JP2018088750A - Power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress noise generated from a reactor in a power conversion device comprising a Z source boost circuit.SOLUTION: A power conversion device 1 comprises: a Z source boost circuit 20; an inverter circuit 30 that is connected to an output side of the Z source boost circuit 20 and includes multiple switching elements 31-36; and a control part 60 which compares a carrier signal with a command value to perform PWM control on the switching elements 31-36. The control part 60 randomly changes a time and a cycle to shorten the switching elements 31-36.SELECTED DRAWING: 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. 9 is a diagram illustrating a configuration example of a power converter having a conventional Z source booster circuit.

  The power conversion device 3 illustrated in FIG. 9 includes a DC power supply 10, a Z source booster circuit 20, an inverter circuit 30, a control unit 50, voltage detection units 71 and 72, and current detection units 73 and 74. The power conversion device 2 supplies power to the electric motor 40, and a rotation speed detection unit 75 is connected to the electric motor 40.

  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 electric motor 40 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 each phase are shifted by 120 degrees from each other.

  FIG. 10 is a diagram illustrating a configuration example assumed as the control unit 50 in the conventional power conversion device 3 as illustrated in FIG. 9.

The short-circuit command calculation unit 56 calculates a positive-side short-circuit command N _p ^* and a negative-side short-circuit command N _n ^* from the boost rate B ^* calculated by the Z source vector control calculation unit 53.

The short-circuit gate calculation unit 57 compares the positive-side short-circuit command N _p ^* calculated by the short-circuit command calculation unit 56 with the carrier signal a generated by the carrier signal generation unit 54, and the carrier signal a is the positive-side short-circuit command N _p. ^* high level when greater than the signal as a positive short command N _p ^* following when a low level, and outputs a positive short gate signal G _sp ^*. Further, the negative side short-circuit command N _n ^* calculated by the short-circuit command calculation unit 56 is compared with the carrier signal a. When the carrier signal a is smaller than the negative side short-circuit command N _n ^* , the high-level negative side short-circuit command N _A signal that becomes low when _n ^* or more is output as a negative-side short-circuited gate signal G _sn ^* .

The short-circuit gate OR unit 58 outputs a logical sum of the positive-side short-circuit gate signal G _sp ^* and the negative-side short-circuit gate signal G _sn ^* calculated by the short-circuit gate calculation unit 57 as the short-circuit gate signal G _s ^* .

The final output gate logic OR 59, a short-circuit gate signal _G ^{s *,} basic gate signal ^{_{G up *, G un *,}} G vp *, G vn *, G wp *, the logical sum of the _{G wn} ^*, respectively final output gate signal ^{_{G sup *, G sun *,}} G svp *, G svn *, G swp *, and outputs it as _{G swn} ^*.

FIG. 11 shows a carrier signal a, a three-phase voltage command V _u ^* , V _v ^* , V _w ^* , a positive short-circuit command N _p ^* , a negative short-circuit command N _n ^*, and a positive short-circuit gate signal G. It is a figure which shows the relationship between _sp ^* , the negative side short circuit gate signal _Gsn ^* , basic gate signal _Gup ^* , _Gun ^* , and final output gate signal _Gsup ^* , _Gsun ^* .

With this configuration, when the short-circuit gate signal G _s ^* is at a low level, the three-phase voltage commands V _u ^* , V _v ^* , V _w ^* calculated by the Z source vector control calculation unit 53, and the carrier signal By the PWM control by comparison with the carrier signal a generated by the generation unit 54, an inverter operation is performed in which the switching elements 31 to 36 are turned on and off. When the short-circuit gate signal G _s ^* is at a high level, a short-circuit operation is performed in which both the switching elements 31 to 36 are turned on.

  When the inverter operation is changed to the short-circuit operation, the capacitors 23 and 24 are discharged, and magnetic energy is accumulated in the reactors 21 and 22, respectively. Next, when any of the switching elements 31 to 36 is turned off to return to the inverter operation, the magnetic energy stored in the reactors 21 and 22 is released, and the capacitors 23 and 24 are charged. Therefore, a voltage boosted with respect to the voltage output from the DC power supply 10 is output to the inverter circuit 30. This short-circuit operation is performed in the inverter circuit 30 when the switching elements 31, 33, and 35 are on and the switching elements 32, 34, and 36 are off, and when the switching elements 31, 33, and 35 are off and the switching elements 32, 34, and 36 are off. It is known to perform in a zero vector state when is turned on (see Non-Patent Document 1, for example).

  In addition, a technique for reducing noise by changing the carrier frequency of an inverter is known (see, for example, Patent Document 1).

JP 2010-207084 A

Fang Zhen Peng, "Z-source Inverter", IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL.39, NO.2, MARCH / APRIL 2003, pp.504-510

  According to Non-Patent Document 1, when the circuit operation is a short-circuit operation, the switching frequency is doubled compared to the inverter operation. At this time, the switching frequency component is included in the current flowing through the reactor of the Z source booster circuit. Therefore, when the switching frequency is low, annoying noise of the switching frequency component is generated from the reactor of the Z source booster circuit. In the method of determining the short-circuit gate signal of the control unit 50 shown in FIG. 10, the time widths of the short-circuit pulses of the positive-side short-circuit gate signal and the negative-side short-circuit gate signal are equal, and the interval of the short-circuit pulses of these ORs is constant. is there. Therefore, there is a problem that the switching frequency component of the current flowing through the reactor of the Z source booster circuit cannot be suppressed.

  An object of the present invention made in view of such circumstances is power conversion capable of suppressing the annoying noise generated from the reactor by suppressing the switching frequency component included in the current flowing through the reactor even when the switching frequency is low. To provide an apparatus.

  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 connected to the output side of the Z-source booster circuit, and a carrier A control unit that performs PWM control on the switching element by comparing a signal and a command value, and the control unit performs a time and a cycle for short-circuiting the switching element. Wherein the randomly changing.

  Further, in the power conversion device according to the present invention, the control unit adds the shift amount that changes every half cycle at the timing of the peak and valley of the carrier signal to the carrier signal of the triangular wave, It is characterized in that the time and period for short-circuiting are randomly changed.

  Furthermore, in the power converter according to the present invention, the control unit subtracts, from the command value, a shift amount that changes every half cycle at a peak and valley timing of the carrier signal of a triangular wave. It is characterized in that the time and period for short-circuiting are randomly changed.

  Furthermore, the power converter according to the present invention is characterized in that the control unit determines the shift amount based on a modulation rate in the PWM control and a random variable.

  According to the present invention, even when the switching frequency is low, the switching frequency component included in the current flowing through the reactor of the Z source booster circuit can be suppressed and noise can be reduced.

It is a circuit diagram showing an example of composition of a power converter concerning a 1st embodiment of the present invention. It is a block diagram which shows the structural example of the control part in the power converter device which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the structural example of the Z source vector control calculating part in the power converter device which concerns on the 1st 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 the 1st Embodiment of this invention. It is a waveform which shows the effect of the power converter device which concerns on the 1st Embodiment of this invention. It is a circuit diagram which shows the structural example of the power converter device which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the structural example of the control part in the power converter device which concerns on the 2nd 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 the 2nd Embodiment of this invention. It is a circuit diagram 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. It is a figure which shows the time chart of the main signals in the conventional power converter device.

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

(First embodiment)
FIG. 1 is a diagram illustrating a configuration example of a power conversion device according to the first 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 60-1, voltage detection units 71 and 72, a current detection unit 73, and 74. The power conversion device 1 supplies electric power to the electric motor 40, and a rotation speed detection unit 75 is connected to the electric motor 40. The control unit 60-1 illustrated in FIG. 1 is different from the power conversion device 3 illustrated in FIG. 9 in that the control unit 60-1 includes a control unit 60-1 instead of the control unit 50.

  The DC power supply 10 is a power supply device for supplying power to the electric motor 40 via the Z source booster circuit 20 and the inverter circuit 30. The DC power supply 10 may be a power storage device such as a battery or a capacitor.

  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 inverter circuit 30 is connected to the output side of the Z source booster circuit 20 and has a plurality of switching elements 31 to 36. In this embodiment, a three-phase inverter circuit is used. The switching elements 31 to 36 are transistors in which a transistor (for example, IGBT or MOSFET) and a free wheel diode are connected in antiparallel. The switching elements 31 and 32 are connected in series and constitute the U-phase upper and lower arms of the inverter circuit 30. The switching elements 33 and 34 are connected in series to constitute the V-phase upper and lower arms of the inverter circuit 30. The switching elements 35 and 36 are connected in series to constitute a W-phase upper and lower arm of the inverter circuit 30. The inverter circuit 30 drives the electric motor 40 connected to the output by controlling the switching elements 31 to 36 by the control unit 60-1 so that the phases of the phases are shifted from each other by 120 degrees.

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 DC link voltage V _dc output to the inverter circuit 30 increases.

  The electric motor 40 is an electric motor driven by a three-phase AC voltage output from the inverter circuit 30.

  The voltage detector 71 detects the output voltage E of the DC power supply 10 and outputs it to the controller 60-1.

Voltage detector 72 detects the voltage (capacitor voltage) _{V C} applied to the capacitor, and outputs to the control unit 60-1. In the example illustrated in FIG. 1, the capacitor voltage V _C of the capacitor 23 is detected, but the capacitor voltage V _C of the capacitor 24 may be detected.

The current detection unit 73 detects the U-phase current _Iu flowing between the U-phase output of the inverter circuit 30 and the electric motor 40, and outputs it to the control unit 60-1. The current detection unit 74 detects the W phase current I _w flowing between the W-phase output and the electric motor 40 of the inverter circuit 30, and outputs it to the control unit 60-1. Since the sum of the U-phase current I _u , the V-phase current I _v , and the W-phase current I _w is 0, in this embodiment, current detection units are provided in the U-phase and the W-phase, and the V-phase current I _v is Although the V-phase current detection unit is omitted because it can be calculated by calculation, a current detection unit may be provided in the U-phase and the V-phase, the V-phase and the W-phase, or all three phases.

  The rotation speed detection unit 75 detects the rotation speed ω of the electric motor 40 and outputs it to the control unit 60-1.

The control unit 60-1 includes a power supply voltage E detected by the voltage detection unit 71, a capacitor voltage V _C detected by the voltage detection unit 72, a U-phase current I _u detected by the current detection unit 73, and a current and the W-phase current I _w detected by the detector 74, and inputs the rotation speed ω detected by the speed detecting unit 75, a torque command T ^*, the magnetic flux command phi ^*. Then, each of the gate signals _G ^sup * to the switching element 31 to 36 based on the comparison of the carrier signal and the command value of the triangular ^{_{wave, G sun, * G svp *}} , G svn *, G swp *, and outputs the _{G swn} ^* The switching elements 31 to 36 are PWM-controlled.

  As will be described in detail below, the control unit 60-1 adds a shift amount that changes every half cycle at the peak and valley timings of the carrier signal to the carrier signal, thereby short-circuiting the switching elements 31 to 36. And the period is changed at random.

  FIG. 2 is a diagram illustrating a configuration example of the control unit 60-1. 2 includes an integrator 51, a current command calculation unit 52, a Z source vector control calculation unit 53, a carrier signal generation unit 54, a basic gate calculation unit 55, and a modulation factor calculation unit. 61, a short-circuit command calculation unit 56, a random variable generation unit 62, a shift amount calculation unit 63, an adder 64, a short-circuit gate calculation unit 57, a short-circuit gate logical sum unit 58, and a final output gate logical sum unit 59.

  The integrator 51 performs time integration from the rotational speed ω detected by the rotational speed detector 75 to calculate the phase θ.

The current command calculation unit 52 calculates a torque component current command I _q ^* and a flux component current command I _d ^* from the torque command T ^* and the flux command φ ^* .

  FIG. 3 is a block diagram illustrating a configuration example of the Z source vector control arithmetic unit 53. 3 includes a three-phase-dq-axis coordinate conversion unit 531, a current control calculation unit 532, a Z-source output voltage calculation unit 533, a dq-axis-three-phase coordinate conversion unit 534, Is provided.

The three-phase-dq-axis coordinate conversion unit 531 converts the q-axis torque component from the U-phase current I _u , the W-phase current I _w, and the phase θ calculated by the integrator 51 by three-phase-dq axis coordinate conversion. Coordinates are converted into the current I _q and the d-axis magnetic flux current I _d .

The current control calculation unit 532 is a torque component current command I _q ^* calculated by the current command calculation unit 52 using the torque component current I _q and the magnetic flux component current I _d coordinate-converted by the three-phase-dq axis coordinate conversion unit 531 ^. Then, control (for example, PI control) is performed so as to match the magnetic flux component current command I _d ^* , and a q-axis voltage command V _q ^* and a d-axis voltage command V _d ^* are output.

The Z source output voltage calculation unit 533 generates a Z source boost from the power supply voltage E detected by the voltage detection unit 71 and the q axis voltage command V _q ^* and the d axis voltage command V _d ^* calculated by the current control calculation unit 532. The boosting rate B ^* for performing the boosting operation in the circuit 20, the inverter q-axis voltage command V _q ^** for performing the PWM control in the inverter circuit 30, and the inverter d-axis voltage command V _d ^** are calculated. To do.

The dq axis-three-phase coordinate conversion unit 534 is calculated by the integrator 51 based on the inverter q-axis voltage command V _q ^** and the inverter d-axis voltage command V _d ^** calculated by the Z source output voltage calculation unit 533. From the phase θ, the coordinates are converted into a U-phase voltage command V _u ^* , a V-phase voltage command V _v ^*, and a W-phase voltage command V _w ^* by dq axis-three-phase coordinate conversion.

  The carrier signal generation unit 54 generates a triangular wave carrier signal a.

The basic gate calculation unit 55 compares the carrier signal a generated by the carrier signal generation unit 54 with the three-phase voltage commands V _u ^* , V _v ^* , and V _w ^* calculated by the Z source vector control calculation unit 53. Then, a signal that is at a high level when the U-phase voltage command V _u ^* is greater than the carrier signal a and at a low level when it is less than or equal to the carrier signal a is output as the basic gate signal G _up ^* . Further, a signal that is low when the U-phase voltage command V _u ^* is greater than the carrier signal a and is high when the U-phase voltage command V _u ^* is less than or equal to the carrier signal a is output as the basic gate signal G _un ^* . Also, a signal that is high when the V-phase voltage command V _v ^* is greater than the carrier signal a and low when it is equal to or less than the carrier signal a is output as the basic gate signal G _vp ^* . In addition, a signal that is low when the V-phase voltage command V _v ^* is greater than the carrier signal a and is high when the V-phase voltage command V _v ^* is less than or equal to the carrier signal a is output as the basic gate signal G _vn ^* . In addition, a signal that is at a high level when the W-phase voltage command V _w ^* is greater than the carrier signal a and at a low level when it is less than or equal to the carrier signal a is output as the basic gate signal G _wp ^* . In addition, a signal that is at a low level when the W-phase voltage command V _w ^* is greater than the carrier signal a and is at a high level when the W-phase voltage command V _w ^* is less than or equal to the carrier signal a is output as the basic gate signal G _wn ^* .

Modulation factor computation unit 61, a power supply voltage E is voltage detecting unit 71 detects the capacitor voltage _{V C} to which the voltage detecting unit 72 detects three-phase voltage command value ^{_V u} _{*, V} v _*, from the _V ^{w *} The modulation factor α in the PWM control is calculated.

A power supply voltage E, and the capacitor voltage _{V C,} the three-phase voltage command value ^{_V u} _{*, V} v _*, and _V ^{w *,} the relation between modulation ratio α represented by formula (1). However, C is a variable determined by the modulation method. For example, C = 1 in the sine wave modulation method and C = (√3) / 2 in the hip modulation method.

The short-circuit command calculation unit 56 calculates a positive-side short-circuit command N _p ^* and a negative-side short-circuit command N _n ^* from the boost rate B ^* calculated by the Z source vector control calculation unit 53. The relationship between the step-up rate B ^* and the positive side short-circuit command N _p ^* is expressed by Equation (2), and the relationship between the step-up rate B ^* and the negative-side short-circuit command N _n ^* is expressed by Equation (3).

  The random variable generation unit 62 generates a random variable p. The range of the value of the random variable p is expressed by Equation (4).

The shift amount calculation unit 63 includes a positive side short-circuit command N _p ^* calculated by the short-circuit command calculation unit 56, a random variable p generated by the random variable generation unit 62, a modulation rate α calculated by the modulation rate calculation unit 61, The shift amount s is calculated using the carrier signal a generated by the carrier signal generation unit 54, calculated every half cycle at the peak and valley timings of the carrier signal a, and the calculation result is held. The relationship among the positive side short-circuit command N _p ^* , the modulation factor α, the random variable p, and the shift amount s is expressed by Expression (5).

  The adder 64 adds the shift amount s calculated by the shift amount calculation unit 63 and the carrier signal a generated by the carrier signal generation unit 54 to calculate the carrier signal b. The relationship among the carrier signal a, the shift amount s, and the carrier signal b is expressed by Expression (6).

The short-circuit gate calculation unit 57 compares the carrier signal b calculated by the adder 64 with the positive-side short-circuit command N _p ^* calculated by the short-circuit command calculation unit 56, and the carrier signal b is obtained from the positive-side short-circuit command N _p ^* . a high-level, the signal becomes a positive short command N _p ^* following time low when large, outputs a positive short gate signal G _sp ^*. Further, the carrier signal b calculated by the adder 64 is compared with the negative-side short-circuit command N _n ^* calculated by the short-circuit command calculation unit 56. When the carrier signal b is smaller than the negative-side short-circuit command N _n ^* , the high level is obtained. A signal that becomes a low level when the negative-side short-circuit command N _n ^* or more is output as a negative-side short-circuit gate signal G _sn ^* .

The short-circuit gate OR unit 58 outputs a logical sum of the positive-side short-circuit gate signal G _sp ^* calculated by the short-circuit gate calculation unit 57 and the negative-side short-circuit gate signal G _sn ^* as a short-circuit gate signal G _s ^* .

The final output gate OR unit 59 includes the short-circuit gate signal G _s ^* output from the short-circuit gate OR unit 58 and the basic gate signals G _up ^* , G _un ^* , G _vp ^* , G calculated by the basic gate calculation unit 55. _{vn ^*, G} ^{wp *,} the logical sum of the _{G wn} ^*, the final output gate signal _G ^sup * ^{_{respectively, G sun *, G svp *}} , G svn *, G swp *, and outputs it as _{G swn} ^*.

FIG. 4 shows a carrier signal a, a three-phase voltage command V _u ^* , V _v ^* , V _w ^* , a modulation factor α, a carrier signal b, a positive short-circuit command N _p ^*, and a negative short-circuit command N. and _n ^*, and the shift amount s, the positive short gate signal _{G sp} ^*, and the negative-side short-circuit gate signal _{G sn} ^*, * basic gate signal _G ^{Stay _up-,} and _{G un} ^*, the final output gate signal _G ^sup *, G It is the figure which showed the relationship with _sun ^* .

  As shown in FIG. 4, by adding the shift amount s to the carrier signal a every half cycle at the peak and valley timings of the triangular carrier signal a, the time width and phase of the short-circuit pulse of the short-circuit gate signal (that is, , The time and period of short-circuiting the switching elements 31 to 36) can be changed randomly, and as a result, the switching frequency component of the current flowing through the reactors 21 and 22 of the Z source booster circuit 20 can be suppressed.

  FIG. 5 shows the frequency analysis of the current flowing through the reactor according to the present invention and the prior art. The horizontal axis represents the frequency and the vertical axis represents the reactor current. This figure also shows that the switching frequency component is suppressed.

(Second Embodiment)
Next, a power conversion device according to a second embodiment of the present invention will be described. FIG. 6 is a block diagram illustrating a configuration example of the power conversion device according to the second embodiment. The power conversion device 2 of the present embodiment is different from the power conversion device 1 of the first embodiment in that a control unit 60-2 is provided instead of the control unit 60-1. Since other configurations are the same as those of the first embodiment, the same reference numerals are given and description thereof is omitted.

Control unit 60-2, details are described below, the command value (positive short command N _{p ^*,} the negative-side short-circuit command N _{n ^*)} change from every half cycle at the timings of the peaks and valleys of the carrier signal a By subtracting the shift amount s to be changed, the time and period for short-circuiting the switching elements 31 to 36 are randomly changed.

  FIG. 7 is a diagram illustrating a configuration example of the control unit 60-2. 7 includes an integrator 51, a current command calculation unit 52, a Z source vector control calculation unit 53, a carrier signal generation unit 54, a basic gate calculation unit 55, and a modulation factor calculation unit. 61, a short-circuit command calculation unit 56, a random variable generation unit 62, a shift amount calculation unit 63, subtracters 65 and 66, a short-circuit gate calculation unit 57, a short-circuit gate logical sum unit 58, and a final output gate logic The sum part 59 is provided. The control unit 60-2 of the present embodiment is different from the control unit 60-1 of the first embodiment in that it does not include the adder 64 but includes subtractors 65 and 66. Since other configurations are the same as those of the first embodiment, the same reference numerals are given and description thereof is omitted.

The subtractor 65 subtracts the shift amount s calculated by the shift amount calculation unit 63 from the positive side short-circuit command N _p ^* calculated by the short-circuit command calculation unit 56 to calculate the positive side short-circuit command N _p ^** . The relationship between the positive-side short-circuit command N _p ^* , the shift amount s, and the positive-side short-circuit command N _p ^** is expressed by Expression (7).

The subtractor 66 subtracts the shift amount s calculated by the shift amount calculation unit 63 from the negative side short-circuit command N _n ^* calculated by the short-circuit command calculation unit 56 to calculate the negative side short-circuit command N _n ^** . The relationship between the negative-side short-circuit command N _n ^* , the shift amount s, and the negative-side short-circuit command N _n ^** is expressed by Expression (8).

The short-circuit gate calculation unit 57 compares the carrier signal a generated by the carrier signal generation unit 54 with the positive-side short-circuit command N _p ^** calculated by the subtractor 65, and the carrier signal a becomes the positive-side short-circuit command N _p ^{*. A} signal that becomes a high level when it is greater than ^* and becomes a low level when it is less than or equal to the positive side short-circuit command N _p ^** is output as a positive-side short-circuit gate signal G _sp ^* . Further, when the carrier signal a generated by the carrier signal generation unit 54 is compared with the negative short-circuit command N _n ^** calculated by the subtractor 66, the carrier signal a is smaller than the negative short-circuit command N _n ^**. A signal that becomes low level when the high level is greater than or _{equal to the} negative side short-circuit command N _n ^** is output as the negative side short-circuit gate signal G _sn ^* .

FIG. 8 shows the carrier signal a, the three-phase voltage commands V _u ^* , V _v ^* , V _w ^* , the modulation factor α, the positive short-circuit commands N _p ^* , N _p ^**, and the negative short-circuit command N. _n ^*, and _n ^{n **,} and the shift amount s, the positive short gate signal _{G sp} ^*, and the negative-side short-circuit gate signal _{G sn} ^*, * basic gate signal _G ^{Stay _up-,} and _{G un} ^*, the final output gate signal G _sup ^*, a diagram showing the relationship between the _{G sun} ^*.

  As shown in FIG. 8, by subtracting the shift amount s from the short-circuit command for each half cycle at the peak and valley timings of the triangular wave carrier signal a, the time width and phase of the short-circuit pulse of the short-circuit gate signal (that is, The time and period of short-circuiting the switching elements 31 to 36 can be changed randomly, and as a result, the switching frequency component of the current flowing through the reactors 21 and 22 of the Z source booster circuit 20 can be suppressed.

  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 is applicable to a power conversion device having a Z source booster circuit.

DESCRIPTION OF SYMBOLS 1, 2 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 40 Electric motor 51 Integrator 52 Current command calculating part 53 Z source vector control calculating part 54 Carrier signal generation unit 55 Basic gate calculation unit 56 Short circuit command calculation unit 57 Short circuit gate calculation unit 58 Short circuit gate OR unit 59 Final output gate OR unit 60-1, 60-2 Control unit 61 Modulation rate calculation unit 62 Random variable generation Unit 63 Shift amount calculation unit 64 Adder 65, 66 Subtractor 71, 72 Voltage detection unit 73, 74 Current detection unit 75 Rotational speed detection unit 531 Three-phase-dq axis coordinate conversion unit 532 Current control calculation unit 533 Z source output voltage Arithmetic unit 534 dq axis-three-phase coordinate conversion unit

Claims (4)

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 connected to the output side of the Z source booster circuit and having a plurality of switching elements;
A control unit that performs PWM control of the switching element by comparing a carrier signal and a command value,
The said control part changes the time and period which short-circuit the said switching element at random, The power converter device characterized by the above-mentioned.   The control unit randomly changes a time and a period for short-circuiting the switching element by adding a shift amount that changes every half cycle at the peak and valley timings of the carrier signal to the carrier signal of the triangular wave. The power conversion device according to claim 1, wherein:   The control unit randomly changes a time and a period for short-circuiting the switching element by subtracting, from the command value, a shift amount that changes every half cycle at the peak and valley timings of the carrier signal of the triangular wave. The power conversion device according to claim 1, wherein:   The power converter according to claim 2, wherein the control unit calculates the shift amount using a modulation factor and a random variable in the PWM control.

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