STATCOM (Static Synchronous Compensator) broadband domain impedance characteristic acquisition method based on hardware-in-loop simulation

Abstract

The invention relates to an STATCOM (Static Synchronous Compensator) broadband domain impedance characteristic acquisition method based on hardware-in-the-loop simulation. The method comprises the following steps: firstly, establishing an STATCOM single machine infinite bus system based on a hardware-in-the-loop simulation platform; then, when the STATCOM operates normally, a three-phase voltage disturbance signal with the amplitude being k% of the nominal voltage and the frequency being within the range of f1-f2 is injected into a body of the STATCOM, and meanwhile, three-phase voltage and current signals at the machine end of the STATCOM are collected; and finally, the broadband impedance of the system to be measured is calculated according to the collected voltage and current signals. According to the method, the impedance characteristic of the STATCOM in the range of f1-f2 can be accurately and quickly obtained, and the obtained result can provide an important basis for influence analysis of the STATCOM accessing a power grid.

Description

Technical Field

[0001] The present invention belongs to the technical field of electromagnetic transient simulation modeling of new energy, and in particular relates to a method for obtaining wide-frequency domain impedance characteristics of a STATCOM based on hardware-in-the-loop simulation. Background Art

[0002] Driven by the "dual carbon" goal, with the continuous increase in the penetration rate of new energy and the proportion of power electronic equipment, the power grid has gradually transformed from a synchronous machine-dominated system to a power electronic equipment-dominated system, which will lead to a reduction in system inertia and a significant decrease in the short-circuit ratio of the common coupling point, making the power grid present weak grid characteristics. Therefore, the power system has put forward higher requirements for the access of new energy and power electronic equipment, requiring power electronic equipment to provide positive damping to suppress the oscillation of the power system. At present, there are few methods for calculating the impedance characteristics of power electronic equipment. Therefore, how to obtain accurate impedance characteristics of power electronic equipment is an urgent problem to be solved in the field of energy electromagnetic transient simulation modeling technology. Summary of the invention

[0003] The purpose of the present invention is to solve the deficiencies of the prior art and to provide a method for obtaining the wide-frequency domain impedance characteristics of STATCOM based on hardware-in-the-loop simulation. The method takes into account the hardware controller characteristics of STATCOM and can accurately obtain the impedance characteristics of STATCOM in a wide frequency domain, providing an important basis for the impact analysis of STATCOM access to the power grid.

[0004] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0005] The method for obtaining the wide-frequency domain impedance characteristics of STATCOM based on hardware-in-the-loop simulation includes the following steps:

[0006] Step (1), building a STATCOM stand-alone infinite system based on a hardware-in-the-loop simulation platform;

[0007] Step (2), setting the amplitude of the voltage disturbance signal to k%U n , k is any constant greater than 0, U n is the nominal voltage of the STATCOM grid-connected point; the lower limit of the frequency of the voltage disturbance signal is set to f1, and the upper limit of the frequency of the voltage disturbance signal is set to f2. Both f1 and f2 are positive integers. Then the three-phase positive sequence voltage disturbance signal is:

[0008]

[0009] Where: U a+ , U b+ , U c+ are the three-phase positive sequence voltage disturbance signals respectively, t is the time, f3 is a positive integer between [f1, f2];

[0010] The three-phase negative sequence voltage disturbance signal is:

[0011]

[0012] Where: U a- , U b- , U c- They are three-phase negative sequence voltage disturbance signals respectively;

[0013] Step (3), injecting the three-phase positive sequence voltage disturbance signal with an amplitude of k% of the nominal voltage and a frequency of f3 obtained in step (2) into the STATCOM body in the STATCOM single-machine infinite system based on the hardware-in-the-loop simulation platform, and simultaneously collecting the three-phase voltage and current signal data at the STATCOM machine end;

[0014] Step (4), using a fast Fourier transform function to perform Fourier transform on the STATCOM machine-end three-phase voltage and three-phase current data collected in step (3), and extract the three-phase voltage amplitude and phase, and the three-phase current amplitude and phase at frequency f3;

[0015] Then the positive sequence voltage ΔU at frequency f3 is p (f3), positive sequence current ΔI p (f3) is;

[0016]

[0017] Among them, U a+ (f3), U b+ (f3), U c+ (f3) respectively represent the amplitudes of the three-phase voltages a, b, and c when the positive sequence voltage disturbance signal is injected

[0018] U θa+ (f3), U θb+ (f3), U θc+ (f3) respectively represent the phases of the three-phase voltages a, b, and c when the positive sequence voltage disturbance signal is injected;

[0019] I a+ (f3), I b+ (f3), I c+ (f3), I θa+ (f3), I θb+ (f3), I θc+ (f3) respectively represent the amplitudes of the three-phase currents a, b, and c when the positive sequence voltage disturbance signal is injected;

[0020] I θa+ (f3), I θb+ (f3), I θc+(f3) respectively represent the phases of the three-phase currents a, b, and c when the positive sequence voltage disturbance signal is injected;

[0021] Step (5), calculate the positive sequence impedance Z1 at frequency f3:

[0022] Z1=ΔU p (f3) / ΔI p (f3) (4)

[0023] Step (6), injecting the three-phase negative sequence voltage disturbance signal with an amplitude of k% of the nominal voltage and a frequency of f3 obtained in step (2) into the STATCOM body in the STATCOM single-machine infinite system based on the hardware-in-the-loop simulation platform, and simultaneously collecting the three-phase voltage and current signal data at the STATCOM machine end;

[0024] Step (7), using a fast Fourier transform function to perform Fourier transform on the STATCOM machine-end three-phase voltage and three-phase current data collected in step (6), and extract the three-phase voltage amplitude and phase, and the three-phase current amplitude and phase at frequency f3;

[0025] Then the negative sequence voltage ΔU at frequency f3 is n (f3), negative sequence current ΔI n (f3) is;

[0026]

[0027] Among them, U a- (f3), U b- (f3), U c- (f3) respectively represent the amplitudes of the three-phase voltages a, b, and c when the negative sequence voltage disturbance signal is injected

[0028] U θa- (f3), U θb- (f3), U θc- (f3) respectively represent the phases of the three-phase voltages a, b, and c when the negative sequence voltage disturbance signal is injected;

[0029] I a- (f3), I b- (f3), I c- (f3) respectively represent the amplitudes of the three-phase currents a, b, and c when the negative sequence voltage disturbance signal is injected;

[0030] I θa- (f3), I θb- (f3), I θc- (f3) respectively represent the phases of the three-phase currents a, b, and c when the negative sequence voltage disturbance signal is injected;

[0031] Step (8), calculate the negative sequence impedance Z2 at frequency f3:

[0032] Z2=ΔU n (f3) / ΔI n (f3) (6)

[0033] Step (9), use the semilogx function in MATLAB to draw the Bode diagram of the positive and negative sequence impedances for the positive sequence impedance Z1 obtained in step (5) and the negative sequence impedance Z2 obtained in step (8), as shown in Figure 2 to Figure 5 As shown, Figure 2-3 is the positive sequence amplitude-frequency and phase-frequency characteristics of STATCOM under the added disturbance signal, Figure 4-5 The figure shows the negative sequence amplitude-frequency and phase-frequency characteristics of STATCOM under the added disturbance signal. Figure 2 to Figure 5 As the final STATCOM impedance characteristic, that is, the impedance characteristic of STATCOM at an amplitude of k% of the nominal voltage and a frequency of f3;

[0034] Step (10), re-set the frequency f3 of the disturbance signal, repeat steps (3) to (9), and the impedance characteristics of the STATCOM at all frequencies between [f1, f2] and an amplitude of k% of the nominal voltage can be obtained.

[0035] Furthermore, preferably, in step (1), in the STAT COM stand-alone infinite system based on the hardware-in-the-loop simulation platform, the STATCOM body is connected to the 35kV bus, then boosted to 220kV through the main transformer, and then connected to the infinite power grid. The STATCOM controller transmits PWM control signals to the RT-LAB simulator via optical fiber, and the STATCOM controller is connected to the analog output board of the simulator via a DB37 connection line to collect the three-phase voltage and current signals of the power grid.

[0036] Furthermore, preferably, in both step (4) and step (7), the FFT function in Matlab is used to perform Fourier transform on the three-phase voltage and three-phase current data at the STATCOM machine end.

[0037] Furthermore, preferably, the value of k is 2-5.

[0038] Furthermore, preferably, f1 is 1 and f2 is not more than 3000.

[0039] The present invention also provides a method for evaluating whether STATCOM can provide positive damping when the power system is unstable, using the above-mentioned STATCOM wide-frequency domain impedance characteristic acquisition method based on hardware-in-the-loop simulation, including the following steps:

[0040] If the phase-frequency characteristic curve in the impedance characteristic is between positive and negative 90 degrees, positive damping can be provided, otherwise it cannot be provided.

[0041] The present invention provides a method for acquiring wide-frequency domain impedance characteristics of a STATCOM based on hardware-in-the-loop simulation. The method can accurately and quickly acquire the impedance characteristics of the STATCOM in a wide-frequency domain.

[0042] In step (4) of the present invention, the method for using FFT in matlab is: input three-phase voltage and current data, which can automatically output the three-phase voltage amplitude and phase, three-phase current amplitude and phase at frequency f3): U a+ (f3), U b+ (f3), U c+ (f3); U θa+ (f3), U θb+ (f3), U θc+ (f3); I a+ (f3), I b+ (f3), I c+ (f3); I θa+ (f3), I θb+ (f3), I θc+ (f3). Among them, U a+ (f3), U b+ (f3), U c+ (f3), U θa+ (f3), U θb+ (f3), U θc+ (f3) respectively represent the amplitude and phase of the three-phase voltages a, b, and c when the positive sequence voltage disturbance signal is injected; I a+ (f3), I b+ (f3), I c+ (f3), I θa+ (f3), I θb+ (f3), I θc+ (f3) respectively represent the amplitude and phase of the three-phase currents a, b, and c when the positive sequence voltage disturbance signal is injected.

[0043] In step (7) of the present invention, the method for using FFT in MATLAB is as follows: input three-phase voltage and current data, which can automatically output the three-phase voltage amplitude and phase, three-phase current amplitude and phase at frequency f3): U a -(f3),U b- (f3), U c- (f3); U θa- (f3), U θb- (f3), U θc- (f3); I a- (f3), I b- (f3), Ic- (f3); I θa- (f3), I θb- (f3), I θc- (f3); U a- (f3), U b- (f3), U c- (f3), U θa- (f3), U θb- (f3), U θc- (f3) respectively represent the amplitude and phase of the three-phase voltages a, b, and c when the negative sequence voltage disturbance signal is injected; I a- (f3), I b- (f3), I c- (f3), I θa- (f3), I θb- (f3), I θc- (f3) respectively represent the amplitude and phase of the three-phase currents a, b, and c when the negative sequence voltage disturbance signal is injected

[0044] The method provided by the present invention can accurately and quickly obtain the impedance characteristics of STATCOM in a wide frequency domain and evaluate whether it can provide positive damping when the power system is unstable. For example, if the phase-frequency characteristic curve is between positive and negative 90 degrees, positive damping is provided, that is, if the curve is between two dotted lines, then STATCOM provides positive damping.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] In view of the problem that "the current large-scale grid connection of new energy sources has resulted in the grid presenting weak grid characteristics, and there is an urgent need to obtain and evaluate the impedance characteristics of new energy power electronic equipment", the present invention provides a method for obtaining the wide-frequency domain impedance characteristics of STATCOM based on hardware-in-the-loop simulation. The method takes into account the hardware controller characteristics of STATCOM, and can quickly and accurately obtain the impedance characteristics of STATCOM in a wide frequency domain, providing an important basis for the impact analysis of STATCOM access to the grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a structural diagram of a STATCOM single-machine infinite system based on a hardware-in-the-loop simulation platform;

[0048] Figure 2 The initial reactive output of STATCOM is 20% capacitive Q N Positive sequence amplitude-frequency characteristics under ;

[0049] Figure 3 The initial reactive output of STATCOM is 20% capacitive Q N Positive sequence phase-frequency characteristics under ;

[0050] Figure 4 The initial reactive output of STATCOM is 20% capacitive Q N Negative sequence amplitude-frequency characteristics under ;

[0051] Figure 5 The initial reactive output of STATCOM is 20% capacitive Q N Negative sequence phase-frequency characteristics under. DETAILED DESCRIPTION

[0052] The present invention is further described in detail below in conjunction with embodiments.

[0053] Those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the art or the product specifications are used. If the manufacturer of the materials or equipment used is not specified, they are all conventional products that can be purchased.

[0054] Example 1

[0055] The method for obtaining the wide-frequency domain impedance characteristics of STATCOM based on hardware-in-the-loop simulation includes the following steps:

[0056] Step (1), building a STATCOM stand-alone infinite system based on a hardware-in-the-loop simulation platform;

[0057] Step (2), setting the amplitude of the voltage disturbance signal to k%U n , k is any constant greater than 0, U n is the nominal voltage of the STATCOM grid-connected point; the lower limit of the frequency of the voltage disturbance signal is set to f1, and the upper limit of the frequency of the voltage disturbance signal is set to f2. Both f1 and f2 are positive integers. Then the three-phase positive sequence voltage disturbance signal is:

[0058]

[0059] Where: U a+ , U b+ , U c+ are the three-phase positive sequence voltage disturbance signals respectively, t is the time, f3 is a positive integer between [f1, f2];

[0060] The three-phase negative sequence voltage disturbance signal is:

[0061]

[0062] Where: U a- , U b- , U c- They are three-phase negative sequence voltage disturbance signals respectively;

[0063] Step (3), injecting the three-phase positive sequence voltage disturbance signal with an amplitude of k% of the nominal voltage and a frequency of f3 obtained in step (2) into the STATCOM body in the STATCOM single-machine infinite system based on the hardware-in-the-loop simulation platform, and simultaneously collecting the three-phase voltage and current signal data at the STATCOM machine end;

[0064] Step (4), using a fast Fourier transform function to perform Fourier transform on the STATCOM machine-end three-phase voltage and three-phase current data collected in step (3), and extract the three-phase voltage amplitude and phase, and the three-phase current amplitude and phase at frequency f3;

[0065] Then the positive sequence voltage ΔU at frequency f3 is p (f3), positive sequence current ΔI p (f3) is;

[0066]

[0067] Among them, U a+ (f3), U b+ (f3), U c+ (f3) respectively represent the amplitudes of the three-phase voltages a, b, and c when the positive sequence voltage disturbance signal is injected

[0068] U θa+ (f3), U θb+ (f3), U θc+ (f3) respectively represent the phases of the three-phase voltages a, b, and c when the positive sequence voltage disturbance signal is injected;

[0069] I a+ (f3), I b+ (f3), I c+ (f3), I θa+ (f3), I θb+ (f3), I θc+ (f3) respectively represent the amplitudes of the three-phase currents a, b, and c when the positive sequence voltage disturbance signal is injected;

[0070] I θa+ (f3), I θb+ (f3), I θc+ (f3) respectively represent the phases of the three-phase currents a, b, and c when the positive sequence voltage disturbance signal is injected;

[0071] Step (5), calculate the positive sequence impedance Z1 at frequency f3:

[0072] Z1=ΔU p (f3) / ΔI p (f3) (4)

[0073] Step (6), injecting the three-phase negative sequence voltage disturbance signal with an amplitude of k% of the nominal voltage and a frequency of f3 obtained in step (2) into the STATCOM body in the STATCOM single-machine infinite system based on the hardware-in-the-loop simulation platform, and simultaneously collecting the three-phase voltage and current signal data at the STATCOM machine end;

[0074] Step (7), using a fast Fourier transform function to perform Fourier transform on the STATCOM machine-end three-phase voltage and three-phase current data collected in step (6), and extract the three-phase voltage amplitude and phase, and the three-phase current amplitude and phase at frequency f3;

[0075] Then the negative sequence voltage ΔU at frequency f3 is n (f3), negative sequence current ΔI n (f3) is;

[0076]

[0077] Among them, U a- (f3), U b- (f3), U c- (f3) respectively represent the amplitudes of the three-phase voltages a, b, and c when the negative sequence voltage disturbance signal is injected

[0078] U θa- (f3), U θb- (f3), U θc- (f3) respectively represent the phases of the three-phase voltages a, b, and c when the negative sequence voltage disturbance signal is injected;

[0079] I a- (f3), I b- (f3), I c- (f3) respectively represent the amplitudes of the three-phase currents a, b, and c when the negative sequence voltage disturbance signal is injected;

[0080] I θa- (f3), I θb- (f3), I θc- (f3) respectively represent the phases of the three-phase currents a, b, and c when the negative sequence voltage disturbance signal is injected;

[0081] Step (8), calculate the negative sequence impedance Z2 at frequency f3:

[0082] Z2=ΔU n (f3) / ΔI n (f3) (6)

[0083] Step (9), using the positive sequence impedance Z1 obtained in step (5) and the negative sequence impedance Z2 obtained in step (8), draw the Bode diagram of the positive and negative sequence impedances, and obtain the amplitude-frequency and phase-frequency characteristics of the STATCOM under the added disturbance signal as the impedance characteristics;

[0084] Step (10), re-set the frequency f3 of the disturbance signal, repeat steps (3) to (9), and the impedance characteristics of the STATCOM at all frequencies between [f1, f2] and an amplitude of k% of the nominal voltage can be obtained.

[0085] Example 2

[0086] The method for obtaining the wide-frequency domain impedance characteristics of STATCOM based on hardware-in-the-loop simulation includes the following steps:

[0087] Step (1), building a STATCOM stand-alone infinite system based on a hardware-in-the-loop simulation platform;

[0088] Step (2), setting the amplitude of the voltage disturbance signal to k%U n , k is any constant greater than 0, U n is the nominal voltage of the STATCOM grid-connected point; the lower limit of the frequency of the voltage disturbance signal is set to f1, and the upper limit of the frequency of the voltage disturbance signal is set to f2. Both f1 and f2 are positive integers. Then the three-phase positive sequence voltage disturbance signal is:

[0089]

[0090] Where: U a+ , U b+ , U c+ are the three-phase positive sequence voltage disturbance signals respectively, t is the time, f3 is a positive integer between [f1, f2];

[0091] The three-phase negative sequence voltage disturbance signal is:

[0092]

[0093] Where: U a- , U b- , U c- They are three-phase negative sequence voltage disturbance signals respectively;

[0094] Step (3), injecting the three-phase positive sequence voltage disturbance signal with an amplitude of k% of the nominal voltage and a frequency of f3 obtained in step (2) into the STATCOM body in the STATCOM single-machine infinite system based on the hardware-in-the-loop simulation platform, and simultaneously collecting the three-phase voltage and current signal data at the STATCOM machine end;

[0095] Step (4), using a fast Fourier transform function to perform Fourier transform on the STATCOM machine-end three-phase voltage and three-phase current data collected in step (3), and extract the three-phase voltage amplitude and phase, and the three-phase current amplitude and phase at frequency f3;

[0096] Then the positive sequence voltage ΔU at frequency f3 is p (f3), positive sequence current ΔI p (f3) is;

[0097]

[0098] Among them, U a+ (f3), U b+ (f3), U c+ (f3) respectively represent the amplitudes of the three-phase voltages a, b, and c when the positive sequence voltage disturbance signal is injected

[0099] U θa+ (f3), U θb+ (f3), U θc+ (f3) respectively represent the phases of the three-phase voltages a, b, and c when the positive sequence voltage disturbance signal is injected;

[0100] I a+ (f3), I b+ (f3), I c+ (f3), I θa+ (f3), I θb+ (f3), I θc+ (f3) respectively represent the amplitudes of the three-phase currents a, b, and c when the positive sequence voltage disturbance signal is injected;

[0101] I θa+ (f3), I θb+ (f3), I θc+ (f3) respectively represent the phases of the three-phase currents a, b, and c when the positive sequence voltage disturbance signal is injected;

[0102] Step (5), calculate the positive sequence impedance Z1 at frequency f3:

[0103] Z1=ΔU p (f3) / ΔI p (f3) (4)

[0104] Step (6), injecting the three-phase negative sequence voltage disturbance signal with an amplitude of k% of the nominal voltage and a frequency of f3 obtained in step (2) into the STATCOM body in the STATCOM single-machine infinite system based on the hardware-in-the-loop simulation platform, and simultaneously collecting the three-phase voltage and current signal data at the STATCOM machine end;

[0105] Step (7), using a fast Fourier transform function to perform Fourier transform on the STATCOM machine-end three-phase voltage and three-phase current data collected in step (6), and extract the three-phase voltage amplitude and phase, and the three-phase current amplitude and phase at frequency f3;

[0106] Then the negative sequence voltage ΔU at frequency f3 is n (f3), negative sequence current ΔI n (f3) is;

[0107]

[0108] Among them, U a- (f3), U b- (f3), U c- (f3) respectively represent the amplitudes of the three-phase voltages a, b, and c when the negative sequence voltage disturbance signal is injected

[0109] U θa- (f3), U θb- (f3), U θc- (f3) respectively represent the phases of the three-phase voltages a, b, and c when the negative sequence voltage disturbance signal is injected;

[0110] I a- (f3), I b- (f3), I c- (f3) respectively represent the amplitudes of the three-phase currents a, b, and c when the negative sequence voltage disturbance signal is injected;

[0111] I θa- (f3), I θb- (f3), I θc- (f3) respectively represent the phases of the three-phase currents a, b, and c when the negative sequence voltage disturbance signal is injected;

[0112] Step (8), calculate the negative sequence impedance Z2 at frequency f3:

[0113] Z2=ΔU n (f3) / ΔI n (f3) (6)

[0114] Step (9), use the semilogx function in MATLAB to draw the Bode diagram of the positive and negative sequence impedances for the positive sequence impedance Z1 obtained in step (5) and the negative sequence impedance Z2 obtained in step (8), as shown in Figure 2 to Figure 5 As shown, Figure 2-3 is the positive sequence amplitude-frequency and phase-frequency characteristics of STATCOM under the added disturbance signal, Figure 4-5 The figure shows the negative sequence amplitude-frequency and phase-frequency characteristics of STATCOM under the added disturbance signal. Figure 2 to Figure 5As the final STATCOM impedance characteristic, that is, the impedance characteristic of STATCOM at an amplitude of k% of the nominal voltage and a frequency of f3;

[0115] Step (10), re-set the frequency f3 of the disturbance signal, repeat steps (3) to (9), and the impedance characteristics of the STATCOM at all frequencies between [f1, f2] and an amplitude of k% of the nominal voltage can be obtained.

[0116] In step (1), in the STATCOM stand-alone infinite system based on the hardware-in-the-loop simulation platform, the STATCOM body is connected to the 35kV bus, then boosted to 220kV through the main transformer, and then connected to the infinite power grid. The STATCOM controller transmits PWM control signals to the RT-LAB simulator through optical fiber, and the STATCOM controller is connected to the analog output board of the simulator through a DB37 connection line to collect the three-phase voltage and current signals of the power grid. Figure 1 As shown.

[0117] In both steps (4) and (7), the FFT function in Matlab is used to perform Fourier transform on the three-phase voltage and three-phase current data at the STATCOM machine end.

[0118] The value of k ranges from 2 to 5.

[0119] f1 is 1 and f2 does not exceed 3000.

[0120] Application Examples

[0121] The STATCOM wide frequency domain impedance characteristic acquisition method based on hardware-in-the-loop simulation of the present invention is adopted. Taking the TSVG-27 / 35-WC STATCOM of TBEA Xi'an Electric Technology Co., Ltd. as an example, the impedance characteristic acquisition based on hardware-in-the-loop simulation is carried out. The rated capacity of the measured equipment is Q N =27MVar, rated voltage U N =35kV, rated current is I N =445.4A;

[0122] (i) Build a STATCOM stand-alone infinite system based on the RT-LAB hardware-in-the-loop simulation platform, transmit the instantaneous values ​​of the three-phase voltage and current of the simulation main circuit to the STATCOM controller through the DB37 connection line, and the STATCOM controller transmits the PWM control signal to the simulator through the optical fiber;

[0123] (II) Set the initial reactive power of STATCOM to be 20% Q N; Set the amplitude of the voltage disturbance signal to 2%*35kV, the frequency range to [1Hz, 3000Hz], the initial frequency to 1Hz, the sweep frequency step from 1 to 300Hz to 1Hz, and the sweep frequency step from 300 to 3000Hz to 10Hz;

[0124] (3) Inject three-phase positive-sequence and negative-sequence voltage disturbance signals into the STATCOM body respectively, and collect three-phase voltage and current signal data at the STATCOM machine end;

[0125] (IV) Obtain the impedance characteristics of STATCOM based on the recorded three-phase voltage and current signal data, such as Figure 2 and Figure 3 As shown;

[0126] (V) Reset the initial reactive power of STATCOM to capacitive 20% Q N , repeat steps (iv) and (v), the test results are as follows Figure 4 and Figure 5 As shown;

[0127] (VI) Acquisition is completed, according to the phase-frequency characteristic curve ( Figure 3 and Figure 5 ) is between the positive and negative 90 degree dashed lines to judge whether STATCOM provides positive damping, that is, if the curve is between the two dashed lines, STATCOM provides positive damping.

[0128] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for obtaining STATCOM wide-frequency domain impedance characteristics based on hardware-in-the-loop simulation, characterized in that: The steps include: Step (1), building a STATCOM stand-alone infinite system based on a hardware-in-the-loop simulation platform; Step (2), setting the amplitude of the voltage disturbance signal to k%U n , k is any constant greater than 0, U n is the nominal voltage of the STATCOM grid-connected point; the lower limit of the frequency of the voltage disturbance signal is set to f1, and the upper limit of the frequency of the voltage disturbance signal is set to f2. Both f1 and f2 are positive integers. Then the three-phase positive sequence voltage disturbance signal is: Where: U a+ , U b+ , U c+ are the three-phase positive sequence voltage disturbance signals respectively, t is the time, f3 is a positive integer between [f1, f2]; The three-phase negative sequence voltage disturbance signal is: Where: U a- , U b- , U c- They are three-phase negative sequence voltage disturbance signals respectively; Step (3), injecting the three-phase positive sequence voltage disturbance signal with an amplitude of k% of the nominal voltage and a frequency of f3 obtained in step (2) into the STATCOM body in the STATCOM single-machine infinite system based on the hardware-in-the-loop simulation platform, and simultaneously collecting the three-phase voltage and current signal data at the STATCOM machine end; Step (4), using a fast Fourier transform function to perform Fourier transform on the STATCOM machine-end three-phase voltage and three-phase current data collected in step (3), and extract the three-phase voltage amplitude and phase, and the three-phase current amplitude and phase at frequency f3; Then the positive sequence voltage ΔU at frequency f3 is p (f3), positive sequence current ΔI p (f3) is; Among them, U a+ (f3), U b+ (f3), U c+ (f3) respectively represent the amplitudes of the three-phase voltages a, b, and c when the positive sequence voltage disturbance signal is injected U θa+ (f3), U θb+ (f3), U θc+ (f3) respectively represent the phases of the three-phase voltages a, b, and c when the positive sequence voltage disturbance signal is injected; I a+ (f3), I b+ (f3), I c+ (f3), I θa+ (f3), I θb+ (f3), I θc+ (f3) respectively represent the amplitudes of the three-phase currents a, b, and c when the positive sequence voltage disturbance signal is injected; I θa+ (f3), I θb+ (f3), I θc+ (f3) respectively represent the phases of the three-phase currents a, b, and c when the positive sequence voltage disturbance signal is injected; Step (5), calculate the positive sequence impedance Z1 at frequency f3: Z1=ΔU p (f3) / ΔI p (f3) (4) Step (6), injecting the three-phase negative sequence voltage disturbance signal with an amplitude of k% of the nominal voltage and a frequency of f3 obtained in step (2) into the STATCOM body in the STATCOM single-machine infinite system based on the hardware-in-the-loop simulation platform, and simultaneously collecting the three-phase voltage and current signal data at the STATCOM machine end; Step (7), using a fast Fourier transform function to perform Fourier transform on the STATCOM machine-end three-phase voltage and three-phase current data collected in step (6), and extract the three-phase voltage amplitude and phase, and the three-phase current amplitude and phase at frequency f3; Then the negative sequence voltage ΔU at frequency f3 is n (f3), negative sequence current ΔI n (f3) is; Among them, U a- (f3), U b- (f3), U c- (f3) respectively represent the amplitudes of the three-phase voltages a, b, and c when the negative sequence voltage disturbance signal is injected U θa- (f3), U θb- (f3), U θc- (f3) respectively represent the phases of the three-phase voltages a, b, and c when the negative sequence voltage disturbance signal is injected; I a- (f3), I b- (f3), I c- (f3) respectively represent the amplitudes of the three-phase currents a, b, and c when the negative sequence voltage disturbance signal is injected; I θa- (f3), I θb- (f3), I θc- (f3) respectively represent the phases of the three-phase currents a, b, and c when the negative sequence voltage disturbance signal is injected; Step (8), calculate the negative sequence impedance Z2 at frequency f3: Z2=ΔU n (f3) / ΔI n (f3) (6) Step (9), using the positive sequence impedance Z1 obtained in step (5) and the negative sequence impedance Z2 obtained in step (8), draw the Bode diagram of the positive and negative sequence impedances, and obtain the amplitude-frequency and phase-frequency characteristics of the STATCOM under the added disturbance signal as the impedance characteristics; Step (10), re-set the frequency f3 of the disturbance signal, repeat steps (3) to (9), and the impedance characteristics of the STATCOM at all frequencies between [f1, f2] and an amplitude of k% of the nominal voltage can be obtained.

2. The method for obtaining STATCOM wide-frequency domain impedance characteristics based on hardware-in-the-loop simulation according to claim 1 is characterized in that: In step (1), in the STATCOM stand-alone infinite system based on the hardware-in-the-loop simulation platform, the STATCOM body is connected to the 35kV bus, then boosted to 220kV through the main transformer, and then connected to the infinite power grid. The STATCOM controller transmits PWM control signals to the RT-LAB simulator via optical fiber, and the STATCOM controller is connected to the analog output board of the simulator via a DB37 connection line to collect the three-phase voltage and current signals of the power grid.

3. The method for acquiring STATCOM wide-frequency domain impedance characteristics based on hardware-in-the-loop simulation according to claim 1 is characterized in that: In both steps (4) and (7), the FFT function in Matlab is used to perform Fourier transform on the three-phase voltage and three-phase current data at the STATCOM machine end.

4. The method for acquiring STATCOM wide-frequency domain impedance characteristics based on hardware-in-the-loop simulation according to claim 1 is characterized in that: The value of k ranges from 2 to 5.

5. The method for acquiring wide-frequency domain impedance characteristics of STATCOM based on hardware-in-the-loop simulation according to claim 1, characterized in that: f1 is 1 and f2 does not exceed 3000.

6. A method for evaluating whether a STATCOM can provide positive damping when a power system is unstable, characterized in that: The method for obtaining STATCOM wide-frequency domain impedance characteristics based on hardware-in-the-loop simulation according to any one of claims 1 to 5 comprises the following steps: If the phase-frequency characteristic curve in the impedance characteristic is between positive and negative 90 degrees, positive damping can be provided, otherwise it cannot be provided.

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