Power converter

Abstract

To provide a power conversion device in which the frequency variation of AC input from a power network including renewable energy can be suppressed.SOLUTION: A power conversion device 1 includes a converter circuit C that is connected to a power network including a renewable energy generator and converts AC input from the power network into DC, a smoothing circuit S connected in series to the converter circuit C and including a capacitor, a power storage device D connected in series to the converter circuit C and connected in parallel to the smoothing circuit S, an inverter circuit I connected in series to the smoothing circuit S and the power storage device D, converting DC from the smoothing circuit S or DC from the power storage device D into AC, and outputting the AC to an AC load, a converter control unit 12 that performs PWM control over the converter circuit C on the basis of a DC voltage command value, and an inverter control unit 13 that performs PWM control over the inverter circuit I. The converter control unit 12 includes a DC voltage control unit including a DC voltage command value correction unit, and a frequency detection unit that detects the frequency of the AC input from the power network.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD

[0001] The present invention relates to a power conversion device. BACKGROUND ART

[0002] At present, in commercial power supplies mainly powered by power generation using synchronous generators such as thermal power generators, frequency fluctuations of the commercial power supply are suppressed by adjusting the power generation amount even when power consumption fluctuates abruptly. However, in recent years, power generation using renewable energy such as sunlight has increased, and the proportion of power generation using synchronous generators in commercial power supplies has decreased. Accordingly, there is a concern that frequency fluctuations in commercial power supplies may occur when power consumption fluctuates abruptly.

[0003] For example, Patent Document 1 discloses a power conversion device that converts AC voltage input from a commercial power supply into direct current, connects a storage battery to a DC bus via a DC / DC converter, and controls charging and discharging of the storage battery by the DC / DC converter. Thereby, the charging and discharging control of the storage battery connected to the DC bus is performed using the voltage command value, and stable power supply is enabled. PRIOR ART DOCUMENTS PATENT DOCUMENTS

[0004] PATENT DOCUMENT 1 Japanese Unexamined Patent Application Publication No. 2022-74842 SUMMARY OF THE INVENTION PROBLEM TO BE SOLVED BY THE INVENTION

[0005] However, the power conversion device disclosed in Patent Document 1 can suppress fluctuations in the load connected to the power conversion device when power consumption fluctuates abruptly, but cannot suppress frequency fluctuations of the commercial power supply.

[0006] Accordingly, the present invention provides a power conversion device capable of suppressing frequency fluctuations of alternating current input from a power grid including renewable energy. [Means for solving the problem]

[0007] The power converter according to one aspect of this embodiment is: A converter circuit connected to a power grid including renewable energy generators, which converts alternating current input from the power grid into direct current, A smoothing circuit consisting of a capacitor is connected in series with the converter circuit, A power storage device connected in series with the converter circuit and in parallel with the smoothing circuit, The smoothing circuit and the energy storage device are connected in series with the smoothing circuit and an inverter circuit that converts the DC from the smoothing circuit or the DC from the energy storage device into AC and outputs it to an AC load. A converter control unit that PWM controls the converter circuit based on a DC voltage command value, An inverter control unit that performs PWM control of the inverter circuit, Equipped with, The converter control unit, A DC voltage control unit having a DC voltage command value correction unit, A frequency detection unit for detecting the frequency of AC input from the power grid, Equipped with, The DC voltage control unit generates the DC voltage command value from the difference between the DC voltage reference value and the DC voltage supplied from the converter circuit to the inverter circuit. The DC voltage command value correction unit is characterized by correcting the DC voltage command value within a range in which the DC voltage command value becomes a positive value, based on the frequency of the AC input from the power grid detected by the frequency detection unit. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a power conversion device that suppresses frequency fluctuations of alternating current input from a power grid that includes renewable energy. [Brief explanation of the drawing]

[0009] [Figure 1]This is a circuit diagram showing the circuit configuration of the power conversion device according to this embodiment. [Figure 2] This is a block diagram showing the circuit configuration of a converter control unit according to the first embodiment of the present invention. [Figure 3] Figure 2 shows the DC voltage command value and converter reference waveform data within the converter control unit. [Figure 4] This is a block diagram showing the circuit configuration of an inverter control unit according to the first embodiment of the present invention. [Figure 5] This is a block diagram showing the circuit configuration of a converter control unit according to a second embodiment of the present invention. [Figure 6] This is a block diagram showing the circuit configuration of a converter control unit according to a third embodiment of the present invention. [Modes for carrying out the invention]

[0010] The following description of this embodiment will be made with reference to the drawings. For the sake of clarity, the description of components having the same reference numeral as those already described in the description of this embodiment will be omitted. Furthermore, the dimensions of the components shown in these drawings may differ from the actual dimensions of the components, for the sake of clarity.

[0011] Figure 1 shows the circuit configuration of the power converter 1 according to this embodiment. As shown in Figure 1, a three-phase AC power supply 91 is connected to the device input terminals 31a to 31c of the power converter 1, and an AC load 92 supplied with three-phase AC Vout output from the inverter circuit I is connected to the device output terminals 71a to 71c of the power converter 1. The power converter 1 comprises an input filter F1, a converter circuit C, a smoothing circuit S, an inverter circuit I, an output filter F2, a DC circuit D, a converter control unit 12, and an inverter control unit 13. Furthermore, three-phase AC power source 91 refers to a power grid that includes renewable energy generators such as solar power, wind power, and wave power, where it is difficult to intentionally adjust the amount of power generated.

[0012] The input filter F1 includes input filter capacitors 2a to 2c and input filter reactors 3a to 3c. One terminal of each of the input filter reactors 3a to 3c is connected to a corresponding one of the device input terminals 31a to 31c of the power conversion device 1. The other terminal of each of the input filter reactors 3a to 3c is connected to a corresponding one of the three-phase (r-phase, s-phase, t-phase) AC input terminals 41a to 41c of the converter circuit C.

[0013] One terminal of each of the input filter capacitors 2a to 2c is connected to the terminal on the device input terminals 31a to 31c side of the corresponding one of the input filter reactors 3a to 3c. The other terminals of the input filter capacitors 2a to 2c are connected to each other. The input filter F1 allows the three-phase AC Vin from the three-phase AC power supply 91 to pass to the converter circuit C, and prevents signals of the carrier frequency (the frequency that determines the pulse width modulation period in the PWM control method) generated in the converter circuit C from flowing into the three-phase AC power supply 91.

[0014] The converter circuit C has six semiconductor switching elements 4a to 4f connected in a three-phase bridge configuration. The semiconductor switching elements 4a to 4f are each composed of, for example, an IGBT (Insulated Gate Bipolar Transistor) and a freewheeling diode connected in antiparallel. The converter circuit C is configured as a three-phase (r-phase, s-phase, t-phase) full-bridge circuit. The converter circuit C converts the three-phase AC input from the three-phase AC power supply 91 into direct current.

[0015] The smoothing circuit S includes the smoothing capacitor 5 of the converter circuit C, and is connected in series to the converter circuit C. The smoothing capacitor 5 is, for example, an electrolytic capacitor, and is connected to the DC output terminals 42a and 42b of the converter circuit C. The smoothing capacitor 5 smoothes the output of the converter circuit C.

[0016] The inverter circuit I includes six semiconductor switching elements 6a to 6f connected in a three-phase bridge configuration, and is connected in series to the smoothing circuit S and the DC circuit D. The semiconductor switching elements 6a to 6f are each composed of, for example, an IGBT and a freewheeling diode connected in antiparallel. The inverter circuit I is configured as a three-phase (u-phase, v-phase, w-phase) full-bridge circuit. In the inverter circuit I, DC input terminals 61a and 61b are connected to the two electrode terminals of the smoothing capacitor 5 and the terminals of the DC-DC converter 11, respectively. The inverter circuit I converts the direct current from the smoothing circuit S (the direct current output by the converter circuit C) into alternating current, or converts the direct current from the DC circuit D into alternating current, through the switching operation of the semiconductor switching elements 6a to 6f.

[0017] The output filter F2 includes output filter reactors 7a to 7c and output filter capacitors 8a to 8c. One terminal of each of the output filter reactors 7a to 7c is connected to a respective one of the AC output terminals 62a to 62c of the three-phase (u-phase, v-phase, w-phase) inverter circuit I. The other terminal of each of the output filter reactors 7a to 7c is connected to a respective one of the device output terminals 71a to 71c of the power conversion device 1.

[0018] One terminal of each of the output filter capacitors 8a to 8c is connected to a respective terminal on the device output terminals 71a to 71c side of the output filter reactors 7a to 7c. The other terminals of the output filter capacitors 8a to 8c are connected to one another. The output filter F2 allows the alternating current output from the inverter circuit I to pass to the AC load 92, and prevents a signal of the carrier frequency generated in the inverter circuit I from flowing into the AC load 92.

[0019] The DC circuit D includes an energy storage device 9 and a DC-DC converter 11. The energy storage device 9 consists of a DC power supply (battery) 10a and an energy storage capacitor 10b. The input terminals 11a and 11c of the DC-DC converter 11 are connected to the energy storage device 9. The output terminals 11b and 11d of the DC-DC converter 11 are connected to the DC input terminals 61a and 61b of the inverter circuit I, respectively. The DC-DC converter 11 converts the input voltages from the DC power supply (battery) 10a and the energy storage capacitor 10b into a predetermined output voltage and outputs it to the inverter circuit I. The energy storage device 9 may consist of either a DC power supply (battery) 10a or an energy storage capacitor 10b. Furthermore, the DC circuit D may not include the DC-DC converter 11.

[0020] DC circuit D is connected in parallel with smoothing circuit S and is configured to continue supplying power to AC load 92 when the AC load 92 increases or when a power outage or momentary interruption occurs. Specifically, during normal operation of power converter 1, DC from smoothing circuit S (DC output by converter circuit C) is input to inverter circuit I. When the energy storage device 9 of power converter 1 is operating, DC from DC circuit D is input to inverter circuit I.

[0021] Figure 2 shows the circuit configuration of the converter control unit 12 according to the first embodiment of the present invention. The converter control unit 12 includes a DC voltage control unit 121, a frequency detection unit 122, a power comparison unit 123, a PLL 124, a converter command generation unit 125, and a converter PWM signal control unit 126, and controls the semiconductor switching elements 4a to 4f of the converter circuit C to a desired state using PWM switching. The DC voltage control unit 121 includes a DC voltage command value correction unit 121A.

[0022] The frequency detection unit 122 receives a three-phase AC Vin input from the three-phase AC power supply 91, detects the frequency fvin of the three-phase AC Vin, and outputs it to the DC voltage command value correction unit 121A.

[0023] The power comparison unit 123 receives the three-phase AC power Vout output from the inverter circuit I through the output filter F2 to the AC load 92, and the DC power supplied from the energy storage device 9 to the inverter circuit I as input. The power comparison unit 123 calculates a threshold Th1 based on the three-phase AC power Pout, compares the DC power Pdc supplied from the energy storage device 9 to the inverter circuit I with the threshold Th1, and outputs the comparison result.

[0024] The DC voltage control unit 121 receives a DC voltage Vdc as input and calculates a DC voltage command value IVdc based on the difference between the DC voltage reference value Vdstd and the DC voltage Vdc. The DC voltage command value correction unit 121A receives the calculated DC voltage command value IVdc and the frequency fvin of the three-phase AC Vin from the frequency detection unit 122. Based on the frequency fvin, the DC voltage command value correction unit 121A corrects the DC voltage command value IVdc within the range in which the DC voltage command value IVdc is a positive value. Specifically, when the frequency fvin increases, the DC voltage command value IVdc is corrected to increase, and when the frequency fvin decreases, the DC voltage command value IVdc is corrected to decrease. As a result, as shown in Figure 3, the corrected DC voltage command value I'Vdc becomes a positive value. The example in Figure 3 shows the case where the corrected DC voltage command value I'Vdc is at its maximum, the case of normal operation with a constant AC load 92, and the case where it is at its minimum.

[0025] Furthermore, the DC voltage command value correction unit 121A receives the comparison result from the power comparison unit 123. Based on the comparison result, the DC voltage command value IVdc may be corrected within the range in which the DC voltage command value IVdc is a positive value. Specifically, if the DC power Pdc exceeds the threshold Th1 based on the comparison result, the DC voltage command value IVdc may be corrected to increase, and if the DC power Pdc falls below the threshold Th1, the DC voltage command value IVdc may be corrected to decrease.

[0026] The PLL124 receives a three-phase AC Vin input from the three-phase AC power supply 91 and outputs a sinusoidal reference signal synchronized with the three-phase AC Vin. The converter reference waveform is generated by integrating the sinusoidal reference signal with the corrected DC voltage command value I'Vdc. As shown in Figure 3, the converter reference waveform is a sine wave synchronized with the sinusoidal reference signal, with the corrected DC voltage command value I'Vdc as its amplitude. Note that the converter control unit 12 may be configured without a PLL 124. In that case, the three-phase AC Vin input from the three-phase AC power supply 91 will directly become the sine wave reference signal.

[0027] The converter command generation unit 125 receives the converter reference waveform as input, generates converter command signals Vr, Vs, and Vt consisting of three-phase AC sine waves, and outputs them to the converter PWM signal control unit 126.

[0028] The converter PWM signal control unit 126 includes a comparator 126a and a carrier signal generation unit 126b. The comparator 126a receives the converter command signals Vr, Vs, and Vt, and the carrier signal Vc, such as a triangular wave, generated by the carrier signal generation unit 126b. It compares the two signals and outputs PWM drive signals Vgr, Vgs, and Vgt. The PWM drive signals Vgr and its inverted signal / Vgr, PWM drive signals Vgs and their inverted signal / Vgs, and PWM drive signals Vgt and their inverted signal / Vgt are input to the gates of the semiconductor switching elements 4a to 4f of the converter circuit C, respectively. In other words, the PWM drive signals Vgr, Vgs, and Vgt are waveforms that turn on the upper semiconductor switching elements 4a, 4c, and 4e and turn off the lower semiconductor switching elements 4b, 4d, and 4f when the converter command signals Vr, Vs, and Vt are greater than the carrier signal Vc. Furthermore, this waveform indicates that when the converter command signals Vr, Vs, and Vt are smaller than the carrier signal Vc, the lower semiconductor switching elements 4b, 4d, and 4f are turned on, and the upper semiconductor switching elements 4a, 4c, and 4e are turned off.

[0029] In this way, the DC voltage command value correction unit 121A corrects the DC voltage command value IVdc based on the frequency fvin from the frequency detection unit 122, the comparison result from the power comparison unit 123, or both the frequency fvin and the comparison result. This allows the semiconductor switching elements 4a to 4f of the converter circuit C to be controlled by PWM switching to suppress fluctuations in the frequency fvin when the frequency fvin of the three-phase AC Vin fluctuates due to rapid fluctuations in the AC load 92, etc. Therefore, fluctuations in the frequency fvin of the power input from the power grid, including renewable energy, can be suppressed.

[0030] Figure 4 shows the circuit configuration of the inverter control unit 13 according to this embodiment. The inverter control unit 13 includes an AC voltage control unit 131, an ideal sine wave generation unit 132, an inverter command generation unit 133, and an inverter PWM signal control unit 134, and controls the semiconductor switching elements 6a to 6f of the inverter circuit I to a desired state using PWM switching.

[0031] The AC voltage control unit 131 receives a three-phase AC Vout as input and calculates an AC voltage command value IVac based on the difference between the AC voltage reference value Vastd and the three-phase AC Vout.

[0032] The ideal sine wave generation unit 132 generates and outputs a sine wave reference signal. By integrating the sine wave reference signal with the AC voltage command value IVac, the inverter reference waveform is generated.

[0033] The inverter command generation unit 133 receives the inverter reference waveform as input, generates converter command signals Vu, Vv, and Vw consisting of three-phase AC sine waves, and outputs them to the inverter PWM signal control unit 134.

[0034] The configuration of the inverter PWM signal control unit 134 is the same as that of the converter PWM signal control unit 126 of the converter control unit 12 shown in Figure 2, so its explanation will be omitted.

[0035] Figure 5 shows the circuit configuration of the converter control unit 12A according to the second embodiment of the present invention. The converter control unit 12A according to the second embodiment has a configuration in which the power comparison unit 123 of the converter control unit 12 according to the first embodiment shown in Figure 2 is replaced with a power determination unit 127.

[0036] The power determination unit 127 consists of a comparator and receives three-phase AC Vin from the three-phase AC power supply 91. The power determination unit 127 compares the three-phase AC power Pin of the three-phase AC Vin with a preset threshold Th2 (for example, Th2=0W) and outputs a determination result.

[0037] The DC voltage command value correction unit 121A receives the judgment result from the power judgment unit 127. Based on the judgment result, the DC voltage command value IVdc may be corrected within the range in which the DC voltage command value IVdc is a positive value. Specifically, if the three-phase AC power Pin exceeds the threshold Th2 based on the comparison result, the DC voltage command value I'Vdc may be corrected to be larger, and if the DC power Pin falls below the threshold Th2, the DC voltage command value I'Vdc may be corrected to be smaller.

[0038] The components other than the power determination unit 127 (DC voltage control unit 121, frequency detection unit 122, PLL 124, converter command generation unit 125, converter PWM signal control unit 126) have the same configuration as the converter control unit 12 shown in Figure 2, so their explanation is omitted.

[0039] In this way, the DC voltage command value correction unit 121A corrects the DC voltage command value IVdc based on the frequency fvin from the frequency detection unit 122, the determination result from the power determination unit 127, or both the frequency fvin and the determination result. This allows the semiconductor switching elements 4a to 4f of the converter circuit C to be controlled by PWM switching to suppress fluctuations in the frequency fvin when the frequency fvin of the three-phase AC Vin fluctuates due to rapid fluctuations in the AC load 92, etc. Therefore, fluctuations in the frequency fvin of the power input from the power grid, including renewable energy, can be suppressed.

[0040] Figure 6 shows the circuit configuration of the converter control unit 12B according to the third embodiment of the present invention. The converter control unit 12B according to the third embodiment has a configuration in which the power comparison unit 123 of the converter control unit 12 according to the first embodiment shown in Figure 2 is replaced with a DC deviation detection unit 128.

[0041] The DC deviation detection unit 128 receives a DC voltage Vdc as input and sequentially outputs the deviation ΔVdc of the DC voltage Vdc at predetermined time intervals.

[0042] The DC voltage command value correction unit 121A receives the deviation ΔVdc from the DC deviation detection unit 128. Based on the deviation ΔVdc, the DC voltage command value IVdc may be corrected within the range in which the DC voltage command value IVdc is a positive value. Specifically, the DC voltage command value I'Vdc may be corrected when the deviation ΔVdc increases.

[0043] The components other than the DC deviation detection unit 128 (DC voltage control unit 121, frequency detection unit 122, PLL 124, converter command generation unit 125, converter PWM signal control unit 126) have the same configuration as the converter control unit 12 shown in Figure 2, so their explanation is omitted.

[0044] In this way, the DC voltage command value correction unit 121A corrects the DC voltage command value IVdc based on the frequency fvin from the frequency detection unit 122, the deviation ΔVdc from the DC deviation detection unit 128, or both the frequency fvin and the deviation ΔVdc. This allows the semiconductor switching elements 4a to 4f of the converter circuit C to be controlled by PWM switching to suppress fluctuations in the frequency fvin when the frequency fvin of the three-phase AC Vin fluctuates due to rapid fluctuations in the AC load 92, etc. Therefore, fluctuations in the frequency fvin of the power input from the power grid, including renewable energy, can be suppressed.

[0045] Although this embodiment has been described above, it goes without saying that the technical scope of this embodiment should not be interpreted as being limited by this description. This embodiment is merely an example, and it will be understood by those skilled in the art that various modifications to the embodiment are possible within the scope of the invention described in the claims. The technical scope of this embodiment should be determined based on the scope of the invention described in the claims and the scope of its equivalents.

[0046] In this embodiment, the three-phase AC power supply 91 is a power grid consisting of a renewable energy generator, but it may also consist of a generator having an internal combustion engine. In that case, in addition to suppressing fluctuations in the frequency fvin of the power input from the power grid, the generator having an internal combustion engine can be miniaturized by suppressing the maximum rating of the output capacity while maintaining the output capacity of the generator having an internal combustion engine. Examples of generators having an internal combustion engine include engine generators, diesel generators, batteries, etc. [Explanation of Symbols]

[0047] 1: Power converter 2a~2c: Input filter capacitors 3a~3c: Input filter reactor 4a~4f: Semiconductor switching elements 5: Smoothing Capacitor 6a~6f: Semiconductor switching elements 7a~7c: Output filter reactor 8a~8c: Output filter capacitors 9: Energy storage devices 10a: DC power supply (storage battery) 10b: Energy storage capacitor 11: DC-DC converter 12, 12A, 12B: Converter control unit 13: Inverter Control Unit 121: DC Voltage Control Unit 121A: DC voltage command value correction unit 122: Frequency detection unit 123: Power Comparison Section 124: PLL 125: Converter Command Generation Unit 126: Converter PWM signal control unit 126a: Comparator 126b: Carrier signal generation unit 127: Power judgment section 128: DC deviation detection unit 131: AC Voltage Control Unit 132: Ideal sine wave generator 133: Inverter Command Generation Unit 134: Inverter PWM signal control unit 31a~31c: Device input terminals 41a~41c: AC input terminals 42a~42b: DC output terminal 61a~61b: DC input terminals 62a~62c: AC output terminals 71a~71c: Device output terminals 91: Three-phase AC power supply 92: AC load C: Converter circuit I: Inverter circuit D: DC circuit F1: Input filter F2: Output filter S: Smoothing circuit

Claims

1. A converter circuit connected to a power grid including renewable energy generators, which converts alternating current input from the power grid into direct current, A smoothing circuit consisting of a capacitor is connected in series with the converter circuit, A power storage device connected in series with the converter circuit and in parallel with the smoothing circuit, The smoothing circuit and the energy storage device are connected in series with the smoothing circuit and an inverter circuit that converts the DC from the smoothing circuit or the DC from the energy storage device into AC and outputs it to an AC load. A converter control unit that performs PWM control of the converter circuit based on a DC voltage command value, The inverter control unit controls the inverter circuit using PWM, Equipped with, The converter control unit, A DC voltage control unit having a DC voltage command value correction unit, A frequency detection unit for detecting the frequency of AC input from the power grid, Equipped with, The DC voltage control unit generates the DC voltage command value from the difference between the DC voltage reference value and the DC voltage supplied from the converter circuit to the inverter circuit. The DC voltage command value correction unit corrects the DC voltage command value within a range in which the DC voltage command value becomes a positive value, based on the frequency of the AC input from the power grid detected by the frequency detection unit. The DC voltage command value correction unit corrects the DC voltage command value to increase when the frequency of the AC detected by the frequency detection unit increases, and corrects the DC voltage command value to decrease when the frequency of the AC decreases. The converter control unit, A converter reference waveform is generated based on a sinusoidal reference signal derived from the AC voltage of the power grid and the corrected DC voltage command value. A power conversion device that performs PWM control of the converter circuit based on the converter reference waveform.

2. The converter control unit includes a power comparison unit that compares the DC power supplied from the energy storage device to the inverter circuit with a threshold value calculated based on the output power of the inverter circuit. The power conversion device according to claim 1, wherein if the power comparison unit determines that the DC power exceeds the threshold, the DC voltage command value correction unit corrects the DC voltage command value to be larger.

3. The power comparison unit is comprised of a comparator, as described in claim 2.

4. The power comparison unit is comprised of a power difference detection unit that detects the power difference between the DC power and the threshold value. The power conversion device according to claim 2, wherein, if the power difference detection unit determines that the DC power exceeds the threshold, the DC voltage command value correction unit corrects the DC voltage command value to increase by a proportion corresponding to the power difference detected by the power difference detection unit.

5. The converter control unit includes a power determination unit that determines whether the AC power input from the power grid exceeds a predetermined threshold, The power conversion device according to claim 1, wherein if the power determination unit determines that the AC power input from the power grid has fallen below the threshold, the DC voltage command value correction unit corrects the DC voltage command value to increase it.

6. The converter control unit has a DC deviation detection unit that detects the deviation of the DC voltage, The power conversion device according to claim 1, wherein if the DC deviation detected by the DC deviation detection unit increases, the DC voltage control unit corrects the DC voltage command value according to the DC deviation.

7. The power conversion device according to claim 1, further comprising a DC circuit connected in series with the converter circuit and in parallel with the smoothing circuit, the DC circuit comprising a DC power supply.

8. A converter circuit connected to a power grid including renewable energy generators and generators with internal combustion engines, which converts alternating current input from the power grid into direct current, A smoothing circuit consisting of a capacitor is connected in series with the converter circuit, A power storage device connected in series with the converter circuit and in parallel with the smoothing circuit, The smoothing circuit and the energy storage device are connected in series with the smoothing circuit and an inverter circuit that converts the DC from the smoothing circuit or the DC from the energy storage device into AC and outputs it to an AC load. A converter control unit that performs PWM control of the converter circuit based on a DC voltage command value, The inverter control unit controls the inverter circuit using PWM, Equipped with, The converter control unit, A DC voltage control unit having a DC voltage command value correction unit, A frequency detection unit for detecting the frequency of AC input from the power grid, Equipped with, The DC voltage control unit generates the DC voltage command value from the difference between the DC voltage reference value and the DC voltage supplied from the converter circuit to the inverter circuit. The DC voltage command value correction unit corrects the DC voltage command value within a range in which the DC voltage command value becomes a positive value, based on the frequency of the AC input from the power grid detected by the frequency detection unit. The DC voltage command value correction unit corrects the DC voltage command value to increase when the frequency of the AC detected by the frequency detection unit increases, and corrects the DC voltage command value to decrease when the frequency of the AC decreases. The converter control unit, A converter reference waveform is generated based on a sinusoidal reference signal derived from the AC voltage of the power grid and the corrected DC voltage command value. A power conversion device that performs PWM control of the converter circuit based on the converter reference waveform.

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