Control device, power conversion device, and control method

Abstract

A technique is provided that can improve current control in a power conversion device under conditions where there is a large phase difference between the measured value and command value of the current of the controlled object. A control device (60) according to an embodiment of the present disclosure controls a voltage V at a connection point GCP between a power supply system (10) including a power conversion device (40) and a power grid (20). D a phase detector 601 for detecting the phase θ of the power converter 40; * and the current measurement value I, and a phase difference detection unit 604 that detects the phase difference δ between the current command value I and the current measurement value I, and a current command value I that is corrected so that the greater the phase difference δ, the smaller the value after correction. * The corrected current command value I ** a current command correction unit 605 that corrects the current measurement value I to the corrected current command value I ** Based on this, the output current of the power conversion device 40 is corrected to the corrected current command value I ** and a DC-ACR unit 606 that controls the frequency response so as to follow the frequency response.

Description

[Technical Field]

[0001] The present disclosure relates to a control device and the like. [Background technology]

[0002] For example, for a power conversion device that performs power conversion between direct current and alternating current, a current controller (ACR: Auto Current Regulator) that controls the current on the AC side so that it follows a command value is known (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 5-300747 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, in a power conversion device, power may be exchanged between a DC power source and an AC power grid. In this case, if the phase difference between the measured value and the command value of the current of the controlled object is large, problems such as overcurrent, overvoltage, and instability of the current control may occur if the current controller operates normally.

[0005] In view of the above problem, an object of the present invention is to provide a technology for a power conversion device that can improve current control in a situation where there is a large phase difference between the measured value and command value of the current of the controlled object. [Means for solving the problem]

[0006] In order to achieve the above object, in one embodiment of the present disclosure, A control device for controlling a power conversion device having one end connected to a DC power source and the other end connected to a power grid, the power conversion device performing power conversion between DC on the one end side and AC on the other end side, a phase detection unit that detects the phase of a voltage at an interconnection point between the power conversion device and the power grid; a phase difference detection unit that detects a phase difference between a command value of the output current of the power conversion device and the measured value; a current control unit that controls the output current so that the output current follows a target value based on the measured value and the command value of the output current; a limiting unit that limits the effect of the control of the output current by the current control unit, and that increases the degree of limitation on the effect of the control of the output current by the current control unit as the phase difference increases; A control device is provided.

[0007] In another embodiment of the present disclosure, a main circuit unit having one end connected to a DC power source and the other end connected to a power grid, and performing power conversion between DC at the one end and AC at the other end; a phase detection unit that detects the phase of a voltage at an interconnection point between the power conversion device and the power grid; a phase difference detection unit that detects a phase difference between a command value of an output current of the power conversion device and the measured value; a current control unit that controls the output current so that the output current follows a target value based on the measured value and the command value of the output current; a limiting unit that limits the effect of the control of the output current by the current control unit, and that increases the degree of limitation on the effect of the control of the output current by the current control unit as the phase difference increases; A power converter is provided.

[0008] In still another embodiment of the present disclosure, A control method for controlling a power conversion device having one end connected to a DC power source and the other end connected to a power grid, the power conversion device performing power conversion between DC on the one end side and AC on the other end side, the method comprising: a phase detection step of detecting a phase of a voltage at an interconnection point between the power conversion device and the power grid; a phase difference detection step of detecting a phase difference between a command value of an output current of the power conversion device and the measured value; a current control step of controlling the output current so that the output current follows a target value based on the measured value and the command value of the output current; a limiting step of limiting the effect of the control of the output current by the current control unit, the degree of limitation of the effect of the control of the output current by the current control unit increasing as the phase difference increases. A control method is provided. [Effects of the Invention]

[0009] According to the above-described embodiment, it is possible to improve current control of a power conversion device in a situation where there is a large phase difference between the measured value and the command value of the current of the controlled object. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating a configuration of an example of a power system. [Figure 2] FIG. 2 is a diagram illustrating the phase relationship between voltage and current in a power system. [Figure 3] FIG. 1 is a diagram illustrating an example of a control method for a power supply system. [Figure 4] FIG. 2 is a control block diagram showing the configuration of a first example of a control device. [Figure 5] FIG. 10 is a diagram illustrating an example of a phase delay of a current command value relative to a current measurement value. [Figure 6] FIG. 10 is a diagram illustrating an example of a phase difference between a current measurement value and a current command value. [Figure 7] FIG. 4 is a diagram showing an example of the relationship between a current command value before correction and a current command value after correction (corrected current command value). [Figure 8] FIG. 10 is a diagram illustrating a first example of a correction gain. [Figure 9] FIG. 10 is a diagram illustrating a second example of a correction gain. [Figure 10] FIG. 10 is a diagram illustrating a third example of a correction gain. [Figure 11] FIG. 10 is a diagram illustrating a fourth example of a correction gain. [Figure 12] FIG. 4 is a control block diagram showing the configuration of a second example of the control device. [Figure 13] FIG. 2 is a diagram illustrating an example of the configuration of an AC-ACR unit. [Figure 14] FIG. 2 is a diagram illustrating a configuration of an example of an AC-ACR unit of a U phase. [Figure 15] FIG. 10 is a flowchart illustrating an example of a process performed by a phase difference detection unit. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment will be described with reference to the drawings.

[0012] [Power system configuration] The configuration of a power system 1 according to this embodiment will be described with reference to FIGS.

[0013] Fig. 1 is a diagram showing the configuration of an example of a power system 1. Fig. 2 is a diagram illustrating the phase relationship between voltage and current in the power system 1. Fig. 3 is a diagram illustrating an example of a method for controlling current in the power supply system 10.

[0014] As shown in FIG. 1, the power system 1 includes a power supply system 10 and a power grid 20.

[0015] In the power system 1, power is exchanged between a power supply system 10 and a power grid 20.

[0016] In the power system 1, the exchange of power between the power supply system 10 and the power grid 20 is, for example, a bidirectional exchange of power. Furthermore, the exchange of power between the power supply system 10 and the power grid 20 may be only a supply of power from one side to the other, such as only a supply of power from the power supply system 10 to the power grid 20 or only a supply of power from the power grid 20 to the power supply system 10.

[0017] The power supply system 10 includes a DC power supply 30 , a power conversion device 40 , an AC filter 50 , and a control device 60 .

[0018] The power supply system 10 uses a power conversion device 40 to exchange power between a DC power supply 30 and a power grid 20. For example, as shown in Fig. 1 , a current flows between the power conversion device 40 and the power grid 20 via a reactor L1, a filter capacitor C, and a reactor L2 of an AC filter 50, a resistance R of the line, and an impedance Z of the line.

[0019] The power system 20 supplies three-phase AC power to an electrical load (not shown).

[0020] The DC power supply 30 is electrically connected to one end of the power conversion device 40 by a DC link.

[0021] The DC power supply 30 is, for example, a system storage battery. The system storage battery is, for example, a liquid-type lithium-ion battery or an all-solid-state battery.

[0022] Furthermore, the DC power supply 30 may be a wind power generator included in a wind power generation system as the power supply system 10. The wind power generator as the DC power supply 30 includes a wind turbine, a generator (for example, a PM (Permanent Magnet) synchronous generator) mechanically coupled to the wind turbine by a rotating shaft, and a power converter that converts AC power generated and output by the generator into DC power. In this case, the only exchange between the power supply system 10 and the power grid 20 is the supply of power from the power supply system 10 to the power grid 20.

[0023] Furthermore, the DC power supply 30 may be, for example, a solar power generator (specifically, a solar panel) included in a solar power generation system as the power supply system 10. In this case, the only exchange between the power supply system 10 and the power grid 20 is the supply of power from the power supply system 10 to the power grid 20.

[0024] One end of the power conversion device 40 is electrically connected to the DC power supply 30 through a DC link, and the other end is electrically connected to the power grid 20 via an AC filter 50. The power conversion device 40 performs power conversion between DC on the DC power supply 30 side and three-phase AC on the power grid 20 side.

[0025] Specifically, when power is supplied from the power supply system 10 to the power grid 20, the DC is converted into three-phase AC of a desired voltage (amplitude) and frequency and output to the power grid 20 via the AC filter 50. When power is supplied from the power grid 20 to the power supply system 10, the three-phase AC is converted into DC and the power is supplied to the DC power supply 30 via a DC link.

[0026] The power conversion device 40 includes, for example, an inverter circuit 42 capable of converting DC power into three-phase AC power of a desired voltage and frequency, or converting three-phase AC power into DC power, and a gate circuit 44 for driving the inverter circuit 42.

[0027] For example, the inverter circuit 42 is a three-phase full-bridge inverter circuit including six semiconductor switches (also referred to as "switching elements"), and for example, a free wheel diode is connected in parallel to each of the semiconductor switches.

[0028] The gate circuit 44 drives the semiconductor switch of the inverter circuit 42 to turn on and off under the control of the control device 60 .

[0029] The AC filter 50 passes the AC output from the power conversion device 40 and the three-phase AC supplied (input) from the power grid 20 to the power supply system 10, and attenuates unnecessary frequency components (e.g., harmonic components). For example, the AC filter 50 is an LCL filter that includes reactors L1 and L2 of the power conversion device 40 and a filter capacitor C provided between the reactors L1 and L2.

[0030] The control device 60 controls the power conversion device 40 to realize the exchange of power between the power supply system 10 (specifically, the DC power supply 30) and the power grid 20. Specifically, the control device 60 controls a main circuit (for example, the above-mentioned inverter circuit 42) that performs power conversion between DC on the DC power supply 30 side and three-phase AC on the power grid 20 side.

[0031] 1, the control device 60 is built into the power conversion device 40. The control device 60 may be a programmable logic controller (PLC), an edge controller, an edge server, or the like, installed in the same facility as the power conversion device 40. The control device 60 may be a server device (for example, an on-premise server or a cloud server) installed in a location different from the facility where the power conversion device 40 is installed.

[0032] For example, as shown in FIG. 2, the voltage V B ,V C ,V D is the current I B ,I C ,I D , and the impedance of each part.

[0033] Voltage V B is the voltage of the line between the power converter 40 and the AC filter 50, and corresponds to the output voltage of the power converter 40. B is the current in the line between the power converter 40 and the AC filter 50, and corresponds to the output current of the power converter 40. When the output current of the power converter 40 is a positive value, it is a current flowing from the power converter 40 to the power grid 20 as shown in the figure, and when it is a negative value, it is a current flowing from the power grid 20 to the power converter 40, in the opposite direction to the figure. C corresponds to the voltage across the filter capacitor C. The current I C corresponds to the current of the filter capacitor C. When the current of the filter capacitor C is a positive value, it flows out of the line between the power conversion device 40 and the power system 20 as shown in the figure, and when it is a negative value, it flows into the line in the opposite direction to the figure. D corresponds to the voltage (connection point voltage) at the interconnection point GCP between the power supply system 10 and the power grid 20. D corresponds to the current at the grid connection point GCP.

[0034] For example, as shown in Figure 3, the voltage V D and current ID Based on this, the active power P and reactive power Q exchanged between the power supply system 10 and the power grid 20 are determined, and the voltage V at the grid connection point GCP is calculated. D and current I D Phase angle θ corresponding to the phase difference with D cosθ D is the power factor. Therefore, the control device 60 controls the power conversion device 40 so that the power factor becomes a desired value, for example.

[0035] [Example of control device 1] A first example of the control device 60 will be described with reference to FIGS. 4 to 7 in addition to FIG.

[0036] 4 is a control block diagram showing the configuration of a first example of the control device 60. B The command value I for the measured value I (hereinafter referred to as "measured current I") * (Hereinafter, "current command value I * 6 is a diagram showing an example of a phase delay DLY of the current command value I. * 7 is a diagram showing an example of a phase difference between the current command value I * and the corrected current command value (corrected current command value I ** ) is a diagram illustrating an example of the relationship.

[0037] Specifically, Fig. 7 shows the current command value I * 7A shows the current command value after correction (corrected current command value I ** 7B, which shows the same.

[0038] As shown in FIG. 4, the control device 60 includes a phase detection unit 601, a three-phase to two-phase conversion unit 602, a current command generation unit 603, a phase difference detection unit 604, a current command correction unit 605, a DC-ACR unit 606, a two-phase to three-phase conversion unit 607, and a PWM conversion unit 608.

[0039] Some or all of the functions of each unit of the control device 60 may be realized solely by hardware such as electrical circuits or electronic circuits. Alternatively, some or all of the functions of each unit of the control device 60 may be realized by a combination of hardware and software, such as a program, an auxiliary storage device corresponding to an installation destination, a load destination, and an execution unit of the program, a memory device, and a processor. Examples of the auxiliary storage device include a hard disk drive (HDD), a solid state drive (SSD), an electrically erasable programmable read-only memory (EEPROM), and a flash memory. Examples of the memory device include a static random access memory (SRAM), a dynamic random access memory (DRAM), and the like. Examples of the processor include a central processing unit (CPU). Examples of the processor may also include a graphics processing unit (GPU), a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), and the like.

[0040] The phase detector 601 detects the voltage V D Based on the measured value (also called the "detected value," "actual value," or "actual measurement value") of D The phase θ of the voltage V D For convenience, the measured value of is called "voltage measurement value V D For example, the phase detector 601 may be referred to as a phase detector. D Based on this, the voltage V at the grid connection point GCP is calculated using a phase locked loop (PLL). D The phase θ of

[0041] The three-phase to two-phase converter 602 converts electrical physical quantities (for example, voltage, current, etc.) of three-phase AC into a voltage V DThe phase θ of the current is converted into an equivalent expression of a two-phase AC current in a dq rotating coordinate system (hereinafter simply referred to as a "dq rotating coordinate system") based on the phase θ of the current.

[0042] For example, the three-phase to two-phase conversion unit 602 calculates the U-phase component A of the electrical physical quantity of the three-phase AC by using the following equation (1): U , V phase component A V , and W phase component A W The d-axis component A in the dq rotating coordinate system d and q-axis component A q Convert to.

[0043]

number

[0044] In this example, the three-phase to two-phase conversion unit 602 converts the three-phase AC current I B The three-phase to two-phase conversion unit 602 converts the measured value of the U-phase current I of the three-phase AC current measured value I into a measured value of the two-phase AC in the dq rotating coordinate system. U , V phase current measurement value I V , and the measured W-phase current I W is the measured value I of the d-axis output current of the power conversion device 40. d and the measured value of the q-axis output current I q Hereafter, the measured current I U , the current measurement I V , and the measured current I W For convenience, we will refer to this as the "U-phase current measurement value I U ", "V phase current measurement value I V " and "W-phase current measurement value I W In addition, the measured value of the d-axis output current I d and the measured value of the q-axis output current I q For convenience, we will call it the "d-axis current measurement value I d " and "q-axis current measurement value I q " may be referred to as ".

[0045] The current command generator 603 generates a voltage V D , and the output current of the power conversion device 40 (current IB ) (current measurement value I), the output current (current I B ) command value I * Hereinafter, the command value I of the output current of the power conversion device 40 is generated. * For convenience, we will call it the "current command value I * "It is sometimes referred to as ".

[0046] Specifically, the current command generator 603 generates a current command value I * As a result, command values ​​for the active current and the reactive current of the output current of the power conversion device 40 are generated.

[0047] The effective current is the current I in the dq rotating coordinate system. B The reactive current corresponds to the d-axis component of the current I B This corresponds to the q-axis component of the current, ie, the q-axis output current of the power conversion device 40.

[0048] The current command generation unit 603 generates a command value I for the d-axis output current and the q-axis output current of the power conversion device 40 so that the active power and reactive power output by the power conversion device 40 become desired values. d * ,I q * The d-axis output current command value I d * , and the q-axis output current command value I q * For convenience, we will call it the "d-axis current command value I d * " and "q-axis current command value I q * " may be referred to as ".

[0049] The phase difference detection unit 604 detects the phase θ of the current measurement value I and the current command value I * The phase difference δ between the phase of

[0050] For example, as shown in FIG. 5A, the current command value I * If a delay DLY occurs in the current measurement value I and the current command value I,* There may be a clear phase difference δ between

[0051] As shown in Figure 5B, the current measurement value I and the current command value I * The phase difference δ is the difference between the measured current I and the current command value I in the dq rotating coordinate system. * It appears as the angular difference between the vectors.

[0052] For example, the current command value I with respect to the current measurement value I may vary depending on factors such as the impedance characteristics of the power system 20, the time constant of the AC filter 50, and the delay in the control calculation in the control device 60. * As a result, there may be a significant delay between the measured current I and the current command I * There may be a clear phase difference δ between

[0053] In addition, for example, when the bus voltage VE of the power system 20 drops due to an accident such as a short circuit or a ground fault in the power system 20, the voltage V at the interconnection point GCP is reduced by the output current of the power conversion device 40 and the impedance Z of the line. D In this case, the phase detector 601 may detect the phase of the voltage output from the power converter 40 as the voltage V at the grid-connection point GCP. D As a result, the phase θ detected by the phase detector 601 may be significantly different from the phase of the bus voltage VE when the voltage is restored. * There is a clear delay between the measured current I and the current command value I * There may be a clear phase difference δ between

[0054] For example, the phase difference detection unit 604 uses the following equations (2.1) to (2.4) to calculate the current measurement value I and the current command value I * The phase difference δ is detected by calculating the cosine cos δ and sine sin δ of the phase difference δ.

[0055]

number

[0056] The current command correction unit 605 calculates the current command value I * (Specifically, the d-axis current command value I d * and q-axis current command value I q * ) is corrected to be less than the original value, and the corrected current command value I ** The corrected current command value I ** is the corrected d-axis current command value I d ** (hereinafter referred to as the "corrected d-axis current command value I d ** ") and the corrected q-axis current command value I q ** (hereinafter referred to as the "corrected q-axis current command value I q ** ").

[0057] As a result, the current command correction unit 605 calculates the corrected current command value I ** Based on this, the output current (current I B ), it is possible to limit the effect of current control by the DC-ACR unit 606 described later.

[0058] Specifically, the current command corrector 605 adjusts the corrected current command value I ** The current command value I * d-axis current command value I d * and q-axis current command value I q * The corrected current command value I ** The corrected d-axis current command value I d ** and q-axis current command value I q ** Correct to.

[0059] As a result, the current command corrector 605 can increase the degree of limitation on the action of current control by the DC-ACR unit 606 as the phase difference δ increases.

[0060] For example, when the voltage is restored after an accident such as a short circuit or a ground fault occurs in the power grid 20, the bus voltage VE of the power grid 20 and the voltage V of the interconnection point GCP D When there is a large phase difference with the DC-ACR unit 606, the power conversion device 40 operates to reduce the control deviation through current control by the DC-ACR unit 606. As a result, if the current control by the DC-ACR unit 606 operates normally, there is a possibility that an overcurrent or overvoltage may occur instantaneously.

[0061] In contrast to this, in this example, the current command corrector 605 can limit the action of the current control by the DC-ACR unit 606 so that the degree of limitation increases as the phase difference δ increases. Therefore, the current command corrector 605 can limit the action of the current control by the DC-ACR unit 606 so that the degree of limitation increases as the phase difference δ increases. D and the phase θ of the power grid 20, resulting in a relatively large phase difference δ, the control device 60 can limit the current control action by the DC-ACR unit 606 at a relatively high level. Therefore, the control device 60 can suppress the occurrence of overcurrent or overvoltage when the voltage is restored after the occurrence of an accident such as a short circuit or a ground fault in the power grid 20.

[0062] In addition, as described above, the current command value I * As a result, there is a possibility that the current control by the control device 60 will become unstable due to a tracking delay of the PLL or the like.

[0063] In contrast to this, in this example, the current command correction unit 605 can limit the action of the current control by the DC-ACR unit 606 so that the degree of limitation increases as the phase difference δ increases. Therefore, the current command correction unit 605 can correct the current command value I *When a clear delay occurs in the current control, the current control action by the DC-ACR unit 606 can be limited at a relatively high level. Therefore, the control device 60 can suppress instability of the current control caused by a tracking delay of the PLL or the like.

[0064] For example, the current command correction unit 605 calculates the d-axis current command value I d * and q-axis current command value I q * By multiplying each of these by the correction gain k, the corrected d-axis current command value I d ** and the corrected q-axis current command value I q ** For example, the correction gain k is a function of the cosine cosδ and sine sinδ of the phase difference δ, as shown in the following equation (3.3), and takes a value in the range of "0" to "1", and is a non-increasing function that does not increase as the phase difference δ increases.

[0065]

number

[0066] As a result, as shown in FIG. 7, the current command correction unit 605 corrects the original current command value I * In the range smaller than , the larger the phase difference δ, the larger the corrected current command value I ** The current command value I* is adjusted to the corrected current command value I ** Therefore, the current command corrector 605 can limit the action of the current control by the DC-ACR unit 606 so that the degree of limitation increases as the phase difference δ increases.

[0067] The DC-ACR unit 606 is a known DC (Direct Current) type ACR (current controller), and outputs a corrected current command value I **and the current measurement value I, and outputs the voltage Δv. In other words, the DC-ACR unit 606 controls the current so as to reduce the deviation between the d-axis current measurement value I and the current measurement value I. d and q-axis current measurement value I q is the corrected current command value I ** The corrected d-axis current command value I d ** and the corrected q-axis current command value I q ** The current is controlled to follow this and a voltage Δv is output.

[0068] For example, the DC-ACR unit 606 calculates the corrected current command value I ** and the measured current I as an input, and is a PI (Proportional Integral) controller in which a proportional term and an integral term are provided in parallel.

[0069] The two-phase to three-phase converter 607 converts the electrical physical quantity of two-phase AC in the dq rotating coordinate system into an equivalent expression of three-phase AC.

[0070] For example, the two-phase to three-phase conversion unit 607 calculates the d-axis component A of the electrical physical quantity of the two-phase AC by using the following equation (4): d and q-axis component A q The U-phase component A of the three-phase AC U , V phase component A V , and W phase component A W Convert to.

[0071]

number

[0072] In this example, the two-phase to three-phase conversion unit 607 converts the two-phase AC voltage Δv (i.e., the d-axis voltage Δvd and the q-axis voltage Δq) in the dq rotating coordinate system into three-phase AC (i.e., the U-phase voltage Δv U , V phase voltage Δv V , and W-phase voltage Δv W )

[0073] The PWM conversion unit 608 converts the voltage measured value V Dand the voltage Δv converted into three-phase AC, B ) command value V * (hereinafter referred to as "voltage command value V * ") into a PWM (Pulse Width Modulation) signal.

[0074] The PWM signal is a rectangular wave signal corresponding to a carrier frequency, and is input to a gate circuit 44 for driving a semiconductor switch of the power conversion device 40 (specifically, the inverter circuit 42). As a result, the control device 60 calculates the corrected current command value I ** Voltage command value V according to * Therefore, the control device 60 can drive the inverter circuit 42 via the gate circuit 44 based on the corrected current command value I. ** The current can be controlled to follow the

[0075] [First example of correction gain] A first example of the correction gain k will be described with reference to FIG.

[0076] FIG. 8 is a diagram showing a first example of the correction gain k.

[0077] In this example, as shown in equation (5.1), a variable x is defined that increases in the range from "0" to "1" as the phase difference δ increases, and the correction gain k is expressed as a function of the variable x by equation (5.2).

[0078]

number

[0079] As shown in FIG. 8, the correction gain k is set to a value of "1" when the variable x is in the range of "0" or more and a threshold value v1 or less, and is set to a value of "0" when the variable x is in the range of a threshold value v2 that is greater than the threshold value v1 and is in the range of "1" or less.

[0080] The above function x is equivalent to the following equation (6), and is a periodic function that takes a minimum value of 0 when the absolute value of the phase difference δ is 0 and a maximum value of 1 when the absolute value of the phase difference δ is π. Because the function x is a periodic function, it takes a minimum value when the phase difference δ is an integer multiple of 2π [rad] (δ = n × 2π), and takes a maximum value when the phase difference δ [rad] is shifted by π [rad] from an integer multiple of 2π [rad] (δ = π + n × 2π, or δ = -π + n × 2π).

[0081]

number

[0082] The threshold value v1 corresponds to the upper limit of the variable x for which it can be determined that the phase difference δ is sufficiently small. A sufficiently small phase difference δ means that the phase difference δ is small enough to ensure that the above-mentioned problems that may occur when the phase difference δ is relatively large do not occur. As a result, the current command corrector 605 can correct the corrected current command value I ** The original current command value I * Therefore, the current command corrector 605 can avoid restricting the action of the DC-ACR unit 606 in a range where the phase difference δ is sufficiently small.

[0083] The threshold value v2 corresponds to the lower limit value of the variable x at which it can be determined that the phase difference δ is sufficiently large. A sufficiently large phase difference δ means that the phase difference δ is large enough to ensure that the above-mentioned problems that may occur when the phase difference δ is relatively large occur. As a result, the current command corrector 605 sets the corrected current command value I ** can be fixed to "0". Therefore, the current command corrector 605 can limit the action of the DC-ACR unit 606 to the maximum extent (in this example, so that the output current of the power converter 40 becomes zero) in a range in which the phase difference δ is sufficiently large.

[0084] The correction gain k is set to linearly decrease from "1" to "0" as the variable x increases within the range of the variable x being equal to or greater than the threshold value v1 and equal to or less than the threshold value v2. As a result, the current command corrector 605 adjusts the corrected current command value I ** The current command value I * The corrected current command value I ** Therefore, the current command corrector 605 can limit the action of the DC-ACR unit 606 so that the degree of limitation increases as the phase difference δ increases.

[0085] [Second example of correction gain] A second example of the correction gain k will be described with reference to FIG.

[0086] FIG. 9 is a diagram showing a second example of the correction gain k.

[0087] In this example, the same variable x as in the first example is defined as shown in equation (7.1), and the correction gain k is expressed as a function of the variable x by equation (7.2).

[0088]

number

[0089] As shown in Fig. 9, in this example, the correction gain k is set to decrease from "1" to "0" as the variable x increases between "0" and "1". As a result, the current command corrector 605 adjusts the corrected current command value I ** The current command value I * The corrected current command value I ** Therefore, the current command corrector 605 can limit the action of the DC-ACR unit 606 so that the degree of limitation increases as the phase difference δ increases.

[0090] In this example, the correction gain k is set so that its rate of change (rate of decrease) increases as the variable x increases. In other words, the correction gain k is set so that its rate of decrease increases as the phase difference δ increases. As a result, the current command corrector 605 can correct the original current command value I * The corrected current command value I ** While maintaining a high ratio, in the range where the phase difference δ is relatively large, the original current command value I * The corrected current command value I ** In other words, the current command corrector 605 can suppress the degree of limitation on the current control action by the DC-ACR unit 606 in a range where the phase difference δ is relatively small, while increasing the degree of limitation on the current control action by the DC-ACR unit 606 in a range where the phase difference δ is relatively large. Therefore, the current command corrector 605 can simultaneously achieve the current control action by the DC-ACR unit 606 in a range where the phase difference δ is relatively small and suppress the above-mentioned problem in a range where the phase difference δ is relatively large.

[0091] [Third example of correction gain] A third example of the correction gain k will be described with reference to FIG.

[0092] FIG. 10 is a diagram showing a third example of the correction gain k.

[0093] In this example, the same variable x as in the first and second examples is defined as shown in equation (8.1), and the correction gain k is expressed as a function of the variable x by equations (8.2) and (8.3).

[0094]

number

[0095] As shown in FIG. 10, the correction gain k is set to "1" when the variable x is in the range of "0" or more and the threshold value v1 or less, similar to the first example described above.

[0096] Furthermore, the correction gain k is set to a fixed value w greater than "0" and less than "1" as shown in the above equation (8.3) when the variable x is greater than or equal to the threshold v2 and less than "1". As a result, even when the phase difference δ is relatively large, including when it is maximum, the minimum value of the correction gain k is limited to the fixed value w greater than "0". In other words, when the DC-ACR unit 606 is at its maximum limit, the current command corrector 605 can limit the current control action by the DC-ACR unit 606 so that the output current of the power conversion device 40 is not fixed to "0". Therefore, for example, when the voltage is restored from a fault such as a short circuit or a ground fault in the power grid 20, the phase difference detector 604 can detect the correct phase difference δ relatively quickly (see, for example, the above equations (2.1) to (2.4)). Therefore, when the voltage is restored from a fault such as a short circuit or a ground fault in the power grid 20, the control device 60 can quickly return to a normal control state, i.e., a state in which the current control action by the DC-ACR unit 606 is not limited.

[0097] The correction gain k is set to linearly decrease from "1" to a fixed value w as the variable x increases within the range of the variable x being equal to or greater than the threshold value v1 and equal to or less than the threshold value v2. As a result, the current command corrector 605 adjusts the corrected current command value I ** The current command value I * The corrected current command value I ** Therefore, the current command corrector 605 can limit the action of the DC-ACR unit 606 so that the degree of limitation increases as the phase difference δ increases.

[0098] [Fourth example of correction gain] A fourth example of the correction gain k will be described with reference to FIG.

[0099] FIG. 11 is a diagram showing a fourth example of the correction gain k.

[0100] In this example, the same variable x as in the first to third examples is defined as shown in equation (9.1), and the correction gain k is expressed as a function of the variable x by equations (9.2) and (9.3).

[0101]

number

[0102] In this example, as shown in FIG. 11, the correction gain k is set to decrease from "1" to a fixed value w as the variable x increases between "0" and "1". As a result, the current command corrector 605 adjusts the corrected current command value I ** The current command value I * The corrected current command value I ** Therefore, the current command corrector 605 can limit the action of the DC-ACR unit 606 so that the degree of limitation increases as the phase difference δ increases.

[0103] In this example, similar to the third example described above, even when the phase difference δ is relatively large, including the maximum, the minimum value of the correction gain k is limited to a fixed value w greater than "0", and the corrected current command value I ** can be prevented from being fixed to 0. Therefore, when the voltage recovers from an accident such as a short circuit or a ground fault in the power grid 20, the control device 60 can quickly recover to a normal control state, that is, a state in which the action of current control by the DC-ACR unit 606 is not restricted.

[0104] Furthermore, in this example, similarly to the second example described above, the correction gain k is set so that its rate of change (rate of decrease) increases with an increase in the variable x. Therefore, the current command corrector 605 can achieve both the effect of current control by the DC-ACR unit 606 in a range where the phase difference δ is relatively small and the suppression of the above-mentioned problem in a range where the phase difference δ is relatively large.

[0105] [Second example of control device] A second example of the control device 60 will be described with reference to FIGS.

[0106] Hereinafter, the same symbols will be used for the same or corresponding configurations as the first example of the control device 60 described above (FIG. 4), and the explanation will focus on the parts that differ from the first example described above, and explanations of the same or corresponding parts as the first example described above may be omitted.

[0107] Fig. 12 is a control block diagram showing the configuration of a second example of the control device 60. Fig. 13 is a diagram showing the configuration of an example of an AC-ACR unit 609. Fig. 14 is a diagram showing the configuration of an example of an AC-ACR unit 609U of the U phase.

[0108] The configurations of the V-phase AC-ACR unit 609V and the W-phase AC-ACR unit 609W are the same as the U-phase AC-ACR unit 609U, and therefore are not shown in the figures, and FIG. 14 is used instead.

[0109] As shown in FIG. 12, the control device 60 according to this example differs from the first example described above mainly in that it includes an AC-ACR unit 609 instead of the DC-ACR unit 606.

[0110] In this example, the two-phase to three-phase conversion unit 607 converts the corrected current command value I ** (That is, the corrected d-axis current command value I d ** and the corrected q-axis current command value I q ** ) is converted into an equivalent three-phase AC expression. The corrected three-phase AC current command value I ** is the corrected current command value I U ** (Hereinafter, the corrected U-phase current command value I U ** " ), the corrected V-phase current command value I V ** (hereinafter referred to as the "corrected V-phase current command value I V ** "), and the corrected current command value I W ** (Hereinafter, the corrected W-phase current command value I W ** ").

[0111] The AC-ACR unit 609 is a known AC (Alternating Current) type ACR (current controller), and outputs corrected current command values ​​I ** and the current measurement value I, and outputs the voltage Δv. In other words, the AC-ACR unit 609 controls the U-phase current measurement value I U , V-phase current measurement value I V , and the W-phase current measurement value is the corrected current command value I ** The corrected U-phase current command value I U ** , corrected V-phase current command value I V ** , and the corrected W-phase current command value I W ** The current is controlled to follow this and a voltage Δv is output.

[0112] Specifically, as shown in FIG. 13, the AC-ACR unit 609 includes a U-phase AC-ACR unit 609U, a V-phase AC-ACR unit 609V, and a W-phase AC-ACR unit 609W.

[0113] The AC-ACR unit 609U calculates the corrected U-phase current command value I U ** and the U-phase current measurement value I U The current is controlled to reduce the deviation from the U-phase voltage Δv U Output.

[0114] Measured voltage V at the grid connection point GCP D U phase component (U phase voltage measurement value V D_U ) and U-phase voltage Δv U are added together, and the three-phase AC voltage command value V * U-phase component (U-phase voltage command value V U * ) and input to the PWM conversion unit 608.

[0115] The AC-ACR unit 609V calculates the corrected V-phase current command value I V ** and V-phase current measurement value I V The current is controlled to reduce the deviation from the V-phase voltage ΔvV Output.

[0116] Measured voltage V at the grid connection point GCP D V phase component (V phase voltage measurement value V D_V ) and V-phase voltage Δv V are added together, and the three-phase AC voltage command value V * V-phase component (V-phase voltage command value V V * ) and input to the PWM conversion unit 608.

[0117] The AC-ACR unit 609W calculates the corrected W-phase current command value I W ** and the W-phase current measurement value I W The current is controlled to reduce the deviation from the W-phase voltage Δv W Output.

[0118] Measured voltage V at the grid connection point GCP D W phase component (W phase voltage measurement value V D_W ) and W-phase voltage Δv W are added together, and the three-phase AC voltage command value V * W-phase component (W-phase voltage command value V W * ) and input to the PWM conversion unit 608.

[0119] For example, as shown in FIG. 14, the AC-ACR unit 609U calculates the corrected U-phase current command value I U ** and the U-phase current measurement value I U It is a PR (Proportional Resonant) controller in which a deviation from the rated frequency f1 of the power grid 20 is input, and a proportional term and a resonant term that resonates at the rated frequency f1 of the power grid 20 are provided in parallel. Also, for example, the AC-ACR units 609V and 609W have a similar configuration.

[0120] The transfer function R(s) of the resonance term in the PR controller is, for example, the resonance gain K r and central angular frequency ω1, it is expressed by the following equations (10.1) and (10.2), and the maximum gain is achieved at central angular frequency ω1.

[0121]

number

[0122] [Third example of control device] A third example of the control device 60 will be described with reference to FIG.

[0123] The following description will focus on the differences from the first example (FIG. 4) and second example (FIG. 12) of the control device 60 described above, and may omit descriptions of parts that are the same as or correspond to the first and second examples described above.

[0124] FIG. 15 is a flowchart schematically illustrating an example of the process of the phase difference detection unit 604.

[0125] The configuration of the control device 60 according to this example is the same as that shown in FIG. 4 or FIG. 12, so its illustration is omitted and FIG. 4 or FIG. 12 is used instead.

[0126] The control device 60 according to this example differs from the first or second example described above mainly in the processing content of the phase difference detection unit 604.

[0127] The phase difference detection unit 604 of this example may be applied to a control device 60 that is based on the DC-ACR unit 606 of the first example described above, or may be applied to a control device 60 that is based on the AC-ACR unit 609 of the second example described above.

[0128] The phase difference detection unit 604 executes the process of the flowchart in FIG. 15, for example, at each predetermined control period.

[0129] As shown in FIG. 15, the phase difference detection unit 604 detects the current measurement value I and the current command value I * The amplitude values ​​|I|, |I * | is calculated (step S102).

[0130] When the process of step S102 is completed, the phase difference detection unit 604 proceeds to step S104.

[0131] The phase difference detector 604 detects the amplitude values ​​|I|, |I * It is determined whether at least one of | is smaller than a minute threshold value ε (step S104).

[0132] The threshold ε is the amplitude value |I|, |I * corresponds to the upper limit value that can be determined to be so small that | can be considered to be "0." Specifically, when the threshold value ε is used as a zero division value in the arithmetic processing in the control device 60, it corresponds to the upper limit value that can result in zero division.

[0133] The phase difference detector 604 detects the amplitude values ​​|I|, |I * If at least one of | is smaller than the minute threshold ε, the process proceeds to step S106; otherwise, the process proceeds to step S108.

[0134] The phase difference detection unit 604 regards the phase difference δ as "0", sets the cosine of the phase difference δ, cos δ, to "1", and sets the sine of the phase difference δ, sin δ, to "0" (step S106).

[0135] This allows the phase difference detection unit 604 to avoid division by zero when calculating the cosine cos δ and sine sin δ of the phase difference δ using the above equations (2.1) to (2.4).

[0136] Meanwhile, the phase difference detection unit 604 calculates the cosine cos δ and sine sin δ of the phase difference δ using the above equations (2.1) to (2.4) (step S108).

[0137] When the process of step S106 or step S108 is completed, the phase difference detection unit 604 ends the process of this flowchart.

[0138] [Other embodiments] Another embodiment will now be described.

[0139] The above-described embodiment may be modified or changed as appropriate. Hereinafter, examples in which the above-described embodiment is modified or changed will be referred to as "modified examples" for convenience.

[0140] For example, in the first to fourth examples of the control device 60 described above, the current command value I * The corrected current command value I ** However, other methods may be used for limiting the current control action by the DC-ACR unit 606 and the AC-ACR unit 609. For example, the current command value I * The corrected current command value I ** By providing a function to correct the current, the effect of current control by the DC-ACR unit 606 and the AC-ACR unit 609 may be limited.

[0141] [Effect] A control device, a power conversion device, and a control method according to this embodiment will be described.

[0142] In a first aspect of the present embodiment, there is provided a control device for controlling a power conversion device having one end connected to a DC power source and the other end connected to a power grid, the control device performing power conversion between DC on the one end side and AC on the other end side. The control device is, for example, the control device 60 described above. The DC power source is, for example, the DC power source 30 described above. The power grid is, for example, the power grid 20. The power conversion device is, for example, the power conversion device 40 described above. Specifically, the control device includes a phase detector, a phase difference detector, a current controller, and a limiter. The phase detector is, for example, the phase detector 601 described above. The phase difference detector is, for example, the phase difference detector 604 described above. The current controller is, for example, the DC-ACR unit 606 or the AC-ACR unit 609 described above. The limiter is, for example, the current command corrector 605 described above. More specifically, the phase detector detects the phase of a voltage at an interconnection point between a power supply system including the power conversion device and the power grid. The power supply system is, for example, the above-mentioned power supply system 10. The phase difference detector detects the phase difference between the command value and the measured value of the output current of the power conversion device. The output current is, for example, the above-mentioned current I B The command value is, for example, the above-mentioned current command value I *The measured value is, for example, the above-mentioned current measured value I. The phase difference is, for example, the above-mentioned phase difference δ. Furthermore, the current control unit controls the output current to follow a target value based on the measured value of the output current and the command value. The target value is, for example, the above-mentioned corrected current command value I ** The limiting unit limits the control of the output current by the current control unit, and the limiting unit increases the degree of limitation on the control of the output current by the current control unit as the phase difference increases.

[0143] For example, when voltage is restored after an accident such as a short circuit or a ground fault occurs in the power system, a large phase difference may occur between the phase of the power system bus and the phase of the interconnection point voltage, resulting in a relatively large phase difference between the measured and commanded values ​​of the output current. In such cases, there is a risk of overcurrent or overvoltage occurring. The control device can significantly limit the action of the current control unit to control the output current while a phase difference occurs between the phase of the power system bus and the phase of the interconnection point voltage during an accident such as a short circuit or a ground fault, thereby preventing a situation in which a relatively large current is output from the power conversion device. Therefore, the control device can prevent overcurrent or overvoltage when voltage is restored after an accident such as a short circuit or a ground fault occurs in the power system.

[0144] Furthermore, in addition to the occurrence of a power system fault, factors such as the impedance characteristics of the power system, the time constant of the AC filter, and delays in control calculations in the control device may cause a clear delay in the command value relative to the measured value of the output current. As a result, for example, there is a possibility that current control by the control device may become unstable due to a tracking delay of the PLL. In such cases, the control device relatively largely limits the effect of controlling the output current by the current control unit, thereby suppressing the instability of current control.

[0145] Therefore, the control device can improve current control under circumstances where there is a large phase difference between the measured value and command value of the output current of the power conversion device as the controlled object.

[0146] In a second aspect of this embodiment, based on the first aspect described above, the limiting unit may correct the original command value to a corrected command value such that the greater the phase difference, the smaller the value after correction. The corrected command value may be, for example, the above-described corrected current command value I ** The current control unit may control the output current to follow the corrected command value as the target value, based on the measured value of the output current and the corrected command value.

[0147] This allows the control device to limit the effect of the control of the output current by the current control section so that the degree of limitation increases as the phase difference between the measured value and command value of the output current increases.

[0148] In a third aspect of the present embodiment, based on the second aspect described above, the limiting unit may acquire the corrected command value by multiplying the original command value by a gain equal to or less than 1, the gain being set to decrease as the phase difference increases. The gain is, for example, the correction gain described above.

[0149] This allows the control device to limit the effect of the control of the output current by the current control section so that the degree of limitation increases as the phase difference between the measured value and command value of the output current increases.

[0150] In addition, in a fourth aspect of the present embodiment, based on any one of the first to third aspects described above, the limiting unit may limit the control of the output current by the current control unit using a predetermined function (specifically, a periodic function) based on the phase difference. The periodic function is, for example, the variable x described above.

[0151] As a result, by using a periodic function, the control device can increase the degree of limitation on the control effect of the output current by the current control unit as the phase difference between the command value and the measured value of the output current of the power conversion device increases.

[0152] In a fifth aspect of this embodiment, based on the fourth aspect described above, the limiting unit may maximize the degree of limiting the effect of the control of the output current by the current control unit when the value of the periodic function, which takes a minimum value when the absolute value of the phase difference is 0 and a maximum value when the absolute value of the phase difference is π, is equal to or greater than a first threshold value that is smaller than the maximum value. The first threshold value is the threshold value v2 described above.

[0153] This allows the control device to limit the effect of the output current control by the current control unit to the maximum extent when it can be determined that the phase difference between the measured value of the output current and the command value is sufficiently large.

[0154] In a sixth aspect of this embodiment, based on the fourth or fifth aspect described above, the limiting unit may stop the control of the output current by the current control unit when the value of the periodic function, which takes a minimum value when the absolute value of the phase difference is 0 and a maximum value when the absolute value of the phase difference is π, is equal to or less than a second threshold value greater than zero. The second threshold value is, for example, the threshold value v1 described above.

[0155] This allows the control device not to limit the control action of the output current by the current control unit when it can be determined that the phase difference between the measured value of the output current and the command value is sufficiently small.

[0156] Furthermore, in a seventh aspect of the present embodiment, on the premise of any one of the above-described fourth to sixth aspects, x as the periodic function may be expressed by the above-described formula (5.1), formula (7.1), formula (8.1), or formula (9.1) using δ as the phase difference.

[0157] This allows the control device to use a periodic function to increase the degree of limitation on the effect of controlling the output current by the current control unit as the phase difference between the command value and the measured value of the output current increases.

[0158] Furthermore, in an eighth aspect of this embodiment, based on any one of the first to seventh aspects described above, the limiting unit may limit the effect of the control of the output current by the current control unit so that the rate of change of the degree of limiting increases as the phase difference increases.

[0159] As a result, the control device can set the degree of limitation on the action of controlling the output current by the current control unit to a relatively low level when the phase difference between the measured value of the output current and the command value is relatively small, and can greatly increase the degree of limitation on the action of controlling the output current by the current control unit when the phase difference is relatively large.

[0160] Furthermore, in a ninth aspect of this embodiment, based on the second or third aspect described above, the limiting unit may limit the control action of the output current by the current control unit so that, when the degree of limitation is at its maximum, the ratio between the absolute value of the corrected command value and the absolute value of the command value is greater than zero.

[0161] As a result, for example, when voltage is restored after the occurrence of a short circuit or a ground fault in the power grid, the control device can be restored to a state in which the correct phase can be detected more quickly by the phase detection unit.

[0162] In addition, in a tenth aspect of this embodiment, based on any one of the first to ninth aspects described above, the phase difference detection unit detects a d-axis component I of the measured value I of the output current in a dq rotating coordinate system based on the phase. d and q-axis component I q and the command value I of the output current * d-axis component I d * and q-axis component I q * the amplitude |I| of the measured value I of the output current, and the command value I of the output current * The amplitude of |I * Based on |, the cosine cos δ and sine sin δ of δ as the phase difference may be calculated using the above equations (2.1) and (2.2).

[0163] This allows the control device to detect the phase difference between the measured value of the output current of the power conversion device and the command value.

[0164] In an eleventh aspect of this embodiment, based on the tenth aspect described above, the limiting unit may limit the control of the output current by the current control unit using a periodic function based on the phase difference, the periodic function taking a minimum value when the absolute value of the phase difference is 0 and a maximum value when the absolute value of the phase difference is π. The periodic function x may be expressed by the following equation:

[0165] As a result, the control device can use the periodic function to increase the degree of limitation on the output current control action by the current control unit as the phase difference between the output current command value and the measured value increases. Furthermore, under the premise that the control device uses the periodic function to limit the output current control action by the current control unit, the control device can easily calculate the value of the periodic function using the calculated values ​​of the cosine cosδ and sine sinδ of the phase difference δ.

[0166] In addition, in a twelfth aspect of the present embodiment, based on the tenth or eleventh aspect described above, the control device is configured such that the phase difference detection unit detects an amplitude |I| of the measured value I of the output current and a command value I of the output current. * The amplitude of |I * When at least one of | is so small that it can be regarded as zero, δ as the phase difference may be regarded as zero.

[0167] This allows the control device to avoid division by zero when calculating the cosine cos δ and sine sin δ of the phase difference δ.

[0168] Furthermore, in a thirteenth aspect of this embodiment, assuming any one of the first to twelfth aspects described above, the current control unit may control the output current so as to suppress the deviation between the measured value of the output current and the target value in a dq rotating coordinate system based on the phase.

[0169] This allows the control device to control the output current using a DC type ACR.

[0170] In addition, in a fourteenth aspect of this embodiment, assuming any one of the first to twelfth aspects described above, the current control unit may control the output current so as to suppress the deviation between the measured value and the target value of the output current of each phase of the three-phase AC.

[0171] This allows the control device to control the output current using an AC type ACR.

[0172] A fifteenth aspect of the present embodiment provides a power conversion device including a main circuit unit, a phase detection unit, a phase difference detection unit, a current control unit, and a limiting unit. The power conversion device is, for example, the power conversion device 40 described above. The main circuit unit is, for example, the inverter circuit 42 described above. The phase detection unit is, for example, the phase detection unit 601 described above. The phase difference detection unit is, for example, the phase difference detection unit 604 described above. The current control unit is, for example, the DC-ACR unit 606 or the AC-ACR unit 609 described above. The limiting unit is, for example, the current command correction unit 605 described above. Specifically, the main circuit unit has one end connected to a DC power source and the other end connected to a power grid, and performs power conversion between DC on the one end side and AC on the other end side. The phase detection unit detects the phase of a voltage at an interconnection point between a power supply system including the power conversion device and the power grid. The power supply system is, for example, the power supply system 10 described above. The phase difference detector detects the phase difference between the command value and the measured value of the output current of the power conversion device. B The command value is, for example, the above-mentioned current command value I * The measured value is, for example, the above-mentioned current measured value I. The phase difference is, for example, the above-mentioned phase difference δ. Furthermore, the current control unit controls the output current to follow a target value based on the measured value of the output current and the command value. The target value is, for example, the above-mentioned corrected current command value I **The limiting unit limits the control of the output current by the current control unit, and the limiting unit increases the degree of limitation on the control of the output current by the current control unit as the phase difference increases.

[0173] As a result, the power conversion device achieves the same functions and effects as the control device of the first aspect described above.

[0174] Furthermore, with respect to the power conversion device, on the premise of the fifteenth aspect, aspects similar to the second to fourteenth aspects of the control device can be realized.

[0175] As a result, the power conversion device achieves the same functions and effects as the control devices of the second to fourteenth aspects described above.

[0176] In addition, a thirteenth aspect of the present embodiment provides a control method for controlling a power conversion device having one end connected to a DC power source and the other end connected to a power grid, the power conversion device performing power conversion between DC at the one end and AC at the other end. The DC power source is, for example, the DC power source 30 described above. The power grid is, for example, the power grid 20. The power conversion device is, for example, the power conversion device 40 described above. Specifically, the control method includes a phase detection step, a phase difference detection step, a current control step, and a limiting step. More specifically, the phase detection step detects the phase of a voltage at an interconnection point between a power supply system including the power conversion device and the power grid. The power supply system is, for example, the power supply system 10 described above. Furthermore, the phase difference detection step detects the phase difference between a command value and a measured value of the output current of the power conversion device. The output current is, for example, the current I described above. B The command value is, for example, the above-mentioned current command value I * The measured value is, for example, the above-mentioned current measured value I. The phase difference is, for example, the above-mentioned phase difference δ. In the current control step, the output current is controlled to follow a target value based on the measured value of the output current and the command value. The target value is, for example, the above-mentioned corrected current command value I **In the limiting step, the effect of controlling the output current by the current control step is limited. In the limiting step, the degree of limitation on the effect of controlling the output current by the current control step is increased as the phase difference increases.

[0177] As a result, the control method has the same functions and effects as the control device of the first aspect described above.

[0178] Also, with regard to the control method, on the premise of the above-mentioned sixteenth aspect, aspects similar to the second to fourteenth aspects of the control device can be realized.

[0179] As a result, the control method has the same functions and effects as the control devices of the second to fourteenth aspects described above.

[0180] Although the embodiments have been described in detail above, the present disclosure is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist described in the claims. [Explanation of symbols]

[0181] 1. Power System 10 Power System 20 Power system 30 DC power supply 40 Power conversion device 42 Inverter circuit 44 Gate Circuit 50 AC filter 60 Control device 601 Phase detection unit 602 3-phase to 2-phase converter 603 Current command generation section 604 Phase difference detection unit 605 Current command correction section 606 DC-ACR section 607 2-phase to 3-phase converter 608 PWM conversion unit 609 AC-ACR section 609U AC-ACR section 609V AC-ACR section 609W AC-ACR section

Claims

1. A control device for controlling a power conversion device having one end connected to a DC power source and the other end connected to a power grid, the power conversion device performing power conversion between DC on the one end side and AC on the other end side, a phase detection unit that detects the phase of a voltage at an interconnection point between a power supply system including the power conversion device and the power grid; a phase difference detection unit that detects a phase difference between a command value and a measured value of an output current of the power conversion device; a current control unit that controls the output current so that the output current follows a target value based on the measured value and the command value of the output current; a limiting unit that limits the effect of the control of the output current by the current control unit, and that increases the degree of limitation on the effect of the control of the output current by the current control unit as the phase difference increases; Control device.

2. the limiting unit corrects the original command value to the corrected command value such that the corrected value becomes smaller as the phase difference increases; the current control unit controls the output current based on the measured value of the output current and the corrected command value so that the output current follows the corrected command value as the target value. The control device according to claim 1 .

3. the limiting unit multiplies the original command value by a gain equal to or less than 1, the gain being set to decrease as the phase difference increases, to thereby obtain the corrected command value. The control device according to claim 2 .

4. the limiting unit limits the effect of the control of the output current by the current control unit using a periodic function based on the phase difference. The control device according to any one of claims 1 to 3.

5. the limiting unit maximizes the degree of limitation of the action of the control of the output current by the current control unit when a value of the periodic function, which takes a minimum value when the absolute value of the phase difference is 0 and a maximum value when the absolute value of the phase difference is π, is equal to or greater than a first threshold value which is smaller than the maximum value. The control device according to claim 4.

6. the limiting unit does not limit the action of the control of the output current by the current control unit when a value of the periodic function, which takes a minimum value when the absolute value of the phase difference is 0 and a maximum value when the absolute value of the phase difference is π, is equal to or less than a second threshold value greater than zero. The control device according to claim 4.

7. The periodic function x is expressed by the following equation using δ as the phase difference: The control device according to claim 4. [Equation 1]

8. the limiting unit limits the effect of the control of the output current by the current control unit such that the rate of change of the limiting degree increases as the phase difference increases. The control device according to any one of claims 1 to 3.

9. the limiting unit limits the action of the control of the output current by the current control unit so that, when the degree of limitation is at a maximum, a ratio between the absolute value of the corrected command value and the absolute value of the command value becomes greater than zero. The control device according to claim 2 or 3.

10. The phase difference detection unit detects a d-axis component I of the measured value I of the output current in a dq rotating coordinate system based on the phase. ｄ and the q-axis component I ｑ and the command value I of the output current ＊ d-axis component I ｄ ＊ and the q-axis component I ｑ ＊ the amplitude |I| of the measured value I of the output current, and the command value I of the output current. ＊ Amplitude of |I ＊ | and calculate the cosine cos δ and sine sin δ of δ as the phase difference using the following equations: The control device according to any one of claims 1 to 3. [Equation 2]

11. the limiting unit limits the action of the control of the output current by the current control unit using a periodic function based on the phase difference, the periodic function taking a minimum value when the absolute value of the phase difference is 0 and a maximum value when the absolute value of the phase difference is π; The periodic function x is expressed by the following formula: The control device according to claim 10. [Equation 3]

12. The phase difference detection unit detects the amplitude |I| of the measured value I of the output current and the command value I of the output current. ＊ Amplitude of |I ＊ If at least one of | is small enough to be considered to be zero, δ as the phase difference is considered to be zero. The control device according to claim 10.

13. the current control unit controls the output current so as to suppress a deviation between the measured value of the output current and the target value in a dq rotating coordinate system based on the phase. The control device according to any one of claims 1 to 3.

14. the current control unit controls the output current so as to suppress a deviation between the measured value of the output current of each phase of the three-phase AC and the target value. The control device according to any one of claims 1 to 3.

15. a main circuit unit having one end connected to a DC power source and the other end connected to a power grid, and performing power conversion between DC at the one end and AC at the other end; a phase detection unit that detects the phase of a voltage at an interconnection point between a power supply system including a power conversion device and the power grid; a phase difference detection unit that detects a phase difference between a command value and a measured value of an output current of the power conversion device; a current control unit that controls the output current so that the output current follows a target value based on the measured value and the command value of the output current; a limiting unit that limits the effect of the control of the output current by the current control unit, and that increases the degree of limitation on the effect of the control of the output current by the current control unit as the phase difference increases; Power conversion device.

16. A control method for controlling a power conversion device having one end connected to a DC power source and the other end connected to a power grid, the power conversion device performing power conversion between DC on the one end side and AC on the other end side, the method comprising: a phase detection step of detecting a phase of a voltage at an interconnection point between a power supply system including the power conversion device and the power grid; a phase difference detection step of detecting a phase difference between a command value and a measured value of an output current of the power conversion device; a current control step of controlling the output current so that the output current follows a target value based on the measured value and the command value of the output current; a limiting step of limiting the effect of control of the output current by the current control step, the degree of limitation of the effect of control of the output current by the current control step increasing as the phase difference increases; Control method.

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