JP2019118172A - Power conversion device - Google Patents

Abstract

In a power converter having a Z-source booster circuit, loss of a switching element is reduced. A power converter 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 voltage applied to the capacitor. The control unit 70 is a modulation rate of a three-phase voltage command that is a command value of the output voltage of the inverter circuit 30. Based on the comparison with the threshold, the inverter circuit 30 is short-circuited. [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 showing a configuration example of a power conversion device 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 the 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. The output is connected to the inverter circuit 30 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 phases of the respective phases are shifted by 120 degrees each other.

  Z source booster circuit 20 discharges capacitors 23 and 24 and charges reactors 21 and 22 when the upper and lower switching elements of any of the U phase, V phase and W phase of inverter circuit 30 are simultaneously turned on and short circuited. And will be done. Next, when one of the switching elements turned on simultaneously is turned off, discharging of the reactors 21 and 22 and charging of the capacitors 23 and 24 are performed. As a result, the voltage output to the inverter circuit 30 rises.

FIG. 6 is a view showing a configuration example assumed as the control unit 60 in the conventional power conversion device 2 as shown in FIG. 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 And by comparing with the carrier signal a.

JP, 2011-160617, A

  Since the power conversion device 2 described above performs the boosting operation while the inverter circuit 30 is operating, the inverter circuit 30 is repeatedly and continuously short-circuited and non-shorted. However, the loss of switching elements 31 to 36 constituting inverter circuit 30 is increased by performing such a boosting operation. As the loss increases, the temperature rises, and the output available capacity of the inverter circuit 30 decreases.

  The object of the present invention made in view of such circumstances is to provide a power conversion device capable of reducing the loss of the switching element.

  In order to solve the above problems, a power converter according to the present invention comprises a diode whose anode side is 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 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 second capacitor An inverter circuit having a Z source booster circuit having a second capacitor connected between input sides of a second reactor, and a plurality of switching elements, and connected to an output of the Z source booster circuit; Control for controlling the plurality of switching elements of the inverter circuit based on a capacitor applied voltage applied to the first capacitor or the second capacitor When, wherein the control unit includes a 3-phase voltage command modulation factor which is a command value of the output voltage of the inverter circuit, based on the comparison with the threshold value, and wherein the shorting said inverter circuit.

  Further, in the power conversion device according to the present invention, the control unit calculates a three-phase voltage command calculation unit that calculates a three-phase voltage command that is a command value of the three-phase voltage output by the inverter circuit; A basic gate signal generation unit that generates a basic gate signal of a switching element based on the capacitor applied voltage, an output voltage of the DC power supply, and a carrier signal, the three-phase voltage command, the capacitor applied voltage, and the DC power supply A modulation factor computing section for computing the modulation factor on the basis of the voltage, a short circuit factor computing pulse generation section for generating a binary short circuit factor computation pulse by comparing and judging the modulation factor and the threshold, and the short circuit The boosting gate signal is compared by comparing the carrier signal with a first-order delay calculating unit that calculates a first-order delay value of the rate calculation pulse, a short circuit ratio obtained by subtracting the first-order delay value from the numerical value 1, and the carrier signal. A boosting gate signal generator for forming, characterized in that it comprises a logic OR unit, a generating a gate signal of the switching element of the basic gate signal and the boosting gate signal to logical sum.

  According to the present invention, it is possible to reduce the loss of the switching element in the power conversion device having the Z-source booster circuit.

It is a figure showing an example of composition of a power converter concerning one embodiment of the present 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 signal in the power converter device which concerns on one Embodiment of this invention. It is the figure which expanded the time-axis of the signal shown in FIG. It is a figure which shows the structural example of the power converter device which has the conventional Z source booster circuit. 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 view showing a configuration example of a power conversion device according to an embodiment of the present invention. In the example shown 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 the motor (load) 50, and the rotation angle sensor 55 is connected to the motor 50. The control unit 70 shown in FIG. 1 is different from the power conversion device 2 shown in FIG. 5 in that a control unit 70 is provided 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. The switching elements 31 and 32 are connected in series to constitute a U-phase arm of the inverter circuit 30. Switching elements 33 and 34 are connected in series to form 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 as the switching elements 31 to 36 are on / off controlled by the control unit 70 such that the phases of the respective phases are shifted by 120 degrees.

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

When the upper and lower switching elements of any of U-phase, V-phase and W-phase of inverter circuit 30 are simultaneously turned on to short-circuit inverter circuit 30 (Z-Arm short circuit), Z source booster circuit 20 Discharge and charging of the reactors 21 and 22 are performed. Next, when one of the switching elements turned on simultaneously is turned off, discharging of the reactors 21 and 22 and charging of the capacitors 23 and 24 are performed. As a result, the voltage (capacitor applied voltage) V _C applied to the capacitors 23 and 24 rises, and the DC link voltage V _dc output to the inverter circuit 30 also rises. 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).

  Voltage sensor 51 detects DC power supply voltage E and outputs it to control unit 70.

Voltage sensor 52 detects capacitor applied voltage V _C and outputs it to control unit 70. In the example shown in FIG. 1, the capacitor applied voltage V _C of the capacitor 23 is detected, but the capacitor applied 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 the current I _u to the control unit 70. Further, the current sensor 54 detects the current I _w flowing in the W phase of the motor 50 and outputs it to the control unit 70.

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

The control unit 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 gate signal G _{up to} the switching element 31, the gate signal G _un to the switching element 32, the gate signal G _{vp to} the switching element 33, the gate signal G _{vn to} the switching element 34, the gate signal G _wp to the switching element 35, and The 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 not to perform a short circuit operation until the output voltage of the inverter circuit 30 approaches the DC link voltage _Vdc . Specifically, as described in detail below, the control unit 70 sets the modulation rates of the three-phase voltage commands V _u ^* , V _v ^* , V _w ^* , which are command values of the three-phase voltage output by the inverter circuit 30. The inverter circuit 30 is short-circuited based on the comparison of α with the maximum modulation rate α _max as its threshold value.

  FIG. 2 is a view showing a configuration example of the control unit 70. As shown in FIG. 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, a modulation ratio calculation unit 67, a short circuit ratio calculation pulse generation unit 68, and a first order delay calculation. A section 69, a subtraction section 63, a boosting gate signal generation section 65, and a logical sum section 66 are provided.

Three-phase voltage command calculation unit 61 includes motor current I _u detected by current sensor 53, motor current I _w detected by current sensor 54, motor rotation angle θ detected by rotation angle sensor 55, and external The three-phase voltage commands V _u ^* , V _v ^* , V _w ^* , which are command values of the three-phase voltage applied to the motor 50 (output from the inverter circuit 30), are calculated based on the motor torque command input from , And to the basic gate signal generator 62.

Basic gate signal generation unit 62 includes carrier signal a, three-phase voltage commands V _u ^* , V _v ^* , V _w ^* calculated by three-phase voltage command calculation unit 61, and capacitor application detected by voltage sensor 52. Based on voltage V _C and DC power supply voltage E detected by voltage sensor 51, basic gate signals G _up0 , G _un0 , G _vp0 , G _{vn 0} , G _{wp 0} and G _{wn 0} are generated, and OR circuit 66 is generated. 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 ^* .

ただし、０≦α≦１

However, 0 ≦ α ≦ 1

The short circuit rate calculation pulse generator 68 compares and determines the modulation rate α with the threshold maximum modulation rate α _max and generates a binary short circuit rate calculation pulse N _pulse according to the equation (3), 1 The next delay calculation unit 69 is output.

The maximum modulation rate α _max is preferably a value close to 1 in order to reduce the number of boostings, but in fact, considering controllability, it is best around 0.95.

The first-order delay calculating unit 69 generates the first order of the short-circuit rate calculating pulse N _pulse according to the transfer function shown in equation (4) based on the short-circuit rate calculating pulse N _pulse generated by the short-circuit rate calculating pulse generator 68. The delay value N _pd is calculated and output to the subtraction unit 63. Here, K is a gain constant, T is a time constant, and s is a Laplace operator.

Subtraction unit 63 calculates the short circuit ratio N by subtracting the first-order delay value N _pd calculated by first-order delay calculation unit 69 from numerical value 1 as shown in equation (5), and generates a gate signal generation unit for boosting. Output to 65.

The boosting gate signal generation unit 65 generates a boosting gate signal Gz, which is a pulse signal, based on the carrier signal a and the short circuit ratio N calculated by the subtraction unit 63, 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 ratio N is used.

The OR circuit 66 generates the basic gate signals _Gup0 , _Gun0 , _Gvp0 , _Gvn0 , _Gwp0 , _Gwn0 generated by the boosting gate signal generating unit 65, and the boosting gate signal generating unit 65. gate signal _G up a boosting 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. The gate signals G _up , G _un , G _vp , G _vn , G _wp , and 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 power converter 1. Three-phase voltage commands V _u ^* , V _v ^* , V _w ^* , DC link voltage V _dc , short circuit ratio N, The modulation rate α, the maximum modulation rate α _max , the short circuit rate calculation pulse N _pulse, and the first-order lag value N _pd are shown. In the initial value, the three-phase voltage commands V _u ^* , V _v ^* and V _w ^* are 0, the modulation rate α = 0 from equation (2), and the short circuit rate calculation pulse N _pulse = 0 from equation (3) . In that case, the first-order delay value N _{pd of} the short circuit rate calculation pulse N _pulse is also 0, and the short circuit rate N = 1 according to the equation (5).

FIG. 4 is a diagram showing a time chart in which the time axis in the vicinity of the start of the output of the short circuit rate calculation pulse N _pulse in FIG. 3 is enlarged. When the modulation factor α calculated by the equation (2) is equal to or less than the maximum modulation factor α _max , the control unit 70 sets the three-phase output voltage output from the inverter circuit 30 to the DC link voltage V _dc . Assuming that it is sufficient, the short circuit rate calculation pulse N _pulse is not output as shown in the equation (3). On the other hand, when the modulation factor α calculated by the equation (2) is higher than the maximum modulation factor α _max , the three-phase output voltage outputted by the inverter circuit 30 is sufficient for the DC link voltage V _dc . If it is not, as shown in equation (3), the pulse N _pulse for short circuit rate calculation is output.

When the short circuit rate calculation pulse N _pulse is output, the first-order delay value N _pd increases and the short circuit rate N decreases from one. Then, the boosting gate signal _Gz is output, and the DC link voltage _Vdc increases. When the DC link voltage _Vdc rises, the modulation rate α relatively decreases, and when it becomes lower than the maximum modulation rate α _max , the short circuit rate calculation pulse N _pulse is not output according to the equation (3). As a result, the modulation ratio α becomes approximately constant at the maximum modulation ratio α _max by changing the short circuit ratio N.

As described above, the control unit 70 of the power conversion device 1 sets the modulation factor α of the three-phase voltage commands V _u ^* , V _v ^* , V _w ^* , which are command values of the three-phase voltage output by the inverter circuit 30; The inverter circuit 30 is short-circuited based on the comparison with the maximum modulation factor α _max , which is the threshold value, and the boosting operation is performed. Therefore, according to the present invention, it is possible to stop the boosting operation until the voltage output from the inverter circuit 30 approaches the DC link voltage V _dc , thereby reducing the number of boosting operations and the loss of the switching elements 31 to 36. Can be reduced.

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

  The present invention can be applied to a power conversion device 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 26 switching element 30 inverter circuit 31-36 switching element 41-46 free wheeling 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 Subtraction unit 65 Boosting gate signal generation unit 66 Logical sum unit 67 Modulation ratio calculation unit 68 Pulse generation unit for short circuit rate calculation 69 First-order delay calculation unit 70 Control unit

Claims (2)

A diode whose anode side is connected to the positive electrode side of a 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 second 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 boost 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 configured to control the plurality of switching elements of the inverter circuit based on a capacitor application voltage applied to the first capacitor or the second capacitor;
The said control part short-circuits the said inverter circuit based on the comparison with the modulation factor of the three-phase voltage command which is a command value of the output voltage of the said inverter circuit, and a threshold value. The control unit
A three-phase voltage command calculation unit that calculates a three-phase voltage command that is a command value of the three-phase voltage output by the inverter circuit;
A basic gate signal generation unit that generates a basic gate signal of a switching element based on the three-phase voltage command, the capacitor applied voltage, an output voltage of the DC power supply, and a carrier signal;
A modulation factor calculation unit that calculates the modulation factor based on the three-phase voltage command, the capacitor applied voltage, and the voltage of the DC power supply;
A pulse generation unit for calculating a short circuit ratio which generates a binary short circuit ratio calculation pulse by comparing and judging the modulation ratio and the threshold value;
A first-order lag calculating unit that calculates a first-order lag value of the short-circuit rate calculation pulse;
A boosting gate signal generation unit that generates a boosting gate signal by comparing the short circuit ratio obtained by subtracting the first order delay value from the numerical value 1 and the carrier signal;
An OR circuit that ORs the basic gate signal and the boosting gate signal to generate a gate signal of the switching element;
The power converter according to claim 1, comprising:

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