JP6207796B2 - Power converter - Google Patents

Description

  The present invention relates to a power conversion device that converts a DC voltage from a DC power source into an AC voltage and outputs it to an AC load by controlling on / off of a switching element, and particularly suppresses a leakage current flowing between the power source and the ground. It is about technology.

A power conversion device having a switching element adjusts an ON period or an OFF period of the switching element in accordance with a voltage command for outputting a predetermined voltage. At that time, depending on the operation pattern (switching pattern) of the switching element, a change in the ground voltage occurs, resulting in a leakage current.
When a leakage current occurs, a potential difference is generated between the device and the ground, and depending on the value, an electric shock accident may occur. In addition, if there is an object such as dust in the path of the leakage current, this may generate heat due to the leakage current, leading to a fire accident.

  Therefore, measures to suppress this leakage current are required. For example, in the example of Patent Document 1, the impedance of the leakage current path is increased by increasing the frequency of the carrier that generates the switching signal of the power converter. How to make it introduced.

JP 2005-57918 A

  However, in the example of Patent Document 1, when the carrier frequency is increased, high-speed switching is required, the switching element itself becomes expensive, the switching loss increases, and the apparatus becomes large and expensive. Further, when the carrier frequency is increased, the ratio of the short-circuit prevention time that does not contribute to the voltage output with respect to the switching cycle increases, and there is a problem that the error of the AC output voltage value with respect to the AC output voltage command value increases.

  The present invention has been made to solve these problems, and an object of the present invention is to obtain a power conversion device capable of suppressing leakage current at low cost with a small size and low loss without increasing the carrier frequency. .

  In the power conversion device according to the present invention, a plurality of switching legs composed of a series body of a plurality of switching elements are connected between both poles of a DC power supply, and are connected to an AC load from an intermediate point of each switching leg via an AC filter. A power converter that converts the DC voltage from the DC power source into an AC voltage by controlling on / off of the switching element and outputs the AC voltage to the AC load, and is connected between one pole of the DC power source and the ground. A leakage current detection unit for detecting current, a voltage command generation unit for generating an instantaneous voltage command of the AC voltage, a carrier signal of each switching leg for on / off control of the switching element so as to suppress the leakage current, A carrier generation unit that generates by shifting the phases of each other, based on the leakage current detected to suppress the leakage current. A corrected voltage command for calculating the voltage command correction amount, correcting the instantaneous voltage command generated by the voltage command generation unit with the voltage command correction amount, and controlling on / off of the switching element of each switching leg, Each switching based on the voltage command correction unit to be generated, and the carrier signal of each switching leg generated by the carrier generation unit and the corrected voltage command of each switching leg generated by the voltage command correction unit A PWM signal generation unit that generates a PWM signal for controlling on / off of the switching element of the leg is provided.

  As described above, the power conversion device according to the present invention employs the carrier generation unit that mutually shifts the phase of the carrier signal of each switching leg and the voltage command correction unit that corrects the instantaneous voltage command of each switching leg. The leakage current can be suppressed inexpensively with a small size and low loss without increasing the carrier frequency.

It is a figure which shows the whole structure of the power converter device which concerns on Embodiment 1 of this invention. It is a figure for demonstrating the leakage current path | route Ro including the ground impedance of alternating current load in FIG. It is a figure which shows the internal structure of the carrier production | generation part 33 of FIG. 6 is a timing chart for explaining the effect of the phase shift of the carrier generation unit 33; It is a figure which shows the internal structure of the voltage command correction | amendment part 32 of FIG. It is a figure which shows the internal structure of the PWM signal generation part 34 of FIG. 3 is a timing chart for explaining the operation of a PWM signal generation unit that generates a PWM signal based on outputs from the carrier generation unit 33 and the voltage command correction unit 32 of FIG. 1. It is a timing chart explaining the situation of leakage current in Embodiment 1 of this invention by comparison with a comparative example. It is a figure which shows an example of the whole structure of the power converter device which concerns on Embodiment 2 of this invention.

Embodiment 1 FIG.
1 is a diagram showing an overall configuration of a power conversion apparatus according to Embodiment 1 of the present invention. The power conversion device in FIG. 1 converts a DC voltage from a DC power supply 10 into an AC voltage and outputs it to an AC load 11, a voltage command value V * from a higher control, the negative electrode of the DC power supply 10, and grounding And a power converter control unit 7 that generates a PWM (pulse width modulation) signal based on the leakage current detection value I1c from the leakage current detection unit 8 connected between the two. Details of these configurations will be described below.

  The power conversion unit 9 includes a switching leg A composed of a series body of the switching element 1 and the switching element 2 and a switching leg B composed of a series body of the switching element 3 and the switching element 4 connected between both poles of the DC power supply 10. In addition, an AC filter including a reactor 5 and a capacitor 6 connected between the intermediate point of both switching legs A and B and the AC load 11 is provided. Each switching element 1, 2, 3, 4 is constituted by, for example, a switching element 1, a semiconductor switching element S 1 such as an IGBT or a MOSFET, and a freewheeling diode D 1 connected in reverse parallel thereto. .

  The power converter control unit 7 includes a voltage command generation unit 31, a voltage command correction unit 32, a carrier generation unit 33, and a PWM signal generation unit 34, and the configuration of each unit will be described below.

The voltage command generator 31 generates an instantaneous voltage command Vo * based on the voltage command value V * from the higher control.
The carrier generation unit 33 calculates the phase shift amount dθ based on the detected leakage current I1c so as to suppress the leakage current I1c. Then, the carrier generation unit 33 generates a carrier signal for on / off control of the switching elements 1 to 4 of the switching legs A and B by shifting the phases thereof by the phase shift amount dθ. Details will be described with reference to FIG.

  The voltage command correction unit 32 calculates voltage command correction amounts dVoa * and dVob * based on the detected leakage current I1c so as to suppress the leakage current I1c. Then, the voltage command correction unit 32 corrects the generated instantaneous voltage command Vo * with the voltage command correction amounts dVoa * and dVob *, and corrects the on / off control of the switching elements 1 to 4 of the switching legs A and B. After voltage commands Voa * and Vob * are generated. Details will be described with reference to FIG.

  The PWM signal generator 34 switches the switching legs A and B based on the generated carrier signals of the switching legs A and B and the corrected voltage commands Voa * and Vob * of the generated switching legs A and B. A PWM signal for controlling on / off of the elements 1 to 4 is generated. Details will be described with reference to FIG.

  FIG. 2 is a diagram showing a leakage current path Ro including the ground impedance of the AC load 11 in FIG. In FIG. 2, one end of the AC load 11 connected via the AC filter from the intermediate point of the switching leg A is defined as PA point, and the other end of the AC load 11 connected via the AC filter from the intermediate point of the switching leg B. Is shown as a PB point. In FIG. 2, a load parallel impedance 41, a load PA side ground impedance 42 (PA point side load ground impedance), and a load PB side ground impedance 43 (PB point side load ground impedance) are shown. The load PA side ground impedance 42 and the load PB side ground impedance 43 are assumed to have a series capacitance. Further, a PA side ground capacitance 12a and a PB side ground capacitance 12b are shown.

As a path of the leakage current I1c (leakage current path Ro), the negative electrode of the DC power supply 10 is connected to the PA side ground capacitance 12a, the load PA side ground impedance 42, and the load PB side ground impedance 43 through the power conversion unit 9. And the parallel circuit of the PB side ground capacitance 12 b and the leakage current detection unit 8, the current flows again through a path reaching the negative electrode of the DC power supply 10.
In addition, when the load PA side ground impedance 42 or the load PB side ground impedance 43 changes, the impedance of the leakage current path may change to cause a leakage current.

  In this embodiment, the leakage current due to the switching pattern is suppressed by changing the switching pattern of the power converter by the power converter controller 7 from the leakage current I1c detected by the leakage current detector 8. Moreover, the leakage current by the change of the load PA side ground impedance 42 or the load PB side ground impedance 43 is suppressed.

In this embodiment, in order to suppress this leakage current I1c, first, the carrier generation unit 33 shifts the phases of the carrier signals of both switching legs A and B to each other.
FIG. 3 shows an internal configuration example of the carrier generation unit 33. The carrier generation unit 33 includes a control input calculation unit 61, a phase shift amount calculation unit 62, a triangular wave generator 63, and a phase shift circuit 64, and each element will be described below.

  The control input calculation unit 61 inputs the leakage current I1c detected by the leakage current detection unit 8, performs the calculation shown in the following equation (1), and outputs the leakage current output dI1c.

  dI1c = | I1crms | −I1c * (1)

Here, | I1crms | is the absolute value of the effective value of leakage current I1c. I1c * is a specified leakage current value that is arbitrarily set in consideration of a level that is harmful as a leakage current.
That is, since a digital voltmeter is generally used for evaluating leakage current, it is considered to suppress the effective value I1crms of leakage current. The carrier generation unit 33 is operated when a leakage current I1c exceeding the arbitrarily set leakage current value I1c * is detected.

  The phase shift amount calculation unit 62 includes an integral calculation element. When the leakage current output dI1c is input, that is, when the detected leakage current effective value | I1crms | exceeds the leakage current specified value I1c *, the phase shift amount calculation unit 62 The phase shift amount dθ is calculated and output so as to be suppressed to the current regulation value I1c *.

  As will be described in detail later with reference to FIG. 4, regarding the phase shift amount dθ, dθ = 180 ° corresponds to the case where the waveforms of the switching elements S1 and S4 coincide, and dθ = 0 ° indicates that both waveforms have opposite polarities. Is equivalent to Then, the phase shift amount calculation unit 62 outputs the phase shift amount dθ within the range of 0 ° ≦ dθ ≦ 180 °.

  The triangular wave generator 63 generates a triangular wave for generating a PWM signal, and outputs a carrier signal ca used for generating a PWM signal of the switching leg A. The phase shift circuit 64 shifts the phase of the triangular wave generated by the triangular wave generator 63 according to the phase shift amount dθ calculated by the phase shift amount calculation unit 62, and uses the carrier signal cb used for generating the PWM signal of the switching leg B. Is output.

Next, the effect of the carrier signal phase shift of the carrier generator 33 will be described with reference to FIG.
FIG. 4 shows a switching operation of the switching elements 1 to 4 that are PWM-controlled based on carrier signals that are phase-shifted from each other. In FIG. 4, Vac is the voltage applied to the AC load 11, and S <b> 1 (here, the sign of the semiconductor switching element is used as it is for the sign of the signal, and so on). Pulse) signal, S2 is a switching (ON / OFF pulse) signal of the switching element 2, S3 is a switching (ON / OFF pulse) signal of the switching element 3, and S4 is a switching (ON / OFF pulse) of the switching element 4. The signal, Vna is the PA side ground voltage in FIG. 2, Vnb is the PB side ground voltage in FIG. 2, Va is the PA side ground voltage acting on the leakage current at the PA point in FIG. 2, and Vb is the PB in FIG. A PB side ground voltage Vdc acting on the point leakage current is an output voltage of the DC power supply 10.

  In the voltage waveforms of Vna and Vnb, the voltage component that varies with Vac is the ground voltage that acts on the current flowing between the points PA and PB. Therefore, when the ground capacitances 12a and 12b with respect to the frequency of Vac are sufficiently small and the impedance is sufficiently large, the influence of Vac on the leakage current is sufficiently small. Therefore, here, the voltages Va and Vb obtained by removing the component of Vac from Vna and Vnb are considered as the ground voltage acting on the leakage current.

  In FIG. 4, for the sake of simplicity, the transient phenomenon of the reactor 5, the impedance of the leakage current detection unit 8, the ground capacitances 12a and 12b, the load PA side ground impedance 42, and the load PB side ground impedance 43 in FIG. All waveforms are completely rectangular waveforms without consideration.

  As a result of the carrier generation unit 33 shifting the phases of the carrier signals ca and cb of both switching legs A and B to each other, the power conversion unit 9 performs switching in one of the periods a to d in FIG. 4 during the carrier period. Works by combining patterns.

  The period a is a period in which the switching element 1 and the switching element 3 are ON, and the ground voltage Va = Vb = Vdc. The period b is a period in which the switching element 1 and the switching element 4 are turned ON, and the ground voltage Va = Vb = Vdc / 2. The period c is a period in which the switching element 2 and the switching element 4 are turned ON, and the ground voltage Va = Vb = 0V. The period d is a period in which the switching element 2 and the switching element 3 are turned ON, and the ground voltage Va = Vb = Vdc / 2.

  Therefore, the average carrier period of the PA-side ground voltage Va and the PB-side ground voltage Vb is the average value of the PA-side ground voltage Va and the PB-side ground voltage Vb of each switching pattern in the carrier period.

  Further, depending on the implementation environment, there is a possibility that the leakage current steadily exceeds the specified value due to fluctuations in the ground voltages Va and Vb due to the switching pattern. This is caused by a change in ground voltage between the state where the switching element 1 and the switching element 3 where the ground voltage is Vdc is ON and the state where the switching element 2 and the switching element 4 where the ground voltage is 0 V are ON. It is.

  In such a case, the phase of the carrier signal ca of the switching leg A and the phase of the carrier signal cb of the switching leg B are shifted from each other. Thereby, the ratio of the state in which the switching element 1 and the switching element 3 are turned on in the switching cycle and the state in which the switching element 2 and the switching element 4 are turned on can be adjusted. Thereby, it is possible to suppress the leakage current from constantly exceeding the specified value due to the fluctuation of the ground voltage due to the switching pattern.

  That is, when the detected leakage current effective value | I1crms | exceeds the leakage current specified value I1c *, the carrier generation unit 33 controls the carrier signal ca of the switching leg A so as to suppress it to the leakage current specified value I1c *. And the carrier signal cb of the switching leg B are shifted from each other by the phase shift amount dθ.

  By the way, in the period when the switching element 1 and the switching element 3 are simultaneously ON or the switching element 2 and the switching element 4 are simultaneously ON, the voltage applied to the switching element side of the reactor 5 becomes 0V. Therefore, by using a switching pattern in which the switching element 1 and the switching element 3 are simultaneously turned on or the switching element 2 and the switching element 4 are simultaneously turned on within the operation range in which the leakage current is suppressed to a specified value, the average reactor voltage of the carrier period There is also an advantage that the change can be reduced and the current ripple of the reactor 5 can be reduced.

  Next, by adjusting the ratio between the period a and the period c described in FIG. 4, in particular, a voltage command correction unit that can effectively suppress an increase in leakage current accompanying changes in the load impedances 42 and 43. 32 will be described with reference to FIG. FIG. 5 is a diagram showing an example of the internal configuration.

The voltage command correction unit 32 includes a correction limiter calculation unit 71, a controller 72, a correction amount calculation unit 73, an adder 74, and an adder 75, and each element will be described below.
In FIG. 5, dVo * is a ground voltage change amount, dVo * lim is a limiter value for obtaining the correction amount of the voltage command from the ground voltage change amount dVo *, and dVoa * is switched with the switching element 1. This is a voltage command correction amount for turning on / off the switching leg A composed of the element 2, and dVob * is for turning on / off the switching leg B composed of the switching element 3 and the switching element 4. This is the voltage command correction amount.

As described with reference to FIG. 4, since the ground voltage in the period a in which the switching element 1 and the switching element 3 are simultaneously turned on is the highest Vdc, increasing the period a increases the ground voltage in the carrier period. In addition, since the ground voltage during the period c in which the switching element 2 and the switching element 4 are simultaneously turned on is 0 V, the ground voltage in the carrier period decreases when the period c is increased.
Therefore, the voltage command correction unit 32 adjusts the voltage command correction amount dVoa * so as to adjust the ratio between the state in which the switching element 1 and the switching element 3 are turned on and the state in which the switching element 2 and the switching element 4 are turned on in the carrier cycle. And dVob * are calculated.

  In FIG. 5, the controller 72 estimates a change in ground voltage from the leakage current I1c, and calculates a ground voltage change amount dVo *. Since the main component of the ground impedance is capacitance, the integral value of the leakage current I1c corresponds to the ground voltage change amount dVo *. For this reason, the controller 72 has a control configuration including at least an integration element.

As described above, the voltage command is corrected in order to adjust the ratio between the period a and the period c shown in FIG. 4, and therefore it is assumed that both periods exist as a switching pattern. In order to secure this premise, the correction limiter calculation unit 71 limits the voltage command correction amounts dVoa * and dVob * obtained from the ground voltage change amount dVo * based on the phase shift amount dθ and the instantaneous voltage command Vo *. The limiter value is calculated.
The correction limiter value dVo * lim is expressed by the following equation (2).

dVo * lim = (1-2 × Td / Tc)
((Vdc- | Vo * |) / 2) (1-dθ / 180 °)
... (2)

  Here, Td is the dead time period of the PWM signal, Tc is the period of the carrier generated by the carrier generation unit 33, and Vdc is the output voltage of the DC power supply 10.

  When dθ = 0 ° at which the third term on the right side of equation (2) is 1, as described above, the waveforms of the switching elements S1 and S4 have opposite polarities, and the period a in FIG. The voltage command can be corrected. The second term reflects the maximum correctable voltage value at that time, and the first term reflects the decrease in output voltage due to dead time.

  The correction amount calculation unit 73 calculates voltage command correction amounts dVoa * and dVob * according to the following equations (3) and (4) based on the ground voltage change amount dVo * and the correction limiter value dVo * lim.

dVoa * = dVo * (3)
[Limiter: -dVo * lim ≦ dVoa * ≦ dVo * lim]
dVob * = − dVo * (4)
[Limiter: -dVo * lim ≦ dVob * ≦ dVo * lim]

  The adders 74 and 75 calculate and output corrected voltage commands Voa * and Vob * according to the following equations (5) and (6).

Voa * = Vo * + dVoa * (5)
Vob * = Vo * + dVob * (6)

Next, the PWM signal generation unit 34 will be described with reference to FIG.
The PWM signal generation unit 34 includes comparators 81 and 82, logic inversion circuits 83 and 84, delay units 85 to 88, AND circuits 89 to 92, and a sign inverter 93.

  In FIG. 6, the PWM signal of the switching element 1 is compared with the carrier signal ca generated by the carrier generation unit 33 and the corrected voltage command Voa * corrected by the voltage command correction unit 32 by the comparator 81, and is further delayed. This is a PWM signal obtained by inserting the dead time Td by the device 85 and the AND circuit 89. The PWM signal of the switching element 2 is a PWM signal obtained by inverting the PWM signal generated by the comparator 81 by the logic inverting circuit 83 and inserting the dead time Td by the delay device 86 and the AND circuit 90.

  As for the PWM signal of the switching element 3, the carrier signal cb generated by the carrier generation unit 33 and the corrected voltage command Vob * corrected by the voltage command correction unit 32 with the sign inverted by the sign inverter 93 are output by the comparator 82. This is a PWM signal obtained by comparing and further inserting a dead time Td by the delay device 87 and the AND circuit 91. The PWM signal of the switching element 4 is a PWM signal obtained by inverting the PWM signal generated by the comparator 82 by the logic inverting circuit 84 and inserting the dead time Td by the delay device 88 and the AND circuit 92.

  FIG. 7 is a timing chart for explaining an operation of generating a PWM signal by the PWM signal generation unit 34 shown in FIG. 6 based on the outputs of the carrier generation unit 33 and the voltage command correction unit 32. In FIG. 7, for simplification, the influence of the dead time Td is not considered.

  In FIG. 7, a phase difference Tc (1−dθ / 180 °) / 2 is generated between the carrier signal ca and the carrier signal cb by the phase shift amount calculation unit 62 of the carrier generation unit 33. The voltage command correction unit 32 performs switching according to the corrected voltage commands Voa * and Vob * obtained by correcting the instantaneous voltage command Vo * by the voltage command correction amounts dVoa * and dVob *.

  As a result, in the example shown in FIG. 7, compared to the case of FIG. 4 in which the voltage command is not corrected, the period a in which the ground voltage is Vdc increases, the period c in which the ground voltage is 0 V decreases, and the carrier cycle It can be seen that the average value of the ground voltage at has changed.

However, as already described in the equation (2), when the phase shift amount dθ = 180 °, the correction limiter value dVo * lim = 0V, and the voltage command correction unit 32 of the present application cannot correct the voltage command. I am doing so. This corresponds to the case where the period a and the period c do not exist. In this case, if the voltage command is corrected, the AC output voltage as the power converter does not coincide with the instantaneous voltage command Vo *. At dθ = 0 °, the period a is 50% and the period c is 50% in the voltage command 0V.
From this, the period a and the period c depend on dθ, and the ratio thereof becomes (1−dθ / 180 °) (see formula (2)).

  FIG. 8 is a timing chart for explaining the situation of the leakage current when this embodiment is applied in comparison with a comparative example in which the above-described countermeasure for suppressing the leakage current I1c is not performed. 8, Vam is an average carrier period value of the PA side ground voltage acting on the leakage current at the PA point in FIG. 2, and Vbm is an average carrier period of the PB side ground voltage acting on the leakage current at the PB point in FIG. Value.

FIG. 8A shows an operation example when there is no steady leakage current, and FIG. 8B shows an operation example when there is a steady leakage current.
Further, the change in the load ground impedance starting from the left and right central positions in the figure is a change in the load PA side ground impedance 42 and the load PB side ground impedance 43 in FIG. 2, and Vam and Vbm due to this impedance change for simplification. Are assumed to be equal.

  In “no steady leakage current” in FIG. 8A, in the comparative example, the effective value I1crms of the leakage current temporarily increases due to the change in the ground voltage due to the change in the load-to-ground impedance. On the other hand, in the present embodiment, the voltage command correction unit 32 operates due to a change in ground voltage due to a change in load ground impedance, the voltage command correction amounts dVoa * and dVob * rise, and the peak of the effective leakage current value I1crms is reduced. doing.

In addition, in “there is a steady leakage current” in FIG. 8B, in the comparative example, an excessive leakage current constantly flows. On the other hand, in the present embodiment, the phase shift operation of the carrier generation unit 33 is executed, and the steady leakage current can be suppressed to the specified leakage current value I1c *.
In FIG. 8 (b), it can be seen that in the present embodiment, both the phase shift and the voltage command correction are operated with respect to the load-to-ground impedance change, and the leakage current is effectively suppressed.

  As described above, in the power conversion device according to Embodiment 1 of the present invention, the phases of the carrier signal ca of the switching leg A and the carrier signal cb of the switching leg B generated by the carrier generation unit 33 are set to each other according to the leakage current. By shifting and correcting the instantaneous voltage command Vo * generated by the voltage command generation unit 31 according to the leakage current, the leakage current can be efficiently and continuously suppressed. Since it is not necessary to increase the carrier frequency as in the prior art, the leakage current can be suppressed at low cost with a small size and low loss.

  In addition, a switching pattern in which the voltage applied to the reactor 5 becomes small within the operating range for suppressing the leakage current to the specified value (the switching element 1 and the switching element 3 are turned on simultaneously or the switching element 2 and the switching element 4 are turned on). By using a switching pattern that is turned on at the same time, the current ripple of the reactor 5 is reduced, and the reactor 5 can be downsized.

  In the present embodiment, the leakage current detection unit 8 is connected between the negative electrode of the DC power supply 10 and the ground, but is not limited to this, and is connected between the positive electrode of the DC power supply 10 and the ground. May be.

Other modifications of the above-described first embodiment will be described below.
In the first embodiment, the case of a power conversion device that converts a DC voltage into a single-phase AC voltage has been described. However, even in a power conversion device that converts a DC voltage into a three-phase AC voltage, By applying the technical contents described, the present invention can be applied in the same manner and achieve the same effect.

  In the first embodiment, the DC power supply 10 is a constant voltage source. However, the present invention is not limited to this, and an apparatus that converts an AC voltage or a DC voltage into a DC voltage (an AC / DC converter or a DC / DC converter). ) May be output from the DC voltage.

Embodiment 2. FIG.
Hereinafter, the second embodiment of the present invention will be described with reference to the drawings, focusing on the differences from the first embodiment. The same parts as those in the first embodiment are denoted by the same reference numerals and the description thereof is omitted.
FIG. 9 is a diagram showing an example of the overall configuration of the power conversion apparatus according to Embodiment 2 of the present invention.
In the power converter shown in FIG. 9, a measuring unit 13 that measures the output voltage Vdc of the DC power supply 10 is added. And you may use Vdc measured by this measurement part 13 for (2) types. By applying a more accurate correction limiter value, an accurate voltage command correction operation is compensated.

  It should be noted that the present invention can be freely combined with each other within the scope of the invention, and each embodiment can be appropriately modified or omitted.

Claims (6)

A plurality of switching legs composed of a series body of a plurality of switching elements are connected between both poles of a DC power source, and connected to an AC load via an AC filter from an intermediate point of each switching leg to control the on / off of the switching elements. A power conversion unit that converts a DC voltage from the DC power source into an AC voltage and outputs the AC voltage to the AC load, a leakage current detection unit that is connected between one pole of the DC power source and the ground, A voltage command generation unit that generates an instantaneous voltage command of the AC voltage, and generates a carrier signal of each switching leg for on / off control of the switching element so as to suppress the leakage current, with the phases thereof shifted from each other. Carrier generator, calculating a voltage command correction amount based on the leakage current detected to suppress the leakage current, A voltage command correction unit that corrects the instantaneous voltage command generated by the pressure command generation unit with the voltage command correction amount and generates a corrected voltage command for on / off control of the switching element of each switching leg; and On / off control of the switching element of each switching leg is performed based on the carrier signal of each switching leg generated by a carrier generation unit and the corrected voltage command of each switching leg generated by the voltage command correction unit. A power conversion device including a PWM signal generation unit that generates a PWM signal. When the effective value of the detected leakage current exceeds a preset leakage current specified value, the carrier generation unit calculates a phase shift amount so as to suppress this to the leakage current specified value, The power converter according to claim 1, wherein the carrier signal of each switching leg is generated by shifting the phase thereof by the phase shift amount. The voltage command correction unit calculates a correction limiter value for limiting the voltage command correction amount based on the instantaneous voltage command and the phase shift amount so that the leakage current is effectively suppressed by correcting the instantaneous voltage command. The power conversion device according to claim 2, further comprising a correction limiter calculation unit that performs the correction. The power conversion device according to claim 3, wherein the correction limiter calculation unit calculates the correction limiter value dVo * lim by the following equation.
dVo * lim =
(1-2 × Td / Tc) · ((Vdc− | Vo * |) / 2) · (1−dθ / 180 °)
Where Td is the dead time period of the PWM signal, Tc is the period of the carrier signal, Vdc is the output voltage of the DC power supply, Vo * is the instantaneous voltage command, and dθ is the phase shift amount. The power converter according to claim 4, further comprising a measuring unit that detects an output voltage Vdc of the DC power supply, and calculating the correction limiter value using the detected output voltage. The voltage command correction unit calculates a ground voltage change amount based on the detected instantaneous value of the leakage current, and outputs the ground voltage change amount within a limit range of the correction limiter value to output the voltage. The power converter according to any one of claims 3 to 5, further comprising a correction amount calculation unit that calculates a command correction amount.

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