Converter harmonic impedance modeling method and related equipment

Abstract

The invention discloses a converter harmonic impedance modeling method and related equipment, and belongs to the technical field of converters, firstly, space vectors of voltage and current of a grid-connected point are obtained, the space vectors can accurately reflect the magnitude and direction of the voltage and current in real time, and compared with traditional scalar modeling, more comprehensive information is provided. Based on the space vector, harmonic power under the influence of positive and negative sequence harmonic waves, reference voltage passing through a power control loop and harmonic voltage output by an inverter are obtained through sequential calculation, and modeling of a harmonic impedance model is carried out based on positive sequence harmonic voltage and negative sequence harmonic voltage of an inverter side and a grid-connected point and a power grid main circuit. A harmonic model in a coupling frequency impedance matrix form is adopted, the interaction relation between harmonic voltage and harmonic current and the coupling relation of harmonic waves with different frequencies after passing through a converter can be described more accurately, and therefore the accuracy and reliability of an analysis result are improved, and a solid model foundation is provided for harmonic power flow research.

Description

Technical Field

[0001] The present invention belongs to the technical field of converters, and in particular relates to a converter harmonic impedance modeling method and related equipment. Background Art

[0002] In recent years, the demand for renewable energy has continued to increase, and power electronic devices and equipment have gradually penetrated into my country's power system. As the core equipment of the new energy grid-connected system, the optimization of the performance of the grid-connected converter and the improvement of its modeling technology are crucial to the stable operation of the power system and the improvement of power quality. Through power control strategies, the grid-connected converter can achieve voltage and frequency support for the power grid and effectively respond to operational challenges under weak grid conditions. Harmonic impedance modeling, as an effective means to analyze the dynamic interaction between the grid-connected converter and the power grid, has become a hot topic in current research.

[0003] In the field of harmonic impedance modeling, the harmonic linearization method is a classic and widely used technology. It establishes a linear relationship between harmonic voltage and harmonic current by linearizing the system under small disturbance conditions. This method is based on the system circuit parameters, control structure and rated working state. By injecting a small voltage signal of a specific frequency and measuring the corresponding current response, the harmonic impedance model of the system is obtained. However, with the increasing complexity and nonlinear characteristics of the new energy grid-connected system, the existing harmonic linearization method has faced challenges in accuracy and scope of application.

[0004] In the harmonic impedance modeling of the converter, the existing technology has the following technical defects: 1) Limited model accuracy: Since the harmonic linearization method ignores high-order nonlinear terms, the model is not accurate enough in complex nonlinear systems and strong coupling effects.

[0005] 2) Improper handling of frequency coupling effects: In power systems, there may be coupling relationships between different harmonics. Existing models often use simplified methods to deal with such coupling effects, resulting in the model being unable to accurately reflect the true behavior of the system.

[0006] 3) Impedance modeling difficulties: When the AC system is unbalanced, the steady-state operating point will no longer be a DC constant value. The existing model has difficulties in impedance modeling under unbalanced conditions, which limits the practical application scope of the model. Summary of the invention

[0007] The present invention provides a method for modeling harmonic impedance of a converter and related equipment, which solves the problems of difficulty in modeling harmonic impedance of a converter and limited model accuracy.

[0008] To achieve the above object, the present invention provides the following technical solutions: A converter harmonic impedance modeling method, comprising: Inject harmonics at the grid connection point to obtain the space vector of the voltage and current at the grid connection point; Calculate the active and reactive power injected into the grid based on the space vector of the voltage and current at the grid connection point; Feeding active power and reactive power into a power control loop to obtain the amplitude and phase of a reference voltage; The amplitude and phase of the reference voltage are synthesized into a reference vector, and the d-axis component and the q-axis component of the reference voltage in the dq coordinate system are obtained according to the reference vector; Based on the d-axis component and the q-axis component of the reference voltage in the dq coordinate system, the reference voltage is converted to the abc coordinate system to obtain the positive-sequence harmonic voltage and the negative-sequence harmonic voltage; The voltage-current relationship of the main circuit of the power grid is obtained, and a harmonic impedance model is established based on the voltage-current relationship of the main circuit of the power grid and the positive-sequence harmonic voltage and the negative-sequence harmonic voltage.

[0009] Preferably, the method for acquiring the space vector of the grid connection point voltage and current is specifically as follows:

[0010] in, is the fundamental voltage amplitude at the grid connection point, is a natural constant, is the fundamental voltage phase of the grid connection point, is an imaginary number, is the positive sequence harmonic voltage amplitude at the grid connection point, is the phase of the positive sequence harmonic voltage at the grid connection point, is the negative sequence harmonic voltage amplitude at the grid connection point, is the phase of the negative sequence harmonic voltage at the grid connection point, is the fundamental current amplitude at the grid connection point, is the fundamental current phase of the grid-connected point, is the positive sequence harmonic current amplitude at the grid connection point, is the phase of the positive sequence harmonic current at the grid connection point, is the negative sequence harmonic current amplitude at the grid connection point, is the phase of negative sequence harmonic current at the grid connection point.

[0011] Preferably, the steps of calculating the active and reactive power injected into the grid according to the space vector of the voltage and current at the grid connection point are specifically as follows: The complex power at the grid connection point is calculated based on the space vector of the voltage and current at the grid connection point, and then the real part and the imaginary part of the complex power are separated to obtain the active and reactive power injected into the grid.

[0012] Preferably, the amplitude and phase of the reference voltage are respectively:

[0013]

[0014] in, is the phase of the reference voltage, is the amplitude of the reference voltage, is the inverter droop coefficient, is the active power reference value, is the reactive power reference value, is the reactive power, is the active power, is the rated angular frequency of the inverter output, It is the rated phase of the inverter output voltage.

[0015] A converter harmonic impedance modeling system, comprising: Vector acquisition module: used to inject harmonics at the grid connection point and obtain the space vector of the voltage and current at the grid connection point; Power calculation module: used to calculate the active and reactive power injected into the grid based on the space vector of the voltage and current at the grid connection point; Feed-in module: used to feed active power and reactive power into the power control loop to obtain the amplitude and phase of the reference voltage; Synthesis module: used to synthesize the amplitude and phase of the reference voltage into a reference vector, and obtain the d-axis component and q-axis component of the reference voltage in the dq coordinate system according to the reference vector; Conversion module: used for converting the reference voltage to the abc coordinate system based on the d-axis component and the q-axis component of the reference voltage in the dq coordinate system to obtain the positive-sequence harmonic voltage and the negative-sequence harmonic voltage; Modeling module: used to obtain the voltage-current relationship of the main circuit of the power grid, and establish a harmonic impedance model based on the voltage-current relationship of the main circuit of the power grid and the positive-sequence harmonic voltage and negative-sequence harmonic voltage.

[0016] Preferably, in the vector acquisition module, the method for acquiring the space vectors of the grid connection point voltage and current is specifically as follows:

[0017] in, is the fundamental voltage amplitude at the grid connection point, is a natural constant, is the fundamental voltage phase of the grid connection point, is an imaginary number, is the positive sequence harmonic voltage amplitude at the grid connection point, is the phase of the positive sequence harmonic voltage at the grid connection point, is the negative sequence harmonic voltage amplitude at the grid connection point, is the phase of the negative sequence harmonic voltage at the grid connection point, is the fundamental current amplitude at the grid connection point, is the fundamental current phase of the grid-connected point, is the positive sequence harmonic current amplitude at the grid connection point, is the phase of the positive sequence harmonic current at the grid connection point, is the negative sequence harmonic current amplitude at the grid connection point, is the phase of negative sequence harmonic current at the grid connection point.

[0018] Preferably, in the power calculation module, the steps of calculating the active and reactive power injected into the power grid according to the space vector of the voltage and current at the grid connection point are specifically as follows: The complex power at the grid connection point is calculated based on the space vector of the voltage and current at the grid connection point, and then the real part and the imaginary part of the complex power are separated to obtain the active and reactive power injected into the grid.

[0019] Preferably, in the feeding module, the amplitude and phase of the reference voltage are respectively:

[0020]

[0021] in, is the phase of the reference voltage, is the amplitude of the reference voltage, is the inverter droop coefficient, is the active power reference value, is the reactive power reference value, is the reactive power, is the active power, is the rated angular frequency of the inverter output, It is the rated phase of the inverter output voltage.

[0022] A computer device comprises a memory, a processor and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of a method for modeling harmonic impedance of a converter are implemented.

[0023] A computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of a method for modeling harmonic impedance of a converter are implemented.

[0024] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for modeling harmonic impedance of a converter, firstly obtaining the space vectors of the voltage and current at the grid connection point, which can reflect the magnitude and direction of the voltage and current in real time and accurately, and provides more comprehensive information compared with the traditional scalar modeling. Based on the space vectors, the harmonic power under the influence of positive and negative sequence harmonics, the reference voltage after the power control loop and the harmonic voltage output by the inverter are calculated in sequence, and the harmonic impedance model is modeled based on the positive sequence harmonic voltage, negative sequence harmonic voltage and main circuit of the power grid on the inverter side and the grid connection point. The harmonic model in the form of a coupled frequency impedance matrix can more accurately describe the interaction relationship between harmonic voltage and harmonic current, and the coupling relationship of different frequency harmonics after the converter, thereby improving the accuracy and reliability of the analysis results, and providing a solid model foundation for harmonic power flow research. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A flow chart of a method for modeling harmonic impedance of a converter according to the present invention; Figure 2 A grid-connected topology diagram of a grid-connected converter according to an embodiment of the present invention; Figure 3 The present invention is a flow chart of a converter harmonic impedance modeling system. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0027] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0029] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0030] like Figure 1As shown, the present invention provides a method for modeling harmonic impedance of a converter, comprising: S101 injects harmonics at the grid connection point to obtain the space vector of the voltage and current at the grid connection point; S102 calculates the active and reactive power injected into the power grid according to the space vector of the voltage and current at the grid connection point; S103 feeds the active power and reactive power into the power control loop to obtain the amplitude and phase of the reference voltage; S104 combines the amplitude and phase of the reference voltage into a reference vector, and obtains a d-axis component and a q-axis component of the reference voltage in a dq coordinate system according to the reference vector; S105 converts the reference voltage to the abc coordinate system based on the d-axis component and the q-axis component of the reference voltage in the dq coordinate system to obtain a positive-sequence harmonic voltage and a negative-sequence harmonic voltage; S106 obtains the voltage-current relationship of the main circuit of the power grid, and establishes a harmonic impedance model based on the voltage-current relationship of the main circuit of the power grid and the positive-sequence harmonic voltage and the negative-sequence harmonic voltage.

[0031] Furthermore, the method for obtaining the space vector of the voltage and current at the grid connection point is specifically as follows:

[0032] in, is the fundamental voltage amplitude at the grid connection point, is a natural constant, is the fundamental voltage phase of the grid connection point, is an imaginary number, is the positive sequence harmonic voltage amplitude at the grid connection point, is the phase of the positive sequence harmonic voltage at the grid connection point, is the negative sequence harmonic voltage amplitude at the grid connection point, is the phase of the negative sequence harmonic voltage at the grid connection point, is the fundamental current amplitude at the grid connection point, is the fundamental current phase of the grid-connected point, is the positive sequence harmonic current amplitude at the grid connection point, is the phase of the positive sequence harmonic current at the grid connection point, is the negative sequence harmonic current amplitude at the grid connection point, is the phase of negative sequence harmonic current at the grid connection point.

[0033] Furthermore, the steps of calculating the active and reactive power injected into the grid according to the space vector of the voltage and current at the grid connection point are specifically as follows: The complex power at the grid connection point is calculated based on the space vector of the voltage and current at the grid connection point, and then the real part and the imaginary part of the complex power are separated to obtain the active and reactive power injected into the grid.

[0034] Furthermore, the amplitude and phase of the reference voltage are respectively:

[0035]

[0036] in, is the phase of the reference voltage, is the amplitude of the reference voltage, is the inverter droop coefficient, is the active power reference value, is the reactive power reference value, is the reactive power, is the active power, is the rated angular frequency of the inverter output, It is the rated phase of the inverter output voltage.

[0037] Another embodiment of the present invention provides a method for modeling harmonic impedance of a converter, for a grid-type converter based on droop control; Compared with traditional grid-following converters, grid-building converters can independently establish the frequency and voltage of the power grid, have the ability to maintain voltage and provide active inertia support, and provide support for the stability of the power system by simulating the functions of synchronous generators. Grid-building converters do not rely on grid-side synchronous generator regulation, enabling AC power systems to operate under complex working conditions.

[0038] Injecting harmonics into the system, the steady-state voltage and current at the grid connection point can be expressed as:

[0039] Since the three-phase voltage and current differ by 120°, the voltage and current expressions of phase b and phase c at the grid connection point can be easily obtained based on the phase relationship under the positive sequence and negative sequence. The active power and reactive power in the control loop are calculated by the grid connection point voltage and current. For the convenience of expression, the complex power at the grid connection point is calculated using the voltage and current space vectors. The complex power expression is shown in Equation (2).

[0040]

[0041] and is the space vector of the voltage and current at the grid connection point, and the specific expression is as shown in formula (3).

[0042]

[0043] Substituting equation (3) into equation (2), separating the real and imaginary parts of the complex power can obtain the active and reactive power injected into the grid.

[0044]

[0045] Formula (4) consists of two types of power, DC power and AC power. DC power is composed of fundamental frequency power and harmonic power of the same frequency, while AC power is determined by voltage and current of different frequencies. and The difference is passed through the power control module to generate a reference voltage, which determines the steady-state operating point of the AC system. Therefore, only the AC component in the power will cause harmonics in the reference voltage.

[0046] Active power and reactive power are fed into the power control loop and generate a reference voltage. The mathematical model is expressed as

[0047] Substituting equation (4) into equation (5) we can get the amplitude and phase of the reference voltage:

[0048] The d-axis component and q-axis component of the reference voltage can be obtained through the voltage synthesis module. When the system reaches a steady state, the voltage reference phase have

[0049] Assuming that the d-axis coincides with the reference voltage space vector, a first-order Taylor series expansion is performed near the steady-state operating point of the system, and high-order nonlinear terms are ignored. The response generated by the harmonics after passing through the voltage synthesis module is obtained as shown in (8).

[0050]

[0051] For low-order harmonics, the output voltage of the voltage synthesis module is the same as the voltage at the terminals of the VSC device. Converting the voltage in the synchronous rotating coordinate system back to the abc coordinate system yields the equation shown in (9).

[0052]

[0053] There is no coupling effect between the positive sequence and the negative sequence, so the kth positive sequence harmonic voltage and the negative sequence harmonic voltage can be expressed as (10) and (11).

[0054]

[0055] according to Figure 1 , inverter voltage The grid voltage and current The relationship is

[0056] Substituting (10) and (11) into (12), we obtain

[0057] From the final expressions of (13) and (14), it can be judged that in addition to the interaction between harmonics of the same frequency, the control loop introduces the interaction between different harmonics, such as the positive fifth harmonic current will cause the positive third harmonic voltage. According to the above derivation, the harmonic impedance model of the grid-type converter can be expressed as

[0058] like Figure 3 As shown, another embodiment of the present invention provides a converter harmonic impedance modeling system, comprising: Vector acquisition module: used to inject harmonics at the grid connection point and obtain the space vector of the voltage and current at the grid connection point; Power calculation module: used to calculate the active and reactive power injected into the grid based on the space vector of the voltage and current at the grid connection point; Feed-in module: used to feed active power and reactive power into the power control loop to obtain the amplitude and phase of the reference voltage; Synthesis module: used to synthesize the amplitude and phase of the reference voltage into a reference vector, and obtain the d-axis component and q-axis component of the reference voltage in the dq coordinate system according to the reference vector; Conversion module: used for converting the reference voltage to the abc coordinate system based on the d-axis component and the q-axis component of the reference voltage in the dq coordinate system to obtain the positive-sequence harmonic voltage and the negative-sequence harmonic voltage; Modeling module: used to obtain the voltage-current relationship of the main circuit of the power grid, and establish a harmonic impedance model based on the voltage-current relationship of the main circuit of the power grid and the positive-sequence harmonic voltage and negative-sequence harmonic voltage.

[0059] In the vector acquisition module, the method for acquiring the space vector of the grid connection point voltage and current is as follows:

[0060] in, is the fundamental voltage amplitude at the grid connection point, is a natural constant, is the fundamental voltage phase of the grid connection point, is an imaginary number, is the positive sequence harmonic voltage amplitude at the grid connection point, is the phase of the positive sequence harmonic voltage at the grid connection point, is the negative sequence harmonic voltage amplitude at the grid connection point, is the phase of the negative sequence harmonic voltage at the grid connection point, is the fundamental current amplitude at the grid connection point, is the fundamental current phase of the grid-connected point, is the positive sequence harmonic current amplitude at the grid connection point, is the phase of the positive sequence harmonic current at the grid connection point, is the negative sequence harmonic current amplitude at the grid connection point, is the phase of negative sequence harmonic current at the grid connection point.

[0061] In the power calculation module, the steps for calculating the active and reactive power injected into the grid based on the space vector of the voltage and current at the grid connection point are as follows: The complex power at the grid connection point is calculated based on the space vector of the voltage and current at the grid connection point, and then the real part and the imaginary part of the complex power are separated to obtain the active and reactive power injected into the grid.

[0062] In the feed-in module, the amplitude and phase of the reference voltage are:

[0063]

[0064] in, is the phase of the reference voltage, is the amplitude of the reference voltage, is the inverter droop coefficient, is the active power reference value, is the reactive power reference value, is the reactive power, is the active power, is the rated angular frequency of the inverter output, It is the rated phase of the inverter output voltage.

[0065] A terminal device is provided in one embodiment of the present invention. The terminal device of this embodiment includes: a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps in the above-mentioned method embodiments are implemented. Alternatively, when the processor executes the computer program, the functions of the modules / units in the above-mentioned device embodiments are implemented.

[0066] The computer program may be divided into one or more modules / units, and the one or more modules / units are stored in the memory and executed by the processor to accomplish the present invention.

[0067] The terminal device may be a computing device such as a desktop computer, a notebook, a PDA, a cloud server, etc. The terminal device may include, but is not limited to, a processor and a memory.

[0068] The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc.

[0069] The memory may be used to store the computer programs and / or modules, and the processor implements various functions of the terminal device by running or executing the computer programs and / or modules stored in the memory and calling the data stored in the memory.

[0070] If the module / unit integrated in the terminal device is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by the processor, the steps of the above-mentioned various method embodiments can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), electric carrier signal, telecommunication signal and software distribution medium. It should be noted that the content contained in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electric carrier signals and telecommunication signals.

[0071] Although the embodiments of the present invention are described above in conjunction with the accompanying drawings, the present invention is not limited to the above-mentioned specific embodiments and application fields, and the above-mentioned specific embodiments are only illustrative and instructive, rather than restrictive. Under the guidance of the specification, a person skilled in the art can also make many forms without departing from the scope of protection of the claims of the present invention, all of which belong to the scope of protection of the present invention.

Claims

1. A method for modeling harmonic impedance of a converter, characterized in that: include: Inject harmonics at the grid connection point to obtain the space vector of the voltage and current at the grid connection point; Calculate the active and reactive power injected into the grid based on the space vector of the voltage and current at the grid connection point; Feeding active power and reactive power into a power control loop to obtain the amplitude and phase of a reference voltage; The amplitude and phase of the reference voltage are synthesized into a reference vector, and the d-axis component and the q-axis component of the reference voltage in the dq coordinate system are obtained according to the reference vector; Based on the d-axis component and the q-axis component of the reference voltage in the dq coordinate system, the reference voltage is converted to the abc coordinate system to obtain the positive-sequence harmonic voltage and the negative-sequence harmonic voltage; The voltage-current relationship of the main circuit of the power grid is obtained, and a harmonic impedance model is established based on the voltage-current relationship of the main circuit of the power grid and the positive-sequence harmonic voltage and the negative-sequence harmonic voltage.

2. A method for modeling converter harmonic impedance according to claim 1, characterized in that: The specific method for obtaining the space vector of the voltage and current at the grid connection point is: in, is the fundamental voltage amplitude at the grid connection point, is a natural constant, is the fundamental voltage phase of the grid connection point, is an imaginary number, is the positive sequence harmonic voltage amplitude at the grid connection point, is the phase of the positive sequence harmonic voltage at the grid connection point, is the negative sequence harmonic voltage amplitude at the grid connection point, is the phase of the negative sequence harmonic voltage at the grid connection point, is the fundamental current amplitude at the grid connection point, is the fundamental current phase of the grid-connected point, is the positive sequence harmonic current amplitude at the grid connection point, is the phase of the positive sequence harmonic current at the grid connection point, is the negative sequence harmonic current amplitude at the grid connection point, is the phase of negative sequence harmonic current at the grid connection point.

3. A method for modeling converter harmonic impedance according to claim 1, characterized in that: The specific steps for calculating the active and reactive power injected into the grid based on the space vector of the voltage and current at the grid connection point are: The complex power at the grid connection point is calculated based on the space vector of the voltage and current at the grid connection point, and then the real part and the imaginary part of the complex power are separated to obtain the active and reactive power injected into the grid.

4. A method for modeling converter harmonic impedance according to claim 1, characterized in that: The amplitude and phase of the reference voltage are: in, is the phase of the reference voltage, is the amplitude of the reference voltage, is the inverter droop coefficient, is the active power reference value, is the reactive power reference value, is the reactive power, is the active power, is the rated angular frequency of the inverter output, It is the rated phase of the inverter output voltage.

5. A converter harmonic impedance modeling system, characterized in that: include: Vector acquisition module: used to inject harmonics at the grid connection point and obtain the space vector of the voltage and current at the grid connection point; Power calculation module: used to calculate the active and reactive power injected into the grid based on the space vector of the voltage and current at the grid connection point; Feed-in module: used to feed active power and reactive power into the power control loop to obtain the amplitude and phase of the reference voltage; Synthesis module: used to synthesize the amplitude and phase of the reference voltage into a reference vector, and obtain the d-axis component and q-axis component of the reference voltage in the dq coordinate system according to the reference vector; Conversion module: used for converting the reference voltage to the abc coordinate system based on the d-axis component and the q-axis component of the reference voltage in the dq coordinate system to obtain the positive-sequence harmonic voltage and the negative-sequence harmonic voltage; Modeling module: used to obtain the voltage-current relationship of the main circuit of the power grid, and establish a harmonic impedance model based on the voltage-current relationship of the main circuit of the power grid and the positive-sequence harmonic voltage and negative-sequence harmonic voltage.

6. A converter harmonic impedance modeling system according to claim 5, characterized in that: In the vector acquisition module, the method for acquiring the space vector of the grid connection point voltage and current is as follows: in, is the fundamental voltage amplitude at the grid connection point, is a natural constant, is the fundamental voltage phase of the grid connection point, is an imaginary number, is the positive sequence harmonic voltage amplitude at the grid connection point, is the phase of the positive sequence harmonic voltage at the grid connection point, is the negative sequence harmonic voltage amplitude at the grid connection point, is the phase of the negative sequence harmonic voltage at the grid connection point, is the fundamental current amplitude at the grid connection point, is the fundamental current phase of the grid-connected point, is the positive sequence harmonic current amplitude at the grid connection point, is the phase of the positive sequence harmonic current at the grid connection point, is the negative sequence harmonic current amplitude at the grid connection point, is the phase of negative sequence harmonic current at the grid connection point.

7. A converter harmonic impedance modeling system according to claim 5, characterized in that: In the power calculation module, the steps for calculating the active and reactive power injected into the grid based on the space vector of the voltage and current at the grid connection point are as follows: The complex power at the grid connection point is calculated based on the space vector of the voltage and current at the grid connection point, and then the real part and the imaginary part of the complex power are separated to obtain the active and reactive power injected into the grid.

8. A converter harmonic impedance modeling system according to claim 5, characterized in that: In the feed-in module, the amplitude and phase of the reference voltage are: in, is the phase of the reference voltage, is the amplitude of the reference voltage, is the inverter droop coefficient, is the active power reference value, is the reactive power reference value, is the reactive power, is the active power, is the rated angular frequency of the inverter output, It is the rated phase of the inverter output voltage.

9. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the converter harmonic impedance modeling method as claimed in any one of claims 1 to 4 are implemented.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the method for modeling harmonic impedance of a converter as claimed in any one of claims 1 to 4 are implemented.

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