Power Conversion Device

Abstract

To provide power conversion equipment capable of supplying power stably in grid-connected operation and autonomous operation.SOLUTION: Power conversion equipment is provided, converting input power into a single-phase or three-phase AC power and outputs the converted AC power, the power conversion equipment comprises: a valid / invalid output current calculation unit that calculates a valid output current value and an invalid output current value on the basis of an output current value detected by a current detector; a valid / invalid output voltage value calculation unit that calculates a valid output voltage value and an invalid output voltage value on the basis of an output voltage value detected by a voltage detector; an invalid output voltage control unit that adjusts an invalid output voltage target value on the basis of a valid output current target value, the valid output current value, and the invalid output voltage value; and a valid output voltage control unit that adjusts a valid output voltage target value on the basis of an invalid output current target value, the invalid output current value, and the valid output voltage value.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a power conversion device that can be connected to a commercial power system and can also operate independently. [Background technology]

[0002] Conventionally, a system has been proposed that is connected to a commercial power grid and operates in parallel with multiple distributed power sources such as storage batteries and solar cells using multiple power conversion devices during stand-alone operation. In such a system, parallel operation control is performed with frequency droop due to effective power, so the frequency changes depending on the output power. As a result, problems occur with loads whose operating frequency range is limited to a specific frequency range (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6809753 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention has been made in view of the above-mentioned problems, and has an object to provide a power conversion device that can supply stable power during grid-connected operation and stand-alone operation. [Means for solving the problem]

[0005] To solve the above problems, the present invention provides: A power conversion device that converts input power into single-phase or three-phase AC power and outputs the power, an effective and reactive output current calculation unit that calculates an effective output current value and a reactive output current value based on the output current value detected by the current detector; an effective / inactive output voltage value calculation unit that calculates an effective output voltage value and an inactive output voltage value based on the output voltage value detected by the voltage detector; a reactive output voltage control unit that adjusts a reactive output voltage target value based on an active output current target value, the active output current value, and the reactive output voltage value; an effective output voltage control unit that adjusts an effective output voltage target value based on a reactive output current target value, the reactive output current value, and the effective output voltage value; The present invention is characterized by the following.

[0006] According to this, the output voltage target value is adjusted based on the detected output current value and output current target value, and single-phase or three-phase output power can be controlled by an output voltage command value generated based on the adjusted output voltage target value. By appropriately setting the output current target value and output voltage target value during grid-connected operation and during stand-alone operation, including parallel operation of multiple units, the output power can be controlled, thereby enabling a stable power supply. Furthermore, since the control system can be shared between grid-connected operation and stand-alone operation, it is sufficient to change the target value setting when transitioning between grid-connected operation and stand-alone operation, and there is no need to switch the control system itself, allowing for uninterrupted switching. The power conversion device of the present invention may be a device that has the function of converting DC power input from a storage battery, a PV panel, etc. into single-phase or three-phase AC power, or may be a device configured as a UPS (uninterruptible power supply).

[0007] In addition, in the present invention, During grid-connected operation in which the power conversion device is operated in connection with a commercial power system, At least one of the active output current target value and the reactive output current target value may be changed between during isolated operation in which the power generation system is paralleled off and during isolated operation in which the power generation system is paralleled off.

[0008] In this way, by changing at least one of the active output current target value and the reactive output current target value, it is possible to supply power stably according to the operating state of the power conversion device. For example, the active output current target value and the reactive output current target value can be set to 0 during stand-alone operation, and can be set to an appropriate value depending on the output current during grid-connected operation. In this way, by setting the active output current target value and the reactive output current target value to 0 during stand-alone operation, it is possible to suppress cross currents caused by imbalance between power conversion devices when multiple power conversion devices are operated in parallel. Furthermore, they may be set to an appropriate value other than 0 depending on the balance of the power conversion devices.

[0009] In addition, in the present invention, At least one of the active output voltage target value and the reactive output voltage target value may be changed between grid-connected operation in which the power conversion device is connected to a commercial power grid and stand-alone operation in which the power conversion device is disconnected from the commercial power grid.

[0010] In this way, by changing at least one of the active output voltage target value and the reactive output voltage target value, it is possible to supply electric power stably according to the operating state of the power conversion device. For example, during grid-connected operation, the active output voltage target value and the reactive output voltage target value may be set to the voltage values of the commercial power grid, and an output voltage value for self-propelled operation may be set.

[0011] In addition, in the present invention, An output impedance control unit may be provided to control the output impedance when the power is output.

[0012] In this way, the output impedance can be controlled to stabilize the system. Furthermore, by adjusting the output impedance through control, there is no need to change components to change the impedance, which helps reduce costs and size.

[0013] In addition, in the present invention, a current rotational coordinate transformation unit that performs a rotational coordinate transformation on the output current value to calculate the active output current value and the reactive output current value; a voltage rotation coordinate transformation unit that performs a rotation coordinate transformation on the output voltage value to calculate the effective output voltage value and the reactive output voltage value; The above configuration may be adopted.

[0014] In this way, by using the rotating coordinate transformation, it is possible to calculate the active output current value and the reactive output current value from the detected output current value, and to calculate the active output voltage value and the reactive output voltage value from the detected output voltage value. For example, in the case of a three-phase power conversion device, the three-phase current or three-phase voltage can be converted into a two-phase current or two-phase voltage by an αβ transformation, and then a dq transformation, which is a rotating coordinate transformation, can be applied. Also, in the case of a single-phase power conversion device, the single-phase voltage or single-phase current can be two-dimensionalized by a Hilbert transform, and then a dq transformation, which is a rotating coordinate transformation, can be applied. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a power conversion device capable of supplying stable power during grid-connected operation and stand-alone operation. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a diagram showing a schematic configuration of a power conditioner according to an embodiment of the present invention; [Figure 2] FIG. 2 is a diagram showing another schematic configuration of a power conditioner according to an embodiment of the present invention. [Figure 3] FIG. 2 is a diagram illustrating an inverter model according to an embodiment of the present invention. [Figure 4] FIG. 2 is a diagram illustrating a control system for current feedback control according to an embodiment of the present invention. [Figure 5] FIG. 1 is a diagram illustrating a control system including virtual impedance control according to an embodiment of the present invention. [Figure 6] FIG. 2 is a diagram illustrating a control system for virtual impedance control according to an embodiment of the present invention. [Figure 7]FIG. 10 is a diagram showing a simulation result of virtual impedance control according to an embodiment of the present invention. [Figure 8] FIG. 10 is a diagram showing a simulation result of virtual impedance control according to an embodiment of the present invention. [Figure 9] FIG. 10 is a diagram showing another simulation result of the virtual impedance control according to the embodiment of the present invention. [Figure 10] FIG. 10 is a diagram showing another simulation result of the virtual impedance control according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] [Application example] Hereinafter, application examples of the present invention will be described with reference to the drawings.

[0018] FIG. 1 is a diagram showing a schematic configuration of a power conditioner 1 according to an application example of the present invention.

[0019] A main circuit 10 of the power conditioner 1 includes a DC / DC converter 13 connected to a PV panel 12, a DC / DC converter 16 connected to a storage battery 15, and an inverter 14, and is capable of interconnected operation with a commercial power grid 11.

[0020] The control unit 20 includes a Hilbert transform unit 23A, a Hilbert transform unit 24A, a dqPLL 25, an αβ / dq conversion unit 26A, an αβ / dq conversion unit 27A, a governor 28, an id / iq feedback control unit 29, an output impedance control unit 30, a decoupling control unit 31, a switch 32, a power command generation unit 33, a compensator 34, and a dq / αβ conversion unit 35A.

[0021] FIG. 4 shows a control system 140 of current feedback control realized by a configuration included in an area 40 of the power conditioner 1 indicated by a dashed line. Here, the d-axis output voltage e od is the q-axis inverter output current i nq and q-axis output current target value I nqref The q-axis output voltage e is regulated by a current loop consisting ofoq is the d-axis inverter output current i nd and d-axis output current target value I ndref The current is adjusted by a current loop consisting of the power conditioner 1 and the grid-connected inverter 2. By using this control system 140, the power conditioner 1 can share a control system for parallel operation control of the power conditioner during stand-alone operation and current control during grid-connected operation. This allows control to be switched from grid-connected operation to stand-alone operation without interruption, enabling stable power supply regardless of whether the operation is stand-alone or grid-connected. In addition, since the output current target values for the d-axis and q-axis can be set, the cross current, which is generally set to 0 during parallel operation, can be controlled to an arbitrary value. In addition, the power conditioner 1 performs parallel operation control using current feedback control without using frequency-based droop control, so there is no frequency change.

[0022] Example 1 Hereinafter, a power conditioner 1 according to a first embodiment of the present invention will be described in more detail with reference to the drawings. However, the configuration of the device and system described in this embodiment may be different from that of each The examples should be appropriately modified depending on various conditions, and the scope of the present invention is not limited to the following examples.

[0023] 1 and 2 are diagrams showing a schematic configuration of a main circuit 10 and a control unit 20 of a power conditioner 1 according to a first embodiment of the present invention. The power conditioner 1 has a function of converting power input from a PV panel 12 or a storage battery 15 into single-phase or three-phase AC power and outputting the power. FIGS. 1 and 2 are diagrams explaining the case where single-phase AC power and three-phase AC power are output, respectively. Below, configurations that differ between the case where single-phase AC power is output from the power conditioner 1 and the case where three-phase AC power is output will be explained with reference to FIGS. 1 and 2, respectively, and configurations that are common between the cases will be explained without distinguishing between FIGS. 1 and 2. A main circuit 10 of the power conditioner 1 includes a DC / DC converter 13 connected to a PV panel 12, a DC / DC converter 16 connected to a storage battery 15, and an inverter 14, and is capable of interconnected operation with a commercial power grid 11. DC / DC converter 13 converts the voltage of DC power generated by PV panel 12 and outputs it to inverter 14. DC / DC converter 16 converts the voltage of power discharged from storage battery 15 and outputs it to inverter 14. DC / DC converter 16 also converts the voltage of input DC power to charge storage battery 15. Inverter 14 converts DC power input from DC / DC converter 13 and / or DC / DC converter 16 into AC power and outputs it to commercial power grid 11 and / or a load.

[0024] 1, the control unit 20 includes a Hilbert transformer 23A, a Hilbert transformer 24A, a dqPLL 25, an αβ / dq converter 26A, an αβ / dq converter 27A, a governor 28, an id / iq feedback controller 29, an output impedance controller 30, a decoupling controller 31, a switch 32, a power command generator 33, a compensator 34, and a dq / αβ converter 35A. The control unit includes a computer including a CPU (Central Processing Unit) and a memory, a DS It can be configured with P (Digital Signal Processor), ASIC (Application Specific Integrated Circuit), etc. Some or all of the functions of each part can be implemented in hardware. The functions may be realized by executing software on a processor or by dedicated hardware. The control unit 20 shown in Figure 2 includes an αβ conversion unit 23B, an αβ conversion unit 24B, a dqPLL 25, an αβ / dq conversion unit 26B, an αβ / dq conversion unit 27B, a governor 28, an id / iq feedback control unit 29, an output impedance control unit 30, a decoupling control unit 31, a switch 32, a power command generation unit 33, a compensator 34, and a dq / αβ conversion unit 35B.

[0025] First, referring to Fig. 1, a case will be described where single-phase AC power is output from inverter 14. An output current value detected by current detector 21 provided on the output side of inverter 14 is Hilbert transformed in Hilbert transformer 23A. The single-phase output current value converted into a two-dimensional vector by Hilbert transform in Hilbert transformer 23A is output to αβ / dq transformer 26A. Next, with reference to Fig. 2, a case where three-phase AC power is output from the inverter 14 will be described. In this case, the control unit 20 has an αβ conversion unit 23B that converts three-phase AC power into two-phase AC power, instead of the Hilbert transformer 23A. The output current value of the three-phase current detected by the current detector 21 is converted into a two-dimensional vector by αβ conversion in the αβ conversion unit 23B, and output to the αβ / dq conversion unit 26B.

[0026] 1, a case will be described where single-phase AC power is output from inverter 14. The output voltage value detected by voltage detector 22 provided on the output side of inverter 14 is subjected to Hilbert transformation in Hilbert transformer 24A. The output voltage value of the single-phase voltage converted into a two-dimensional vector by the Hilbert transform in 24A is output to an αβ / dq conversion unit 27A. Next, with reference to Fig. 2, a case where three-phase AC power is output from the inverter 14 will be described. In this case, the control unit 20 has an αβ conversion unit 24B that converts a three-phase voltage into a two-phase voltage, instead of the Hilbert transformer 24A. The output voltage value detected by the voltage detector 22 is converted into a two-dimensional vector by αβ conversion in the αβ conversion unit 24B, and is output to the αβ / dq conversion unit 27B.

[0027] The output voltage value detected by the voltage detector 22 is input to the dqPLL 25. The dqPLL 25 is a dq-based PLL (Phase Lock Loop). calculates the phase θ of the output voltage from the output voltage value, and also calculates the frequency change Δf of the output voltage. The phase θ calculated in the dqPLL 25 is output to an αβ / dq converter 26A(B) (this abbreviation is used instead of listing the αβ / dq converter 26A and the αβ / dq converter 26B separately; the same applies below), an αβ / dq converter 27A(B), and a dq / αβ converter 35A(B), and the frequency change Δf is output to a governor 28.

[0028] First, referring to Fig. 1, a case where single-phase AC power is output from the inverter 14 will be described. When the output current value converted into a two-dimensional vector from the Hilbert transformer 23A is input to the αβ / dq converter 26A, the αβ / dq converter 26A converts the output current value into an output current value in a dq coordinate system, which is a rotating coordinate system, by dq transformation. The q axis corresponds to the active component (here, the active output current value), and the d axis corresponds to the reactive component (here, the reactive output current value). At this time, the phase θ input from the dq PLL 25 is used for the dq transformation. Here, the dq transformation corresponds to the rotating coordinate transformation, and the αβ / dq converter 26A corresponds to the current rotating coordinate transformation unit. The Hilbert transformer 23A and the αβ / dq converter 26A correspond to the active and reactive current calculation unit of the present invention. Next, referring to Fig. 2, a case where three-phase AC power is output from the inverter 14 will be described. In this case, when the output current value obtained by converting the three-phase current value detected by the current detector 21 into a two-phase current value is input from the αβ conversion unit 23B, the αβ / dq conversion unit 26B converts the output current value into an output current value in a dq coordinate system by dq transformation. Here, the dq transformation corresponds to a rotational coordinate transformation, and the αβ / dq conversion unit 26B corresponds to a current rotational coordinate transformation unit. The αβ conversion unit 23B and the αβ / dq conversion unit 26B correspond to an active and reactive current calculation unit of the present invention.

[0029] First, referring to Fig. 1, a case where single-phase AC power is output from the inverter 14 will be described. When the output voltage value converted into a two-dimensional vector is input from the Hilbert transformer 24A, the αβ / dq converter 27A converts it into an output voltage value in a dq coordinate system, which is a rotating coordinate system, by dq transformation. The q axis corresponds to the active component (here, the active output voltage value), and the d axis corresponds to the reactive component (here, the reactive output voltage value). At this time, the phase θ input from the dq PLL 25 is used for the dq transformation. Here, the dq transformation corresponds to the rotating coordinate transformation of the present invention, and the αβ / dq converter 27A corresponds to the voltage rotating coordinate converter of the present invention. The Hilbert transformer 24A and the αβ / dq converter 27A correspond to the active and reactive current calculation unit of the present invention. Next, referring to FIG. 2, a case where three-phase AC power is output from the inverter 14 will be described. In this case, when the output voltage value obtained by converting the three-phase voltage values detected by the voltage detector into two-phase voltage values is input from the αβ conversion unit 24B, the αβ / dq conversion unit 27B converts the output voltage value into an output voltage value in the dq coordinate system by dq transformation. The q axis corresponds to the active component (here, the active output voltage value), and the d axis corresponds to the reactive component (here, the reactive output voltage value). In this case, the phase θ input from the dq PLL 25 is used for the dq transformation. Here, the dq transformation corresponds to the rotating coordinate transformation of the present invention, and the αβ / dq conversion unit 27B corresponds to the voltage rotating coordinate conversion unit of the present invention. The αβ conversion unit 24B and the αβ / dq conversion unit 27B correspond to the active and reactive current calculation unit of the present invention.

[0030] When the frequency is decreased / increased due to the frequency conversion Δf detected by the dqPLL 25, the governor 28 performs governor control to increase / decrease the output power of the inverter 14.

[0031] The id / iq feedback control unit 29 performs id / iq current feedback control, which will be described later.

[0032] The output impedance control section 30 performs output impedance control, which will be described later.

[0033] The decoupling control unit 31 decouplings the d-axis component and the q-axis component by feedforward control.

[0034] The power command generation unit 33 is capable of calculating the amount of power consumption from the commercial power system 11, and generates commands regarding the power to be output from the DC / DC converters 13 and 16, and outputs these to the DC / DC converters 13 and 16.

[0035] When the power conditioner 1 is operated in a grid-connected manner with the commercial power grid, the switch 32 connects the αβ / dq conversion unit 27A(B) to the inputs of the output impedance control unit 30 and the decoupling control unit 31. When the power conditioner 1 is disconnected from the commercial power grid and operated in an independent manner, the switch 32 is switched, and the set output voltage target value is input to the output impedance control unit 30 and the decoupling control unit 31.

[0036] First, referring to Fig. 1, a case where single-phase AC power is output from the inverter 14 will be described. The compensator 34 and the dq / αβ converter 35A constitute the inverter control unit. The compensator 34 generates an output voltage command in the dq coordinate system, and the dq / αβ converter 35A uses the phase θ input from the dq PLL 25 to perform inverse conversion to a single-phase voltage value and output it to the inverter 14. Next, with reference to Fig. 2, a case where three-phase AC power is output from the inverter 14 will be described. The compensator 34 and the dq / αβ converter 35B constitute an inverter control unit. The compensator 34 generates an output voltage command in the dq coordinate system, and the dq / αβ converter 35B uses the phase θ input from the dq PLL 25 to perform inverse conversion to a three-phase voltage value and output it to the inverter 14.

[0037] (id / dq current feedback control) In FIG. 1, the current feedback control realized by the configuration included in an area 40 indicated by a dashed line and including the id / dq feedback control unit 29 will be described.

[0038] Conventionally, when power conditioners are operated in parallel, the output active power can be controlled by the phase difference, and the reactive power can be controlled by the amplitude, so parallel operation control has been achieved by frequency droop due to active power and amplitude droop due to reactive power. Figure 2 shows a model of each inverter in a system in which N inverters are operated in parallel. n is the inverter voltage, r is the resistance, L is the inductance, i n is the inverter output current, C is the capacitor, i c is the current through the capacitor, e o is the output voltage, i crn indicates a cross current. Z LN is the total system load Z L This is converted into a per unit figure.

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[0039] Here, since the parallel operation of inverters is equivalent to the parallel operation of a commercial power grid and a power conditioner, the same scheme as for controlling the parallel operation of inverters can be used to control the grid-connected operation of a power conditioner. For example, the control system 140 shown in Figure 4 can be considered as a control system that sets an output current target value for the droop control using the above-mentioned active current and reactive current and configures a feedback loop.

[0040] The q-axis inverter output current i input to the summing point nq From the above, the q-axis output current target value I nqref is subtracted, multiplied by the gain element kqr, and input to the summing point. The d-axis system voltage e od and at the summing point, the d-axis system voltage e od is subtracted and input to the compensator. Also, the d-axis inverter output current i nd From the above, the d-axis output current target value I ndref is subtracted, multiplied by the gain element kdr, and input to the summing point. The q-axis system voltage e oq and at the summing point, the q-axis system voltage e oq is subtracted and input to the compensator. Here, the q-axis output current target value I nqref and d-axis output current target value I ndref correspond to the active output current target value and the reactive output current target value of the present invention, respectively. Here, since the system is in interconnected operation, the d-axis system voltage e od and q-axis system voltage e oq is input, but in parallel operation during stand-alone operation, the d-axis output voltage target value e odref and q-axis output voltage target value e oqref Here, the d-axis output voltage target value e odref and q-axis output voltage target value e oqrefcorrespond to the active output voltage target value and the reactive output voltage target value of the present invention, respectively. The control system 140 corresponds to the reactive output voltage control unit and the active output voltage control unit of the present invention.

[0041] Here, the d-axis output voltage target value, which is an active component, is adjusted by the q-axis output current, which is a reactive component, and the q-axis output voltage target value, which is a reactive component, is adjusted by the d-axis output current, which is an active component.

[0042] In this way, by making the droop control a current loop, it is possible to share the control system for parallel operation control of power conditioners during stand-alone operation and current control during grid-connected operation.

[0043] In addition, the control system 140 determines the d-axis output current target value I ndref and q-axis output current target value I nqref Therefore, the cross current, which is generally set to 0 during parallel operation, can be set to any value. The cross current can be controlled to a value. Parallel operation is generally performed between similar devices. However, when power conditioners with different capacities are operated in parallel, setting the cross current to zero results in the large-capacity power conditioner having the same output power as the small-capacity power conditioner, resulting in ineffective utilization of the large-capacity power conditioner. Furthermore, when power storage power conditioners are operated in parallel, setting the cross current to zero results in the same output power regardless of the charge level of the storage batteries, resulting in the problem of limited operating time due to batteries with low charge levels. The control system 140 of this embodiment can set an output current target value for each power conditioner operated in parallel, thereby controlling the cross current to any value. Therefore, the large-capacity power conditioner can be effectively utilized in the parallel operation of power conditioners with different capacities, and the operating time is not limited by batteries with low charge levels even in the parallel operation of power storage power conditioners.

[0044] (output impedance control) Next, the output impedance control realized by an area 50 enclosed by a dotted line in FIGS. 1 and 2, which includes the output impedance control unit 30, will be described. A configuration for virtually changing the output impedance in the control system during parallel operation will be described.

[0045] First, the control system of the configuration shown in FIG. 5 will be examined. In the control system shown in Figure 5, the feedback output current i o is input to the compensator Zps for changing the impedance. Then, at the summing point 61, the output voltage target value e orf The output of the compensator Zps is subtracted from the summation point 62. drp The feedback output voltage eo is subtracted from e and input to the compensator 34. The output of the compensator 34 is then input to the plant (here, the inverter 14). drp is expressed by the following equation, which gives a drooping characteristic to the target value of the voltage control system.

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[0046] If there is a voltage control system, the transfer functions of the plant and compensator are G dv and C mp Here, G dv is expressed by the following equation:

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[0047] At this time, the block diagram of the control system 150 is as shown in FIG. 6. Here, Δe oref From the feedback Δe o is subtracted, and the transfer function C mp , the transfer function G representing the plant dv The transfer function G dv At the summing point on the output side of dv From the output of vr Δi multiplied by o Δe subtracted o will be output. According to Figure 6,

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[0048] As described above, the power conditioner 1 performs parallel operation control using current feedback control without using droop control, so there is no change in frequency. Furthermore, because current feedback control is used, output current control during grid-connected operation and parallel operation control during islanded operation can be achieved using a common control system. In this way, by sharing a control system between output current control during grid-connected operation and parallel operation control during islanded operation, control can be switched from grid-connected operation to islanded operation without interruption, enabling a stable power supply regardless of whether the operation is islanded or grid-connected.

[0049] Figure 8 shows the simulation results for a single unit, switching from output current control to islanded operation without interruption. There was a 1.5-second power outage before switching to islanded operation without interruption, and before the power outage the system was controlled at a current target value with a peak of 10A and a lagging power factor of 0.8, and after the power outage a resistive load was used with a peak of 20A. Also, before the power outage the system frequency was 50.2Hz, and after the power outage the system was operated at a free-running frequency. Figure 8 shows that the system continued to operate normally even after the switchover without interruption.

[0050] Figure 9 shows the simulation results for a resistive load when switching to two-unit parallel operation without interruption. Figure 10 shows the simulation results for a rectifier load when switching to two-unit parallel operation without interruption. In both cases, after switching, there is a disturbance in the waveform for a similar period, which is thought to depend on the response time of the control system, but it can be seen that regardless of the load, normal operation continues even after switching without interruption.

[0051] In the above-described embodiment, the power conditioner 1 is described as a power conversion device. However, the configuration of the control system including the current feedback control and virtual feedback control in the control unit 20 described above can be similarly applied to a UPS as a power conversion device. In the event of a power outage or other trouble in the commercial power system, it is possible to switch without interruption from normal operation in which power is supplied to a load from the commercial power system to backup operation in which power is supplied from the storage battery 15 or the like, thereby enabling a stable power supply.

[0052] <Appendix 1> A power conversion device (1) that converts input power into single-phase or three-phase AC power and outputs the power, an effective and ineffective output current calculation unit (23A, 26A) that calculates an effective output current value and an ineffective output current value based on the output current value detected by the current detector (21); an effective / ineffective output voltage value calculation unit (24A, 27A) that calculates an effective output voltage value and an ineffective output voltage value based on the output voltage value detected by the voltage detector (22); a reactive output voltage control unit (140) that adjusts a reactive output voltage target value based on an active output current target value, the active output current value, and the reactive output voltage value; an active output voltage control unit (140) that adjusts an active output voltage target value based on a reactive output current target value, the reactive output current value, and the active output voltage value; A power conversion device (1) comprising: [Explanation of symbols]

[0053] 1: Power conditioner 21: Power detector 22: Voltage detector 23A, 24A: Hilbert transformer 23B, 24B: αβ conversion section 26A, 26B, 27A, 27B: αβ / dq conversion section

Claims

1. A power conversion device that converts input power into single-phase or three-phase AC power and outputs the power, an effective and reactive output current calculation unit that calculates an effective output current value and a reactive output current value based on the output current value detected by the current detector; an effective / inactive output voltage value calculation unit that calculates an effective output voltage value and an inactive output voltage value based on the output voltage value detected by the voltage detector; a reactive output voltage control unit that adjusts a reactive output voltage target value based on an active output current target value, the active output current value, and the reactive output voltage value; an effective output voltage control unit that adjusts an effective output voltage target value based on a reactive output current target value, the reactive output current value, and the effective output voltage value; A power conversion device comprising:

2. 2. The power conversion device according to claim 1, wherein at least one of the active output current target value and the reactive output current target value is changed during grid-connected operation in which the power conversion device is connected to a commercial power grid and during stand-alone operation in which the power conversion device is disconnected from the commercial power grid.

3. 2. The power conversion device according to claim 1, wherein at least one of the active output voltage target value and the reactive output voltage target value is changed during grid-connected operation in which the power conversion device is connected to a commercial power grid and during stand-alone operation in which the power conversion device is disconnected from the commercial power grid.

4. 4. The power conversion device according to claim 1, further comprising an output impedance control unit that controls an output impedance when the power is output.

5. a current rotational coordinate transformation unit that performs a rotational coordinate transformation on the output current value to calculate the active output current value and the reactive output current value; a voltage rotation coordinate transformation unit that performs a rotation coordinate transformation on the output voltage value to calculate the effective output voltage value and the reactive output voltage value; The power conversion device according to any one of claims 1 to 4, further comprising:

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