Control device and control method

Abstract

A control device controls an inverter so as to exert a frequency fluctuation suppression effect as designed even when the specifications, configuration, or operating conditions of the inverter's connected destination change. The control device controls an inverter so that the frequency of the output voltage of the inverter has a virtual inertial force with respect to an active power supplied to a connected destination of the inverter, the control device comprising: a first virtual synchronous generator control unit that calculates a frequency deviation by a transfer function based on an oscillation equation in a synchronous generator using an actual measured value of the active power supplied by the inverter to the connected destination; a first command value generating unit that generates a frequency command value for the output voltage of the inverter using the frequency deviation; and a first error correction control unit that determines a gain of the transfer function in the first virtual synchronous generator control unit using a first error that is a difference between an active power reference value, which is the active power supplied by the inverter to a connected destination in a predetermined reference state, and the actual measured value of the active power.

Description

[Technical field]

[0001] The present disclosure relates to a control device and a control method for controlling an inverter provided in a power supply. [Background technology]

[0002] In a power system that supplies AC power from a power source to a load, control is performed to maintain the output voltage and frequency. In a power system, when the amount of AC power introduced from a renewable energy power source increases compared to the amount of AC power introduced from a synchronous generator, the inertia of the power source decreases, making it difficult to maintain the frequency when the supply and demand balance changes suddenly.

[0003] In response to this, for example, in the distributed power source control device disclosed in Patent Document 1, the inverter that connects the distributed power source to the grid is operated under virtual synchronous generator (hereinafter abbreviated as VSG for Virtual Synchronous Generator) control, thereby giving the distributed power source a pseudo-inertial force of a synchronous generator, thereby suppressing frequency fluctuations in the grid. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-176584 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in conventional distributed power supply control devices, when the specifications, configuration, or operating conditions of the equipment connected to the grid change, it is necessary to change the inverter settings and check the settings after the change so that the frequency fluctuation suppression effect can be maintained as before the change. This is because the active power output by the inverter, which is the input value for the calculation process related to the VSG control, changes due to the influence of the connected equipment. In other words, when the specifications, configuration, or operating conditions of the connected equipment change, it is necessary to adjust the gain of the inverter, for example, to correct the change in the active power.

[0006] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a control device and control method that are configured to be able to calculate an active power reference value to be output by an inverter to a connection destination in a predetermined reference state, and that can control an inverter so as to exert the effect of suppressing frequency fluctuations according to the design value, even when the specifications, configuration, or operating conditions of the connection destination change, by feeding back the difference between the active power reference value and the actual active power measurement value, or the difference between the VSG control output based on the active power reference value and the VSG control output based on the actual active power measurement value, to calculation processing related to VSG control. [Means for solving the problem]

[0007] The control device according to the present disclosure is a control device that controls an inverter so that the frequency of the inverter's output voltage has a virtual inertial force with respect to the active power supplied to a destination of the inverter, and includes a first virtual synchronous generator control unit that calculates a frequency deviation by a transfer function based on an oscillation equation in the synchronous generator using an actual measured value of the active power supplied by the inverter to a destination of the inverter, a first command value generation unit that generates a frequency command value for the inverter's output voltage using the frequency deviation calculated by the first virtual synchronous generator control unit, and a first error correction control unit that determines a gain of the transfer function in the first virtual synchronous generator control unit using a first error that is the difference between an active power reference value, which is the active power supplied by the inverter to a destination of the inverter in a predetermined reference state, and the actual measured value of the active power.

[0008] Another embodiment of the control device according to the present disclosure includes a first virtual synchronous generator control unit that calculates a first frequency deviation by a transfer function based on an oscillation equation in the synchronous generator using an actual measured value of active power supplied by the inverter to a connection destination; a first command value generation unit that generates a first frequency command value as a frequency command value for an output voltage of the inverter using the first frequency deviation calculated by the first virtual synchronous generator control unit; a second virtual synchronous generator control unit that calculates a second frequency deviation by a transfer function using an active power reference value that is the active power supplied by the inverter to a connection destination in a predetermined reference state; and a second error correction control unit that feeds back a second error, which is the difference between the first frequency deviation calculated by the first virtual synchronous generator control unit and the second frequency deviation calculated by the second virtual synchronous generator control unit, to the first virtual synchronous generator control unit.

[0009] The control method disclosed herein is a control method for controlling an inverter so that the frequency of the inverter's output voltage has a virtual inertial force with respect to the active power supplied to a destination of the inverter, and includes the steps of: calculating a frequency deviation by a transfer function based on an oscillation equation in a synchronous generator using an actual measured value of the active power supplied by the inverter to a destination; generating a frequency command value for the inverter's output voltage using the frequency deviation; and determining a gain of the transfer function using a first error, which is the difference between an active power reference value, which is the active power supplied by the inverter to a destination in a predetermined reference state, and the actual measured value of the active power.

[0010] Another embodiment of the control method according to the present disclosure includes the steps of: calculating a first frequency deviation by a transfer function based on an oscillation equation in a synchronous generator using an actual measured value of active power supplied by the inverter to a connected destination; generating a frequency command value for an output voltage of the inverter using the first frequency deviation; calculating a second frequency deviation by a transfer function using an active power reference value, which is the active power supplied by the inverter to a connected destination in a predetermined reference state; and feeding back a second error, which is the difference between the first frequency deviation and the second frequency deviation, to the step of calculating the first frequency deviation. Effect of the Invention

[0011] According to the present disclosure, it is possible to provide a control device and a control method that controls an inverter so as to achieve the frequency fluctuation suppression effect according to the design value even when the specifications, configuration, or operating conditions of the inverter's connection destination change. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram showing a configuration example of a microgrid according to a first embodiment; [Diagram 2] FIG. 1 is a block diagram showing a control system including a control device and an inverter to be controlled in a first embodiment. [Diagram 3] 1 is a flowchart showing a control process performed by a control device according to the first embodiment. [Figure 4] FIG. 1 is a diagram showing the relationship between an inverter to be controlled and its connection destination in the first embodiment. [Diagram 5] FIG. 1 is a block diagram showing a hardware configuration of a PLC that realizes a control device according to a first embodiment. [Figure 6] FIG. 11 is a block diagram showing a control system including a control device and an inverter to be controlled in a second embodiment. [Figure 7] 11 is a flowchart showing a control process performed by a control device according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Embodiment 1 The first embodiment will be described in detail with reference to Fig. 1. Fig. 1 is a diagram showing a configuration example of a microgrid 1 in the first embodiment. In Fig. 1, the microgrid 1 is an independent power system that generates and consumes power independently, and includes a power generation facility 11, a load 12, a storage battery 13, a power conversion device 14, and a transducer 15, which are connected to each other via a power transmission and distribution network 21. Among these, the operation of the power conversion device 14, i.e., the operation of supplying the amount of power generated by the power generation facility 11 to the storage battery 13 and the operation of supplying the amount of power charged in the storage battery 13 to the load 12, is controlled by an integrated controller 31.

[0014] The power generation facility 11 is a renewable energy power source whose output is difficult to control, such as wind power generation, solar power generation, or hydroelectric power generation, and includes a watt-hour meter that measures the amount of generated power and a communication device that transmits the measured value of the amount of power.

[0015] The load 12 is a device that consumes power, and includes a power meter that measures the amount of power consumed by the load 12 and a communication device that transmits the measured value of the amount of power consumed.

[0016] The storage battery 13 is a secondary battery such as a lead storage battery, a nickel-metal hydride battery, a lithium ion battery, a sodium-sulfur battery, or a redox flow battery, and has a communication device for transmitting a State Of Charge (SOC) and receiving control commands related to charging and discharging.

[0017] The power conversion device 14 includes a control device 41, an inverter 42, and a communication device (not shown). In the power conversion device 14, the inverter 42 is an inverter capable of mutual AC / DC conversion, which converts the DC voltage output by the storage battery 13 to the power transmission / distribution network 21 into AC voltage when the storage battery 13 discharges, and converts the AC voltage received by the storage battery 13 from the power transmission / distribution network 21 into DC voltage when the storage battery 13 charges. The control device 41 controls the above AC / DC mutual conversion performed by the inverter 42, and also controls the inverter 42 so that the frequency of the output voltage of the inverter 42 has a virtual inertial force with respect to the active power supplied to the connection destination of the inverter. The communication device receives an output command value transmitted from the integrated controller 31. The power conversion device 14 causes the storage battery 13 to act as a voltage source based on the output command value transmitted from the integrated controller 31, and functions as a GFM (Grid forming) inverter.

[0018] The transducer 15 detects the actual active power P measure The transducer 15 is connected to the control device 41 by a signal line such as a coaxial cable, and measures the actual effective power value Pmeasure is output to the control device 41 via a signal line.

[0019] The integrated controller 31 is connected to the power generation equipment 11, the load 12, the storage battery 13, and the power conversion device 14, and controls the storage battery 13 and the power conversion device 14 based on information regarding power supply and demand, such as the amount of power generated and the amount of power consumed, transmitted from communication devices provided in each device. In detail, when the power consumption of the load 12 is small relative to the power generation amount of the power generation equipment 11, the integrated controller 31 controls the power conversion device 14 to convert the AC voltage supplied by the power generation equipment 11 to a DC voltage, and charges the storage battery 13 with the power generation amount of the power generation equipment 11 converted to DC by the power conversion device 14. On the other hand, when the power consumption amount of the load 12 is large relative to the power generation amount of the power generation equipment 11, the integrated controller 31 controls the power conversion device 14 to discharge the storage battery 13 within the range permitted by the SOC so as to make up for the difference between the power generation amount of the power generation equipment 11 and the power consumption amount of the load 12, and to convert the DC voltage supplied by the storage battery 13 to an AC voltage. When controlling the storage battery 13 and the power conversion device 14 to the discharge side, the integrated controller 31 sets an active power command value P ref is output to the power conversion device 14.

[0020] Here, the above measured effective power value P measure , active power command value P ref Unless otherwise specified, the active powers described below are values ​​according to the PU method (PU: Per Unit), and the units are pu rather than W. For example, the active power is expressed by the PU method by dividing it by the rated output of the inverter 42.

[0021] Here, the integrated controller 31 is realized by a computer system having an arithmetic device such as a CPU (Central Processing Unit), a storage device such as a memory such as a RAM (Random Access Memory) and a storage such as a HDD (Hard Disc Drive), a communication device, and a system bus connecting these. Specifically, the storage device stores a program expressing the above-mentioned control process, the arithmetic device executes the above-mentioned program stored in the storage device, and the communication device communicates with the power generation facility 11, the load 12, the storage battery 13, and the power conversion device 14. Furthermore, the integrated controller 31 is not limited to a single computer system, and may be realized by multiple computer systems or a cloud system.

[0022] Next, the configuration and operation of the control device 41 will be described in detail with reference to Fig. 2 and Fig. 3. Fig. 2 is a block diagram showing a control system including the control device 41 and the inverter 42 to be controlled in the first embodiment, and Fig. 3 is a flowchart showing the control process performed by the control device 41 in the first embodiment. The control device 41 includes a subtractor 111, a first virtual synchronous generator control unit 101 (hereinafter, referred to as a first VSG control unit 101), a first governor control unit 113, a first command value generation unit 102, a ZOH circuit 116 (ZOH: Zero Order Hold), a reference output calculation unit 117, a subtractor 118, and a first error correction control unit 103. The control device 41 calculates the active power command value P ref Based on this, the frequency of the output voltage of the inverter 42 is controlled. Hereinafter, the operation of each functional block of the control device 41 will be described.

[0023] The subtractor 111 subtracts the active power command value P ref The first governor control unit 113 subtracts the output value from this and outputs the value to the first VSG control unit 101. Here, the first governor control unit 113 is a functional block that performs calculations simulating a governor for keeping the rotation speed of a synchronous generator constant, and its operation will be described later.

[0024] The first VSG control unit 101 includes a subtractor 121, a multiplier 122, and a first-order lag circuit 123. The first VSG control unit 101 performs VSG control to stabilize the power system by simulating the inertial force caused by the inertial moment of the rotor in the synchronous generator to the output voltage of the inverter 42. The stabilization of the power system refers to gently inducing frequency fluctuations in the Pf drooping characteristic in which the frequency of the output voltage of the power source decreases when the load applied to the AC power source increases, and the frequency of the output voltage increases when the load decreases. Taking a synchronous generator as an example, for example, in a rotor with a large mass and a strong inertial force, the effect of load fluctuations on the rotation speed of the rotor is small. Since the rotation speed of the rotor of the synchronous generator and the frequency of the output voltage are synchronized, in the case of a rotor with a large moment of inertia, the frequency fluctuation of the output voltage in response to an increase in load becomes gentle. In the VSG control, by simulating such inertial force of the rotor, the frequency fluctuation of the output voltage is gentle with respect to the fluctuation of the active power corresponding to the load fluctuation, thereby stabilizing the power system.

[0025] In step S11 shown in FIG. 3, the first VSG control unit 101 calculates the actual active power value P measure The frequency deviation Δω1 is calculated using In detail, in the first VSG control unit 101, a subtractor 121 subtracts the actual active power measurement value P measure from the output value of the subtractor 111 to calculate an active power deviation ΔP1. Furthermore, the subtractor 121 outputs the calculated active power deviation ΔP1 to the multiplier 122. Here, the zero-order hold refers to holding a certain signal value at a constant value until the next sampling point.

[0026] In the first VSG control unit 101, the multiplier 122 multiplies the active power deviation ΔP1 by a gain (1 / D) and outputs the result to the first-order lag circuit 123. Next, the first-order lag circuit 123 multiplies the output value of the multiplier 122 by a transfer function {1 / (1+sM / D)} formed by an inertia constant M and a damping constant D to calculate a frequency deviation Δω1, and outputs the frequency deviation Δω1 to the first governor control unit 113 and the first command value generating unit 102. Here, s is the Laplace operator in the transfer function.

[0027] Here, the transfer function that the first VSG control unit 101 applies to the input value will be described. As described above, the first VSG control unit 101 performs control that simulates the inertial force caused by the moment of inertia of the rotor in a synchronous generator. This control is based on the oscillation equation of the rotor in a synchronous generator, which is expressed by equation (1-1). Here, equation (1-1) is expressed by the PU method, where M is the inertia constant of the rotor (unit: s), D is the damping constant (unitless), and ω is the rotational speed of the rotor (unit: pu).

[0028]

number

[0029] When equation (1-1) is transformed using equation (1-2) and then subjected to Laplace transformation to obtain a transfer function from ΔP to Δω, it is given as equation (1-3). In light of the description in Fig. 2, it can be seen that the transfer function that the first VSG control unit 101 applies to the input value corresponds to the transfer function expressed by equation (1-3). Also, ΔP and Δω in equation (1-3) correspond to ΔP1 and Δω1 in this embodiment, respectively.

[0030]

number

[0031] Returning to Fig. 2, the first governor control unit 113 simulates the operation of a governor in a synchronous generator. In detail, the first governor control unit 113 multiplies the frequency deviation Δω1 output from the first VSG control unit 101 by a transfer function {K / (1+sT)}, and outputs the resultant value to the subtractor 111. Here, T is a time constant corresponding to the integral time, and K is a governor gain.

[0032] In step S12 shown in FIG. 3, the first command value generating unit 102 uses the frequency deviation Δω1 calculated by the first VSG control unit 101 to generate a frequency command value f v Furthermore, the first command value generating unit 102 generates the generated frequency command value f v to the inverter 42 and the reference output calculation unit 117. The first command value generation unit 102 has a constant multiplier 114a, a ZOH circuit 114b, and an adder 115, as shown in FIG.

[0033] In the first command value generating unit 102, a constant multiplier 114a multiplies the frequency deviation Δω1 by a rated frequency fn (unit: Hz) to convert the unit to Hz, and outputs the frequency deviation df1 to a ZOH circuit 114b. The ZOH circuit 114b outputs a signal value obtained by performing zero-order hold on the frequency deviation df1 to an adder 115. The adder 115 adds the rated frequency fn to the signal value output from the ZOH circuit 114b to obtain a frequency command value f v and outputs it to the inverter 42 and the reference output calculation unit 117 as a control command value for the inverter 42. Here, the rated frequency fn is the frequency of the system, which is set to 50 Hz in eastern Japan and 60 Hz in western Japan, for example.

[0034] The inverter 42 is driven in response to the frequency command value f output from the first command value generating unit 102. v The effective power is output based on the frequency command value f v When fluctuates, the effective power output by the inverter 42 changes depending on, for example, the voltage or frequency of the inverter 42. In this way, the frequency command value f vand the active power output by the inverter 42 will be described in detail with reference to Fig. 4. Fig. 4 is a diagram showing the relationship between the inverter 42, which is the control target, and the connection destination of the inverter 42. Fig. 4 shows the inverter 42 controlled by the control device 41 and the connection destination (hereinafter simply referred to as the connection destination), such as the load 12, connected to the inverter 42 via the line reactance L. Here, the connection destination is not limited to the load 12, and when, for example, a plurality of storage batteries 13 and power conversion devices 14 are connected, these are also included as the connection destination.

[0035] In FIG. 4, the AC voltage output from the inverter 42 is v v , the line reactance of the power transmission and distribution network 21 is L, the current flowing through the power transmission and distribution network 21 is i, and the AC voltage at the connection destination is v o Then, these relations are expressed as the following equation (1-4). Here, f v is the frequency of the AC voltage output from the inverter 42, and f o is the frequency of the AC voltage at the connection destination, θ o is the current i and the voltage v at the connection o is the phase difference with

[0036]

number

[0037] Furthermore, to facilitate subsequent transformations, equation (1-5) is introduced, and equation (1-4) is solved for current i, resulting in the following equation (1-6). Considering that apparent power S is expressed as in equation (1-7), active power P output by inverter 42 is expressed as in equation (1-8). Here, Q is reactive power output by inverter 42.

[0038]

number

[0039] In the effective power P expressed by the formula (1-8), the controllable parameters are the amplitude V of the AC voltage output by the inverter 42, v and the frequency command value f of the AC voltage output by the inverter 42 v Of these, the amplitude of the AC voltage V v In the VSG control, the frequency command value f of the AC voltage is determined based on the Qv drooping characteristic, which is the relationship between the reactive power Q and the voltage v in the synchronous generator. v By controlling only the output of the inverter 42, the active power P output by the inverter 42 is changed.

[0040] On the other hand, the effective power P expressed by equation (1-8) is the voltage amplitude V o , frequency f o , phase difference θ o , and line reactance L as variables. These values ​​change depending on the load 12, other inverters 42, and other storage batteries 13 connected to the inverter 42. In other words, the active power P output from the inverter 42 changes depending on, for example, the specifications, configuration, and operating conditions of the equipment to which it is connected.

[0041] Returning to FIG. 2, the reference output calculation unit 117 calculates the frequency command value f v Based on this, the active power output by the inverter 42 when connected to the load 12 in a predetermined reference state is calculated, and the active power reference value P st to the subtractor 118. In detail, the reference output calculation unit 117 calculates the frequency command value f v Using this, the effective power reference value P st In equation (1-8a), the voltage amplitude V s , frequency f s , phase difference θ s , and the line reactance L s is a constant representing the connection destination in the reference state. Here, the reference state is a design condition of the control device 41 used when the power conversion device 14 determines the inertial force realized by the VSG control. That is, when the connection destination is a voltage amplitude Vs , frequency f s , phase difference θ s , and the line reactance L s In the state represented by (a), the control device 41 can cause the power conversion device 14 to exert the effect of suppressing the frequency fluctuation according to the design value.

[0042]

number

[0043] Next, the subtractor 118 subtracts the active power reference value P st From the measured effective power value P measure The first error correction control unit 103 calculates the first error dP1 by subtracting Here, the first error dP1 calculated by the subtractor 118 is the effective power reference value P st The actual measured active power value P measure This represents the magnitude relationship between the first error dP1 and the frequency fluctuation suppression effect, and affects the frequency fluctuation suppression effect. Specifically, when the first error dP1 is a positive value, the frequency fluctuation suppression effect is insufficient, and when the first error dP1 is a negative value, the frequency fluctuation suppression effect is excessive.

[0044] 3, first error correction control section 103 uses first error dP1 that affects the suppression effect of frequency fluctuation to determine the gain in first VSG control section 101. First error correction control section 103 has first-order lag circuit 124, adder 125, and limiter 126, as shown in FIG.

[0045] In the first error correction control unit 103, a first-order lag circuit 124 applies a transfer function {K obs / (1+sT obs )} and outputs the result to an adder 125. The adder 125 adds 1 / D, which is the gain set in the multiplier 122, to the value input from the first-order lag circuit 124 and outputs the result to a limiter 126. obs is the time constant, K obsare gains, and these values ​​may be determined using general control theory, such as the ultimate sensitivity method.

[0046] In the first error correction control section 103, the limiter 126 compares whether the value input from the adder 125 is greater than a predetermined lower limit value, and if it is greater than the lower limit value, sets the value as the gain of the multiplier 122, and if it is equal to or less than the lower limit value, sets the lower limit value as the gain of the multiplier 122. That is, the limiter 126 changes the gain of the multiplier 122 according to the magnitude relationship between the value input from the adder 125 and the predetermined lower limit value, and the multiplier 122 multiplies the active power deviation ΔP1 by the changed gain. Here, the lower limit value is set so that the value input from the adder 125 does not become 0, and 0 must not be set. If the lower limit value is set to 0 and the value input from the adder 125 is equal to or less than 0, 0 is set as the gain of the multiplier 122, so that the output value of the first VSG control section 101 becomes 0, and the first VSG control section 101 does not function.

[0047] The first error correction control unit 103 calculates the actual effective power value P measure and the active power reference value P st The gain of the multiplier 122 is set so as to compensate for the difference between the voltage amplitude V o , frequency f o , phase difference θ o , and acts to reduce the first error dP1, regardless of the line reactance L.

[0048] Here, a hardware configuration of the control device 41 will be described. The control device 41 is realized by a PLC (Programmable Logic Controller). The hardware configuration of the PLC will be described with reference to Fig. 5. Fig. 5 is a block diagram showing the hardware configuration of the PLC that realizes the control device 41. Each functional block of the control device 41 shown in Fig. 2 is realized by executing a program (hereinafter, referred to as a control program) on the PLC, in which the processing to be performed by the control device 41 is described. As shown in Fig. 5, this PLC includes a calculation device 51, a storage device 52, and a communication device 53, which are connected via a system bus 54. Here, Fig. 5 is an example, and the configuration of the PLC is not limited to the example of Fig. 5.

[0049] In the PLC, the arithmetic device 51 is, for example, a processor such as a CPU, and executes a control program. The storage device 52 includes a volatile memory such as a RAM and a non-volatile memory such as a flash memory, and stores the control program executed by the arithmetic device 51 and data obtained in the process of processing, and is used as a temporary storage area for the program. The communication device 53 is, for example, a receiver and a transmitter that communicates with the integrated controller 31. Here, unlike a computer system with a similar hardware configuration, a PLC does not have an OS (Operating System) installed, and has the characteristic that delays and slowdowns in processing due to, for example, interrupts of resident programs caused by the operation of the OS are unlikely to occur. In this embodiment, based on these characteristics, an example is shown in which the control device 41 is realized by a PLC, but the present invention is not limited to this example and may be realized by a computer system.

[0050] In this way, the first VSG control unit 101 calculates the frequency deviation Δω1 by a transfer function based on the oscillation equation in a synchronous generator, and the first command value generating unit 102 uses the frequency deviation Δω1 to generate a frequency command value f v The reference output calculation unit 117 generates a frequency command value f v Based on the above, the inverter 42 outputs a reference active power value P st The subtractor 118 calculates the active power reference value P st From the measured effective power value P measureThe first error correction control unit 103 is configured to set the gain of the transfer function of the first VSG control unit 101 by subtracting the first error dP1 from the first error dP1, and therefore it is possible to provide a control device 41 that controls the inverter 42 so as to exert the effect of suppressing frequency fluctuations according to the design value even when the specifications, configuration, or operating conditions of the connected device change.

[0051] In this embodiment, an example has been shown in which the first error correction control section 103 determines the gain in the first VSG control section 101, but the present invention is not limited to this example, and (M / D), which corresponds to the time constant of the first VSG control section 101, may be changed in accordance with the determined gain. In detail, the first error correction control section 103 sets the reciprocal of the determined gain as D again, and determines the value of M so that the transfer function {1 / (1+sM / D)} when this D is used is controlled stably. The method for determining this value of M may use a general control theory such as the Nyquist stability criterion, or a pattern of values ​​of M against D may be stored in advance and the value of M may be determined by fitting the pattern. As a result, the actual measured active power value P measure and the active power reference value P st This makes it possible to prevent the occurrence of controlled oscillation when the first error dP1, which is the difference between the first error dP1 and the gain set in the multiplier 122, becomes large.

[0052] Also, in the example shown, limiter 126 compares whether the input value is greater than a predetermined lower limit value, and if it is equal to or less than the lower limit value, sets the lower limit value to multiplier 122. However, the present invention is not limited to this example, and an upper limit value may also be set, and further comparison may be made to see if the input value is smaller than the upper limit value, and if it is equal to or greater than the upper limit value, the upper limit value may be set to multiplier 122. This makes it possible to prevent controlled oscillation from occurring due to an excessively large gain setting.

[0053] Embodiment 2 The second embodiment will be described in detail with reference to Figs. 6 and 7. Fig. 6 is a block diagram showing a control system including a control device 41 and an inverter 42 to be controlled in the second embodiment, and Fig. 7 is a flowchart showing a control process performed by the control device 41 in the second embodiment. Among the components shown in Fig. 6, the same reference numerals as those in Fig. 2 indicate the same or corresponding parts, and their description will be omitted. Furthermore, the configuration of the microgrid 1 in the second embodiment is the same as that in the first embodiment, and therefore illustration and description will be omitted.

[0054] In the second embodiment, the control device 41 includes a subtractor 111a, a first VSG control unit 101a (hereinafter referred to as the first VSG control unit 101a), a first governor control unit 113, a first command value generating unit 102, a ZOH circuit 116, a subtractor 211, a second VSG control unit 201, a second governor control unit 213, a second command value generating unit 202, a reference output calculating unit 117, a ZOH circuit 216, a subtractor 217, and a second error correction control unit 218. Hereinafter, the operation of each functional block of the control device 41 in the second embodiment will be described.

[0055] The subtractor 111a subtracts the active power command value P ref The output value of the first governor control unit 113 is subtracted from the sum of this and a second error dP2 output from a second error correction control unit 218, the details of which will be described later, and the result is output to the first VSG control unit 101a.

[0056] The first VSG control unit 101a has a subtractor 121, a multiplier 122a, and a first-order lag circuit 123, and is similar to the first VSG control unit 101 in the first embodiment in that it performs VSG control to impart a pseudo inertial force of a synchronous generator to the power conversion device 14. On the other hand, the multiplier 122a differs from the first embodiment in that the gain (1 / D) by which the input value is multiplied is a fixed value.

[0057] In step S21 shown in FIG. 7, the first VSG control unit 101a calculates the actual measured active power value P measure The first frequency deviation Δω1 is calculated using: In detail, in the first VSG control unit 101a, the multiplier 122a multiplies the active power deviation ΔP1 calculated by the subtractor 121 by a gain (1 / D) and outputs the result to the first-order lag circuit 123. Next, the first-order lag circuit 123 multiplies the output value of the multiplier 122a by a transfer function {1 / (1+sM / D)} to calculate the first frequency deviation Δω1 and outputs it to the first governor control unit 113, the first command value generation unit 102, and the subtractor 217.

[0058] The first governor control unit 113 is the same functional block as in the first embodiment, and multiplies the first frequency deviation Δω1 output from the first VSG control unit 101a by a transfer function {K / (1+sT)} and outputs the resultant value to the subtractor 111a. Here, the time constant T and the gain K have the same values ​​as in the first embodiment.

[0059] In step S22 shown in FIG. 7, the first command value generating unit 102 uses the first frequency deviation Δω1 calculated by the first VSG control unit 101a to generate a first frequency command value f v1 Furthermore, the first command value generating unit 102 generates the generated first frequency command value f v1 to the inverter 42. The first command value generating unit 102 includes a constant multiplier 114a, a ZOH circuit 114b, and an adder 115, similarly to the first embodiment. In detail, the constant multiplier 114a multiplies the first frequency deviation Δω1 by the rated frequency fn to calculate the frequency deviation df1, and outputs the frequency deviation df1 to the ZOH circuit 114b. The ZOH circuit 114b outputs a signal value obtained by performing zero-order hold on the frequency deviation df1 to the adder 115. The adder 115 adds the rated frequency fn to the signal value output from the ZOH circuit 114b to calculate the first frequency command value f v1 and outputs it to the inverter 42 as a control command value for the inverter 42.

[0060] The inverter 42 operates in response to the first frequency command value f v1In this manner, the active power output by the inverter 42 is controlled by the frequency command value, as in the first embodiment.

[0061] In the second embodiment, the active power command value P ref is also input to the subtractor 211. The subtractor 211 subtracts the active power command value P ref The output value of the second governor control unit 213 is subtracted from the calculated value, and the result is output to the second VSG control unit 201.

[0062] In step S23 shown in FIG. 7, the second VSG control unit 201 calculates an active power reference value P st 6, the second VSG control unit 201 has the same functional blocks as the first VSG control unit 101a, that is, a subtractor 121, a multiplier 122a, and a first-order lag circuit 123, and calculates the second frequency deviation Δω2 by performing the same arithmetic processing as the first VSG control unit 101a, and outputs it to the second governor control unit 213, the second command value generation unit 202, and the subtractor 217. Here, the gain (1 / D) by which the second VSG control unit 201 multiplies the input value, the transfer function {1 / (1+sM / D)}, and the inertia constant M and braking constant D that constitute these are the same as those of the first VSG control unit 101a.

[0063] Similar to the first governor control section 113, the second governor control section 213 multiplies the second frequency deviation Δω2 output from the second VSG control section 201 by a transfer function {K / (1+sT)} and outputs the resultant value to the subtractor 211. Here, the time constant T and the gain K have the same values ​​as those of the first governor control section 113.

[0064] The second command value generating unit 202 includes a constant multiplier 214a, a ZOH circuit 214b, and an adder 215, and generates a second frequency command value f v2In detail, the constant multiplier 214a calculates the frequency deviation df2 by the same arithmetic processing as the constant multiplier 114a, and outputs it to the ZOH circuit 214b. The ZOH circuit 214b outputs a signal value obtained by zero-order holding the frequency deviation df2 to the adder 215. The adder 215 adds the rated frequency fn to the signal value output from the ZOH circuit 214b to obtain the second frequency command value f v2 and outputs it to the reference output calculation unit 117.

[0065] The reference output calculation unit 117 calculates the second frequency command value f v2 Based on this, the active power output by the inverter 42 when connected to the load 12 in a predetermined reference state is calculated, and the active power reference value P st To be more specific, the reference output calculation unit 117 outputs f v =f v2 As the effective power reference value P st Calculate.

[0066] The subtractor 217 calculates a difference value of the frequency deviations by subtracting the first frequency deviation Δω1 output by the first VSG control unit 101a from the second frequency deviation Δω2 output by the second VSG control unit 201. Furthermore, the subtractor 217 outputs the calculated difference value of the frequency deviations to the second error correction control unit 218.

[0067] In step S24 shown in FIG. 7, the second error correction control unit 218 calculates a second error dP2 from the difference between the first frequency deviation Δω1 calculated by the first VSG control unit 101a and the second frequency deviation Δω2 calculated by the second VSG control unit 201, and feeds it back to the first VSG control unit 101a. In detail, the second error correction control unit 218 functions as an integrator and applies a transfer function (K s / s) to calculate a second error dP2, which is output to the subtractor 111a. This second error dP2 is measure and the active power reference value P stSince this value is generated according to the difference with the actual active power measurement value P measure and the active power reference value P st Here, the difference between the transfer function (K s / s), K s is an integral gain in the second error correction control section 218, and its value may be determined using general control theory so that the entire control system including the second error correction control section 218 is stable. Also, s is a Laplace operator.

[0068] In this way, the first VSG control unit 101a calculates the actual measured value P measure The second VSG control unit 201 calculates a first frequency deviation Δω1 by a transfer function based on an oscillation equation in a synchronous generator using the above equation, and calculates an active power reference value P st The first command value generating unit 102 calculates a second frequency deviation Δω2 by a transfer function based on an oscillation equation in a synchronous generator using the first frequency deviation Δω1 as a frequency command value for the output voltage of the inverter 42. v1 and outputs it to the inverter 42, and the second command value generating unit 202 generates a second frequency command value f as a frequency command value for the output voltage of the inverter 42 using the second frequency deviation Δω2. v2 and outputs it to the reference output calculation unit 117, which calculates the second frequency command value f v2 Based on the above, the inverter 42 outputs a reference active power value P st and the second error correction control unit 218 is configured to calculate the second error dP2 using the first frequency deviation Δω1 and the second frequency deviation Δω2 and feed it back to the first VSG control unit 101a. Therefore, even if the specifications, configuration, or operating state of the connected device change, it is possible to provide a control device 41 that controls the inverter 42 so as to exert the effect of suppressing frequency fluctuations according to the design value.

[0069] In the first and second embodiments, an example in which there are a plurality of power generation facilities 11 and a plurality of loads 12 is shown using Fig. 1, but the present invention is not limited to this example, and there may be only one power generation facility 11 and one load 12. In addition, an example in which there is only one storage battery 13 is shown using Fig. 1, but the present invention is not limited to this example, and there may be a plurality of storage batteries 13, and the plurality of storage batteries 13 may be a combination of a plurality of types of secondary batteries.

[0070] Furthermore, in the first and second embodiments, when there are multiple power generation facilities 11, the multiple power generation facilities 11 may be a combination of multiple types of renewable energy power sources. Furthermore, the power generation facilities 11 do not need to have one or more watt-hour meters and communication devices that transmit the measurement values ​​of the watt-hour meters for each power generation facility 11, and when there are multiple power generation facilities 11, it is sufficient that they are configured to measure and transmit the total amount of generated power. Similarly, the load 12 does not need to have one or more watt-hour meters and communication devices that transmit the measurement values ​​of the amount of power for each load 12, and when there are multiple loads 12, it is sufficient that they are configured to measure and transmit the total amount of consumed power.

[0071] In the first and second embodiments, the microgrid 1 includes the power generation facility 11, the load 12, the storage battery 13, the power conversion device 14, and the transducer 15. However, the present invention is not limited to this example, and the microgrid 1 may further include power receiving and distribution facilities such as a circuit breaker, a disconnecting switch, and a transformer. The microgrid 1 may be connected to another power system via the power transmission and distribution network 21, i.e., may be interconnected, and interconnection facilities such as a circuit breaker, a disconnecting switch, and a transformer may be provided between the microgrid 1 and the other power system.

[0072] In addition, in the first and second embodiments, an example in which the microgrid 1 has the load 12 has been described, but the present invention is not limited to this example, and the microgrid 1 does not need to have the load 12. In this case, however, it should be noted that the microgrid 1 needs to have a plurality of storage batteries 13. This is because the power charged in the storage batteries 13 needs to be consumed by a consumer. In other words, when a storage battery 13 discharges power to charge another storage battery 13, the present control device 41 controls the storage battery 13 that performs the discharge. In this case, the charging and discharging of each storage battery 13 may be controlled by the integrated controller 31.

[0073] In the first and second embodiments, the transducer 15 detects the actual effective power P measure However, the present invention is not limited to this example. The actual values ​​of the voltage and current are measured and output to the control device 41, and the control device 41 uses the output measurement values ​​to calculate the actual active power value P measure The transducer 15 may also calculate VT(V o ltage Transfer o rmer) and CT (Current Transf o rmer).

[0074] In addition, in the first and second embodiments, the method of connecting the integrated controller 31 to the power generation equipment 11, the load 12, the storage battery 13, and the power conversion device 14 is not limited in any way, and may be, for example, a signal line such as a coaxial cable, may be connected by wireless communication, or may be connected via the Internet or an intranet.

[0075] In addition, in the first and second embodiments, the integrated controller 31 may be configured as, for example, a CEMS (Community Energy Management System), an AEMS (Aria Energy Management System), or a BEMS (Building and Energy Management System), and may also control the supply and demand of electricity in, for example, another power system in parallel.

[0076] Although a number of embodiments have been described, in addition to the above disclosure, as long as the features described in each embodiment are not contradictory, the embodiments may be freely combined, any components of each embodiment may be modified, or each embodiment may be omitted. For example, in both embodiments 1 and 2, the order of the constant multiplier 114a and the ZOH circuit 114b may be interchanged. In addition, in embodiment 2, the second error correction control unit 218 may output the second error dP2, which is the output value, to the subtractor 121 instead of to the subtractor 111a. [Explanation of symbols]

[0077] REFERENCE SIGNS LIST 1 Microgrid, 11 Power generation equipment, 12 Load, 13 Storage battery, 14 Power conversion device, 15 Transducer, 21 Power transmission and distribution network, 31 Integrated controller, 41 Control device, 42 Inverter, 101, 101a First VSG control unit, 102 First command value generation unit, 103 First error correction control unit, 117 Reference output calculation unit, 201 Second VSG control unit, 202 Second command value generation unit, 218 Second error correction control unit

Claims

1. A control device that controls an inverter so that a frequency of an output voltage of the inverter has a virtual inertial force with respect to an active power supplied to a destination of the inverter, a first virtual synchronous generator control unit that calculates a frequency deviation by a transfer function based on an oscillation equation in a synchronous generator using an actual measured value of active power supplied by the inverter to the connected destination; a first command value generation unit that generates a frequency command value for an output voltage of the inverter using the frequency deviation calculated by the first virtual synchronous generator control unit; a first error correction control unit that determines a gain of the transfer function in the first virtual synchronous generator control unit by using a first error that is a difference between an active power reference value that is active power supplied by the inverter to the connected destination in a predetermined reference state and the active power actual measurement value; A control device comprising:

2. a reference output calculation unit that calculates the active power reference value using the frequency command value generated by the first command value generation unit; The control device according to claim 1 , comprising:

3. The control device according to claim 1 , wherein the first error correction control unit further determines a time constant of the transfer function using the determined gain of the transfer function.

4. A control device as described in Claim 2, wherein the first error correction control unit further determines the time constant of the transfer function using the determined gain of the transfer function.

5. The control device according to claim 1 , wherein the first error correction control unit sets at least one of an upper limit and a lower limit for the gain of the transfer function to be determined.

6. A control device that controls an inverter so that a frequency of an output voltage of the inverter has a virtual inertial force with respect to an active power supplied to a destination of the inverter, a first virtual synchronous generator control unit that calculates a first frequency deviation by a transfer function based on an oscillation equation in a synchronous generator using an actual measured value of active power supplied by the inverter to the connected destination; a first command value generation unit that generates a first frequency command value as a frequency command value for an output voltage of the inverter by using the first frequency deviation calculated by the first virtual synchronous generator control unit; a second virtual synchronous generator control unit that calculates a second frequency deviation by the transfer function using an active power reference value that is active power supplied by the inverter to the connection destination in a predetermined reference state; a second error correction control unit that calculates a second error from the difference between the first frequency deviation calculated by the first virtual synchronous generator control unit and the second frequency deviation calculated by the second virtual synchronous generator control unit, and feeds the second error back to the first virtual synchronous generator control unit; A control device comprising:

7. a second command value generation unit that generates a second frequency command value as a frequency command value for an output voltage of the inverter by using the second frequency deviation calculated by the second virtual synchronous generator control unit; a reference output calculation unit that calculates the active power reference value using the second frequency command value generated by the second command value generation unit; The control device according to claim 6 , comprising:

8. A control method for controlling an inverter so that a frequency of an output voltage of the inverter has a virtual inertial force with respect to an active power supplied to a destination of the inverter, the method comprising: calculating a frequency deviation by a transfer function based on an oscillation equation in a synchronous generator using an actual measured value of active power supplied by the inverter to the connected destination; generating a frequency command value for an output voltage of the inverter using the frequency deviation; determining a gain of the transfer function using a first error that is a difference between an active power reference value that is active power supplied by the inverter to the connection destination in a predetermined reference state and the active power actual measurement value; A control method comprising:

9. A control method for controlling an inverter so that a frequency of an output voltage of the inverter has a virtual inertial force with respect to an active power supplied to a destination of the inverter, the method comprising: calculating a first frequency deviation by a transfer function based on an oscillation equation in a synchronous generator using an actual measured value of active power supplied by the inverter to the connected destination; generating a frequency command value for an output voltage of the inverter using the first frequency deviation; calculating a second frequency deviation by the transfer function using an active power reference value that is active power supplied by the inverter to the connection destination in a predetermined reference state; calculating a second error based on a difference between the first frequency deviation and the second frequency deviation, and feeding the second error back to the step of calculating the first frequency deviation; A control method comprising:

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