Control device and power conversion device

Abstract

The control device (10) includes a generator simulation unit (101) that generates a first voltage command value by simulating characteristics of a synchronous generator based on an AC voltage in the power system (2), and a signal generation unit (103) that generates a control signal for the power converter (20) based on the first voltage command value. The generator simulation unit (101) includes an angular frequency generation unit (11) that outputs a first angular frequency by integrating a first difference between a first active power and an active power target value over time, a phase generation unit (13) that outputs a first phase by integrating a sum of the first angular frequency and a reference angular frequency over time, and a voltage command generation unit (15) that generates a first voltage command value to suppress an overcurrent in the power converter (20) based on the AC voltage, the target value of the AC voltage, and the first phase. The voltage command generation unit (15) generates a second voltage command value based on the target value and the first phase of the AC voltage, and calculates a first active power based on the AC voltage and the second voltage command value.

Description

[Technical field]

[0001] The present disclosure relates to a control device and a power conversion device. [Background technology]

[0002] In recent years, many distributed power sources using renewable energy such as solar power generation facilities have been introduced into power systems. Distributed power sources are often connected to the power system via power converters. Therefore, as the number of distributed power sources connected to the power system increases, the proportion of synchronous machines connected to the power system decreases, and the inertial energy in the power system decreases. Therefore, virtual synchronous machine control has been proposed, which compensates for the reduced inertial energy by making the power converter behave like a synchronous machine.

[0003] A power converter equipped with voltage-controlled virtual synchronous machine control (hereinafter also referred to as a "virtual synchronous machine") is controlled to simulate the behavior of a synchronous generator to be simulated when it is connected to a power grid. The behavior of the synchronous generator to be simulated is realized by solving an oscillation equation. For example, JP 2020-43688 A (Patent Document 1) considers suppressing overcurrent while maintaining virtual synchronous machine control in a converter equipped with virtual synchronous control. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-43688 A Summary of the Invention [Problem to be solved by the invention]

[0005] A voltage-controlled virtual synchronous machine cannot control current because it controls voltage and operates as a voltage source. Therefore, there is a possibility that an overcurrent occurs during system disturbance, and the power converter stops. In Patent Document 1, a compensation means is provided for compensating an output voltage command value to suppress the overcurrent. The compensation means is configured to set a compensated output voltage command value existing on the control circle as the output voltage command value on the condition that the output voltage command value is outside the control circle. As a result, although the overcurrent is suppressed, since this output voltage command value is not based on the result of the oscillation equation, the synchronous generator to be simulated cannot be synchronized with the power system. Therefore, if the period during which the overcurrent is suppressed becomes long, step-out may occur when performing control simulating a synchronous generator. In this case, even after the disturbance in the power system has subsided, the control simulating a synchronous generator cannot be stably performed.

[0006] An object in one aspect of the present disclosure is to provide a control device and a power conversion device that are capable of stably performing control of a power converter that simulates a synchronous generator while suppressing overcurrent. [Means for solving the problem]

[0007] According to an embodiment, there is provided a control device for controlling a power converter connected to a power system. The control device includes a generator simulation unit that generates a first voltage command value for the power converter by simulating characteristics of a synchronous generator based on an AC voltage in the power system, and a signal generation unit that generates a control signal for the power converter based on the first voltage command value generated by the generator simulation unit. The generator simulation unit includes an angular frequency generation unit that outputs a first angular frequency by time integrating a first difference between a first active power and an active power target value, a phase generation unit that outputs a first phase by time integrating a sum of the first angular frequency and a reference angular frequency, and a voltage command generation unit that generates a first voltage command value to suppress an overcurrent of the power converter based on the AC voltage, the target value of the AC voltage, and the first phase. The voltage command generation unit generates a second voltage command value based on the target value and first phase of the AC voltage, and calculates the first active power based on the AC voltage and the second voltage command value.

[0008] A power conversion device according to another embodiment includes a power converter connected to a power system and a control device that controls the power converter. The control device includes a generator simulation unit that generates a first voltage command value for the power converter by simulating characteristics of a synchronous generator based on an AC voltage in the power system, and a signal generation unit that generates a control signal for the power converter based on the first voltage command value generated by the generator simulation unit. The generator simulation unit includes an angular frequency generation unit that outputs a first angular frequency by time integrating a first difference between a first active power and an active power target value, a phase generation unit that outputs a first phase by time integrating a sum of the first angular frequency and a reference angular frequency, and a voltage command generation unit that generates a first voltage command value that suppresses an overcurrent of the power converter based on the AC voltage, the target value of the AC voltage, and the first phase. The voltage command generation unit generates a second voltage command value based on the target value and first phase of the AC voltage, and calculates the first active power based on the AC voltage and the second voltage command value. Effect of the Invention

[0009] According to the present disclosure, it is possible to stably perform control of a power converter simulating a synchronous generator while suppressing overcurrent. [Brief description of the drawings]

[0010] [Figure 1] 1 is a diagram for explaining an example of an overall configuration of a power conversion system. [Diagram 2] FIG. 2 is a diagram illustrating an example of a hardware configuration of a control device. [Diagram 3] 4 is a diagram for explaining a method of generating a voltage command value by a voltage command generating unit; FIG. [Figure 4] 10 is a flowchart illustrating an example of a processing procedure of a voltage command generating unit. [Diagram 5] 4 is a block diagram showing a specific functional configuration of an angular frequency generating unit. FIG. [Figure 6] 4 is a block diagram showing a specific functional configuration of a phase generating unit. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the present embodiment will be described with reference to the drawings. In the following description, the same components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

[0012] <Overall composition> 1 is a diagram for explaining an example of the overall configuration of a power conversion system. The power conversion system includes a power system 2, a transformer 3, a power conversion device 6, a current detector 7, a voltage detector 8, and a DC system 30. The power conversion device 6 includes a control device 10 and a power converter 20.

[0013] The power converter 20 is a power converter that performs power conversion between the DC system 30 and the power system 2. Specifically, the power converter 20 is connected to the power system 2 via a bus 5 and a transformer 3, converts DC power from the DC system 30 into AC power, and outputs the AC power to the power system 2. The power converter 20 is, for example, a self-commutated converter such as a two-level converter, a three-level converter, or a modular multilevel converter. The power system 2 is, for example, a three-phase AC system. The DC system 30 is, for example, a DC transmission line.

[0014] The current detector 7 detects three-phase AC currents in the power system 2. Specifically, the current detector 7 detects an a-phase AC current Ia, a b-phase AC current Ib, and a c-phase AC current Ic in the power system 2. The AC currents Ia, Ib, and Ic are input to the control device 10. Hereinafter, the AC currents Ia, Ib, and Ic are also collectively referred to as an AC current Isys.

[0015] The voltage detector 8 detects three-phase AC voltages of the power system 2. Specifically, the voltage detector 8 detects an a-phase AC voltage Va, a b-phase AC voltage Vb, and a c-phase AC voltage Vc of the power system 2. The AC voltages Va, Vb, and Vc are input to the control device 10. Hereinafter, the AC voltages Va, Vb, and Vc are also collectively referred to as an AC voltage Vsys.

[0016] The control device 10 is a device that controls the operation of the power converter 20. Specifically, the control device 10 includes, as main functional components, a generator simulation unit 101 and a signal generation unit 103. The functions of the generator simulation unit 101 and the signal generation unit 103 are realized by a processing circuit. The processing circuit may be dedicated hardware, or may be a CPU that executes a program stored in the internal memory of the control device 10. When the processing circuit is dedicated hardware, the processing circuit is configured, for example, by an FPGA, an ASIC, or a combination of these.

[0017] The generator simulation unit 101 generates a voltage command value for the power converter 20 by simulating the characteristics of a synchronous generator based on the AC voltage Vsys in the power system 2. Typically, the generator simulation unit 101 simulates the behavior of the synchronous generator by solving the equation of motion shown in the following formula (1).

[0018]

number

[0019] "P0" is the target value of the active power to be output by power converter 20 (hereinafter also referred to as "active power target value"), "Pe" is the active power output from power converter 20, "M" is the moment of inertia of the simulated generator, "Δω" is the difference between the angular frequency ω of the rotor of the simulated generator and the reference angular frequency ω0 of power system 2, and "D" is the damping coefficient of the simulated generator. In addition, if the voltage phase angle (hereinafter also referred to simply as "phase") of the simulated generator is "θ", then the following equation (2) regarding the phase θ is established.

[0020]

number

[0021] Specifically, the generator simulation unit 101 includes an angular frequency generation unit 11 , a phase generation unit 13 , and a voltage command generation unit 15 .

[0022] The angular frequency generating unit 11 generates the angular frequency deviation Δω based on the active power Pk from the voltage command generating unit 15. The active power Pk is calculated in the voltage command generating unit 15. The angular frequency generating unit 11 replaces "Pe" in equation (1) with "Pk" and generates the angular frequency deviation Δω by time integration according to equation (1). A specific configuration of the angular frequency generating unit 11 will be described later.

[0023] The phase generation unit 13 generates a phase θ based on the angular frequency deviation Δω generated by the angular frequency generation unit 11 and a reference angular frequency ω0. The phase generation unit 13 generates the phase θ by time integration according to equation (2). A specific configuration of the phase generation unit 13 will be described later. The reference angular frequency ω0 is the angular frequency of the reference frequency of power in the power system 2 (for example, 50 Hz or 60 Hz).

[0024] The voltage command generating unit 15 generates a voltage command value Vref to suppress an overcurrent in the power converter 20, based on the AC voltage Vsys of the power system 2, a target value (hereinafter also referred to as a target voltage) Vo of the AC voltage Vsys, and the phase θ. In the following description, the magnitude (i.e., absolute value) of the voltage command value Vref is also written as |Vref|. This also applies to other voltages.

[0025] Furthermore, the voltage command generating unit 15 generates a voltage command value Vk based on the target voltage Vo and the phase θ. Specifically, the magnitude of the voltage command value Vk (i.e., |Vk|) is the absolute value |Vo| of the target voltage Vo, and the phase of the voltage command value Vk is the phase θ. Next, the voltage command generating unit 15 calculates an active power Pk based on the AC current Vsys and the voltage command value Vk. The calculation method of the active power Pk will be described later.

[0026] The voltage command value Vref is a voltage command value for current suppression that takes into account the upper limit of the output current of the power converter 20. In contrast, the voltage command value Vk is a voltage command value that does not take into account the upper limit. A method for generating the voltage command value Vref for current suppression will be described later.

[0027] The signal generating unit 103 generates a control signal for the power converter 20 based on the absolute value |Vref| and phase θref of the voltage command value Vref generated by the generator simulation unit 101, and outputs the control signal to the power converter 20. Specifically, the signal generating unit 103 includes a three-phase voltage generating unit 17 and a PWM (Pulse Width Modulation) control unit 19.

[0028] The three-phase voltage generating unit 17 generates three-phase sinusoidal voltages Va*, Vb*, and Vc* based on the absolute value |Vref| and phase θref from the voltage command generating unit 15. Specifically, Va*=|Vref|×sin(θref), Vb*=|Vref|×sin(θref+2π / 3), and Vc*=|Vref|×sin(θref+4π / 3) are generated.

[0029] The PWM control unit 19 performs pulse width modulation on each of the three-phase sinusoidal voltages Va*, Vb*, and Vc* to generate a control signal as a PWM signal. The PWM control unit 19 outputs the control signal to the power converter 20. Typically, the control signal is a gate control signal for controlling the on and off of each switching element included in the power converter 20.

[0030] <Hardware configuration> Fig. 2 is a diagram showing an example of a hardware configuration of the control device 10. Fig. 2 shows an example of the control device 10 configured by a computer.

[0031] 2, the control device 10 includes one or more input converters 70, one or more sample-and-hold (S / H) circuits 71, a multiplexer (MUX) 72, an A / D converter 73, one or more central processing units (CPUs) 74, a random access memory (RAM) 75, a read-only memory (ROM) 76, one or more input / output interfaces 77, and an auxiliary storage device 78. The control device 10 also includes a bus 79 that interconnects the components.

[0032] The input converter 70 has an auxiliary transformer for each input channel. Each auxiliary transformer converts the detection signals from the current detector 7 and the voltage detector 8 in FIG. 1 into signals of a voltage level suitable for subsequent signal processing.

[0033] A sample-and-hold circuit 71 is provided for each input converter 70. The sample-and-hold circuit 71 samples and holds a signal representing an electrical quantity received from the corresponding input converter 70 at a specified sampling frequency.

[0034] The multiplexer 72 sequentially selects the signals held in the multiple sample-and-hold circuits 71. The A / D converter 73 converts the signal selected by the multiplexer 72 into a digital value. Note that by providing multiple A / D converters 73, A / D conversion may be performed in parallel on detection signals of multiple input channels.

[0035] The CPU 74 controls the entire control device 10 and executes arithmetic processing according to a program. The RAM 75 as a volatile memory and the ROM 76 as a non-volatile memory are used as the main memory of the CPU 74. The ROM 76 stores programs and setting values ​​for signal processing. The auxiliary storage device 78 is a non-volatile memory with a larger capacity than the ROM 76, and stores programs, data on detected electric quantity values, and the like.

[0036] The input / output interface 77 is an interface circuit for communication between the CPU 74 and an external device.

[0037] Unlike the example of FIG. 2, at least a part of the control device 10 can be configured using circuits such as a field programmable gate array (FPGA) and an application specific integrated circuit (ASIC).

[0038] <Specific configuration of the generator simulation section> The specific configurations of the angular frequency generating section 11, the phase generating section 13, and the voltage command generating section 15 of the generator simulator 101 will be described.

[0039] (Voltage command generator) The voltage command generating unit 15 mainly executes a process of calculating an active power Pk using a voltage command value Vk that does not take current suppression into consideration, and a process of generating a voltage command value Vref for current suppression. First, a calculation method of the active power Pk will be described.

[0040] The voltage command generating unit 15 generates a voltage command value Vk based on the target voltage Vo of the AC voltage Vsys and the phase θ output from the phase generating unit 13. Next, the voltage command generating unit 15 calculates a differential voltage ΔVk by subtracting the AC voltage Vsys from the voltage command value Vk, and calculates a current Ik based on the differential voltage ΔVk and the leakage impedance Zt of the transformer 3. Specifically, "Ik=ΔVk / Zt". Here, the current Ik indicates a virtual current output from the power converter 20 to the transformer 3 when it is assumed that the power converter 20 is controlled based on the voltage command value Vk that does not take current suppression into consideration.

[0041] Then, the voltage command generating unit 15 calculates the active power Pk based on the voltage command value Vk and the current Ik. If the complex conjugate of the current Ik is "Ik*", then "Pk = Vk x Ik*". Note that "Vk = |Vo| x (cosθ + j sinθ)". The active power Pk indicates the virtual active power output from the power converter 20 when it is assumed that the power converter 20 is controlled based on the voltage command value Vk.

[0042] Next, a method for generating the voltage command value Vref will be described. Note that the method itself for generating the voltage command value Vref in the voltage command generating unit 15 to suppress an overcurrent is similar to the content disclosed in Patent Document 1.

[0043] 3 is a diagram for explaining a method of generating a voltage command value by the voltage command generating unit. Referring to FIG. 3, a voltage vector obtained by converting the target voltage Vo into a rotating coordinate system consisting of d-axis and q-axis is <vo>and the voltage vector obtained by transforming the AC voltage Vsys into the rotating coordinate system <vsys>The voltage command generator 15 calculates such a voltage vector <vo>and the voltage vector <vsys>Generate.

[0044] Voltage Vector <vsys>is created by the absolute value |Vsys| and phase θsys of the AC voltage Vsys, and the voltage vector <vo>is generated from the absolute value |Vo| of the target voltage Vo and the phase θ generated by the phase generator 13. In addition, the voltage command generator 15 generates a voltage vector <vsys>The control circle G with a radius r is defined with the end point of the target voltage Vo as the center. The radius r is a preset value and corresponds to a threshold value Th described later. The dq transformation is performed based on the rotor phase of the virtual synchronous machine, and the voltage vector of the target voltage Vo is <vo>is assumed to exist on the d-axis.

[0045] In Fig. 3(a), power system 2 is relatively normal, and the voltage vector <vsys>and the voltage vector <vo>When the voltage difference ΔV between the vector and the radius r is less than or equal to the voltage vector <vo>is within the control circle G). <vo> ― <vsys>In this case, the voltage command generating unit 15 determines that it is not necessary to suppress the current, and generates the voltage command value Vk that does not take current suppression into consideration as the voltage command value Vref. Specifically, the voltage command generating unit 15 generates the voltage vector <vo>The absolute value of |Vo| is set as the absolute value of the voltage command value Vref |Vref|, and the voltage vector <vo>(that is, the phase θ output from the phase generating unit 13) is set as the phase θref of the voltage command value Vref.

[0046] In Fig. 3(b), the power system 2 is disturbed and the voltage vector <vsys>and the voltage vector <vo>When the voltage difference ΔV between the vector and the point is greater than the radius r (i.e., the voltage vector <vo>exists outside the control circle G). In this case, the voltage command generating unit 15 determines that the current needs to be suppressed, and generates a voltage command value Vref for suppressing the current.

[0047] Specifically, the voltage command generating unit 15 generates a voltage vector <vx>The intersection point K is the voltage vector <vsys>The end points and voltage vectors of <vo>The voltage command generator 15 calculates the voltage vector <vx>The absolute value |Vx| of the voltage command value Vref is set as the absolute value |Vref| of the voltage vector <vx>The phase θx of the voltage command value Vref is set as the phase θref of the voltage command value Vref.

[0048] As described above, the voltage command generating unit 15 determines whether or not to suppress the current flowing through the power converter 20 based on the voltage difference ΔV between the AC voltage Vsys and the target voltage Vo. When the voltage difference ΔV is equal to or smaller than the threshold value Th (where the threshold value Th corresponds to the above-mentioned radius r), the voltage command generating unit 15 determines not to suppress the current, and generates the voltage command value Vk as the voltage command value Vref. On the other hand, when the voltage difference ΔV is larger than the threshold value Th, the voltage command generating unit 15 determines to suppress the current, and generates the voltage command value Vref for current suppression.

[0049] Fig. 4 is a flowchart showing an example of a processing procedure of the voltage command generating unit. Each step in Fig. 4 is typically performed by a processing circuit of the control device 10. Referring to Fig. 4, the voltage command generating unit 15 calculates a virtual active power Pk by using a voltage command value Vk based on a target voltage Vo of the AC voltage Vsys and a phase θ output from the phase generating unit 13 (step S10). The active power Pk is provided to the angular frequency generating unit 11.

[0050] Next, the voltage command generating unit 15 determines whether or not to suppress the current (step S12). Specifically, the voltage command generating unit 15 determines not to suppress the current when the voltage difference ΔV between the AC voltage Vsys and the target voltage Vo is equal to or smaller than the threshold value Th (i.e., the radius r of the control circle G), and determines to suppress the current when the voltage difference ΔV is larger than the threshold value Th.

[0051] When the current is to be suppressed (YES in step S12), the voltage command generating unit 15 outputs a voltage command value Vref based on the absolute value |Vx| and the phase θx in order to suppress the current (step S14).

[0052] When the current is not suppressed (NO in step S12), the voltage command generating unit 15 outputs a voltage command value Vk based on the absolute value |Vo| and the phase θ as a voltage command value Vref (step S16).

[0053] (Angular frequency generator) 5 is a block diagram showing a specific functional configuration of the angular frequency generation unit 11. Referring to FIG. 5, the angular frequency generation unit 11 includes a subtractor 211, an integrator (denoted as "1 / MS" in the drawing) 212, and a proportional unit (denoted as "D" in the drawing) 213.

[0054] The subtractor 211 subtracts the output value of the proportional unit 213 from the difference ΔP between the active power target value Pо and the active power Pk. The active power target value Pо is appropriately set by a system operator. The output value of the proportional unit 213 is the multiplication value "D×Δω" of the angular frequency deviation Δω and the damping coefficient D. By subtracting the multiplication value "D×Δω", the angular frequency generation unit 11 simulates the damping force of the synchronous generator in controlling the power converter 20. Note that the output value of the proportional unit 213 may not be input to the subtractor 211.

[0055] The integrator 212 time-integrates the output value of the subtractor 211 and outputs the angular frequency deviation Δω. When the output value of the proportional unit 213 is not input to the subtractor 211, the integrator 212 time-integrates the difference ΔP between the active power target value Pо and the active power Pk and outputs the angular frequency deviation Δω.

[0056] Here, the voltage command generating unit 15 changes the voltage command value Vk to the voltage command value Vref so that the output current of the power converter 20 does not become an overcurrent, and outputs the voltage command value Vref to the signal generating unit 103. However, as described above, the angular frequency generating unit 11 generates the angular frequency deviation Δω based on the virtual active power Pk calculated based on the voltage command value Vk before the change. Therefore, the angular frequency generating unit 11 can generate the angular frequency deviation Δω in accordance with the formula (1), and can accurately simulate the behavior of a synchronous generator.

[0057] (Phase generation section) 6 is a block diagram showing a specific functional configuration of the phase generating unit 13. With reference to FIG. 6, the phase generating unit 13 includes an adder 302 and an integrator 304.

[0058] The adder 302 outputs an angular frequency ω (=Δω+ω0) which is the sum of the angular frequency deviation Δω generated by the angular frequency generation unit 11 and the reference angular frequency ω0. The integrator 304 time-integrates the angular frequency ω to output a phase θ. The phase generation unit 13 generates the phase θ using the angular frequency deviation Δω according to equation (1) by the angular frequency generation unit 11, and therefore can accurately simulate the behavior of a synchronous generator.

[0059] <Advantages> According to this embodiment, the control device 10 can suppress an overcurrent of the output current of the power converter 20 by the voltage command value Vref for suppressing the overcurrent while making the power converter 20 execute the control simulating a synchronous generator. Furthermore, even while suppressing the overcurrent, the control device 10 generates the angular frequency deviation Δω and the phase θ by using the active power Pk generated by the voltage command value Vk according to the formulas (1) and (2). Therefore, the voltage phase as a synchronous generator can be maintained at an appropriate value. Therefore, even if the period during which the overcurrent is suppressed becomes long, the occurrence of an unstable response such as step-out can be prevented when performing the control simulating a synchronous generator. Furthermore, when the disturbance in the power system 2 subsides, it becomes easy to return the power converter 20 to the control simulating a synchronous generator.

[0060] Other embodiments. (1) In the above embodiment, the voltage command generating unit 15 determines whether or not to suppress the current flowing through the power converter 20 based on the voltage difference ΔV between the AC voltage Vsys and the target voltage Vo, but the present invention is not limited to this configuration. For example, the voltage command generating unit 15 may determine whether or not to suppress the current flowing through the power converter 20 based on the AC current Isys and a threshold Ith. Specifically, when the AC current Isys is equal to or smaller than the threshold Ith, the voltage command generating unit 15 determines not to suppress the current. When the AC current Isys is larger than the threshold Ith, the voltage command generating unit 15 determines to suppress the current.

[0061] The processes after the process of determining whether or not to suppress the current are the same as the processes in steps S14 and S16 in Fig. 4. Specifically, when the current is not suppressed, the voltage command generating unit 15 outputs the voltage command value Vk as the voltage command value Vref. When the current is suppressed, the voltage command generating unit 15 outputs the voltage command value Vref based on the absolute value |Vx| and the phase θx.

[0062] (2) The configurations exemplified as the above-mentioned embodiments are examples of the configurations of the present disclosure, and may be combined with other known technologies, or may be modified, such as by omitting some parts, without departing from the scope of the present disclosure. In addition, the above-mentioned embodiments may be implemented by appropriately adopting the processes and configurations described in other embodiments.

[0063] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is defined by the claims, not the above description, and is intended to include all modifications within the scope and meaning equivalent to the claims. [Explanation of symbols]

[0064] 2 Power system, 3 Transformer, 5 Busbar, 6 Power conversion device, 7 Current detector, 8 Voltage detector, 10 Control device, 11 Angular frequency generation unit, 13 Phase generation unit, 15 Voltage command generation unit, 17 Voltage generation unit, 19 PWM control unit, 20 Power converter, 30 DC system, 70 Input converter, 71 Sample and hold circuit, 72 Multiplexer, 73 A / D converter, 75 RAM, 76 ROM, 77 Input / output interface, 78 Auxiliary storage device, 79 Bus, 101 Generator simulation unit, 103 Signal generation unit, 211 Subtractor, 212, 304 Integrator, 213 Proportional converter, 302 Adder.< / vx> < / vx> < / vo> < / vsys> < / vx> < / vo> < / vo> < / vsys> < / vo> < / vo> < / vsys> < / vo> < / vo> < / vo> < / vsys> < / vo> < / vsys> < / vo> < / vsys> < / vsys> < / vo> < / vsys> < / vo>

Claims

1. A control device for controlling a power converter connected to a power grid, a generator simulation unit that generates a first voltage command value for the power converter by simulating characteristics of a synchronous generator based on an AC voltage in the power system; a signal generating unit that generates a control signal for the power converter based on the first voltage command value generated by the generator simulation unit, The generator simulation unit includes: an angular frequency generating unit that outputs a first angular frequency by time-integrating a first difference between the first active power and an active power target value; a phase generating unit that outputs a first phase by time-integrating a sum of the first angular frequency and a reference angular frequency; a voltage command generating unit that generates the first voltage command value based on the AC voltage, a target value of the AC voltage, and the first phase so as to suppress an overcurrent of the power converter, The voltage command generating unit generating a second voltage command value based on the target value of the AC voltage and the first phase; A control device that calculates the first active power based on the AC voltage and the second voltage command value.

2. The voltage command generating unit calculating a first current based on a difference between the AC voltage and the second voltage command value and a leakage impedance of a transformer provided in the power system; The control device according to claim 1 , wherein the first active power is calculated based on the second voltage command value and the first current.

3. 3. The control device according to claim 1, wherein when a voltage difference between the AC voltage and a target value of the AC voltage is equal to or smaller than a first threshold value or when an AC current in the power grid is equal to or smaller than a second threshold value, the voltage command generation unit generates the second voltage command value as the first voltage command value.

4. The voltage command generating unit transforming the AC voltage and a target value of the AC voltage into a rotating coordinate system having a d-axis and a q-axis, and defining a control circle centered on the AC voltage; when the voltage difference is greater than the first threshold value or when the AC current is greater than the second threshold value, a voltage vector is generated to an intersection between the vector of the target value of the AC voltage and a line connecting the vector of the AC voltage and the control circle, and a magnitude of the voltage vector is set as a magnitude of the first voltage command value, and a phase of the voltage vector is set as a phase of the first voltage command value; The control device according to claim 3 , wherein the first threshold value is a radius of the control circle.

5. A power converter connected to a power grid; A control device for controlling the power converter, The control device includes: a generator simulation unit that generates a first voltage command value for the power converter by simulating characteristics of a synchronous generator based on an AC voltage in the power system; a signal generating unit that generates a control signal for the power converter based on the first voltage command value generated by the generator simulation unit, The generator simulation unit includes: an angular frequency generating unit that outputs a first angular frequency by time-integrating a first difference between the first active power and an active power target value; a phase generating unit that outputs a first phase by time-integrating a sum of the first angular frequency and a reference angular frequency; a voltage command generating unit that generates the first voltage command value based on the AC voltage, a target value of the AC voltage, and the first phase so as to suppress an overcurrent of the power converter, The voltage command generating unit generating a second voltage command value based on the target value of the AC voltage and the first phase; The power conversion device calculates the first active power based on the AC voltage and the second voltage command value.

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