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

Abstract

The present invention provides a power converter control device that can simultaneously supply inertial force to the power grid and detect islanding. [Solution] The power converter control device 60 includes a non-fundamental wave injection voltage calculation unit 63 that calculates a non-fundamental wave injection voltage, which is the voltage output by the power converter 40 when a non-fundamental wave current is injected into the power line B, based on the phase command value and amplitude command value of a non-fundamental wave current, which is a current with a frequency different from the fundamental frequency of the power system 10; and an islanding operation detection unit 65 that calculates the non-fundamental wave voltage and non-fundamental wave current injected into the power line B based on the voltage and current at the connection point P where the power converter 40 is connected to the power line B, and detects islanding operation of a generator connected to the power line B based on the non-fundamental wave voltage and non-fundamental current.

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, such as those caused by loads connected to power lines supplied with power from the power grid or distributed power sources, can cause fluctuations in the voltage or frequency of the power grid. Therefore, to suppress these voltage or frequency fluctuations in 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 batteries into AC power) to the power lines and control the voltage output from these 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 power system voltage, 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 converter outputs a current according to the current command value. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 7495654 [Overview of the project] [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 non-rotating generators, such as solar power generators, which do not possess inertia, will be connected to power lines. In this case, the power converter control device described above may include inertia in the current command value output to the power converter. Here, "including inertia" means having the ability to autonomously reduce frequency changes in the power system.

[0006] However, if a power converter is capable of supplying inertial force to the power system, adding an islanding detection function that uses the fundamental wave to detect islanding to the power converter control device could lead to interference between the frequency used to supply inertial force to the power system and the frequency used to detect islanding. Therefore, it is difficult to achieve both the supply of inertial force to the power system and the detection of islanding with the above-mentioned power converter control device.

[0007] Therefore, the present invention has been made in view of the above problems, and its main objective is to provide a power converter control device that can simultaneously supply inertial force to the power system and detect islanding. [Means for solving the problem]

[0008] That is, the power converter control device according to the present invention is 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, and includes: 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; a voltage change amount calculation unit that obtains an output current command value that is a current to be output to the power converter and includes an inertial force and the phase of the power system, and calculates, by open-loop control from the output current command value, a voltage change amount when the power converter outputs the output current command value; a non-fundamental wave injection voltage calculation unit that calculates a non-fundamental wave injection voltage that is a voltage output by the power converter when the non-fundamental wave current is injected into the power line, based on a phase command value and an amplitude command value of a non-fundamental wave current that is a current having a frequency different from the fundamental frequency of the power system; a voltage command value output unit that outputs, to the power converter, a voltage command value that is a voltage obtained by synthesizing the counter-voltage, the voltage change amount, and the non-fundamental wave injection voltage; and a single-operation detection unit that calculates a non-fundamental wave voltage and a non-fundamental wave current injected into the power line based on the voltage and current at a connection point where the power converter is connected to the power line, and detects a single operation of a generator connected to the power line based on the non-fundamental wave voltage and the non-fundamental wave current.

[0009] In this power converter control device, since the non-fundamental wave injection voltage calculation unit calculates the non-fundamental wave injection voltage based on the phase command value and the amplitude command value in a current having a frequency different from the fundamental wave frequency, even if the power converter outputs a voltage command value obtained by synthesizing the counter-voltage, the voltage change amount for supplying the inertial force, and the non-fundamental wave injection voltage, the frequency for supplying the inertial force and the frequency for detecting the single operation do not interfere with each other. As a result, it is possible to supply sufficient inertial force from the power converter to the power system, and it is possible to detect the single operation using a non-fundamental wave component that does not interfere with the frequency for supplying the inertial force.

[0010] Examples of the amplitude command value include those configured to be adjustable.

[0011] With this configuration, the amplitude of the non-fundamental current injected into the power line can be changed. Therefore, by significantly changing the amplitude command value to such an extent that it does not affect the distortion or quality degradation of the current flowing through the power line, the single-operation detection unit can accurately calculate the non-fundamental voltage and non-fundamental current. As a result, the single-operation detection unit can accurately detect the single operation of the generator.

[0012] The single-operation detection unit extracts the non-fundamental voltage and the non-fundamental current from the voltage and current at the connection point by using a fundamental wave filter that suppresses the fundamental wave components included in the voltage and current at the connection point.

[0013] With this configuration, the fundamental wave components are suppressed from the voltage and current at the connection point, and the non-fundamental voltage and non-fundamental current can be extracted more accurately.

[0014] The voltage change amount calculation unit includes a positive-phase voltage calculation unit that acquires the phase of the power system and the output current command value, and calculates the positive-phase voltage as the voltage change amount so as to be synchronized with the phase of the power system by open control from the output current command value; a reverse-phase voltage calculation unit that acquires the phase command value of the reverse-phase voltage and the output current command value, and calculates the reverse-phase voltage as the voltage change amount by open control from the phase command value of the reverse-phase voltage and the output current command value; and a non-fundamental wave component calculation unit that acquires the phase command value of the non-fundamental wave component and the output current command value, and calculates the non-fundamental wave component as the voltage change amount by open control from the phase command value of the non-fundamental wave component and the output current command value.

[0015] With this configuration, a current to compensate for voltage imbalance or non-fundamental wave components can be output from the power converter, thereby suppressing the equivalent reverse-sequence current of the generator, preventing overheating and burnout of the windings, and improving the generator's utilization rate. In addition, since reverse-sequence voltage or non-fundamental wave components can be output as desired, harmonic voltage distortion or voltage imbalance caused by single-phase loads or rectifier loads can be suppressed, thereby improving power quality. Furthermore, since the power converter outputs a voltage that is a combination of the inverse-sequence voltage or non-fundamental wave component and the counter voltage, the voltage of the power system is canceled out by the counter voltage, and only the inverse-sequence voltage or non-fundamental wave component is output to the power system. Therefore, regardless of fluctuations in the voltage of the power system, it is possible to reliably output only the inverse-sequence voltage or non-fundamental wave component to the power converter.

[0016] A control method 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 includes: calculating a counter voltage which is a voltage with the same phase and amplitude as the voltage of the power system; obtaining an output current command value which includes inertial force and is the current to be output by the power converter, and the phase of the power system; calculating the amount of voltage change when the power converter outputs the output current command value from the output current command value by open control; calculating a non-fundamental wave injection voltage which is the voltage output by the power converter when the non-fundamental wave current is injected into the power line, based on the phase command value and amplitude command value of a non-fundamental wave current which is a current with a frequency different from the fundamental frequency of the power system; outputting a voltage command value to the power converter which is a voltage obtained by combining the counter voltage, the amount of voltage change and the non-fundamental wave injection voltage; and calculating the non-fundamental wave voltage and non-fundamental wave current injected into the power line based on the voltage and current at the connection point where the power converter is connected to the power line; and detecting the isolated operation of a generator connected to the power line based on the non-fundamental wave voltage and non-fundamental wave current. Furthermore, the control program for a power converter that controls the voltage output by a power converter connected to a power line for supplying power from the power system to a load includes a function 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; a function as a voltage change amount calculation unit that obtains the output current command value, which is the current to be output by the power converter and includes inertial force, and the phase of the power system, and calculates the voltage change amount when the power converter outputs the output current command value by open control from the output current command value; and a function as a voltage change amount calculation unit that calculates the voltage change amount when the power converter outputs the output current command value based on the phase command value and amplitude command value of a non-fundamental wave current which is a current with a frequency different from the fundamental frequency of the power system. The computer is characterized by performing the following functions: a non-fundamental wave injection voltage calculation unit that calculates a non-fundamental wave injection voltage, which is the voltage output by the power converter when a wave current is injected into the power line; a voltage command value output unit that outputs a voltage command value to the power converter, which is a voltage obtained by combining the counter voltage, the voltage change amount, and the non-fundamental wave injection voltage; and an islanding detection unit that calculates the non-fundamental wave voltage and non-fundamental wave current injected into the power line based on the voltage and current at the connection point where the power converter is connected to the power line, and detects islanding operation of a generator connected to the power line based on the non-fundamental wave voltage and non-fundamental current.

[0017] With this configuration, the same effects and benefits as those of the power converter control device described above can be obtained. [Effects of the Invention]

[0018] According to the present invention configured in this manner, it is possible to provide a power converter control device that can simultaneously supply inertial force to the power system and detect islanding. [Brief explanation of the drawing]

[0019] [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 isolated operation detection unit in the same embodiment. [Modes for carrying out the invention]

[0020] 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.

[0021] <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. In this embodiment, for example, a distributed power source G such as a solar power generator or a wind power generator is connected to the power line B in parallel with the power system 100. The following describes each part.

[0022] 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. The DC power source 30 is connected to the power line B via a circuit breaker S, a grid-connecting transformer T, a grid-connecting reactor L, and a power converter 40.

[0023] 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.

[0024] The measuring unit 50 has the function of a voltage measuring unit that measures the voltage of power line B using, for example, a known instrument transformer, and the function of a current measuring unit that measures the current flowing through power line B using, for example, a known instrument current transformer. Specifically, the measuring unit 50 measures the voltage and current at connection point P where the power converter 40 is connected to power line B. In this embodiment, the voltage and current at connection point P are the current and voltage between the circuit breaker S and the interconnection transformer T, as shown in Figure 1. Here, the voltage measured by the measuring unit 50 corresponds to the voltage of the power system 10.

[0025] 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; a non-fundamental wave injection voltage calculation unit 63 that calculates a non-fundamental wave injection voltage, which is the voltage output by the power converter 40 when a non-fundamental wave current, which is a current with a frequency different from the fundamental frequency of the power system 10, is injected into power line B; and a voltage command value output unit 64 that outputs a voltage command value Vref, which is the command value of the voltage to be output by the power converter 40. Note that 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.

[0026] 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).

[0027] 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.

[0028] 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.

[0029] 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.

[0030] Specifically, the voltage change calculation unit 62 includes a positive-sequence voltage calculation unit 621 that calculates the positive-sequence voltage change ΔV1abc, a negative-sequence voltage calculation unit 622 that calculates the negative-sequence voltage change ΔV2abc, and a non-fundamental wave component change ΔV n It includes a non-fundamental wave component calculation unit 623 that calculates abc.

[0031] 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 from the output current command value by open-loop control so as to be synchronized with the phase of the power system 10. Specifically, the positive-phase voltage calculation unit 621 calculates the instantaneous voltage value ΔV p ref of the active power and the instantaneous voltage value ΔV q ref of the reactive power from the active current command value i p abc and the reactive current command value i q abc by open-loop control, respectively, and calculates the positive-phase voltage change amount ΔV1abc by synthesizing the instantaneous voltage value ΔV p abc of the active power and the instantaneous voltage value ΔV q abc of the reactive power. The method by which the positive-phase voltage calculation unit 621 calculates the positive-phase voltage change amount ΔV1abc will be described below.

[0032] 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 via an external input means (not shown). Here, the active current command value i p 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.

[0033] 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 q respectively.By 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.

[0034] Furthermore, the positive-sequence voltage calculation unit 621 obtains the phase of the power system 10 from the voltage measured by the measurement unit 50. The positive-sequence voltage calculation unit 621 then calculates a first phase θp which is in phase with the power system 10 and a second phase θq which is 90 degrees behind the phase of the power system 10. The positive-sequence voltage calculation unit 621 may also obtain the phase of the power system 10 from phase information input via an external input means (not shown).

[0035] 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 θp 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 θq 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. p abc and the instantaneous voltage value ΔV of reactive power q By combining abc, the positive-sequence voltage change ΔV1abc is calculated.

[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, 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.

[0037] 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).

[0038] 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.

[0039] 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.

[0040] 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. Here, the non-fundamental wave component calculated by the non-fundamental wave component calculation unit 623 is a non-fundamental wave component that suppresses harmonic distortion of voltage or current in power line B, for example, a harmonic component or an inter-order harmonic. Below, the non-fundamental wave component calculation unit 623 calculates the non-fundamental wave component change amount ΔV n This explains how to calculate abc.

[0041] 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). nObtain 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.

[0042] 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).

[0043] 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.

[0044] The non-fundamental wave injection voltage calculation unit 63 calculates the non-fundamental wave injection voltage ΔV, which is the voltage output by the power converter when the non-fundamental current is injected into power line B, based on the phase command value and amplitude command value of the non-fundamental wave current. inj This calculates abc. Here, the non-fundamental wave injection voltage ΔV inj abc is a non-fundamental voltage of a different order than the non-fundamental component calculated by the non-fundamental component calculation unit 623. Specifically, it is the non-fundamental injection voltage ΔV inj abc is a non-fundamental wave component voltage injected into power line B to an extent that does not affect the quality of the power supplied to power line B, and is used to detect islanding of the DC power supply 30. For example, a non-fundamental wave voltage has an amplitude value such as 1 / 200th of the amplitude value of the fundamental wave voltage. The non-fundamental wave current may be injected into a three-phase power line B or into a single-phase power line B. Referring to Figure 2 below, the non-fundamental wave injection voltage calculation unit 63 calculates the non-fundamental wave injection voltage ΔV inj This explains how to calculate abc.

[0045] The non-fundamental wave injection voltage calculation unit 63 receives a phase command value θ of the non-fundamental wave current via an external input means (not shown). inj ref and amplitude command value I inj Obtain the reference value. Here, the phase command value θ of the non-fundamental wave current is obtained. inj ref and amplitude command value I inj ref is a value determined by the order of the non-fundamental wave component. Also, the amplitude command value I inj The ref is configured to be adjustable.

[0046] Next, the non-fundamental wave injection voltage calculation unit 63 calculates the amplitude command value I inj The voltage amplitude command value ΔEinj of the non-fundamental wave injection voltage is calculated by multiplying ref by a predetermined gain Kinj. The gain Kinj 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).

[0047] The non-fundamental wave injection voltage calculation unit 63 then calculates the voltage amplitude command value ΔEinj of the non-fundamental wave injection voltage and the phase command value θ of the non-fundamental wave current. inj From ref, the non-fundamental wave injection voltage ΔV is controlled by instantaneous voltage control. inj Calculate abc.

[0048] The voltage command value output unit 64 outputs the opposing voltage Vabc, the voltage change amount, and the non-fundamental wave injection voltage ΔV. inj The voltage command value Vref is calculated by combining abc, and the voltage command value Vref is output to the power converter 40. Specifically, the voltage command value output unit 64 outputs 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 64 outputs the opposing voltage Vabc, the voltage change, and the non-fundamental wave injection voltage ΔV. injabc are combined to calculate the voltage command value Vref. When the voltage command value Vref is output from the voltage command value output unit 64, the power converter 40 outputs a voltage to the load 20 according to the voltage command value Vref, for example by PWM control.

[0049] The power converter control device 60 further includes an islanding detection unit 65 that calculates the non-fundamental voltage and non-fundamental current injected into the power line B based on the voltage and current at connection point P, and detects islanding of the DC power supply 30 based on the non-fundamental voltage and non-fundamental current. Specifically, as shown in Figure 3, the islanding detection unit 65 includes a non-fundamental component extraction unit 651 that extracts the non-fundamental voltage and non-fundamental current from the voltage and current at connection point P, a setting value comparison unit 652 that compares the non-fundamental voltage and / or non-fundamental current extracted by the non-fundamental component extraction unit 651 with a predetermined setting value, and a trip signal output unit 653 that outputs a trip signal to open the circuit breaker S when it is determined that the DC power supply 30 is operating islanding.

[0050] The non-fundamental component extraction unit 651 acquires the voltage and current at connection point P from the measurement unit 50 and extracts the non-fundamental voltage and non-fundamental current at connection point P. Specifically, the non-fundamental component extraction unit 651 uses a fundamental wave filter to suppress the fundamental wave components contained in the voltage and current at connection point P, and extracts the non-fundamental voltage and non-fundamental current at connection point P from the voltage and current at connection point P. The non-fundamental component extraction unit 651 may extract a non-fundamental voltage of the same order as the non-fundamental injection voltage calculated by the non-fundamental injection voltage calculation unit 63, or it may extract a non-fundamental voltage of a different order.

[0051] The setting value comparison unit 652 acquires the non-fundamental wave voltage and / or non-fundamental wave current from the non-fundamental wave component extraction unit 651, and determines that the DC power supply 30 is operating independently if the non-fundamental wave voltage and / or non-fundamental wave current remain above a predetermined setting value for a predetermined period of time. Here, the predetermined setting value is, for example, a predetermined value for the non-fundamental wave voltage and a predetermined value for the impedance obtained from the non-fundamental wave voltage and non-fundamental wave current.

[0052] The trip signal output unit 653 outputs a trip signal to open the circuit breaker S when the setting value comparison unit 652 determines that the DC power supply 30 is operating independently. When the trip signal is output, the drive circuit (not shown) that drives the circuit breaker S opens the circuit breaker S, and the DC power supply 30 is electrically isolated from the power line B. After the circuit breaker S is opened, if the non-fundamental voltage and / or non-fundamental current are below a predetermined setting value and it is determined that the DC power supply 30 can be electrically connected to the power line B, the trip signal output unit 653 may output a signal to close the circuit breaker S again.

[0053] <Effects of this embodiment> In this embodiment, the power converter control device 60 calculates the non-fundamental wave injection voltage based on the phase command value and amplitude command value of a non-fundamental wave current with a frequency different from the fundamental wave frequency. Therefore, even if the power converter 40 outputs a voltage command value which is a combination of the counter voltage, the voltage change amount for supplying inertial force, and the non-fundamental wave injection voltage, the frequency for supplying inertial force and the frequency injected to detect islanding do not interfere with each other. As a result, sufficient inertial force can be supplied from the power converter 40 to the power system 10, and islanding can be detected using a non-fundamental wave component that does not interfere with the frequency used to supply inertial force.

[0054] <Other Embodiments> However, the present invention is not limited to the embodiments described above.

[0055] In the above embodiment, the order of the non-fundamental wave injection voltage calculated by the non-fundamental wave injection voltage calculation unit 63 may be one or more.

[0056] In the above embodiment, the non-fundamental wave injection voltage calculation unit 63 calculated the non-fundamental wave injection voltage for one power converter 40, but it may also calculate the non-fundamental wave injection voltage for multiple power converters 40. In this case, the non-fundamental wave injection voltage calculation unit 63 may calculate non-fundamental wave injection voltages of different orders for multiple power converters 40, or it may calculate non-fundamental wave injection voltages of the same order. When multiple power converters 40 output non-fundamental wave injection voltages of different orders, interference due to the output of non-fundamental wave injection voltages can be prevented.

[0057] 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]

[0058] 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 wave component calculation unit 63 ···Non-fundamental wave injection voltage calculation unit 64...Output section for voltage command value 65 ···Isolated Operation Detection Unit G...Distributed power supply B...power line P ···Connection point 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 voltage change calculation unit obtains the output current command value, which is the current to be output to the power converter and includes inertial force, and the phase of the power system, and calculates the voltage change amount when the power converter outputs the output current command value by open control from the output current command value. A non-fundamental wave injection voltage calculation unit calculates a non-fundamental wave injection voltage, which is the voltage output by the power converter when the non-fundamental wave current is injected into the power line, based on the phase command value and amplitude command value of the non-fundamental wave current, which is a current with a frequency different from the fundamental frequency of the power system; A voltage command value output unit outputs a voltage command value to the power converter, which is a voltage obtained by combining the counter voltage, the voltage change amount, and the non-fundamental wave injection voltage. A power converter control device comprising: a unit that calculates non-fundamental voltage and non-fundamental current injected into the power line based on the voltage and current at the connection point where the power converter is connected to the power line; and an islanding detection unit that detects islanding of a generator connected to the power line based on the non-fundamental voltage and non-fundamental current.

2. The power converter control device according to claim 1, wherein the amplitude command value is configured to be adjustable.

3. The power converter control device according to claim 1, wherein the isolated operation detection unit extracts the non-fundamental voltage and the non-fundamental current from the voltage and current at the connection point using a fundamental wave filter that suppresses the fundamental wave component contained in the voltage and current at the connection point.

4. The aforementioned voltage change amount calculation unit is: A positive-sequence voltage calculation unit acquires the phase of the power system and the output current command value, and calculates the positive-sequence voltage as the voltage change amount synchronized with the phase of the power system by open control from the output current command value, A reverse-phase voltage calculation unit that acquires the phase command value of the reverse-phase voltage and the output current command value, and calculates the reverse-phase voltage as the voltage change amount from the phase command value of the reverse-phase voltage and the output current command value by open control, A power converter control device according to any one of claims 1 to 3, further comprising: a non-fundamental wave component calculation unit that acquires the phase command value of the non-fundamental wave component and the output current command value, and calculates the non-fundamental wave component as the voltage change amount from the phase command value of the non-fundamental wave component and the output current command value by open control.

5. 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. The current to be output by the power converter, the output current command value including inertial force and the phase of the power system are obtained, and the amount of voltage change when the power converter outputs the output current command value is calculated from the output current command value by open control. Based on the phase command value and amplitude command value of the non-fundamental current, which is a current with a frequency different from the fundamental frequency of the power system, the non-fundamental injection voltage, which is the voltage output by the power converter when the non-fundamental current is injected into the power line, is calculated. A voltage command value output unit outputs a voltage command value to the power converter, which is a voltage obtained by combining the counter voltage, the voltage change amount, and the non-fundamental wave injection voltage. A power converter control method comprising: calculating non-fundamental voltage and non-fundamental current injected into the power line based on the voltage and current at the connection point where the power converter is connected to the power line; and detecting the isolated operation of a generator connected to the power line based on the non-fundamental voltage and non-fundamental current.

6. 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 is to output a current, and the power converter has a current command value that includes inertial force, and the phase of the power system, and the power converter has a voltage change calculation unit that calculates the voltage change amount when the power converter outputs the output current command value by open control from the output current command value. A non-fundamental wave injection voltage calculation unit that calculates the non-fundamental wave injection voltage, which is the voltage output by the power converter when the non-fundamental wave current is injected into the power line, based on the phase command value and amplitude command value of the non-fundamental wave current, which is a current with a frequency different from the fundamental frequency of the power system, It functions as a voltage command value output unit that outputs a voltage command value, which is a voltage obtained by combining the aforementioned counter voltage, the voltage change amount, and the non-fundamental wave injection voltage, to the power converter. A power converter control program that causes a computer to perform the function of an islanding detection unit, which calculates non-fundamental voltage and non-fundamental current injected into the power line based on the voltage and current at the connection point where the power converter is connected to the power line, and detects islanding of a generator connected to the power line based on the non-fundamental voltage and non-fundamental current.

Images