiment 1, the burden to the switch means 4 becomes small, and the lifetime of the switch means 4 can be lengthened. In the case of a large power element such as a train, since it is not necessary to use a diode, the switch means 4 can be made small, which is effective in further downsizing the power conversion device.
Other configurations and operational effects are the same as those of the first embodiment, and thus detailed description thereof is omitted here.

It is a block diagram which shows the structure of the power converter device in Embodiment 1 of this invention. It is a timing chart used for operation | movement description of the power converter device in Embodiment 1 of this invention. It is explanatory drawing of field weakening control. It is a characteristic view which shows the simulation result for the operation | movement confirmation of the power converter device in Embodiment 1 of this invention. It is a block diagram which shows the structure of the power converter device in Embodiment 2 of this invention. It is a block diagram which shows the structure of the power converter device in Embodiment 3 of this invention. It is a timing chart with which it uses for operation | movement description of the power converter device in Embodiment 3 of this invention. It is a block diagram which shows the structure of the power converter device in Embodiment 4 of this invention. It is a block diagram which shows the structure of the power converter device in Embodiment 5 of this invention. It is a timing chart used for operation | movement description of the power converter device in Embodiment 5 of this invention.

Explanation of symbols

1 Synchronous machine 2 Power converter 3 Second capacitor 4 Switch means
4a diode, 4b, 4c switching element, 5 first capacitor,
6 DC power supply, 7 speed detection means, 8 second voltage detection means, 9 control means,
10 dq axis current command calculation means, 11 voltage command calculation means,
12 switch open / close command means, 16 first voltage detection means.

Claims (7)

A first capacitor connected in parallel to the DC power supply; a power converter for driving the synchronous machine; a second capacitor connected in parallel to the DC side of the power converter; the second capacitor; A switching means composed of a semiconductor element inserted into a DC power supply path between the first capacitor and turning on / off the supply path; a speed detection means for detecting the speed of the synchronous machine; and the second Second voltage detection means for detecting the voltage of the capacitor, and control means for controlling the power converter based on speed information detected by the speed detection means and voltage information detected by the second voltage detection means And
When the control means stops the power converter from the operating state, the torque current is made zero while controlling the excitation current so that the terminal voltage of the synchronous machine becomes a predetermined value, and then the switch means is turned on. The operation of the power converter is stopped by turning off, the switch means is continuously turned off while the power converter is stopped, and at the same time as the switch means is turned on at the start of the operation of the power converter, The exciting current is controlled so that the terminal voltage of the machine becomes a predetermined value, and after the terminal voltage of the synchronous machine reaches the predetermined value, the torque current of the synchronous machine is controlled to accelerate / decelerate the synchronous machine. The power converter characterized by the above-mentioned. When the control means stops the power converter from the operating state, the torque current is made zero while controlling the excitation current so that the terminal voltage of the synchronous machine becomes a predetermined value, and then the switch means is turned on. Instead of turning off and stopping the operation of the power converter, the torque current is set to a predetermined positive value while controlling the excitation current so that the terminal voltage of the synchronous machine becomes a predetermined value, and then the switch The power converter according to claim 1, wherein the power converter is stopped by turning off the means. The first voltage detection means for detecting the voltage of the first capacitor is provided, and the control means is obtained based on the detection output of the speed detection means when the power converter is stopped from the operating state. The on-state is maintained without turning off the switch means when the no-load induced voltage of the synchronous machine is smaller than the voltage of the first capacitor detected by the first voltage detection means. The power converter device of Claim 1 or Claim 2. First voltage detecting means for detecting the voltage of the first capacitor is provided, and when the power converter is stopped from the operating state, the control means is configured so that the terminal voltage of the synchronous machine becomes a predetermined value. Instead of turning off the switch means and stopping the operation of the power converter after setting the torque current to zero while controlling the excitation current, the above-mentioned obtained based on the speed information detected by the speed detection means When the no-load induced voltage of the synchronous machine is larger than the voltage of the first capacitor detected by the first voltage detecting means, the terminal of the synchronous machine is based on the voltage detection value of the first and second voltage detecting means. The torque current is set to zero or the torque current is set to a predetermined positive value while controlling the excitation current so that the voltage becomes a predetermined value, and then the switch means is turned off to stop the operation of the power converter. Power converter according to claim 1, characterized in Rukoto. The power conversion device according to any one of claims 1 to 4, wherein the switch means has the same configuration as the switch means constituting the power converter. The power conversion device according to any one of claims 1 to 4, wherein the switch means includes a bidirectional switch. 7. The capacity of the second capacitor is set in a range of 1/100 or more and 1/10 or less of the capacity of the first capacitor. The power converter device described in 1.

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