Method for simultaneously acquiring positive and negative sequence impedance characteristics of energy storage system based on semi-physical simulation

Abstract

The invention provides a method for simultaneously obtaining positive and negative sequence impedance characteristics of an energy storage system based on semi-physical simulation, and belongs to the field of new energy electromagnetic transient simulation modeling, and the method comprises the following steps: firstly, building an energy storage system single-machine infinite bus system based on a semi-physical simulation platform; when the energy storage system operates normally, a three-phase voltage disturbance signal containing positive and negative sequence components is injected into the body of the energy storage system, and three-phase voltage and current signals of an outlet of the energy storage system are collected; and finally, calculating the impedance characteristic of the energy storage system by using discrete Fourier transform according to the collected voltage and current signals. According to the method, the positive and negative sequence impedance characteristics of the energy storage system can be rapidly obtained, and an important basis can be provided for broadband oscillation characteristic evaluation of an access power grid.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy electromagnetic transient simulation modeling, and in particular to a method for simultaneously obtaining positive and negative sequence impedance characteristics of an energy storage system based on semi-physical simulation. Background Art

[0002] With the large-scale grid connection of new energy, the power system presents the "double high" development characteristics of a high proportion of renewable energy and a high proportion of power electronic equipment. At present, new energy generators are generally connected to the grid through power electronic converters. With the continuous increase in the penetration rate of new energy in the power system, the impact of converter control strategies on the dynamic characteristics and stability of the power system has gradually become prominent. It is worth noting that in recent years, the stability problems of the system caused by new energy units have become increasingly prominent. Large-scale new energy unit off-grid accidents and system stability problems have occurred frequently, posing a severe challenge to the safe operation of the new power system. Therefore, the power system has put forward higher requirements for the access of energy storage systems, which are required to play a suppressive role when the system becomes unstable. The present invention proposes a method for simultaneously obtaining the positive and negative sequence impedance characteristics of the energy storage system based on semi-physical simulation, which can quickly and accurately obtain the impedance characteristics of the energy storage system, and can provide an important basis for the evaluation of the broadband oscillation characteristics of its access to the power grid. Summary of the Invention

[0003] In view of this, an object of the present invention is to provide a method for simultaneously obtaining positive and negative sequence impedance characteristics of an energy storage system based on semi-physical simulation, so as to at least solve the above problems.

[0004] The technical solution adopted in the present invention is as follows:

[0005] A method for simultaneously obtaining positive and negative sequence impedance characteristics of an energy storage system based on hardware-in-the-loop simulation, the method comprising the following steps:

[0006] S1. Build a single-machine infinite semi-physical simulation model of the energy storage system;

[0007] S2, set the three-phase voltage disturbance signals to be U a 、U b 、U c ;

[0008] S3, three-phase voltage disturbance signal U injected into the energy storage system a 、U b 、U c , while collecting the instantaneous value data of three-phase voltage and current at the machine end of the energy storage system;

[0009] S4. Performing a discrete Fourier transform on the instantaneous three-phase voltage and three-phase current data at the energy storage system terminal using a fast Fourier transform function, and extracting the three-phase positive and negative sequence voltage / current amplitudes and phases at frequency f;

[0010] S5. Calculate the positive-sequence impedance Zp and the negative-sequence impedance Zn according to the positive-sequence and negative-sequence voltage / current components, respectively, to obtain the impedance characteristics of the energy storage system.

[0011] Furthermore, in step S2, the three-phase voltage disturbance signal U a 、U b 、U c The calculation formula is:

[0012]

[0013] Where t is time, f is the specified frequency, is a constant greater than or equal to 1, and U n is the nominal voltage of the energy storage system grid connection point, and M is any constant greater than 0.

[0014] Furthermore, in step S2, the amplitude M% / 2 of the voltage disturbance signal is obtained by halving the amplitude of the harmonic voltage to avoid triggering harmonic protection of the energy storage system.

[0015] Furthermore, in step S4, the three-phase positive sequence voltage and current disturbance components U at frequency f are p (f) I p The calculation formula for (f) is:

[0016]

[0017] Among them, U a+ (f) U b+ (f) U c+ (f) U θa+ (f) U θb+ (f) U θc+ (f) are the positive sequence voltage amplitude / phase of phases A, B, and C respectively; I a+ (f) I b+ (f) I c+ (f); I θa+ (f) I θb+ (f) I θc+ (f) are the positive sequence current amplitude / phase of phases A, B, and C respectively.

[0018] Furthermore, in step S4, the three-phase positive sequence voltage and current disturbance components U at frequency f are n (f) I n The calculation formula for (f) is:

[0019]

[0020] Among them, U a- (f) U b-(f) U c- (f) U θa- (f) U θb- (f) U θc- (f) are the negative sequence voltage amplitude / phase of phases A, B, and C respectively; I a- (f) I b- (f) I c- (f); I θa- (f) I θb- (f) I θc- (f) are the negative sequence current amplitude / phase of phases A, B, and C respectively.

[0021] Further, in step S5, the positive sequence impedance Z at frequency f p The calculation formula is:

[0022] Z p =U p (f) / I p (f) (4).

[0023] Furthermore, in step S5, the negative sequence impedance Z at frequency f n :

[0024] Z n =U n (f) / I n (f) (5).

[0025] Further, in step S4, the frequency f ranges from 1 Hz to 3000 Hz, wherein the frequency in the range of 1 Hz to 300 Hz increases by 1 Hz / second, and the frequency in the range of 300 Hz to 3000 Hz increases by 10 Hz / second.

[0026] Furthermore, in step S1, a stand-alone infinite semi-physical simulation model is built based on the RT-LAB hardware-in-the-loop simulation platform, and signal transmission between the simulation main circuit and the converter controller is achieved through a DB37 connection line.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] In view of the large-scale grid connection of new energy, the power system presents the characteristics of dual high development, and there is an urgent need to evaluate the broadband oscillation characteristics of new energy power electronic equipment. The purpose of the present invention is to provide a method for simultaneously obtaining the positive and negative sequence impedance characteristics of an energy storage system based on semi-physical simulation. This method can quickly and accurately obtain the impedance characteristics of the energy storage system. Compared with separately obtaining the positive and negative sequence impedance characteristics of the energy storage system, this method can save more than half of the time. At the same time, the measurement results can be consistent with the individual measurement results, providing a very worthy reference method for accelerating the broadband oscillation characteristic evaluation of the energy storage system connected to the power grid. At the same time, the present invention can also simultaneously obtain the positive and negative sequence impedance characteristics of photovoltaic inverters, wind turbines, SVG, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only preferred embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 It is a schematic diagram of the overall flow of a method for simultaneously obtaining the positive and negative sequence impedance characteristics of an energy storage system based on semi-physical simulation, proposed in an embodiment of the present invention.

[0031] Figure 2 Obtain a schematic diagram for the impedance characteristics of the energy storage system;

[0032] Figure 3 Schematic diagram of the positive sequence impedance characteristics of the energy storage system under 20% PN discharge conditions;

[0033] Figure 4 Schematic diagram of negative sequence impedance characteristics of the energy storage system under 20% PN discharge conditions; DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the present invention more apparent, exemplary embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments of the present invention, and it should be understood that the present invention is not limited to the exemplary embodiments described herein. Based on the embodiments of the present invention described in the present invention, all other embodiments obtained by those skilled in the art without creative work should fall within the scope of protection of the present invention.

[0035] In the following description, numerous specific details are provided to provide a more thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without one or more of these details. In other instances, certain technical features well known in the art are not described to avoid confusion with the present invention.

[0036] It should be understood that the present invention can be implemented in different forms and should not be interpreted as being limited to the embodiments set forth herein. On the contrary, these embodiments are provided to make disclosure thorough and complete and to fully convey the scope of the present invention to those skilled in the art.

[0037] The purpose of the terms used herein is only to describe specific embodiments and is not intended to limit the present invention. When used herein, the singular forms "a", "an", and "the" are intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "comprising" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0038] In order to fully understand the present invention, a detailed structure will be provided in the following description to illustrate the technical solution proposed by the present invention. Optional embodiments of the present invention are described in detail below. However, in addition to these detailed descriptions, the present invention may also have other implementations.

[0039] Reference Figure 1-4 The present invention provides a method for simultaneously obtaining positive and negative sequence impedance characteristics of an energy storage system based on hardware-in-the-loop simulation, the method comprising the following steps:

[0040] S1. Build a single-machine infinite semi-physical simulation model of the energy storage system;

[0041] S2, set the three-phase voltage disturbance signals to be U a 、U b 、U c ;

[0042] S3, three-phase voltage disturbance signal U injected into the energy storage system a 、U b 、U c , while collecting the instantaneous value data of three-phase voltage and current at the machine end of the energy storage system;

[0043] S4. Performing a discrete Fourier transform on the instantaneous three-phase voltage and three-phase current data at the energy storage system terminal using a fast Fourier transform function, and extracting the three-phase positive and negative sequence voltage / current amplitudes and phases at frequency f;

[0044] S5. Calculate the positive-sequence impedance Zp and the negative-sequence impedance Zn according to the positive-sequence and negative-sequence voltage / current components, respectively, to obtain the impedance characteristics of the energy storage system.

[0045] In step S2, the three-phase voltage disturbance signal U a 、U b 、U c The calculation formula is:

[0046]

[0047] Where t is time, f is the specified frequency, is a constant greater than or equal to 1, and U n is the nominal voltage of the energy storage system grid connection point, and M is any constant greater than 0.

[0048] In step S2, the amplitude M% / 2 of the voltage disturbance signal is obtained by halving the amplitude of the harmonic voltage to avoid triggering harmonic protection of the energy storage system.

[0049] In step S4, the three-phase positive sequence voltage and current disturbance components U at frequency f p (f) I p The calculation formula for (f) is:

[0050]

[0051] Among them, U a+ (f) U b+ (f) U c+ (f) U θa+ (f) U θb+ (f) U θc+ (f) are the positive sequence voltage amplitude / phase of phases A, B, and C respectively; I a+ (f) I b+ (f) I c+ (f); I θa+ (f) I θb+ (f) I θc+ (f) are the positive sequence current amplitude / phase of phases A, B, and C respectively.

[0052] In step S4, the three-phase positive sequence voltage and current disturbance components U at frequency f n (f) I n The calculation formula for (f) is:

[0053]

[0054] Among them, U a- (f) U b- (f) U c- (f) U θa- (f) U θb- (f) U θc- (f) are the negative sequence voltage amplitude / phase of phases A, B, and C respectively; I a- (f) I b- (f) I c- (f); I θa- (f) I θb- (f) I θc- (f) are the negative sequence current amplitude / phase of phases A, B, and C respectively.

[0055] In step S5, the positive sequence impedance Z at frequency f p The calculation formula is:

[0056] Z p =U p (f) / I p (f) (4).

[0057] In step S5, the negative sequence impedance Z at frequency f n :

[0058] Z n =U n (f) / I n (f) (5).

[0059] In step S4 , the frequency f ranges from 1 Hz to 3000 Hz, wherein the frequency increases at a rate of 1 Hz / second within the range from 1 Hz to 300 Hz, and increases at a rate of 10 Hz / second within the range from 300 Hz to 3000 Hz.

[0060] In step S1, a stand-alone infinite semi-physical simulation model is built based on the RT-LAB hardware-in-the-loop simulation platform, and signal transmission between the simulation main circuit and the converter controller is achieved through a DB37 connection line.

[0061] Specific application examples are as follows:

[0062] Taking the PCS-9567-1750 energy storage system of Nanjing Nari Relay Protection Electric Co., Ltd. as an example, an impedance characteristic evaluation based on semi-physical simulation was carried out. The rated capacity of the device under test was PN = 1.75MW and the rated voltage UN = 690V.

[0063] Build a single-machine infinite system for energy storage system based on RT-LAB hardware-in-the-loop simulation platform. Transmit the instantaneous values of the three-phase voltage and current of the simulated main circuit to the converter controller via DB37 cables. The controller transmits the digital input and output control signals to the simulation platform via DB37 cables.

[0064] The initial reactive power of the energy storage system is set to 0, and the initial active power is set to 20% PN; the amplitude of the voltage disturbance signal is set to M% = 5%, the range of f is [1Hz, 3000Hz], the initial frequency is 1Hz, the frequency increases by 1Hz per second in the range of 1 to 300Hz, and the frequency increases by 10Hz per second in the range of 300 to 3000Hz;

[0065] Inject three-phase positive-sequence and negative-sequence voltage disturbance signals into the energy storage system (method one), and simultaneously inject voltage disturbance signals containing both positive and negative sequences into the energy storage system (method two). Collect three-phase voltage and current signal data at the energy storage system generator end.

[0066] The impedance characteristics of the energy storage system are calculated based on the recorded three-phase voltage and current signal data, such as Figure 3 and Figure 4 As shown;

[0067] Depend on Figure 3 and Figure 4 As shown in the figure, the impedance characteristics calculated by the method proposed in the present invention (method 2) are consistent with the results of calculating the positive / negative sequence impedance characteristics (method 1) separately (the error is almost negligible), but the method proposed in the present invention can greatly reduce the test time and improve the efficiency of obtaining the impedance characteristics of the energy storage system.

[0068] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for simultaneously obtaining positive and negative sequence impedance characteristics of an energy storage system based on hardware-in-the-loop simulation, characterized in that: The method comprises the following steps: S1. Build a single-machine infinite semi-physical simulation model of the energy storage system; S2, set the three-phase voltage disturbance signals to be U a 、U b 、U c ; S3, three-phase voltage disturbance signal U injected into the energy storage system a 、U b 、U c , while collecting the instantaneous value data of three-phase voltage and current at the machine end of the energy storage system; S4. Performing a discrete Fourier transform on the instantaneous three-phase voltage and three-phase current data at the energy storage system terminal using a fast Fourier transform function, and extracting the three-phase positive and negative sequence voltage / current amplitudes and phases at frequency f; S5. Calculate the positive-sequence impedance Zp and the negative-sequence impedance Zn according to the positive-sequence and negative-sequence voltage / current components, respectively, to obtain the impedance characteristics of the energy storage system.

2. The method for simultaneously obtaining positive and negative sequence impedance characteristics of an energy storage system based on hardware-in-the-loop simulation according to claim 1, characterized in that: In step S2, the three-phase voltage disturbance signal U a 、U b 、U c The calculation formula is: Where t is time, f is the specified frequency, is a constant greater than or equal to 1, and U n is the nominal voltage of the energy storage system grid connection point, and M is any constant greater than 0.

3. The method for simultaneously obtaining positive and negative sequence impedance characteristics of an energy storage system based on hardware-in-the-loop simulation according to claim 2, characterized in that: In step S2, the amplitude M% / 2 of the voltage disturbance signal is obtained by halving the harmonic voltage amplitude to avoid triggering harmonic protection of the energy storage system.

4. The method for simultaneously obtaining positive and negative sequence impedance characteristics of an energy storage system based on hardware-in-the-loop simulation according to claim 1, characterized in that: In step S4, the three-phase positive sequence voltage and current disturbance components U at frequency f p (f) I p The calculation formula for (f) is: Among them, U a+ (f) U b+ (f) U c+ (f) U θa+ (f) U θb+ (f) U θc+ (f) are the positive sequence voltage amplitude / phase of phases A, B, and C respectively; I a+ (f) I b+ (f) I c+ (f); I θa+ (f) I θb+ (f) I θc+ (f) are the positive sequence current amplitude / phase of phases A, B, and C respectively.

5. The method for simultaneously obtaining positive and negative sequence impedance characteristics of an energy storage system based on hardware-in-the-loop simulation according to claim 4, characterized in that: In step S4, the three-phase positive sequence voltage and current disturbance components U at frequency f n (f) I n The calculation formula for (f) is: Among them, U a- (f) U b- (f) U c- (f) U θa- (f) U θb- (f) U θc- (f) are the negative sequence voltage amplitude / phase of phases A, B, and C respectively; I a- (f) I b- (f) I c- (f); I θa- (f) I θb- (f) I θc- (f) are the negative sequence current amplitude / phase of phases A, B, and C respectively.

6. The method for simultaneously obtaining positive and negative sequence impedance characteristics of an energy storage system based on hardware-in-the-loop simulation according to claim 5, characterized in that: In step S5, the positive sequence impedance Z at frequency f p The calculation formula is: Z p =U p (f) / I p (f) (4)。 7. The method for simultaneously obtaining positive and negative sequence impedance characteristics of an energy storage system based on hardware-in-the-loop simulation according to claim 6, characterized in that: In step S5, the negative sequence impedance Z at frequency f n : Z n =U n (f) / I n (f) (5)。 8. The method for simultaneously obtaining positive and negative sequence impedance characteristics of an energy storage system based on hardware-in-the-loop simulation according to claim 1, characterized in that: In step S4 , the frequency f ranges from 1 Hz to 3000 Hz, wherein the frequency increases at a rate of 1 Hz / second within the range from 1 Hz to 300 Hz, and increases at a rate of 10 Hz / second within the range from 300 Hz to 3000 Hz.

9. The method for simultaneously obtaining positive and negative sequence impedance characteristics of an energy storage system based on hardware-in-the-loop simulation according to claim 1, characterized in that: In step S1, a stand-alone infinite semi-physical simulation model is built based on the RT-LAB hardware-in-the-loop simulation platform, and signal transmission between the simulation main circuit and the converter controller is achieved through a DB37 connection line.

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