JP2019030047A - Electric power conversion system - Google Patents

Abstract

In a power converter having a Z-source booster circuit, loss of a switching element is reduced. A power conversion apparatus includes a Z source booster circuit, a plurality of switching elements, and an inverter circuit connected to an output of the Z source booster circuit, a capacitor, and a capacitor. And a control unit 70 that controls the plurality of switching elements 31 to 36 based on the applied capacitor applied voltage. The control unit 70 is a three-phase voltage command that is a command value of the three-phase voltage output from the inverter circuit 30. The switching elements 31 to 36 are short-circuited on the basis of a comparison between the value corresponding to 1 and the capacitor applied voltage. [Selection] Figure 1

Description

  The present invention relates to a power converter having a Z source booster circuit.

  Conventionally, a power conversion device having a Z source booster circuit is known (see, for example, Patent Document 1). FIG. 5 is a diagram illustrating a configuration example of a power converter having a conventional Z source booster circuit.

  The power conversion device 2 shown in FIG. 5 includes a DC power supply 10, a Z source booster circuit 20, an inverter circuit 30, a control unit 60, voltage sensors 51 and 52, and current sensors 53 and 54. The power conversion device 2 supplies power to the motor 50, and a rotation angle sensor 55 is connected to the motor 50.

  The Z-source booster circuit 20 includes a diode 25, reactors 21 and 22, and capacitors 23 and 24, and is connected to the inverter circuit 30 at the output via a DC link unit.

  The inverter circuit 30 drives the motor 50 connected to the output of the inverter circuit 30 by turning on and off the switching elements 31 to 36 so that the phase of each phase is shifted by 120 degrees from each other.

  The Z source booster circuit 20 discharges the capacitors 23 and 24 and charges the reactors 21 and 22 when the upper and lower switching elements of the U phase, V phase, and W phase of the inverter circuit 30 are simultaneously turned on and short-circuited. And done. Next, when one of the switching elements turned on at the same time is turned off, the reactors 21 and 22 are discharged and the capacitors 23 and 24 are charged. As a result, the voltage output to the inverter circuit 30 increases.

FIG. 6 is a diagram illustrating a configuration example assumed as the control unit 60 in the conventional power conversion device 2 as illustrated in FIG. 5. Boosting gate signal G _z for causing the step-up operation described above, generates a short-circuit ratio N based on the deviation [Delta] V _C of the voltage V _C and the capacitor voltage command V _C ^*, which is applied to the capacitor 23, for example by PID control Then, it is generated by comparing with the carrier signal a.

JP 2011-160617 A

In the power conversion device 2 described above, the capacitor voltage command V _C ^* is a fixed value, and a boost operation is performed while the inverter circuit 30 is operating. Therefore, the inverter circuit 30 is repeatedly short-circuited and non-short-circuited repeatedly. ing. However, the loss of the switching elements 31 to 36 constituting the inverter circuit 30 increases by performing such a boosting operation. When the loss increases, the temperature rises and the output capacity of the inverter circuit 30 decreases.

  The objective of this invention made | formed in view of this situation is to provide the power converter device which can reduce the loss of a switching element.

  In order to solve the above problems, a power conversion device according to the present invention includes a diode having an anode connected to the positive electrode side of a DC power supply, a first reactor connected to the cathode side of the diode, and a negative electrode of the DC power supply. A second reactor connected to the side, a first capacitor connected between the input side of the first reactor and the output side of the second reactor, the output side of the first reactor, and the A Z-source booster circuit having a second capacitor connected between the input sides of the second reactor, an inverter circuit having a plurality of switching elements and connected to the output of the Z-source booster circuit; A controller that controls the plurality of switching elements based on a capacitor applied voltage applied to the first capacitor and the second capacitor. Parts, based on a comparison between the 3-phase voltage the capacitor voltage applied to the value corresponding to the command is a command value of three-phase voltages the inverter circuit outputs, and wherein the shorting said inverter circuit.

  Furthermore, in the power converter according to the present invention, the control unit includes a three-phase voltage command calculation unit that calculates the three-phase voltage command, the three-phase voltage command, the capacitor applied voltage, the output voltage of the DC power supply, And a basic gate signal generation unit that generates a basic gate signal of the switching element based on the carrier signal, and a short-circuit rate calculation that calculates a short-circuit rate according to a difference between a value corresponding to the three-phase voltage command and the applied voltage of the capacitor A boosting gate signal generating unit that generates a boosting gate signal based on the short-circuit rate and the carrier signal; and ORing the basic gate signal and the boosting gate signal to generate a gate signal of the switching element And a logical sum part.

  Furthermore, in the power converter according to the present invention, the value corresponding to the three-phase voltage command is a value obtained by adding an offset to the effective value of the three-phase voltage command.

  According to the present invention, the loss of the switching element can be reduced in the power conversion device having the Z source booster circuit.

It is a figure which shows the structural example of the power converter device which concerns on one Embodiment of this invention. It is a figure which shows the structural example of the control part in the power converter device which concerns on one Embodiment of this invention. It is a figure which shows the time chart of the main signals in the power converter device which concerns on one Embodiment of this invention. It is a figure which shows the time chart of the main signals at the time of the pressure | voltage rise operation start in the power converter device which concerns on one Embodiment of this invention. It is a figure which shows the structural example of the conventional power converter device. It is a figure which shows the structural example assumed as a control part in the conventional power converter device.

  Hereinafter, embodiments of the present invention will be described in detail.

  FIG. 1 is a diagram illustrating a configuration example of a power conversion device according to an embodiment of the present invention. In the example illustrated in FIG. 1, the power conversion device 1 includes a DC power supply 10, a Z source booster circuit 20, an inverter circuit 30, a control unit 70, voltage sensors 51 and 52, and current sensors 53 and 54. . The power conversion device 1 supplies power to a motor (load) 50, and a rotation angle sensor 55 is connected to the motor 50. The control unit 70 illustrated in FIG. 1 is different from the power conversion device 2 illustrated in FIG. 5 in that the control unit 70 includes a control unit 70 instead of the control unit 60.

  The inverter circuit 30 includes a plurality of switching elements 31 to 36 and free wheel diodes 41 to 46 connected in antiparallel to the respective switching elements 31 to 36. Switching elements 31 and 32 are connected in series and constitute a U-phase arm of inverter circuit 30. Switching elements 33 and 34 are connected in series to constitute a V-phase arm of inverter circuit 30. Switching elements 35 and 36 are connected in series to constitute a W-phase arm of inverter circuit 30. The inverter circuit 30 drives the motor 50 connected to the output by controlling the switching elements 31 to 36 by the control unit 70 so that the phases of each phase are shifted from each other by 120 degrees.

  The Z source booster circuit 20 is connected to a diode 25 whose anode side is connected to the positive side of the DC power source 10, a reactor (first reactor) 21 connected to the cathode side of the diode 25, and a negative side of the DC power source 10. Reactor (second reactor) 22, a capacitor (first capacitor) 23 connected between the input side of reactor 21 and the output side of reactor 22, the output side of reactor 21, and the input side of reactor 22 And a capacitor (second capacitor) 24 connected between the two.

The Z source booster circuit 20 includes capacitors 23 and 24 that are connected to each other when the upper and lower switching elements of the U phase, V phase, and W phase of the inverter circuit 30 are simultaneously turned on and the inverter circuit 30 is short-circuited (upper and lower arm short-circuit). Discharging and charging of reactors 21 and 22 are performed. Next, when one of the switching elements that are on at the same time is turned off, the reactors 21 and 22 are discharged and the capacitors 23 and 24 are charged. As a result, the voltage applied (capacitor voltage applied) _{V C} rises to the capacitor 23, the DC link voltage _{V dc} output to the inverter circuit 30 is also increased. DC link voltage V _dc after the boosting operation, the output voltage of the DC power supply 10 (DC power supply voltage) E, and the capacitor voltage applied V _C, determined by Equation (1).

  The voltage sensor 51 detects the output voltage E of the DC power supply 10 and outputs it to the control unit 70.

Voltage sensor 52 detects the capacitor voltage applied _{V C,} to the control unit 70. In the example illustrated in FIG. 1, the capacitor application voltage V _C of the capacitor 23 is detected, but the capacitor application voltage V _C of the capacitor 24 may be detected.

The current sensor 53 detects the current I _u flowing in the U phase of the motor 50 and outputs it to the control unit 70. The current sensor 54 detects a current _{I w} flowing through the W-phase of the motor 50, and outputs to the control unit 70.

  The rotation angle sensor 55 detects the rotation angle θ of the motor 50 and outputs it to the control unit 70.

The controller 70 inputs the values detected by the voltage sensors 51 and 52, the values detected by the current sensors 53 and 54, and the value detected by the rotation angle sensor 55. The switching element 31 has a gate signal G _up , the switching element 32 has a gate signal G _un , the switching element 33 has a gate signal G _vp , the switching element 34 has a gate signal G _vn , the switching element 35 has a gate signal G _wp , and the switching element 36. A gate signal G _wn is output to control the switching elements 31 to 36.

There is no need to boost the DC link voltage V _dc when the output voltage of the inverter circuit 30 is lower than the DC link voltage V _dc. Therefore, the control unit 70 controls the inverter circuit 30 so as not to short-circuit until the output voltage of the inverter circuit 30 approaches the DC link voltage V _dc . Specifically, as described in detail below, the control unit 70 corresponds to the three-phase voltage commands V _u ^* , V _v ^* , and V _w ^* that are the command values of the three-phase voltage output from the inverter circuit 30. and values, based on a comparison of the capacitor voltage applied V _C applied to the capacitor 23, thereby shorting the inverter circuit 30. In the present embodiment, values corresponding to the three-phase voltage commands V _u ^* , V _v ^* , and V _w ^* are values obtained by adding an offset to the effective value of the three-phase voltage command.

  FIG. 2 is a diagram illustrating a configuration example of the control unit 70. In the example shown in FIG. 2, the control unit 70 includes a three-phase voltage command calculation unit 61, a basic gate signal generation unit 62, an effective value calculation unit 67, an adder 68, a subtractor 63, and a short-circuit rate calculation unit. 64, a boosting gate signal generation unit 65, and a logical sum unit 66.

The three-phase voltage command calculation unit 61 includes a motor current I _u detected by the current sensor 53, a motor current I _w detected by the current sensor 54, a motor rotation angle θ detected by the rotation angle sensor 55, and an external The three-phase voltage commands V _u ^* , V _v ^* , V _w ^* , which are the command values of the three-phase voltages V _u , V _v , V _w applied to the motor 50, are calculated based on the motor torque command input from the motor 50. To the basic gate signal generation unit 62

The basic gate signal generation unit 62 includes a three-phase voltage command V _u ^* , V _v ^* , V _w ^* calculated by the three-phase voltage command calculation unit 61, a capacitor application voltage V _C detected by the voltage sensor 52, Based on the DC power supply voltage E detected by the voltage sensor 51 and the carrier signal a, basic gate signals G _up0 , G _un0 , G _vp0 , G _vn0 , G _wp0 , G _wn0 are generated, and the logical sum unit 66 Output. For example, a triangular wave comparison method is used in which the carrier signal a is a triangular wave and the carrier signal a is compared with the three-phase voltage commands V _u ^* , V _v ^* , and V _w ^* .

The effective value calculation unit 67 corresponds to the output voltage of the inverter circuit 30 according to the equation (2) based on the three-phase voltage commands V _u ^* , V _v ^* , and V _w ^* calculated by the three-phase voltage command calculation unit 61. The three-phase voltage command effective value V _out ^* is calculated and output to the adder 68.

The adder 68 adds the offset value V _offset to the three-phase voltage command effective value V _out ^* calculated by the effective value calculation unit 67 to obtain a capacitor voltage command V _C ^* , and outputs it to the subtracter 63. The offset value V _offset is an arbitrary value of 0 or more.

The subtractor 63 subtracts the capacitor applied voltage V _C from the capacitor voltage command V _C ^* calculated by the adder 68 to obtain a differential voltage ΔV _C and outputs it to the short-circuit rate calculating unit 64.

The short-circuit rate calculation unit 64 calculates the short-circuit rate N according to the differential voltage ΔV _C calculated by the subtracter 63 and outputs the short-circuit rate N to the boosting gate signal generation unit 65. For example, the short-circuit rate N such that the differential voltage ΔV _C approaches 0 is calculated by PI control.

The boosting gate signal generating unit 65 generates a boosting gate signal Gz that is a pulse signal based on the short circuit rate N calculated by the short circuit rate calculating unit 64 and the carrier signal a, and outputs the boosting gate signal _Gz to the logical sum unit 66. . For example, a triangular wave comparison method in which the carrier signal a is a triangular wave and the carrier signal a is compared with the short-circuit rate N is used.

The OR unit 66 includes the basic gate signals G _up0 , G _un0 , G _vp0 , G _vn0 , G _wp0 , G _wn0 generated by the basic gate signal generation unit 62 and the boosting gate signal generation unit 65. gate signal _G up and use the gate signal _{G z} and logical sum, _{respectively, G un, G vp, G} vn, G wp, generates _{G wn,} and outputs to the switching element 31 to 36. These gate signals G _up , G _un , G _vp , G _vn , G _wp , G _wn turn on and off the switching elements 31 to 36 of the inverter circuit 30, respectively.

FIG. 3 is a diagram showing a time chart of main signals in the power conversion device 1, and includes a DC link voltage V _dc , a three-phase voltage command V _u ^* , V _v ^* , V _w ^* , a short circuit rate N, A boosting gate signal _Gz is shown. In the initial value, the three-phase voltage commands V _u ^* , V _v ^* , and V _w ^* are 0, and the capacitor applied voltage V _C is larger than the capacitor voltage command V _C ^* , so that the differential voltage ΔV _C is negative. Since there is no need to boost when the difference voltage [Delta] V _C is negative, the short circuit ratio N 1 does not output the boosting gate signal G _z.

FIG. 4 is a diagram showing a time chart of main signals at the start of the boosting operation. The DC link voltage V _dc , the capacitor applied voltage V _C , the capacitor voltage command V _C ^*, and the three-phase voltage command V _u ^*. , V _v ^* , V _w ^* . When the three-phase voltage commands V _u ^* , V _v ^* , and V _w ^* are gradually increased, the capacitor voltage command V _C ^{* obtained} by adding the offset value V _offset to the three-phase voltage command effective value V _out ^* is also gradually increased. When the capacitor voltage command V _C ^* becomes larger than the capacitor applied voltage V _C , the control unit 70 determines the short-circuit rate N to a value smaller than 1 so that the differential voltage ΔV _C becomes 0, and the boost gate signal G _z is output. As the short-circuit rate N changes, the capacitor applied voltage V _C becomes approximately the same value as the capacitor voltage command V _C.

As described above, the control unit 70 of the power conversion device 1 has values corresponding to the three-phase voltage commands V _u ^* , V _v ^* , and V _w ^* , which are the command values of the three-phase voltage output from the inverter circuit 30; based on the comparison of the capacitor voltage applied V _C applied to the capacitor 23 and 24, to short-circuit the inverter circuit 30 performs the boosting operation. Therefore, according to the present invention, it is possible to stop the boost operation until the voltage output from the inverter circuit 30 approaches the DC link voltage V _dc , thereby reducing the number of boost operations and the loss of the switching elements 31 to 36. Can be reduced.

  Although the above embodiment has been described as a representative example, it will be apparent to those skilled in the art that many changes and substitutions can be made within the spirit and scope of the invention. Therefore, the present invention should not be construed as being limited by the above-described embodiments, and various modifications and changes can be made without departing from the scope of the claims. For example, it is possible to combine a plurality of constituent blocks described in the configuration diagram of the embodiment into one, or to divide one constituent block.

  The present invention can be used for a power converter having a Z source booster circuit.

DESCRIPTION OF SYMBOLS 1 Power converter 10 DC power supply 20 Z source booster circuit 21,22 Reactor 23,24 Capacitor 25 Diode 30 Inverter circuit 31-36 Switching element 41-46 Free wheel diode 51,52 Voltage sensor 53,54 Current sensor 55 Rotation angle sensor 61 Three-phase voltage command calculation unit 62 Basic gate signal generation unit 63 Subtractor 64 Short-circuit rate calculation unit 65 Gate signal generation unit for boosting 66 Logical sum unit 67 Effective value calculation unit 68 Adder 70 Control unit

Claims (3)

A diode having an anode connected to the positive electrode side of the DC power supply, a first reactor connected to the cathode side of the diode, a second reactor connected to the negative electrode side of the DC power supply, and the first reactor A first capacitor connected between the input side of the first reactor and the output side of the second reactor, and a second capacitor connected between the output side of the first reactor and the input side of the second reactor. A Z source booster circuit having a capacitor;
An inverter circuit having a plurality of switching elements and connected to the output of the Z source booster circuit;
A control unit that controls the plurality of switching elements based on a capacitor applied voltage applied to the first capacitor and the second capacitor;
The control unit short-circuits the inverter circuit based on a comparison between a value corresponding to a three-phase voltage command that is a command value of a three-phase voltage output from the inverter circuit and the capacitor applied voltage. Conversion device. The controller is
A three-phase voltage command calculation unit for calculating the three-phase voltage command;
A basic gate signal generating unit that generates a basic gate signal of a switching element based on the three-phase voltage command, the capacitor applied voltage, the output voltage of the DC power supply, and a carrier signal;
A short-circuit rate calculating unit that calculates a short-circuit rate according to a difference between a value corresponding to the three-phase voltage command and the capacitor applied voltage;
A boosting gate signal generator for generating a boosting gate signal based on the short-circuit rate and the carrier signal;
ORing the basic gate signal and the boosting gate signal to generate a gate signal of the switching element;
The power conversion device according to claim 1, comprising: 3. The power conversion device according to claim 1, wherein the value corresponding to the three-phase voltage command is a value obtained by adding an offset to an effective value of the three-phase voltage command.

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