Power conversion apparatus and control device

Abstract

Provided is a power conversion apparatus comprising: a main circuit unit which performs conversion of power; and a control device which controls the conversion of power performed by the main circuit unit. The control device has a command value calculation unit which calculates a phase-voltage phase command value and a phase-voltage amplitude command value for an AC current to be outputted from the main circuit unit. When the occurrence of disturbance is detected in a power system, the command value calculation unit: calculates a command value for a frequency by adding a correction value for a frequency at the time of the occurrence of disturbance to a reference value for the frequency of the AC voltage outputted from the main circuit unit; and calculates the phase-voltage phase command value by multiplying the integration result of the command value for the frequency by 2π. When the occurrence of disturbance is detected in the power system, the command value calculation unit calculates the phase-voltage amplitude command value by adding a correction value for the magnitude of the AC voltage at the time of the occurrence of disturbance to a reference value for the magnitude of the AC voltage to be outputted from the main circuit unit. As a result, a power conversion apparatus and a control device therefor capable of improving continuity in coordinated operation with a power system even when disturbance occurs in a power system side are provided.

Description

Power conversion device and control device

[0001] An embodiment of the present invention relates to a power conversion device and a control device thereof.

[0002] A voltage source voltage control type power conversion device (grid forming inverter) is known. Compared to a voltage source current control type power conversion device (grid following inverter), the voltage source voltage control type power conversion device can achieve a seamless transition between grid-connected operation and stand-alone operation.

[0003] However, in a voltage source voltage control type power conversion device, when a system disturbance such as a voltage drop occurs on the power system side, an overcurrent may flow between the power conversion device and the power system, causing the power conversion device to stop.

[0004] For this reason, it is desirable that the power conversion device and its control device be able to improve the continuity of interconnected operation with the power grid even when a disturbance occurs on the power grid side.

[0005] Japanese Patent Application Laid-Open No. 2022-148986

[0006] An embodiment of the present invention provides a power conversion device and a control device thereof that can improve the continuity of interconnected operation with the power grid even when a disturbance occurs on the power grid side.

[0007] According to an embodiment of the present invention, a power conversion system includes a main circuit unit that has a power conversion unit that converts input power into AC power compatible with a power grid and outputs the converted AC power to the power grid, and a control device that calculates an instantaneous value voltage output command value of AC power to be output from the power conversion unit based on an active power command value and a reactive power command value, and controls the operation of the power conversion unit so that a voltage corresponding to the instantaneous value voltage output command value is output from the power conversion unit, thereby controlling the conversion of power by the main circuit unit, and the control device controls the active power command value and the reactive power command value of the main circuit unit. a command value calculation unit that calculates a phase voltage phase command value of AC power output from the main circuit unit based on a measured value of active power at an output end of the main circuit unit, and calculates a phase voltage amplitude command value of AC power output from the main circuit unit based on the reactive power command value and the measured value of reactive power at the output end of the main circuit unit; and a command value generation unit that calculates the instantaneous value voltage output command value based on the phase voltage phase command value and the phase voltage amplitude command value, wherein the command value calculation unit includes a system disturbance detection unit that detects the occurrence of a disturbance in the power system, and a command value generation unit that calculates the instantaneous value voltage output command value based on the active power command value and the measured value of active power. and a voltage amplitude control unit that calculates the phase voltage phase command value of the AC power output from the main circuit unit based on the reactive power command value and the measured value of the reactive power, wherein the power synchronization control unit calculates a correction value for the frequency of the AC voltage output from the main circuit unit to bring the measured value of the active power closer to the active power command value, and when the occurrence of a disturbance in the power system is not detected by the system disturbance detection unit, adjusts the reference value of the frequency of the AC voltage output from the main circuit unit by adjusting the reference value of the frequency of the AC voltage output from the main circuit unit. a frequency command value for the AC voltage output from the main circuit unit is calculated by adding a wave number correction value to the reference value of the frequency of the AC voltage output from the main circuit unit; when the occurrence of a disturbance in the power system is detected by the system disturbance detection unit, the frequency correction value at the time when the occurrence of the disturbance in the power system is detected is stored as the frequency correction value at the time of the disturbance occurrence; the frequency command value is calculated by adding the frequency correction value at the time of the disturbance occurrence to the reference value of the frequency of the AC voltage output from the main circuit unit; the frequency command value is integrated; and the integration result is multiplied by 2π;a voltage amplitude control unit that calculates the phase voltage phase command value, and the voltage amplitude control unit that calculates a correction value for the magnitude of the AC voltage output from the main circuit unit so as to bring the measured value of the reactive power closer to the reactive power command value, and when the occurrence of a disturbance in the power system is not detected by the system disturbance detection unit, calculates the phase voltage amplitude command value by adding the correction value for the magnitude of the AC voltage to a reference value of the magnitude of the AC voltage output from the main circuit unit, and when the occurrence of a disturbance in the power system is detected by the system disturbance detection unit, stores the correction value for the magnitude of the AC voltage at the time when the occurrence of the disturbance in the power system is detected by the system disturbance detection unit as a correction value for the magnitude of the AC voltage at the time of disturbance occurrence, and calculates the phase voltage amplitude command value by adding the correction value for the magnitude of the AC voltage at the time of disturbance occurrence to the reference value of the magnitude of the AC voltage output from the main circuit unit.

[0008] According to the embodiments of the present invention, a power conversion device and a control device therefor are provided that can improve the continuity of interconnected operation with the power grid even when a disturbance occurs on the power grid side.

[0009] FIG. 1 is a block diagram schematically showing a power conversion device according to an embodiment; FIG. 2 is a block diagram schematically showing an example of a command value calculation unit according to an embodiment; FIG. 3 is a block diagram schematically showing an example of a command value generation unit according to an embodiment; FIG. 4 is a graph schematically showing an example of an operation of a power conversion device according to an embodiment; FIG. 5 is a graph schematically showing an example of an operation of a reference power conversion device; FIG. 6 is a block diagram schematically showing a modified example of a command value calculation unit according to an embodiment; FIG. 7 is a block diagram schematically showing a modified example of a command value calculation unit according to an embodiment;

[0010] Each embodiment will be described below with reference to the drawings. The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between parts, etc., are not necessarily the same as those in reality. Even when the same part is shown, the dimensions and ratios may be different depending on the drawing. In this specification and each drawing, elements similar to those previously described with reference to the previous drawings are designated by the same reference numerals, and detailed descriptions thereof will be omitted as appropriate.

[0011] Fig. 1 is a block diagram schematically illustrating a power conversion device according to an embodiment. As illustrated in Fig. 1, the power conversion device 10 includes a main circuit unit 12, a control device 14, a first measurement device 16, and a second measurement device 18. The main circuit unit 12 converts power. The control device 14 controls the power conversion performed by the main circuit unit 12.

[0012] The main circuit unit 12 is connected to the power system 2 and the power supply device 4. The power system 2 is an AC power system. The AC power of the power system 2 is, for example, three-phase AC power. However, the AC power of the power system 2 may be single-phase AC power or the like. The power supply device 4 is, for example, a power storage device using a storage battery or the like. The power supply device 4 outputs DC power to the main circuit unit 12.

[0013] The main circuit unit 12, for example, converts DC power input from the power supply device 4 into AC power compatible with the power grid 2, outputs the converted AC power to the power grid 2, and also converts AC power input from the power grid 2 into DC power, thereby charging the power supply device 4. In this way, the main circuit unit 12 connects the power supply device 4 to the power grid 2.

[0014] The power supply device 4 is not limited to a power storage device, and may be, for example, a solar panel, etc. In this case, the main circuit unit 12 does not need to have the function of converting AC power input from the power grid 2 into DC power.

[0015] Furthermore, the power supply device 4 may be another type of generator, such as a wind power generator or a gas turbine generator. The power input from the power supply device 4 to the main circuit unit 12 is not limited to DC power, and may be AC ​​power. The main circuit unit 12 may be configured to convert the AC power input from the power supply device 4 into another AC power compatible with the power grid 2. The power supply device 4 may be, for example, a separate power grid different from the power grid 2. The main circuit unit 12 may be, for example, a frequency converter that interconnects two power grids with different frequencies.

[0016] In this way, the power conversion by the main circuit unit 12 is not limited to conversion from DC to AC, but may be any conversion that converts the power of the power supply device 4 into AC power compatible with the power grid 2.

[0017] The main circuit unit 12 has a power conversion unit 20 and a filter circuit 22. The power conversion unit 20 converts power. The power conversion unit 20 has, for example, a plurality of switching elements and converts power by switching the plurality of switching elements. The power conversion unit 20 has, for example, a plurality of switching elements connected in a three-phase bridge configuration. The power conversion unit 20 may have any configuration that can convert input power into AC power compatible with the power grid 2 by switching the plurality of switching elements, for example.

[0018] The filter circuit 22 is provided on the AC side of the power conversion unit 20. In other words, the filter circuit 22 is provided between the power conversion unit 20 and the power grid 2. The filter circuit 22 causes the AC power output from the power conversion unit 20 to resemble a sine wave. The filter circuit 22 causes the AC power output from the power conversion unit 20 to resemble a sine wave, for example, by suppressing high-frequency components contained in the AC power output from the power conversion unit 20.

[0019] The filter circuit 22 includes, for example, a reactor 24 connected in series to the AC output point of the power conversion unit 20, and a capacitor 26 connected in parallel to the AC output point of the power conversion unit 20. The reactor 24 and the capacitor 26 are provided for each phase of the AC power output from the power conversion unit 20.

[0020] However, the configuration of the filter circuit 22 is not limited to this, and may be any configuration that can make the AC power output from the power conversion unit 20 closer to a sine wave. Furthermore, the configuration of the main circuit unit 12 is not limited to the above, and may be any configuration that has at least the power conversion unit 20, converts input power into AC power compatible with the power grid 2, and can output the converted AC power to the power grid 2.

[0021] The first measuring device 16 measures the phase voltages Va(INV), Vb(INV), and Vc(INV) of each phase of the AC power output from the power conversion unit 20, and the line currents Ia(INV), Ib(INV), and Ic(INV) of each phase, and inputs the measurement results to the control device 14.

[0022] The second measuring device 18 measures the phase voltages Va(PCS), Vb(PCS), Vc(PCS) of each phase of the AC power output from the main circuit unit 12 (filter circuit 22), the line currents Ia(PCS), Ib(PCS), Ic(PCS) of each phase, the active power P(PCS) at the output end of the main circuit unit 12, and the reactive power Q(PCS) at the output end of the main circuit unit 12, and inputs the measurement results to the control device 14.

[0023] The control device 14 controls the operation of the power conversion unit 20, thereby controlling the power conversion by the main circuit unit 12. In other words, the control device 14 controls the switching of a plurality of switching elements in the power conversion unit 20.

[0024] The control device 14 receives the measurement results of the first measuring device 16 and the second measuring device 18, and also receives the active power command value and reactive power command value of the AC power output from the main circuit section 12 from a higher-level controller or the like.

[0025] The control device 14 controls the operation of the power conversion unit 20 based on the measurement results input from the first measuring device 16 and the second measuring device 18, and the active power command value and reactive power command value input from a higher-level controller, etc.

[0026] More specifically, the control device 14 calculates instantaneous voltage output command values ​​Va(ref), Vb(ref), and Vc(ref) for each phase of the AC power output from the power conversion unit 20 based on the input measurement results, active power command value, and reactive power command value, and controls the operation of the power conversion unit 20 so that voltages corresponding to the calculated instantaneous voltage output command values ​​Va(ref), Vb(ref), and Vc(ref) are output from the power conversion unit 20.

[0027] In this way, the control device 14 controls the output voltage of the main circuit unit 12. The control device 14 performs voltage control operation of the main circuit unit 12. Note that the measurement results do not necessarily have to be input directly from the first measuring device 16 and the second measuring device 18 to the control device 14, but may also be input to the control device 14 via, for example, a higher-level controller.

[0028] Furthermore, the measured value of the active power P(PCS) at the output end of the main circuit unit 12 and the measured value of the reactive power Q(PCS) at the output end of the main circuit unit 12 are not limited to being input from the second measuring device 18 to the control device 14, but may be calculated within the control device 14 based on the measured values ​​of the phase voltages Va(PCS), Vb(PCS), and Vc(PCS) of each phase and the line currents Ia(PCS), Ib(PCS), and Ic(PCS) of each phase. The second measuring device 18 does not necessarily have to measure the active power P(PCS) and the reactive power Q(PCS).

[0029] The control device 14 has a command value calculation unit 30 and a command value generation unit 32. The command value calculation unit 30 receives an active power command value and a reactive power command value input from a higher-level controller or the like, as well as the measured values ​​of the active power P(PCS) and the reactive power Q(PCS) measured by the second measurement device 18.

[0030] The command value calculation unit 30 calculates a phase voltage phase command value θ of the AC power output from the main circuit unit 12 based on the active power command value and the measured value of the active power P(PCS). Then, the command value calculation unit 30 calculates a phase voltage amplitude command value |V| of the AC power output from the main circuit unit 12 based on the reactive power command value and the measured value of the reactive power Q(PCS). The command value calculation unit 30 inputs the calculated phase voltage phase command value θ and phase voltage amplitude command value |V| to the command value generation unit 32.

[0031] The command value generating unit 32 receives the phase voltage phase command value θ and the phase voltage amplitude command value |V| from the command value calculating unit 30, as well as the measured values ​​of the phase voltages Va(INV), Vb(INV), Vc(INV), and line currents Ia(INV), Ib(INV), and Ic(INV) measured by the first measuring device 16, and the phase voltages Va(PCS), Vb(PCS), Vc(PCS), and line currents Ia(PCS), Ib(PCS), and Ic(PCS) measured by the second measuring device 18.

[0032] The command value generating unit 32 calculates instantaneous voltage output command values ​​Va(ref), Vb(ref), and Vc(ref) using input information including the phase voltage phase command value θ, the phase voltage amplitude command value |V|, the phase voltages Va(INV), Vb(INV), and Vc(INV), the line currents Ia(INV), Ib(INV), and Ic(INV), the phase voltages Va(PCS), Vb(PCS), and Vc(PCS), and the line currents Ia(PCS), Ib(PCS), and Ic(PCS).

[0033] The command value generating unit 32 calculates instantaneous voltage output command values ​​Va(ref), Vb(ref), and Vc(ref) based on, for example, each piece of input information so as to suppress an overcurrent at the output terminal of the main circuit unit 12. The command value generating unit 32 may also be called, for example, an overcurrent suppression control unit.

[0034] 2 is a block diagram illustrating an example of a command value calculation unit according to an embodiment. As illustrated in FIG. 2, the command value calculation unit 30 includes a grid disturbance detection unit 40, a power synchronization control unit 42, and a voltage amplitude control unit 44.

[0035] The system disturbance detection unit 40 detects the occurrence of a disturbance in the power system 2. For example, the system disturbance detection unit 40 receives the phase voltages Va(PCS), Vb(PCS), and Vc(PCS) of each phase of the AC power output from the main circuit unit 12 (filter circuit 22). In other words, the phase voltages Va(PCS), Vb(PCS), and Vc(PCS) are voltages at the own terminals of the power conversion device 10 (main circuit unit 12). In other words, the phase voltages Va(PCS), Vb(PCS), and Vc(PCS) are voltages at the interconnection point of the power conversion device 10 with the power system 2.

[0036] For example, when at least one of the magnitudes of the phase voltages Va(PCS), Vb(PCS), and Vc(PCS) falls outside a normal operation range, the system disturbance detection unit 40 detects the occurrence of a disturbance in the power system 2. Furthermore, for example, when the magnitudes of the phase voltages Va(PCS), Vb(PCS), and Vc(PCS) fall within a normal operation range after detecting the occurrence of a disturbance in the power system 2, the system disturbance detection unit 40 detects recovery from the disturbance in the power system 2.

[0037] The system disturbance detection unit 40 sets a system disturbance occurrence flag (Flag) to ON when it detects the occurrence of a disturbance in the power system 2. Then, the system disturbance detection unit 40 sets the system disturbance occurrence flag (Flag) to OFF when it detects recovery from the disturbance in the power system 2. In other words, the system disturbance detection unit 40 switches the system disturbance occurrence flag (Flag) from OFF to ON when it detects the occurrence of a disturbance in the power system 2, and switches the system disturbance occurrence flag (Flag) from ON to OFF when it detects recovery from the disturbance in the power system 2.

[0038] The power synchronization control unit 42 calculates a phase voltage phase command value θ of the AC power output from the main circuit unit 12 based on the active power command value Pref and the measured value of the active power P(PCS). The power synchronization control unit 42 includes, for example, a low-pass filter 50, a subtractor 51, a calculator 52, a switch 53, an adder 54, and an integrator 55.

[0039] The measured value of active power P(PCS) is input to the low-pass filter 50. The low-pass filter 50 performs a process of attenuating components above a predetermined frequency contained in the measured value of active power P(PCS), and inputs the processed measured value of active power P(PCS) to the subtractor 51. This makes it possible to suppress noise components, such as temporary measurement anomalies, contained in the measured value of active power P(PCS). Note that the power synchronization control unit 42 does not necessarily have to include the low-pass filter 50. For example, the measured value of active power P(PCS) may be input directly to the subtractor 51.

[0040] The processed measurement value of the active power P(PCS) and the active power command value Pref are input to the subtractor 51. The subtractor 51 subtracts the measurement value of the active power P(PCS) from the active power command value Pref and inputs the subtraction result to the calculator 52.

[0041] The calculator 52 receives the subtraction result of the subtractor 51 and also receives the detection result of the occurrence of a disturbance in the power grid 2 by the grid disturbance detection unit 40. In other words, the calculator 52 receives the subtraction result of the subtractor 51 and also receives a grid disturbance occurrence flag.

[0042] When the system disturbance detection unit 40 has not detected the occurrence of a disturbance in the power system 2, the calculator 52 calculates, based on the input subtraction result, a correction value Δf of the frequency of the AC voltage output from the main circuit unit 12, for bringing the measured value of the active power P (PCS) closer to the active power command value Pref. In other words, when the system disturbance occurrence flag is OFF, the calculator 52 calculates the frequency correction value Δf based on the subtraction result. The calculator 52 inputs the calculated frequency correction value Δf to the switch 53.

[0043] When the measured value of the active power P(PCS) is smaller than the active power command value Pref, the calculator 52 calculates a correction value Δf so as to increase the frequency in accordance with the magnitude of the difference between the active power command value Pref and the measured value of the active power P(PCS). This increases the measured value of the active power P(PCS) and makes it possible to approach the active power command value Pref. Conversely, when the measured value of the active power P(PCS) is greater than the active power command value Pref, the calculator 52 calculates a correction value Δf so as to decrease the frequency in accordance with the magnitude of the difference between the active power command value Pref and the measured value of the active power P(PCS). This decreases the measured value of the active power P(PCS) and makes it possible to approach the active power command value Pref.

[0044] On the other hand, when the system disturbance detection unit 40 detects the occurrence of a disturbance in the power system 2, the calculator 52 sets the difference between the active power command value Pref and the measured value of the active power P(PCS) to 0 and calculates the correction value Δf. In other words, when the system disturbance occurrence flag is ON, the calculator 52 sets the difference between the active power command value Pref and the measured value of the active power P(PCS) to 0 and calculates the correction value Δf.

[0045] The calculator 52 calculates the frequency correction value Δf based on the subtraction result, for example, by proportional-integral control. As described above, when the system disturbance detection unit 40 detects the occurrence of a disturbance in the power system 2, the calculator 52 sets the difference between the active power command value Pref and the measured value of the active power P(PCS) to zero and calculates the correction value Δf. This prevents, for example, an abnormal value due to the occurrence of the system disturbance from being included in the integral calculation by the calculator 52. This prevents, for example, the correction value Δf calculated by the calculator 52 from becoming an abnormal value when the power system 2 recovers from the disturbance. For example, the accuracy of the calculation of the correction value Δf by the calculator 52 can be further improved. However, the method of calculating the frequency correction value Δf by the calculator 52 is not limited to the above, and any method that can appropriately calculate the frequency correction value Δf based on the subtraction result may be used.

[0046] The switch 53 receives the frequency correction value Δf calculated by the calculator 52 and also receives the detection result of the occurrence of a disturbance in the power system 2 by the system disturbance detection unit 40. In other words, the switch 53 receives the frequency correction value Δf and also receives a system disturbance occurrence flag.

[0047] When the system disturbance detection unit 40 has not detected the occurrence of a disturbance in the power system 2, the switch 53 inputs the frequency correction value Δf calculated by the calculator 52 to the adder 54. In other words, when the system disturbance occurrence flag is OFF, the switch 53 inputs the frequency correction value Δf calculated by the calculator 52 to the adder 54.

[0048] When the system disturbance detection unit 40 detects the occurrence of a disturbance in the power system 2, the switch 53 changes the frequency correction value Δf at the time when the system disturbance detection unit 40 detects the occurrence of the disturbance in the power system 2 to the frequency correction value Δf at the time of the disturbance occurrence. ｐｒｅｖ The stored frequency correction value Δf ｐｒｅｖ is input to the adder 54.

[0049] In other words, when the grid disturbance occurrence flag is switched from OFF to ON, the switch 53 changes the frequency correction value Δf at the time when the grid disturbance occurrence flag is switched from OFF to ON to the frequency correction value Δf at the time when the disturbance occurs. ｐｒｅｖ Then, during the period when the grid disturbance occurrence flag is ON, the switch 53 stores the stored frequency correction value Δf ｐｒｅｖ is input to the adder 54.

[0050] The adder 54 outputs the frequency correction value Δf or the frequency correction value Δf when disturbance occurs. ｐｒｅｖ is input, and a reference value of the frequency of the AC voltage output from the main circuit unit 12 is input. The adder 54 adds the frequency correction value Δf or the frequency correction value Δf when a disturbance occurs to the reference value of the frequency of the AC voltage output from the main circuit unit 12. ｐｒｅｖ By adding the above, the command value f of the frequency of the AC voltage output from the main circuit unit 12 is obtained. ０ Calculate the frequency command value f ０ is input to the integrator 55.

[0051] The reference value of the frequency of the AC voltage output from the main circuit unit 12 is expressed as, for example, 1. The frequency correction value Δf and the frequency correction value Δf when a disturbance occurs are ｐｒｅｖ is a correction value expressed as a proportional rate when the reference value of the frequency is set to 1, for example.

[0052] The integrator 55 receives the command value f of the frequency of the AC voltage output from the main circuit unit 12 from the adder 54. ０ is integrated and the integration result is multiplied by 2π to obtain the frequency command value f ０ Based on this, a phase voltage phase command value θ of the AC power output from the main circuit unit 12 is calculated.

[0053] As a result, the power synchronization control unit 42 calculates a phase voltage phase command value θ of the AC power output from the main circuit unit 12 based on the active power command value Pref and the measured value of the active power P(PCS).

[0054] In this way, the power synchronization control unit 42 calculates the correction value Δf of the frequency of the AC voltage output from the main circuit unit 12 in order to bring the measured value of the active power P (PCS) closer to the active power command value Pref, and when the system disturbance detection unit 40 does not detect the occurrence of a disturbance in the power system 2, the power synchronization control unit 42 calculates the command value f of the frequency of the AC voltage output from the main circuit unit 12 by adding the frequency correction value Δf to the reference value of the frequency of the AC voltage output from the main circuit unit 12. ０ When the occurrence of a disturbance in the power system 2 is detected by the system disturbance detection unit 40, the frequency correction value Δf at the time when the occurrence of the disturbance in the power system 2 is detected by the system disturbance detection unit 40 is calculated as the frequency correction value Δf at the time of the disturbance occurrence. ｐｒｅｖ The reference value of the frequency of the AC voltage output from the main circuit unit 12 is stored as a correction value Δf of the frequency when the disturbance occurs. ｐｒｅｖ By adding ０ is calculated, and the frequency command value f ０ is integrated and the integration result is multiplied by 2π to calculate the phase voltage phase command value θ.

[0055] However, the configuration of the power synchronization control unit 42 is not limited to the above, and any configuration that can appropriately calculate the phase voltage phase command value θ may be used.

[0056] Based on the reactive power command value Qref and the measured value of the reactive power Q(PCS), the voltage amplitude control unit 44 calculates a phase voltage amplitude command value |V| of the AC power output from the main circuit unit 12. The voltage amplitude control unit 44 has, for example, a low-pass filter 60, a subtractor 61, a calculator 62, a switch 63, and an adder 64.

[0057] The measured value of reactive power Q(PCS) is input to the low-pass filter 60. The low-pass filter 60 performs a process of attenuating components above a predetermined frequency contained in the measured value of reactive power Q(PCS), and inputs the processed measured value of reactive power Q(PCS) to the subtractor 61. This makes it possible to suppress noise components, such as temporary measurement anomalies, contained in the measured value of reactive power Q(PCS). Note that the voltage amplitude control unit 44 does not necessarily have to include the low-pass filter 60. For example, the measured value of reactive power Q(PCS) may be input directly to the subtractor 61.

[0058] The measured value of the reactive power Q(PCS) after processing and the reactive power command value Qref are input to the subtractor 61. The subtractor 61 subtracts the measured value of the reactive power Q(PCS) from the reactive power command value Qref and inputs the subtraction result to the calculator 62.

[0059] The calculator 62 receives the subtraction result of the subtractor 61 and also receives the detection result of the occurrence of a disturbance in the power grid 2 by the grid disturbance detection unit 40. In other words, the calculator 62 receives the subtraction result of the subtractor 61 and also receives a grid disturbance occurrence flag.

[0060] When the system disturbance detection unit 40 has not detected the occurrence of a disturbance in the power system 2, the calculator 62 calculates, based on the input subtraction result, a correction value ΔV of the magnitude (amplitude) of the AC voltage output from the main circuit unit 12 in order to bring the measured value of reactive power Q (PCS) closer to the reactive power command value Qref. The calculator 62 inputs the calculated correction value ΔV of the magnitude of the AC voltage to the switch 63.

[0061] When the measured value of reactive power Q(PCS) is smaller than the reactive power command value Qref, the calculator 62 calculates a correction value ΔV so as to reduce the magnitude of the AC voltage in accordance with the magnitude of the difference between the reactive power command value Qref and the measured value of reactive power Q(PCS). This increases the measured value of reactive power Q(PCS) and makes it possible to approach the reactive power command value Qref. Conversely, when the measured value of reactive power Q(PCS) is larger than the reactive power command value Qref, the calculator 62 calculates a correction value ΔV so as to increase the magnitude of the AC voltage in accordance with the magnitude of the difference between the reactive power command value Qref and the measured value of reactive power Q(PCS). This decreases the measured value of reactive power Q(PCS) and makes it possible to approach the reactive power command value Qref.

[0062] On the other hand, when the system disturbance detection unit 40 detects the occurrence of a disturbance in the power system 2, the calculator 62 sets the difference between the reactive power command value Qref and the measured value of the reactive power Q(PCS) to 0 and calculates the correction value ΔV. In other words, when the system disturbance occurrence flag is ON, the calculator 62 sets the difference between the reactive power command value Qref and the measured value of the reactive power Q(PCS) to 0 and calculates the correction value ΔV.

[0063] The calculator 62 calculates the correction value ΔV of the AC voltage magnitude based on the subtraction result, for example, by proportional-integral control. As described above, when the system disturbance detection unit 40 detects the occurrence of a disturbance in the power system 2, the difference between the reactive power command value Qref and the measured value of the reactive power Q(PCS) is set to 0 to calculate the correction value ΔV. This prevents, for example, an abnormal value due to the occurrence of the system disturbance from being included in the integral calculation of the calculator 62. This prevents, for example, the correction value ΔV calculated by the calculator 62 from becoming an abnormal value when the power system 2 recovers from the disturbance. For example, the accuracy of the calculation of the correction value ΔV by the calculator 62 can be further improved. However, the method of calculating the correction value ΔV of the AC voltage magnitude by the calculator 62 is not limited to the above, and any method that can appropriately calculate the correction value ΔV of the AC voltage magnitude based on the subtraction result may be used.

[0064] The switch 63 receives the correction value ΔV for the magnitude of the AC voltage calculated by the calculator 62, as well as the detection result of the occurrence of a disturbance in the power system 2 by the system disturbance detection unit 40. In other words, the switch 63 receives the correction value ΔV for the magnitude of the AC voltage and a system disturbance occurrence flag.

[0065] When the system disturbance detection unit 40 has not detected the occurrence of a disturbance in the power system 2, the switch 63 inputs the correction value ΔV of the AC voltage magnitude calculated by the calculator 62 to the adder 64. In other words, when the system disturbance occurrence flag is OFF, the switch 63 inputs the correction value ΔV of the AC voltage magnitude calculated by the calculator 62 to the adder 64.

[0066] When the system disturbance detection unit 40 detects the occurrence of a disturbance in the power system 2, the switch 63 changes the correction value ΔV of the magnitude of the AC voltage at the time when the system disturbance detection unit 40 detects the occurrence of the disturbance in the power system 2 to the correction value ΔV of the magnitude of the AC voltage at the time when the disturbance occurs. ｐｒｅｖ The correction value ΔV of the magnitude of the AC voltage when the disturbance occurs is stored as ｐｒｅｖ is input to the adder 64.

[0067] In other words, when the grid disturbance occurrence flag is switched from OFF to ON, the switch 63 changes the correction value ΔV of the AC voltage magnitude at the time when the grid disturbance occurrence flag is switched from OFF to ON to the correction value ΔV of the AC voltage magnitude at the time when the disturbance occurs. ｐｒｅｖ Then, during the period when the grid disturbance occurrence flag is ON, the switch 63 stores the stored correction value ΔV of the magnitude of the AC voltage at the time of the disturbance occurrence. ｐｒｅｖ is input to the adder 64.

[0068] The adder 64 outputs a correction value ΔV of the magnitude of the AC voltage or a correction value ΔV of the magnitude of the AC voltage when a disturbance occurs. ｐｒｅｖ is input, and a reference value of the magnitude of the AC voltage output from the main circuit unit 12 is input. The adder 64 adds a correction value ΔV of the AC voltage magnitude or a correction value ΔV of the AC voltage magnitude when a disturbance occurs to the reference value of the AC voltage magnitude output from the main circuit unit 12. ｐｒｅｖBy adding these, the phase voltage amplitude command value |V| of the AC power output from the main circuit unit 12 is calculated.

[0069] The reference value of the magnitude of the AC voltage output from the main circuit unit 12 is expressed as, for example, 1. The correction value ΔV of the AC voltage magnitude and the correction value ΔV of the AC voltage magnitude when a disturbance occurs are ｐｒｅｖ is a correction value expressed as a proportional rate when the reference value of the magnitude of the AC voltage is set to 1, for example.

[0070] As a result, the voltage amplitude control unit 44 calculates the phase voltage amplitude command value |V| of the AC power output from the main circuit unit 12 based on the reactive power command value Qref and the measured value of the reactive power Q(PCS).

[0071] In this way, the voltage amplitude control unit 44 calculates the correction value ΔV of the magnitude of the AC voltage output from the main circuit unit 12 in order to bring the measured value of the reactive power Q (PCS) closer to the reactive power command value Qref, and when the occurrence of a disturbance in the power system 2 is not detected by the system disturbance detection unit 40, calculates the phase voltage amplitude command value |V| by adding the correction value ΔV of the AC voltage magnitude to the reference value of the AC voltage magnitude output from the main circuit unit 12, and when the occurrence of a disturbance in the power system 2 is detected by the system disturbance detection unit 40, calculates the phase voltage amplitude command value |V| by adding the correction value ΔV of the AC voltage magnitude at the time when the occurrence of a disturbance in the power system 2 is detected by the system disturbance detection unit 40. ｐｒｅｖ The reference value of the magnitude of the AC voltage output from the main circuit unit 12 is stored as a correction value ΔV of the magnitude of the AC voltage when a disturbance occurs. ｐｒｅｖ The phase voltage amplitude command value |V| is calculated by adding

[0072] However, the configuration of the voltage amplitude control unit 44 is not limited to the above, and any configuration that can appropriately calculate the phase voltage amplitude command value |V| may be used.

[0073] 3 is a block diagram schematically illustrating an example of a command value generator according to an embodiment. As illustrated in FIG. 3, the command value generator 32 includes, for example, a subtractor 70, calculators 71 and 72, an adder 73, a limiter 74, a subtractor 75, calculators 76 and 77, a subtractor 78, an adder 79, a subtractor 80, calculators 81 and 82, an adder 83, a limiter 84, a subtractor 85, calculators 86 and 87, adders 88 and 89, and an inverse converter 90.

[0074] The subtractor 70 receives the phase voltage amplitude command value |V| calculated by the command value calculation unit 30, as well as the voltage signal Vod of the d-axis component of the AC power output from the main circuit unit 12. The voltage signal Vod of the d-axis component of the AC power output from the main circuit unit 12 is calculated, for example, by performing a dq transformation (Park transformation) on the phase voltages Va(PCS), Vb(PCS), and Vc(PCS) of each phase of the AC power output from the main circuit unit 12.

[0075] The subtractor 70 subtracts the voltage signal Vod from the phase voltage amplitude command value |V| and inputs the subtraction result to the calculator 71 .

[0076] Based on the input subtraction result, the calculator 71 calculates a correction value for the magnitude of the d-axis component of the AC current output from the power conversion unit 20, in order to bring the voltage signal Vod closer to the phase voltage amplitude command value |V|. The calculator 71 inputs the calculated correction value to the adder 73. The calculator 71 calculates the correction value based on the subtraction result, for example, by proportional control or proportional-integral control. However, the calculation method by the calculator 71 is not limited to this, and any method that can appropriately calculate a correction value based on the subtraction result may be used.

[0077] The calculator 72 receives a voltage signal Voq of the q-axis component of the AC power output from the main circuit unit 12. Similar to the voltage signal Vod of the d-axis component, the voltage signal Voq of the q-axis component of the AC power output from the main circuit unit 12 is calculated by, for example, performing a dq transformation (Park transformation) on the phase voltages Va(PCS), Vb(PCS), and Vc(PCS) of each phase of the AC power output from the main circuit unit 12.

[0078] The calculator 72 calculates a correction value for the magnitude of the d-axis component of the AC current output from the power conversion unit 20 based on the input voltage signal Voq of the q-axis component. The calculator 72 calculates the correction value based on the voltage signal Voq, for example, by proportional control or proportional-integral control. However, the calculation method by the calculator 72 is not limited to this, and any method that can appropriately calculate a correction value based on the voltage signal Voq may be used. The calculator 72 inputs the calculated correction value to the adder 73.

[0079] The adder 73 receives the correction values ​​calculated by the calculators 71 and 72, as well as the current signal Igd of the d-axis component of the AC power output from the power conversion unit 20. The current signal Igd of the d-axis component of the AC power output from the power conversion unit 20 is calculated, for example, by performing a dq transformation (Park transformation) on the line currents Ia(INV), Ib(INV), and Ic(INV) of each phase of the AC power output from the power conversion unit 20.

[0080] The adder 73 adds the correction value calculated by the calculator 71 and the correction value calculated by the calculator 72 to the d-axis component current signal Igd, thereby obtaining a current command value Icd of the d-axis component of the AC current output from the main circuit unit 12. ＊ The adder 73 calculates the calculated d-axis component current command value Icd ＊ is input to the limiter 74.

[0081] The limiter 74 determines the d-axis component current command value Icd ＊ The value of Icd is limited to a predetermined range, and the current command value Icd of the d-axis component after the processing is ＊ is input to the subtractor 75.

[0082] The subtractor 75 receives the current command value Icd of the d-axis component. ＊ is input, and a current signal Icd of the d-axis component of the AC power output from the main circuit unit 12 is input. The current signal Icd of the d-axis component of the AC power output from the main circuit unit 12 is calculated, for example, by performing a dq transformation (Park transformation) on the line currents Ia(PCS), Ib(PCS), and Ic(PCS) of each phase of the AC power output from the main circuit unit 12.

[0083] The subtractor 75 calculates the d-axis component current command value Icd ＊ The d-axis component current signal Icd is subtracted from the output of the arithmetic unit 76, and the subtraction result is calculated.

[0084] The calculator 76 calculates the current signal Icd based on the input subtraction result. ＊ The calculator 76 calculates a correction value for the magnitude of the d-axis component of the AC voltage output from the power conversion unit 20 so as to bring the magnitude closer to . The calculator 76 inputs the calculated correction value to the subtractor 78. The calculator 76 calculates the correction value based on the subtraction result, for example, by proportional control or proportional-integral control. However, the calculation method by the calculator 76 is not limited to this, and any method that can appropriately calculate the correction value based on the subtraction result may be used.

[0085] The calculator 77 receives a current signal Icq of the q-axis component of the AC power output from the main circuit unit 12. The current signal Icq of the q-axis component of the AC power output from the main circuit unit 12 is calculated, similar to the current signal Icd of the d-axis component, by performing a dq transformation (Park transformation) on the line currents Ia(PCS), Ib(PCS), and Ic(PCS) of each phase of the AC power output from the main circuit unit 12, for example.

[0086] The calculator 77 calculates a correction value for the magnitude of the d-axis component of the AC voltage output from the power conversion unit 20 based on the input current signal Icq of the q-axis component. The calculator 77 inputs the calculated correction value to the subtractor 78. The calculator 77 calculates the correction value based on the current signal Icq, for example, by proportional control or proportional-integral control. However, the calculation method by the calculator 77 is not limited to this, and any method that can appropriately calculate a correction value based on the subtraction result may be used.

[0087] The subtractor 78 subtracts the correction value input from the calculator 77 from the correction value input from the calculator 76 , and inputs the result of the subtraction to the adder 79 .

[0088] The adder 79 receives the correction value calculated by the subtractor 78 and also receives the voltage signal Vgd of the d-axis component of the AC power output from the power conversion unit 20. The voltage signal Vgd of the d-axis component of the AC power output from the power conversion unit 20 is calculated, for example, by performing a dq transformation (Park transformation) on the phase voltages Va(INV), Vb(INV), and Vc(INV) of each phase of the AC power output from the power conversion unit 20.

[0089] The adder 79 adds the correction value to the input d-axis component voltage signal Vgd, thereby calculating a voltage command value for the d-axis component of the AC power to be output from the power conversion unit 20. The adder 79 inputs the calculated voltage command value for the d-axis component to the inverter 90.

[0090] The subtractor 80 receives as input the voltage command value of the q-axis component of the AC power output from the main circuit unit 12, as well as the voltage signal Voq of the q-axis component of the AC power output from the main circuit unit 12. The voltage command value of the q-axis component of the AC power output from the main circuit unit 12 is set to 0, for example.

[0091] The subtractor 80 subtracts the voltage signal Voq from the voltage command value of the q-axis component, and inputs the subtraction result to the calculator 81 .

[0092] Based on the input subtraction result, the calculator 81 calculates a correction value for the magnitude of the q-axis component of the AC current output from the power conversion unit 20, in order to bring the voltage signal Voq closer to the voltage command value of the q-axis component. The calculator 81 inputs the calculated correction value to the adder 83. The calculator 81 calculates the correction value based on the subtraction result, for example, by proportional control or proportional-integral control. However, the calculation method by the calculator 81 is not limited to this, and any method that can appropriately calculate a correction value based on the subtraction result may be used.

[0093] The calculator 82 receives a voltage signal Vod of the d-axis component of the AC power output from the main circuit unit 12. Based on the input voltage signal Vod of the d-axis component, the calculator 82 calculates a correction value for the magnitude of the q-axis component of the AC current output from the power conversion unit 20. The calculator 82 inputs the calculated correction value to the adder 83. The calculator 82 calculates the correction value based on the voltage signal Vod, for example, by proportional control or proportional-integral control. However, the calculation method used by the calculator 82 is not limited to this, and any method that can appropriately calculate a correction value based on the voltage signal Vod may be used.

[0094] The adder 83 receives the correction values ​​calculated by the calculators 81 and 82, as well as the current signal Igq of the q-axis component of the AC power output from the power conversion unit 20. The current signal Igq of the q-axis component of the AC power output from the power conversion unit 20 is calculated, for example, by performing a dq transformation (Park transformation) on the line currents Ia(INV), Ib(INV), and Ic(INV) of each phase of the AC power output from the power conversion unit 20.

[0095] The adder 83 adds the correction value calculated by the calculator 81 and the correction value calculated by the calculator 82 to the q-axis component current signal Igq, thereby obtaining a current command value Icq of the q-axis component of the AC current output from the main circuit unit 12. ＊ The adder 83 calculates the calculated q-axis component current command value Icq ＊ is input to the limiter 84.

[0096] The limiter 84 determines the current command value Icq of the q-axis component. ＊ The current command value Icq of the q-axis component after the processing is limited to a predetermined range. ＊ is input to the subtractor 85.

[0097] The subtractor 85 receives the current command value Icq of the q-axis component. ＊ is input to the subtractor 85, and a current signal Icq of the q-axis component of the AC power output from the main circuit unit 12 is also input to the subtractor 85. The subtractor 85 calculates a current command value Icq of the q-axis component ＊ The q-axis component current signal Icq is subtracted from the current signal Icq, and the subtraction result is calculated by a calculator 86.

[0098] Based on the input subtraction result, the calculator 86 calculates the current signal Icq as the current command value Icq ＊ The calculator 86 calculates a correction value for the magnitude of the q-axis component of the AC voltage output from the power conversion unit 20 so as to bring the magnitude closer to . The calculator 86 inputs the calculated correction value to the adder 88. The calculator 86 calculates the correction value based on the subtraction result by, for example, proportional control or proportional-integral control. However, the calculation method by the calculator 86 is not limited to this, and any method that can appropriately calculate the correction value based on the subtraction result may be used.

[0099] A current signal Icd of the d-axis component of the AC power output from the main circuit unit 12 is input to the calculator 87. Based on the input current signal Icd of the d-axis component, the calculator 87 calculates a correction value for the magnitude of the q-axis component of the AC voltage output from the power conversion unit 20. The calculator 87 inputs the calculated correction value to an adder 88. The calculator 87 calculates the correction value based on the current signal Icd, for example, by proportional control or proportional-integral control. However, the calculation method used by the calculator 87 is not limited to this, and any method that can appropriately calculate a correction value based on the current signal Icd may be used.

[0100] The adder 88 adds the correction value input from the calculator 86 and the correction value input from the calculator 87 , and inputs the addition result to the adder 89 .

[0101] The adder 89 receives the correction value calculated by the adder 88 and also receives the voltage signal Vgq of the q-axis component of the AC power output from the power conversion unit 20. The voltage signal Vgq of the q-axis component of the AC power output from the power conversion unit 20 is calculated, for example, by performing a dq transformation (Park transformation) on the phase voltages Va(INV), Vb(INV), and Vc(INV) of each phase of the AC power output from the power conversion unit 20.

[0102] The adder 89 adds the correction value to the input voltage signal Vgq of the q-axis component to calculate a voltage command value of the q-axis component of the AC power to be output from the power conversion unit 20. The adder 89 inputs the calculated voltage command value of the q-axis component to the inverter 90.

[0103] The inverter 90 receives the d-axis component voltage command value and the q-axis component voltage command value as input, as well as the phase voltage phase command value θ calculated by the command value calculation unit 30. The inverter 90 calculates instantaneous voltage output command values ​​Va(ref), Vb(ref), and Vc(ref) corresponding to the phase voltage phase command value θ from the d-axis component voltage command value and the q-axis component voltage command value, for example, by performing an inverse dq transformation (inverse Park transformation) on the d-axis component voltage command value and the q-axis component voltage command value based on the phase voltage phase command value θ.

[0104] As a result, the instantaneous voltage output command values ​​Va(ref), Vb(ref), and Vc(ref) are calculated by the command value generating unit 32. However, the configuration of the command value generating unit 32 is not limited to the above. The configuration of the command value generating unit 32 may be any configuration that can appropriately calculate the instantaneous voltage output command values ​​Va(ref), Vb(ref), and Vc(ref) based on each input information.

[0105] 4 is a graph schematically illustrating an example of the operation of the power conversion device according to the embodiment. The graph illustrates an example of AC current supplied from the main circuit unit 12 of the power conversion device 10 to the power grid 2.

[0106] Fig. 5 is a graph schematically showing an example of the operation of the reference power conversion apparatus. Fig. 5 shows an example of AC current supplied from the reference power conversion apparatus to the power grid 2. In the reference power conversion apparatus, the power synchronization control unit 42 uses the correction value Δf to calculate the phase voltage phase command value θ even when a grid disturbance occurs, and the voltage amplitude control unit 44 uses the correction value ΔV to calculate the phase voltage amplitude command value |V| even when a grid disturbance occurs.

[0107] In Figures 4 and 5, the horizontal axis represents time, and the vertical axis represents the magnitude of the AC current. Figures 4 and 5 show an example of an upper limit value UL and a lower limit value LL of the AC current supplied from the power conversion device 10 (main circuit unit 12) to the power grid 2. Note that in Figures 4 and 5, due to the scale of the time axis (horizontal axis), the lines representing the amplitude of the AC current touch each other in the time axis direction, appearing as bands.

[0108] Fig. 4 also shows an example of AC current when a system disturbance occurs at time t1. In other words, Fig. 4 shows an example of AC current when the system disturbance detection unit 40 detects the occurrence of a disturbance in the power system 2 at time t1. Fig. 5 shows an example of AC current when a system disturbance occurs at time t2.

[0109] 5 , in the reference power conversion device, when a grid disturbance occurs at time t2, the magnitude of the AC current exceeds the upper limit value UL and the lower limit value LL. That is, in the reference power conversion device, when a grid disturbance occurs at time t2, an overcurrent flows between the power conversion device and the power grid 2.

[0110] In the reference power conversion device, as described above, even when a system disturbance occurs, the correction value Δf is used to calculate the phase voltage phase command value θ, and the correction value ΔV is used to calculate the phase voltage amplitude command value |V|. Therefore, in the reference power conversion device, when a system disturbance such as a voltage sag occurs in the power system 2, the deviation between the active power command value Pref to the power conversion device and the active power output (active power P(PCS)) of the power conversion device increases, which also increases the deviation between the phase angle of the output voltage of the power conversion device (phase voltage phase command value θ) and the phase angle of the AC voltage of the power system 2. This is thought to be why an overcurrent occurs in the reference power conversion device in response to the occurrence of the system disturbance.

[0111] Therefore, in the reference power conversion device, an overcurrent may occur in response to a system disturbance, causing the magnitude of the AC current output from the power conversion device to exceed the upper limit value UL and the lower limit value LL, which may cause the power conversion device to stop operating.

[0112] In contrast, in the power conversion device 10 according to this embodiment, when the system disturbance detection unit 40 detects the occurrence of a disturbance in the power system 2, the power synchronization control unit 42 sets the frequency correction value Δf at the time when the system disturbance detection unit 40 detects the occurrence of the disturbance in the power system 2 as the frequency correction value Δf at the time of the disturbance occurrence. ｐｒｅｖ The stored frequency correction value Δf ｐｒｅｖIn the power conversion device 10 according to this embodiment, when the system disturbance detection unit 40 detects the occurrence of a disturbance in the power system 2, the voltage amplitude control unit 44 calculates the phase voltage phase command value θ based on the phase voltage phase command value θ. ｐｒｅｖ The correction value ΔV of the magnitude of the AC voltage when the disturbance occurs is stored as ｐｒｅｖ Based on this, the phase voltage amplitude command value |V| is calculated.

[0113] In this way, the frequency correction value Δf ｐｒｅｖ By calculating the phase voltage phase command value θ based on the above, even when a system disturbance occurs and the deviation between the active power command value Pref and the measured value of the active power P(PCS) becomes large, it is possible to prevent the phase voltage phase command value θ from becoming an unintended value. It is also possible to prevent the deviation between the phase voltage phase command value θ and the phase angle of the AC voltage of the power system 2 from becoming large.

[0114] Then, the correction value ΔV of the magnitude of the AC voltage when the disturbance occurs ｐｒｅｖ By calculating the phase voltage amplitude command value |V| based on the above, even when a system disturbance occurs and the deviation between the reactive power command value Qref and the measured value of the reactive power Q(PCS) becomes large, it is possible to prevent the phase voltage amplitude command value |V| from becoming an unintended value. It is also possible to prevent the deviation between the phase voltage amplitude command value |V| and the amplitude of the AC voltage of the power system 2 from becoming large.

[0115] As a result, in the power conversion device 10 according to this embodiment, even when a temporary system disturbance such as a voltage dip occurs in the power system 2, it is possible to prevent an overcurrent from flowing between the power conversion device 10 and the power system 2. For example, as shown in Fig. 4 , in the power conversion device 10 according to this embodiment, even when a system disturbance occurs at time t1, the magnitude of the AC current is kept lower than the upper limit value UL and the lower limit value LL.

[0116] Therefore, in the power conversion device 10 according to this embodiment, even when a temporary system disturbance such as a voltage dip occurs in the power system 2, it is possible to prevent an overcurrent from flowing between the power conversion device 10 and the power system 2, which would otherwise cause the power conversion device 10 to stop operating. In the power conversion device 10 and the control device 14 according to this embodiment, it is possible to improve the continuity of interconnected operation with the power system 2, even when a disturbance occurs on the power system 2 side.

[0117] Furthermore, in the power conversion device 10 according to this embodiment, when the system disturbance detection unit 40 detects the occurrence of a disturbance in the power system 2, the power synchronization control unit 42 sets the difference between the active power command value Pref and the measured value of the active power P(PCS) to 0 and calculates the correction value Δf, and when the system disturbance detection unit 40 detects the occurrence of a disturbance in the power system 2, the voltage amplitude control unit 44 sets the difference between the reactive power command value Qref and the measured value of the reactive power Q(PCS) to 0 and calculates the correction value ΔV.

[0118] As a result, in the power conversion device 10 according to this embodiment, for example, when the power grid 2 recovers from a disturbance, it is possible to prevent the correction values ​​Δf and ΔV from becoming abnormal values, and it is possible to further improve the calculation accuracy of the correction values ​​Δf and ΔV. For example, it is possible to further improve the stability of the operation of the power conversion device 10 and further improve the continuity of the interconnected operation with the power grid 2.

[0119] Fig. 6 is a block diagram schematically illustrating a modified example of the command value calculation unit according to the embodiment. As illustrated in Fig. 6, in the command value calculation unit 30a, system frequency information indicating a measured value of the frequency of the power system 2 is input to a system disturbance detection unit 40a. Note that components that are substantially the same in function and configuration as those in the above embodiment are given the same reference numerals, and detailed description thereof will be omitted.

[0120] The system frequency information is measured by, for example, the second measuring device 18 and input from the second measuring device 18 to the command value calculation unit 30a and the system disturbance detection unit 40a. In other words, the system disturbance detection unit 40a acquires the system frequency information from, for example, the second measuring device 18. The system disturbance detection unit 40a may acquire the system frequency information by, for example, internally calculating a frequency based on phase voltages Va(PCS), Vb(PCS), Vc(PCS), etc. However, the method of acquiring the system frequency information by the system disturbance detection unit 40a is not limited to the above and may be any method that can appropriately acquire the system frequency information.

[0121] For example, when the measured value of the frequency of the power system 2 represented by the system frequency information falls outside the normal operation range, the system disturbance detection unit 40a detects the occurrence of a disturbance in the power system 2. Then, for example, when the measured value of the frequency of the power system 2 represented by the system frequency information falls within the normal operation range after detecting the occurrence of a disturbance in the power system 2, the system disturbance detection unit 40a detects the recovery of the power system 2 from the disturbance.

[0122] The system disturbance detection unit 40a may, for example, calculate a differential value of the frequency of the power system 2 based on the acquired system frequency information, detect the occurrence of a disturbance in the power system 2 when the differential value of the frequency of the power system 2 falls outside the normal operation range, and detect recovery from the disturbance in the power system 2 when the differential value of the frequency of the power system 2 falls within the normal operation range after detecting the occurrence of a disturbance in the power system 2.

[0123] In this way, the system disturbance detection unit 40a may detect the occurrence of a disturbance in the power system 2 and recovery from the disturbance based on the measured value of the frequency of the power system 2, without being limited to the magnitude of the self-terminal voltage of the main circuit unit 12. The system disturbance detection unit 40a may detect the occurrence of a disturbance in the power system 2 and recovery from the disturbance based on, for example, the magnitude of the self-terminal voltage of the main circuit unit 12 and the measured value of the frequency of the power system 2. In other words, the system disturbance detection unit 40a may detect the occurrence of a disturbance in the power system 2 and recovery from the disturbance based on at least one of the magnitude of the self-terminal voltage of the main circuit unit 12 and the measured value of the frequency of the power system 2.

[0124] 7 is a block diagram schematically illustrating a modified example of the command value calculation unit according to the embodiment. As illustrated in FIG. 7, in the command value calculation unit 30b, a disturbance detection signal indicating the detection result of the occurrence of a disturbance in the power system 2 is input to a system disturbance detection unit 40b. The system disturbance detection unit 40b receives the disturbance detection signal.

[0125] The disturbance detection signal is input to the command value calculation unit 30b and the system disturbance detection unit 40b from an external device such as a higher-level controller. However, the method of inputting the disturbance detection signal to the system disturbance detection unit 40b is not limited to the above, and any method may be used as long as it can appropriately input the disturbance detection signal to the system disturbance detection unit 40b.

[0126] The system disturbance detection unit 40b detects the occurrence of a disturbance in the power system 2, for example, when the disturbance detection signal indicates that a disturbance has been detected in the power system 2. Then, after detecting the occurrence of a disturbance in the power system 2, the system disturbance detection unit 40b detects recovery from the disturbance in the power system 2, for example, when the disturbance detection signal switches from a state in which the occurrence of a disturbance in the power system 2 has been detected to a state in which the disturbance has not been detected.

[0127] In this way, the system disturbance detection unit 40b may detect the occurrence of a disturbance in the power system 2 and recovery from the disturbance based on a disturbance detection signal input from an external device, etc. In other words, the occurrence of a disturbance in the power system 2 and recovery from the disturbance may be determined by an external device such as a higher-level controller.

[0128] The method by which the system disturbance detector detects the occurrence of a disturbance in the power system 2 is not limited to the above, and any method may be used that allows the system disturbance detector to appropriately detect the occurrence of a disturbance.

[0129] The present embodiment includes the following aspects. (Supplementary Note 1) A power converter includes a main circuit unit having a power conversion unit for converting power, converting input power into AC power compatible with a power grid, and outputting the converted AC power to the power grid; and a control device that calculates an instantaneous voltage output command value of AC power to be output from the power conversion unit based on an active power command value and a reactive power command value, and controls the operation of the power conversion unit so that a voltage corresponding to the instantaneous voltage output command value is output from the power conversion unit, thereby controlling the conversion of power by the main circuit unit, wherein the control device includes: a command value calculation unit that calculates a phase voltage phase command value of AC power to be output from the main circuit unit based on the active power command value and a measured value of active power at an output terminal of the main circuit unit, and calculates a phase voltage amplitude command value of AC power to be output from the main circuit unit based on the reactive power command value and the measured value of reactive power at an output terminal of the main circuit unit; and a command value generation unit that calculates the instantaneous voltage output command value based on the phase voltage phase command value and the phase voltage amplitude command value, wherein the command value calculation unit the power system includes a system disturbance detection unit that detects the occurrence of a disturbance in the power system; a power synchronization control unit that calculates the phase voltage phase command value of the AC power output from the main circuit unit based on the active power command value and the measured value of the active power; and a voltage amplitude control unit that calculates the phase voltage amplitude command value of the AC power output from the main circuit unit based on the reactive power command value and the measured value of the reactive power, wherein the power synchronization control unit calculates a correction value of the frequency of the AC voltage output from the main circuit unit so as to bring the measured value of the active power closer to the active power command value, and when the occurrence of a disturbance in the power system is not detected by the system disturbance detection unit, calculates a command value of the frequency of the AC voltage output from the main circuit unit by adding the frequency correction value to a reference value of the frequency of the AC voltage output from the main circuit unit,When the occurrence of a disturbance in the power system is detected by the system disturbance detection unit, the frequency correction value at the time when the occurrence of the disturbance in the power system is detected by the system disturbance detection unit is stored as the frequency correction value at the time of the disturbance occurrence, and the frequency command value is calculated by adding the frequency correction value at the time of the disturbance occurrence to a reference value of the frequency of the AC voltage output from the main circuit unit; the frequency command value is integrated and the integration result is multiplied by 2π to calculate the phase voltage phase command value; the voltage amplitude control unit calculates a correction value for the magnitude of the AC voltage output from the main circuit unit so as to bring the measured value of the reactive power closer to the reactive power command value; when the occurrence of a disturbance in the power system is not detected by the system disturbance detection unit, the phase voltage amplitude command value is calculated by adding the correction value for the magnitude of the AC voltage to the reference value of the magnitude of the AC voltage output from the main circuit unit; when the occurrence of a disturbance in the power system is detected by the system disturbance detection unit, a correction value of the magnitude of the AC voltage at the time when the occurrence of the disturbance in the power system is detected by the system disturbance detection unit is stored as a correction value of the magnitude of the AC voltage at the time when the disturbance occurs, and the phase voltage amplitude command value is calculated by adding the correction value of the magnitude of the AC voltage at the time when the disturbance occurs to a reference value of the magnitude of the AC voltage output from the main circuit unit.

[0130] (Supplementary Note 2) The power conversion device according to Supplementary Note 1, wherein the power synchronization control unit, when the occurrence of a disturbance in the power grid is not detected by the grid disturbance detection unit, calculates a correction value for the frequency of the AC power output from the main circuit unit to bring the measured value of the active power closer to the active power command value, and when the occurrence of a disturbance in the power grid is detected by the grid disturbance detection unit, calculates the correction value for the frequency by setting a difference between the active power command value and the measured value of the active power to 0.

[0131] (Supplementary Note 3) The power conversion device according to Supplementary Note 1 or 2, wherein the voltage amplitude control unit, when the occurrence of a disturbance in the power grid is not detected by the grid disturbance detection unit, calculates a correction value for the magnitude of the AC voltage output from the main circuit unit to bring the measured value of the reactive power closer to the reactive power command value, and when the occurrence of a disturbance in the power grid is detected by the grid disturbance detection unit, sets a difference between the reactive power command value and the measured value of the reactive power to 0 and calculates the correction value for the magnitude of the AC voltage.

[0132] (Supplementary Note 4) The power conversion device according to any one of Supplementary Notes 1 to 3, wherein the system disturbance detection unit detects the occurrence of a disturbance in the power system when a magnitude of a phase voltage of the AC power output from the main circuit unit falls outside a steady operation range, and detects recovery from the disturbance in the power system when a magnitude of the phase voltage falls within the steady operation range after detecting the occurrence of the disturbance in the power system.

[0133] (Supplementary Note 5) The power conversion device according to any one of Supplementary Notes 1 to 4, wherein the system disturbance detection unit acquires system frequency information representing a measured value of a frequency of the power system, detects an occurrence of a disturbance in the power system when the measured value of the frequency of the power system is outside a steady operation range, and detects recovery of the power system from the disturbance when the measured value of the frequency of the power system is within the steady operation range after detecting the occurrence of the disturbance in the power system.

[0134] (Supplementary Note 6) The power conversion device according to any one of Supplementary Notes 1 to 5, wherein the system disturbance detection unit receives an input of a disturbance detection signal indicating a detection result of an occurrence of a disturbance in the power system, detects the occurrence of a disturbance in the power system when the disturbance detection signal indicates a state in which the occurrence of a disturbance in the power system has been detected, and detects recovery from the disturbance in the power system when the disturbance detection signal switches from a state in which the occurrence of a disturbance in the power system has been detected to a state in which the disturbance detection signal has not been detected after the occurrence of the disturbance in the power system has been detected.

[0135] (Supplementary Note 7) A control device used in a power conversion device having a power conversion unit that converts power, and a main circuit unit that converts input power into AC power compatible with a power grid and outputs the converted AC power to the power grid, calculates an instantaneous voltage output command value of AC power to be output from the power conversion unit based on an active power command value and a reactive power command value, and controls the operation of the power conversion unit so that a voltage corresponding to the instantaneous voltage output command value is output from the power conversion unit, thereby controlling the conversion of power by the main circuit unit, the control device comprising: a command value calculation unit that calculates a phase voltage phase command value of AC power to be output from the main circuit unit based on the active power command value and a measured value of active power at an output terminal of the main circuit unit, and calculates a phase voltage amplitude command value of AC power to be output from the main circuit unit based on the reactive power command value and the measured value of reactive power at an output terminal of the main circuit unit; and a command value generation unit that calculates the instantaneous voltage output command value based on the phase voltage phase command value and the phase voltage amplitude command value, wherein the command value calculation unit the power system includes a system disturbance detection unit that detects the occurrence of a disturbance in the power system; a power synchronization control unit that calculates the phase voltage phase command value of the AC power output from the main circuit unit based on the active power command value and the measured value of the active power; and a voltage amplitude control unit that calculates the phase voltage amplitude command value of the AC power output from the main circuit unit based on the reactive power command value and the measured value of the reactive power, wherein the power synchronization control unit calculates a correction value of the frequency of the AC voltage output from the main circuit unit so as to bring the measured value of the active power closer to the active power command value, and when the occurrence of a disturbance in the power system is not detected by the system disturbance detection unit, calculates a command value of the frequency of the AC voltage output from the main circuit unit by adding the frequency correction value to a reference value of the frequency of the AC voltage output from the main circuit unit, when the occurrence of a disturbance in the power system is detected by the system disturbance detection unit, a correction value of the frequency at the time when the occurrence of the disturbance in the power system is detected by the system disturbance detection unit is stored as a correction value of the frequency at the time when the disturbance occurs, and a command value of the frequency is calculated by adding the correction value of the frequency at the time when the disturbance occurs to a reference value of the frequency of the AC voltage output from the main circuit unit;the voltage amplitude control unit calculates the phase voltage amplitude command value by integrating the frequency command value and multiplying the integration result by 2π, and the voltage amplitude control unit calculates a correction value for the magnitude of the AC voltage to be output from the main circuit unit so as to bring the measured value of the reactive power closer to the reactive power command value, and when the occurrence of a disturbance in the power system is not detected by the system disturbance detection unit, calculates the phase voltage amplitude command value by adding the correction value for the magnitude of the AC voltage to a reference value of the magnitude of the AC voltage to be output from the main circuit unit, and when the occurrence of a disturbance in the power system is detected by the system disturbance detection unit, stores the correction value for the magnitude of the AC voltage at the time when the occurrence of the disturbance in the power system is detected by the system disturbance detection unit as a correction value for the magnitude of the AC voltage at the time when a disturbance occurs, and calculates the phase voltage amplitude command value by adding the correction value for the magnitude of the AC voltage at the time when the disturbance occurs to the reference value of the magnitude of the AC voltage to be output from the main circuit unit.

[0136] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims.

[0137] DESCRIPTION OF SYMBOLS 2...power system, 4...power supply device, 10...power conversion device, 12...main circuit section, 14...control device, 16...first measuring device, 18...second measuring device, 20...power conversion section, 22...filter circuit, 24...reactor, 26...capacitor, 30, 30a, 30b...command value calculation section, 32...command value generation section, 40, 40a, 40b...system disturbance detection section, 42...power synchronization control section, 44...voltage amplitude control section, 51...subtractor, 52...operator, 53...switching device, 54...adder, 55...integrator, 61...subtractor, 62...operator, 63...switching device, 64...adder, 70...subtractor, 71, 72...operator, 73...adder, 74...limiter, 75... subtractor, 76, 77... computing unit, 78... subtractor, 79... adder, 80... subtractor, 81, 82... computing unit, 83... adder, 84... limiter, 85... subtractor, 86, 87... computing unit, 88, 89... adder, 90... inverse converter

Claims

1. A power converter comprising: a main circuit unit having a power conversion unit for converting power, converting input power into AC power compatible with a power grid, and outputting the converted AC power to the power grid; and a control device that calculates an instantaneous voltage output command value for AC power to be output from the power conversion unit based on an active power command value and a reactive power command value, and controls the operation of the power conversion unit so that a voltage corresponding to the instantaneous voltage output command value is output from the power conversion unit, thereby controlling the conversion of power by the main circuit unit, wherein the control device comprises: a command value calculation unit that calculates a phase voltage phase command value for AC power to be output from the main circuit unit based on the active power command value and a measured value of active power at an output terminal of the main circuit unit, and calculates a phase voltage amplitude command value for AC power to be output from the main circuit unit based on the reactive power command value and the measured value of reactive power at an output terminal of the main circuit unit; and a command value generation unit that calculates the instantaneous voltage output command value based on the phase voltage phase command value and the phase voltage amplitude command value, wherein the command value calculation unit the power system includes a system disturbance detection unit that detects the occurrence of a disturbance in the power system; a power synchronization control unit that calculates the phase voltage phase command value of the AC power output from the main circuit unit based on the active power command value and the measured value of the active power; and a voltage amplitude control unit that calculates the phase voltage amplitude command value of the AC power output from the main circuit unit based on the reactive power command value and the measured value of the reactive power, wherein the power synchronization control unit calculates a correction value of the frequency of the AC voltage output from the main circuit unit so as to bring the measured value of the active power closer to the active power command value, and when the occurrence of a disturbance in the power system is not detected by the system disturbance detection unit, calculates a command value of the frequency of the AC voltage output from the main circuit unit by adding the frequency correction value to a reference value of the frequency of the AC voltage output from the main circuit unit, when the occurrence of a disturbance in the power system is detected by the system disturbance detection unit, a correction value of the frequency at the time when the occurrence of the disturbance in the power system is detected by the system disturbance detection unit is stored as a correction value of the frequency at the time when the disturbance occurs, and a command value of the frequency is calculated by adding the correction value of the frequency at the time when the disturbance occurs to a reference value of the frequency of the AC voltage output from the main circuit unit;the voltage amplitude control unit calculates a correction value for the magnitude of the AC voltage to be output from the main circuit unit so as to bring the measured value of reactive power closer to the reactive power command value, and when the occurrence of a disturbance in the power system is not detected by the system disturbance detection unit, calculates the phase voltage amplitude command value by adding the correction value for the magnitude of the AC voltage to a reference value of the magnitude of the AC voltage to be output from the main circuit unit, and when the occurrence of a disturbance in the power system is detected by the system disturbance detection unit, stores the correction value for the magnitude of the AC voltage at the time when the occurrence of the disturbance in the power system is detected by the system disturbance detection unit as a correction value for the magnitude of the AC voltage at the time when a disturbance occurs, and calculates the phase voltage amplitude command value by adding the correction value for the magnitude of the AC voltage at the time when the disturbance occurs to the reference value of the magnitude of the AC voltage to be output from the main circuit unit.

2. The power conversion device according to claim 1, wherein the power synchronization control unit calculates a correction value for the frequency of the AC power output from the main circuit unit to bring the measured value of active power closer to the active power command value when the system disturbance detection unit has not detected the occurrence of a disturbance in the power system, and when the system disturbance detection unit has detected the occurrence of a disturbance in the power system, sets the difference between the active power command value and the measured value of active power to zero and calculates the correction value for the frequency.

3. The power conversion device according to claim 1, wherein the voltage amplitude control unit calculates a correction value for the magnitude of the AC voltage output from the main circuit unit to bring the measured value of the reactive power closer to the reactive power command value when the system disturbance detection unit does not detect the occurrence of a disturbance in the power system, and when the system disturbance detection unit detects the occurrence of a disturbance in the power system, sets the difference between the reactive power command value and the measured value of the reactive power to 0 and calculates the correction value for the magnitude of the AC voltage.

4. The power conversion device according to claim 1, wherein the system disturbance detection unit detects the occurrence of a disturbance in the power system when the magnitude of the phase voltage of the AC power output from the main circuit unit falls outside a steady-state operating range, and detects recovery from the disturbance in the power system when the magnitude of the phase voltage falls within the steady-state operating range after detecting the occurrence of a disturbance in the power system.

5. The power conversion device according to claim 1, wherein the system disturbance detection unit acquires system frequency information representing a measured value of the frequency of the power system, detects the occurrence of a disturbance in the power system when the measured value of the frequency of the power system falls outside a steady-state operating range, and detects recovery from the disturbance in the power system when the measured value of the frequency of the power system falls within the steady-state operating range after detecting the occurrence of a disturbance in the power system.

6. The power conversion device according to claim 1, wherein the system disturbance detection unit receives an input of a disturbance detection signal indicating a detection result of the occurrence of a disturbance in the power system, detects the occurrence of a disturbance in the power system when the disturbance detection signal indicates that the occurrence of a disturbance in the power system has been detected, and detects recovery from the disturbance in the power system when, after detecting the occurrence of a disturbance in the power system, the disturbance detection signal switches from a state in which the occurrence of a disturbance in the power system has been detected to a state in which the disturbance detection signal has not been detected.

7. A control device used in a power conversion device having a power conversion unit that converts power, converts input power into AC power compatible with a power grid, and outputs the converted AC power to the power grid, the control device calculating an instantaneous voltage output command value for AC power to be output from the power conversion unit based on an active power command value and a reactive power command value, and controlling the operation of the power conversion unit so that a voltage corresponding to the instantaneous voltage output command value is output from the power conversion unit, thereby controlling the conversion of power by the main circuit unit, the control device comprising: a command value calculation unit that calculates a phase voltage phase command value for AC power to be output from the main circuit unit based on the active power command value and a measured value of active power at an output terminal of the main circuit unit, and calculates a phase voltage amplitude command value for AC power to be output from the main circuit unit based on the reactive power command value and the measured value of reactive power at an output terminal of the main circuit unit; and a command value generation unit that calculates the instantaneous voltage output command value based on the phase voltage phase command value and the phase voltage amplitude command value, the command value calculation unit the power system includes a system disturbance detection unit that detects the occurrence of a disturbance in the power system; a power synchronization control unit that calculates the phase voltage phase command value of the AC power output from the main circuit unit based on the active power command value and the measured value of the active power; and a voltage amplitude control unit that calculates the phase voltage amplitude command value of the AC power output from the main circuit unit based on the reactive power command value and the measured value of the reactive power, wherein the power synchronization control unit calculates a correction value of the frequency of the AC voltage output from the main circuit unit so as to bring the measured value of the active power closer to the active power command value, and when the occurrence of a disturbance in the power system is not detected by the system disturbance detection unit, calculates a command value of the frequency of the AC voltage output from the main circuit unit by adding the frequency correction value to a reference value of the frequency of the AC voltage output from the main circuit unit, when the occurrence of a disturbance in the power system is detected by the system disturbance detection unit, a correction value of the frequency at the time when the occurrence of the disturbance in the power system is detected by the system disturbance detection unit is stored as a correction value of the frequency at the time when the disturbance occurs, and a command value of the frequency is calculated by adding the correction value of the frequency at the time when the disturbance occurs to a reference value of the frequency of the AC voltage output from the main circuit unit;the voltage amplitude control unit calculates the phase voltage amplitude command value by integrating the frequency command value and multiplying the integration result by 2π, and the voltage amplitude control unit calculates a correction value for the magnitude of the AC voltage to be output from the main circuit unit so as to bring the measured value of the reactive power closer to the reactive power command value, and when the occurrence of a disturbance in the power system is not detected by the system disturbance detection unit, calculates the phase voltage amplitude command value by adding the correction value for the magnitude of the AC voltage to a reference value of the magnitude of the AC voltage to be output from the main circuit unit, and when the occurrence of a disturbance in the power system is detected by the system disturbance detection unit, stores the correction value for the magnitude of the AC voltage at the time when the occurrence of the disturbance in the power system is detected by the system disturbance detection unit as a correction value for the magnitude of the AC voltage at the time when a disturbance occurs, and calculates the phase voltage amplitude command value by adding the correction value for the magnitude of the AC voltage at the time when the disturbance occurs to the reference value of the magnitude of the AC voltage to be output from the main circuit unit.

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