Power converter control device, power converter control method, and power converter control program

Abstract

This invention provides a specific method for incorporating inertial force into the command value of the current output by a power converter in a power converter control device that controls the voltage output by a power converter connected to a power line for supplying power from a power system to a load. [Solution] The power converter control device 60 includes a frequency fluctuation suppression unit 64 that outputs a current command value to suppress frequency fluctuations of the generator G based on the connection point voltage, which is the voltage at the connection point where the power converter 40 is connected to the power line B, and the output current of the generator G connected to the power line B.

Description

[Technical Field]

[0001] This invention relates to a power converter control device, a power converter control method, and a power converter control program. [Background technology]

[0002] Power fluctuations in the power grid cause voltage fluctuations due to power fluctuations from loads or distributed power sources connected to power lines supplied with power from the power grid. Therefore, in order to suppress the voltage of the power grid, power converter control devices have been developed that connect power converters, which convert DC power from DC power sources such as solar cells or storage batteries into AC power, to the power lines and control the voltage output from those power converters.

[0003] Examples of this type of power converter control device include, for instance, as shown in Patent Document 1, a device that calculates a counter voltage, which is a voltage with the same phase and amplitude as the voltage of the power system, and the amount of voltage change when the power converter outputs a desired current command value. By outputting a voltage obtained by combining the counter voltage and the amount of voltage change from the power converter, the voltage fluctuations of the power system are canceled out by the counter voltage, and the power system outputs a current according to the current command value. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 7495654 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] Incidentally, with the recent shift towards renewable energy as the primary power source, it is anticipated that many renewable energy sources, such as solar power generators, wind turbines, and storage batteries, will be connected to power lines via power converters that do not have the function to suppress frequency fluctuations. In this case, if a renewable energy source is disconnected, the frequency of the power grid will become unstable, and in the worst case, there is a risk of widespread power outages.

[0006] Therefore, it has been considered to include inertial force in the output current command value of the power converter control device described above. Here, "including inertial force" means that the generator supplying power to the load has the ability to autonomously reduce the frequency change of the power system. However, no specific method for including inertial force in the output current command value of the power converter control device described above is currently known.

[0007] Therefore, the present invention has been made in view of the above problems, and its main objective is to provide a specific method for including inertial force in the command value of the current to be output by a power converter in a power converter control device that controls the voltage output by a power converter connected to a power line for supplying power from a power system to a load. [Means for solving the problem]

[0008] In other words, the power converter control device according to the present invention is a power converter control device that controls the voltage output of a power converter connected to a power line for supplying power from a power system to a load, and is characterized by comprising: a counter voltage calculation unit that calculates a counter voltage which is a voltage having the same phase and amplitude as the voltage of the power system; a frequency fluctuation suppression unit that outputs a current command value to suppress frequency fluctuations of the generator based on a connection point voltage which is the voltage at the connection point where the power converter is connected to the power line and the output current of a generator connected to the power line; a positive-sequence voltage calculation unit that acquires the current command value output from the frequency fluctuation suppression unit and the phase of the power system, and calculates a positive-sequence voltage synchronized with the phase of the power system by open control from the current command value; and a voltage command value output unit that outputs a voltage command value which is a voltage obtained by combining the counter voltage and the positive-sequence voltage to the power converter.

[0009] With this power converter control device, the counter voltage calculation unit calculates a counter voltage that is in phase and has the same amplitude as the power system voltage, and the frequency fluctuation suppression unit outputs a current command value that suppresses the frequency fluctuation of the generator based on the connection point voltage and the generator output current. As a result, fluctuations in the system voltage are canceled out by the counter voltage, and the positive-sequence voltage output by the power converter can reliably suppress fluctuations in the system frequency. Consequently, the power converter can reliably impart inertial force to the power system.

[0010] The frequency fluctuation suppression unit calculates instantaneous active power based on the connection point voltage and the output current of the generator, and uses the difference between the instantaneous active power and the instantaneous active power applied to a low-pass filter having a predetermined time constant, divided by the rated amplitude value of the grid voltage, as the current command value.

[0011] With this configuration, the frequency fluctuation suppression unit calculates the instantaneous active power from the generator's output current, allowing it to respond instantly to fluctuations in the generator's output and suppress the generator's frequency fluctuations.

[0012] An inverse voltage calculation unit that obtains a phase command value of an inverse voltage and an output current command value that is an output current to be output to the power converter, and calculates an inverse voltage by open-loop control from the phase command value of the inverse voltage and the output current command value; and a non-fundamental wave component calculation unit that obtains a phase command value of a non-fundamental wave component, which is a frequency different from the fundamental frequency of the power system, and the output current command value, and calculates the non-fundamental wave component by open-loop control from the phase command value of the non-fundamental wave component and the output current command value. The voltage command value output unit outputs a voltage command value obtained by synthesizing the counter voltage, the positive-phase voltage, the inverse voltage, and the non-fundamental wave component to the power converter.

[0013] With this configuration, a current for compensating for voltage imbalance or non-fundamental wave components can be output from the power converter, so that the equivalent inverse-phase current of the generator can be suppressed, the heating and burnout of the winding can be prevented, and the utilization rate of the generator can be improved. In addition, since the inverse voltage or non-fundamental wave components can be arbitrarily output, harmonic voltage distortion or voltage imbalance caused by a single-phase load or a rectifier load can be suppressed, and the power quality can be improved. Also, in addition to the inverse voltage or non-fundamental wave components, the power converter outputs a voltage synthesized with the counter voltage, so that the voltage of the power system is canceled by the counter voltage, and only the inverse voltage or non-fundamental wave components are output to the power system. Therefore, regardless of the voltage fluctuation of the power system, only the inverse voltage or non-fundamental wave components can be reliably output to the power converter.

[0014] A method for controlling a power converter that controls the voltage output by a power converter connected to a power line for supplying power from a power system to a load calculates a counter voltage that is a voltage having the same phase and the same amplitude as the voltage of the power system, and based on a connection point voltage that is the voltage at the location where the power converter is connected to the power line and an output current of a generator connected to the power line, outputs a current command value for suppressing frequency fluctuations of the generator, obtains the current command value for suppressing frequency fluctuations of the generator and the phase of the power system, and calculates a positive-phase voltage so as to synchronize with the phase of the power system by open-loop control from the current command value, and outputs a voltage command value, which is a voltage obtained by synthesizing the counter voltage and the positive-phase voltage, to the power converter. A control program for a power converter that controls the voltage output by a power converter connected to a power line for supplying power from a power system to a load causes a computer to exhibit functions as a counter voltage calculation unit that calculates a counter voltage that is a voltage having the same phase and the same amplitude as the voltage of the power system, functions as a frequency fluctuation suppression unit that outputs a current command value for suppressing frequency fluctuations of the generator based on a connection point voltage that is the voltage at the location where the power converter is connected to the power line and an output current of a generator connected to the power line, functions as a positive-phase voltage calculation unit that obtains the current command value output from the frequency fluctuation suppression unit and the phase of the power system and calculates a positive-phase voltage so as to synchronize with the phase of the power system by open-loop control from the current command value, and functions as a voltage command value output unit that outputs a voltage command value, which is a voltage obtained by synthesizing the counter voltage and the positive-phase voltage, to the power converter.

[0015] With this configuration, the same operational effects as those of the above-described power converter control device can be obtained.

Advantages of the Invention

[0016] According to the present invention configured as described above, in a power converter control device that controls the voltage output by a power converter connected to a power line for supplying power from a power system to a load, a specific method for including an inertial force in a command value of a current to be output to the power converter can be provided. [Brief explanation of the drawing]

[0017] [Figure 1] This is a schematic diagram showing the configuration of the power system in this embodiment. [Figure 2] This figure shows the functional block of the power converter control device in the same embodiment. [Figure 3] This figure shows the functional block of the power converter control device in the same embodiment. [Modes for carrying out the invention]

[0018] An embodiment of the power system according to the present invention will be described below with reference to the drawings. Note that, for the sake of clarity, some details may be omitted or exaggerated in the following diagrams. The same components are denoted by the same reference numerals, and their descriptions are omitted as appropriate.

[0019] <System Configuration> In this embodiment, the power system 100 is connected to a power line B that supplies power from a power grid 10 to a load 20, and supplies AC power to the load 20. Specifically, the power system 100 includes a DC power supply 30 that supplies DC power, a power converter 40 that converts DC power to AC power and supplies AC power to the power line B, a measuring unit 50 that measures the current flowing through the power line B or the voltage of the power line B, and a power converter control device 60 that controls the voltage output by the power converter 40. As shown in Figure 1, the generator G is connected to the power line B via a power converter (not shown) that does not have a function to suppress frequency fluctuations. Here, the generator G is a distributed power source other than a battery, such as a solar power generator and / or a wind power generator. Each part will be described below.

[0020] The DC power source 30 is, for example, a non-rotating generator such as a solar power generator or a wind power generator, or a power storage device such as a storage battery or a secondary battery.

[0021] The power converter 40 converts the DC power supplied from the DC power source 30 into AC power and supplies it to power line B. Specifically, the power converter 40 is a GFM inverter (Grid forming inverter), which is a voltage-controlled inverter capable of supplying inertial force to power line B. As shown in Figure 1, the power converter 40 is connected to power line B from the high-voltage side via a circuit breaker S, a grid-connecting transformer T, and a grid-connecting reactor L.

[0022] The measuring unit 50 functions as a voltage measuring unit that measures the voltage of power line B using, for example, a known instrument transformer. Specifically, as shown in Figure 1, the measuring unit 50 measures the connection point voltage at connection point P, which is the point where the power converter 40 is connected to power line B. In this embodiment, the connection point voltage is the voltage between the circuit breaker S and the interconnection transformer T, and corresponds to the voltage of the power system 10.

[0023] Furthermore, the measuring unit 50 also functions as a current measuring unit that measures the current flowing through power line B using, for example, a known current transformer. Specifically, as shown in Figure 1, the measuring unit 50 measures the output current output from generator G.

[0024] The power converter control device 60 is a dedicated or general-purpose computer equipped with a CPU, internal memory, input / output interface, A / D converter, etc., and controls the voltage output by the power converter 40 based on predetermined command values. Specifically, the power converter control device 60 includes a counter voltage calculation unit 61 that calculates a counter voltage Vabc which is a voltage with the same phase and amplitude as the voltage of the power system 10, a voltage change amount calculation unit 62 that calculates the voltage change amount when the power converter 40 outputs an output current command value which is the current to be output by the power converter 40, and a voltage command value output unit 63 that outputs a voltage command value Vref which is the command value of the voltage to be output by the power converter 40. The power converter control device 60 may be integrated with the power converter 40, or it may be a separate device from the power converter 40.

[0025] The counter voltage calculation unit 61 acquires the voltage measured by the measurement unit 50, calculates a voltage with the same phase and amplitude as the voltage measured by the measurement unit 50, and defines the calculated voltage as the counter voltage Vabc. The phase used by the counter voltage calculation unit 61 when calculating the counter voltage Vabc may be obtained from the voltage measured by the measurement unit 50, or from phase information input via an external input means (not shown).

[0026] The voltage change calculation unit 62 acquires the output current command value, which is the current to be output by the power converter 40, and calculates the voltage change amount when the power converter 40 outputs the output current command value from the output current command value using open control. Open control, as used here, means calculating the voltage change amount from the output current command value using a known calculation method without feeding back the current output by the power converter 40.

[0027] In this embodiment, the output current command value is the effective current command value i, which is the command value of the current used to suppress voltage fluctuations in the power system 10. p ref and reactive current command value i q ref, the reverse-sequence current command value I2ref which is the command value of the current to suppress the imbalance between the fundamental voltage and fundamental current, and the non-fundamental current command value I which is the command value of the current to suppress harmonic voltage distortion. n It must contain at least one reference.

[0028] In this embodiment, the voltage change amount is the effective current command value i of the power converter 40. p ref and reactive current command value i q The positive-sequence voltage change ΔV1abc is the voltage change when outputting ref, the negative-sequence voltage change ΔV2abc is the voltage change when the power converter 40 outputs the negative-sequence current command value I2ref, and the non-fundamental wave current command value I n ΔV is the change in the non-fundamental wave component, which is the voltage change when outputting ref. n It must contain at least one of the letters a, b, or bc.

[0029] Specifically, the voltage change amount calculation unit 62 includes a positive-phase voltage calculation unit 621 that calculates the positive-phase voltage change amount ΔV1abc, a negative-phase voltage calculation unit 622 that calculates the negative-phase voltage change amount ΔV2abc, and a non-fundamental wave component calculation unit 623 that calculates the non-fundamental wave component change amount ΔV n abc.

[0030] The positive-phase voltage calculation unit 621 acquires the output current command value and the phase of the power system 10, and calculates the positive-phase voltage change amount ΔV1abc so as to be synchronized with the phase of the power system 10 by open-loop control from the output current command value. Specifically, the positive-phase voltage calculation unit 621 calculates the instantaneous voltage value ΔV p ref of the active current and the instantaneous voltage value ΔV q ref of the reactive current by open-loop control from the active current command value i p abc and the instantaneous voltage value ΔV q abc of the reactive power, and synthesizes the instantaneous voltage value ΔV p abc of the active power and the instantaneous voltage value ΔV q abc of the reactive power to calculate the positive-phase voltage change amount ΔV1abc. Hereinafter, the method by which the positive-phase voltage calculation unit 621 calculates the positive-phase voltage change amount ΔV1abc will be described.

[0031] The positive-phase voltage calculation unit 621 acquires the active current command value i p ref and the reactive current command value i q ref. Here, the active current command value i p ref and the reactive current command value i q ref include inertial forces. Note that "including inertial forces" means that the power converter 40 has the ability to autonomously reduce the frequency change of the power system 100.

[0032] Then, the positive-phase voltage calculation unit 621 multiplies the active current gain Kp corresponding to the active current and the reactive current gain Kq corresponding to the reactive current by the active current command value i p ref and the reactive current command value i qBy multiplying by ref, the voltage amplitude command value ΔEp for active power and the voltage amplitude command value ΔEq for reactive power are calculated. In this embodiment, the voltage amplitude command value ΔEp for active power and the voltage amplitude command value ΔEq for reactive power are RMS values. Here, the active current gain Kp and the reactive current gain Kq are determined by the connection impedance, which is the impedance of the equipment connecting the power converter 40 to the power line B. The connection impedance is determined to be approximately 10% to 15% of the equipment capacity of the connected equipment. The equipment capacity of the connected equipment referred to here is, for example, the equipment capacity of the connection transformer T and the equipment capacity of the harmonic filter reactor inside the power converter 40.

[0033] Furthermore, the positive-sequence voltage calculation unit 621 calculates the phase of the power system 10 based on the connection point voltage measured by the measurement unit 50. Specifically, as shown in Figures 2 and 3, the positive-sequence voltage calculation unit 621 acquires the connection point voltage measured by the measurement unit 50 and calculates the phase θ of the connection point voltage by applying that connection point voltage to a phase-locked loop (PLL). If the phase θ of the connection point voltage is out of phase with respect to a preset phase of the power system 10 voltage, the positive-sequence voltage calculation unit 621 corrects the phase θ of the connection point voltage using a phase correction value that corrects the out of phase and calculates the corrected phase θ'. In this embodiment, the corrected phase θ' is a second phase θ'q, which is 90 degrees behind the phase of the power system 10 voltage, and the positive-sequence voltage calculation unit 621 calculates a first phase θ'p, which is 90 degrees ahead of the second phase θ'q. The first phase θ'p is in phase with the phase of the power system 10 voltage.

[0034] Then, the positive-sequence voltage calculation unit 621 calculates the instantaneous voltage value ΔV in the active power using positive-sequence instantaneous voltage control, which is a control that converts the effective value of the voltage into an instantaneous value of the voltage from the voltage amplitude command value ΔEp and the first phase θ'p of the active power. p The positive-sequence voltage calculation unit 621 calculates the instantaneous voltage value ΔV of the reactive power from the reactive power voltage amplitude command value ΔEq and the second phase θ'q by positive-sequence instantaneous voltage control. q The positive-sequence voltage calculation unit 621 calculates abc. Then, the instantaneous voltage value ΔV of the active power is calculated. pabc and the instantaneous voltage value ΔV of reactive power q By combining abc, the positive-sequence voltage change ΔV1abc is calculated.

[0035] The reverse-phase voltage calculation unit 622 obtains the phase command value θ2ref of the reverse-phase voltage and the reverse-phase current command value I2ref, and calculates the reverse-phase voltage change ΔV2abc from the phase command value θ2ref of the reverse-phase voltage and the reverse-phase current command value I2ref using open-circuit control. The method by which the reverse-phase voltage calculation unit 622 calculates the reverse-phase voltage change ΔV2abc will be described below.

[0036] The reverse-phase voltage calculation unit 622 obtains the phase command value θ2ref of the reverse-phase voltage and the reverse-phase current command value I2ref via an external input means (not shown).

[0037] Next, the reverse-sequence voltage calculation unit 622 calculates the voltage amplitude command value ΔE2 of the reverse-sequence voltage by multiplying the reverse-sequence current command value I2ref by a predetermined gain K2. The gain K2 is determined by the interconnection impedance, similar to the active current gain Kp and the reactive current gain Kq.

[0038] Then, the reverse-phase voltage calculation unit 622 calculates the reverse-phase voltage change amount ΔV2abc from the voltage amplitude command value ΔE2 and the phase command value θ2ref of the reverse-phase voltage by reverse-phase instantaneous voltage control.

[0039] The non-fundamental wave component calculation unit 623 calculates the phase command value θn and the non-fundamental wave current command value I of the non-fundamental wave component. n Obtain the reference value and the phase command value θn and non-fundamental current command value I for the non-fundamental wave component. n From ref, open control is used to determine the change in non-fundamental wave components ΔV n This calculates abc. In this embodiment, non-fundamental components are, for example, harmonic components or inter-order harmonics. Below, the non-fundamental component calculation unit 623 calculates the non-fundamental component change amount ΔV n This explains how to calculate abc.

[0040] The non-fundamental wave component calculation unit 623 receives the phase command value θn and the non-fundamental wave current command value I from an external input means (not shown). n Obtain the reference value. Here, the phase command value θn of the non-fundamental wave component and the non-fundamental wave current command value I n Ref is a value determined by the order of the non-fundamental wave component.

[0041] Next, the non-fundamental wave component calculation unit 623 calculates the non-fundamental wave current command value I n The voltage amplitude command value ΔEn for the non-fundamental wave component is calculated by multiplying ref by a predetermined gain Kn. The gain Kn is determined by multiplying the interconnection impedance by the order of the non-fundamental wave component when the inductance component of the interconnection impedance is dominant (i.e., when the resistance component can be sufficiently ignored compared to the inductance component).

[0042] The non-fundamental wave component calculation unit 623 then calculates the voltage amplitude command value ΔEn of the non-fundamental wave component and the phase command value θ of the non-fundamental wave component. n From ref, instantaneous voltage control is used to determine the change in non-fundamental wave component ΔV. n Calculate abc.

[0043] The voltage command value output unit 63 calculates the voltage command value Vref by combining the opposing voltage Vabc and the voltage change amount, and outputs the voltage command value Vref to the power converter 40. Specifically, the voltage command value output unit 63 calculates the positive-sequence voltage change amount ΔV1abc, the negative-sequence voltage change amount ΔV2abc, and the non-fundamental wave component change amount ΔV n The voltage change is calculated by combining abc. Then, the voltage command value output unit 63 combines the opposing voltage Vabc and the voltage change to calculate the voltage command value Vref. When the voltage command value Vref is output from the voltage command value output unit 63, the power converter 40 outputs a voltage to the load 20 according to the voltage command value Vref, for example by PWM control.

[0044] The power converter control device 60 further includes a frequency fluctuation suppression unit 64 that outputs a current command value to suppress frequency fluctuations of the generator G based on the connection point voltage and the output current of the generator G. Specifically, as shown in Figure 3, the frequency fluctuation suppression unit 64 includes an instantaneous active power calculation unit 641 that calculates instantaneous active power based on the connection point voltage and the output current of the generator G, and a current command value calculation unit 642 that calculates a current command value to suppress frequency fluctuations of the generator G based on the instantaneous active power calculated by the instantaneous active power calculation unit 641.

[0045] The instantaneous active power calculation unit 641 obtains the connection point voltage and the output current of the generator G from the measurement unit 50 and calculates the instantaneous active power from the connection point voltage and the output current of the generator G.

[0046] The current command value calculation unit 642 obtains the instantaneous active power from the instantaneous active power calculation unit 641. The current command value calculation unit 642 then multiplies the instantaneous active power by a low-pass filter having a predetermined time constant to calculate the difference ΔP between the instantaneous active power and the instantaneous active power that has passed through the low-pass filter. The current command value calculation unit 642 then calculates the current command value by dividing the difference ΔP by the rated amplitude value of the voltage of the power system 10. Since the current command value is calculated based on the instantaneous active power, it is a value that includes inertial force.

[0047] The current command value calculated by the current command value calculation unit 642 is output to the positive-sequence voltage calculation unit 621. The positive-sequence voltage calculation unit 621 converts the current command value calculated by the current command value calculation unit 642 into an effective current command value i p Obtain it as a reference.

[0048] <Effects of this embodiment> In this embodiment, the power converter control device 60 calculates a counter voltage, which is a voltage with the same phase and amplitude as the voltage of the power system 10, and the frequency fluctuation suppression unit 64 outputs a current command value that suppresses the frequency fluctuation of the generator G based on the connection point voltage and the output current of the generator G. As a result, fluctuations in the system voltage are canceled out by the counter voltage, and fluctuations in the system frequency can be reliably suppressed by the positive-sequence voltage output by the power converter 40.

[0049] <Other Embodiments> However, the present invention is not limited to the embodiments described above.

[0050] In the above embodiment, the power converter 40 was a GFM inverter, which is a voltage-controlled inverter capable of supplying inertial force to the power line B, but it may also be a single-phase inverter.

[0051] In the above embodiment, the positive-sequence voltage calculation unit 621 obtained the connection point voltage measured by the measurement unit 50 and calculated the phase θ of the connection point voltage by applying the connection point voltage to a phase-locked loop (PLL), but is not limited to this.

[0052] Furthermore, it goes without saying that the present invention is not limited to the embodiments described above, and various modifications are possible without departing from its spirit. [Explanation of Symbols]

[0053] 100 ···Power Systems 10...Electric power system 20 ···Load 30...DC power supply 40 ···Power converter 50...Measuring section 60 ···Power converter control device 61 ···Counter Voltage Calculation Unit 62...Voltage change calculation unit 621 ···Positive-sequence voltage calculation unit 622 ···Reverse-phase voltage calculation unit 623...Non-fundamental component calculation unit 63...Output section for voltage command value 64. Frequency fluctuation suppression unit G...Distributed power supply B...power line S ··· Circuit breaker T ··· Injection transformer L ··· interconnected reactor

Claims

1. A power converter control device that controls the voltage output by a power converter connected to a power line for supplying power from a power system to a load, A counter voltage calculation unit calculates a counter voltage which is a voltage with the same phase and amplitude as the voltage of the power system, A frequency fluctuation suppression unit outputs a current command value to suppress frequency fluctuations of the generator based on the connection point voltage, which is the voltage at the point where the power converter is connected to the power line, and the output current of the generator connected to the power line. A positive-sequence voltage calculation unit obtains the current command value and the phase of the power system output from the frequency fluctuation suppression unit, and calculates a positive-sequence voltage synchronized with the phase of the power system by open control from the current command value, A power converter control device comprising: a voltage command value output unit that outputs a voltage command value, which is a voltage obtained by combining the counter voltage and the positive-sequence voltage, to the power converter.

2. The power converter control device according to claim 1, wherein the frequency fluctuation suppression unit calculates instantaneous active power based on the connection point voltage and the output current of the generator, and the current command value is the value obtained by dividing the difference between the instantaneous active power and the instantaneous active power applied to a low-pass filter having a predetermined time constant by the rated amplitude value of the grid voltage.

3. A reverse-phase voltage calculation unit obtains the phase command value of the reverse-phase voltage and the output current command value, which is the current to be output to the power converter, and calculates the reverse-phase voltage from the phase command value of the reverse-phase voltage and the output current command value by open control. The system further includes a non-fundamental wave component calculation unit that acquires a phase command value and an output current command value of a non-fundamental wave component having a frequency different from the fundamental frequency of the power system, and calculates the non-fundamental wave component from the phase command value and the output current command value of the non-fundamental wave component by open control, The power converter control device according to claim 1 or 2, wherein the voltage command value output unit outputs a voltage command value obtained by combining the opposing voltage, the positive-sequence voltage, the negative-sequence voltage, and the non-fundamental wave component to the power converter.

4. A power converter control method for controlling the voltage output by a power converter connected to a power line for supplying power from a power system to a load, The counter voltage, which is a voltage with the same phase and amplitude as the voltage of the power system, is calculated. Based on the connection point voltage, which is the voltage at the point where the power converter is connected to the power line, and the output current of the generator connected to the power line, the power converter outputs a current command value to suppress the frequency fluctuation of the generator. The current command value and the phase of the power system are obtained to suppress frequency fluctuations of the generator, and the positive-sequence voltage is calculated from the current command value by open control to synchronize with the phase of the power system. A power converter control method that outputs a voltage command value, which is a combined voltage of the counter voltage and the positive-sequence voltage, to the power converter.

5. A power converter control program that controls the voltage output by a power converter connected to a power line for supplying power from a power system to a load, It functions as a counter voltage calculation unit that calculates a counter voltage which is a voltage with the same phase and amplitude as the voltage of the power system, The power converter has a function as a frequency fluctuation suppression unit that outputs a current command value to suppress frequency fluctuations of the generator based on the connection point voltage, which is the voltage at the point where it is connected to the power line, and the output current of the generator connected to the power line. The unit functions as a positive-sequence voltage calculation unit, which acquires the current command value and the phase of the power system output from the frequency fluctuation suppression unit, and calculates a positive-sequence voltage synchronized with the phase of the power system by open control from the current command value. A power converter control program that causes a computer to function as a voltage command value output unit that outputs a voltage command value, which is a voltage obtained by combining the aforementioned counter voltage and the aforementioned positive-sequence voltage, to the power converter.

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