A small signal equivalent modeling method and system for new energy grid-connected inverter

Abstract

The present invention relates to a small signal equivalent modeling method and system for a new energy grid-connected inverter, including: based on an established linearized mathematical model of a new energy grid-connected inverter, obtaining an impedance transfer function from the output current to the grid-connected point voltage of a single inverter in a unified coordinate system; determining an inverter synchronization criterion based on the impedance transfer function, and calculating the difference in the amplitude-frequency characteristics of n inverters, and performing synchronization grouping on the n inverters; based on the inverter grouping results, calculating the aggregation parameters of the inverters in each synchronization group, and obtaining a synchronization equivalent model of a multi-inverter system, which is used for simulation analysis of a multi-inverter system of a new energy station. The present invention proposes a practical inverter synchronization criterion, realizes equivalent order reduction of a multi-inverter grid-connected system, greatly simplifies the multi-inverter grid-connected system model and improves the simulation speed while ensuring the simulation accuracy, and can be widely used in the field of power electronics technology.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronics, and in particular relates to a method and system for small signal equivalent modeling of a new energy grid-connected inverter based on a frequency domain transfer function. Background Art

[0002] With the rapid development of renewable energy grid-connected power generation technology, the penetration rate of grid-connected inverters, as an important interface for renewable energy grid-connected power generation, in the power system continues to increase. In large-scale wind farms and photovoltaic power stations, there are many grid-connected inverters with complex control methods. If each renewable energy grid-connected inverter is modeled in detail, the complexity of simulation analysis will be greatly increased. A model that can accurately characterize the overall dynamic characteristics of the system and is equivalently simplified can solve this problem well.

[0003] At present, there are two main methods for dynamic equivalent modeling of new energy stations: order reduction method and dynamic aggregation method. The order reduction method generally uses mathematical methods or system theory. In order to reduce the order of the overall model of the new energy station, it is necessary to reduce the order and simplify the detailed system differential equations. However, the order reduction method will discard some state variables of the system for different analysis problems, destroying the original physical structure of the new energy grid-connected inverter.

[0004] The dynamic aggregation method is divided into single-machine aggregation and multi-machine aggregation, which is a more commonly used method. Single-machine aggregation treats the entire new energy station as a unit, which will produce a large error. Multi-machine aggregation is to group first and then aggregate, and the selection of grouping criteria will significantly affect the error before and after the equivalent. At present, most multi-machine aggregation methods are divided according to simple indicators such as the type of new energy unit, operating mode, and installation location. Therefore, the accuracy of the equivalent model obtained by the existing equivalent method under different external environmental conditions varies greatly. Summary of the invention

[0005] In view of the above problems, the purpose of the present invention is to provide a small signal equivalent modeling method and system for a new energy grid-connected inverter, which performs equivalent aggregation on the system based on the linearization model of the grid-connected inverter, improves the accuracy of the multi-machine aggregation model, and improves the efficiency of the simulation operation.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a small signal equivalent modeling method for a new energy grid-connected inverter, which comprises the following steps:

[0008] Based on the established linearized mathematical model of the new energy grid-connected inverter, the impedance transfer function from the output current to the grid-connected point voltage of a single inverter in a unified coordinate system is obtained;

[0009] Determining the inverter coherence criterion based on the impedance transfer function, calculating the difference of the amplitude-frequency characteristics of n inverters, and performing coherence grouping on the n inverters;

[0010] Based on the inverter grouping results, the aggregation parameters of the inverters in each synchronization group are calculated to obtain the synchronization equivalent model of the multi-inverter system, which is used to simulate and analyze the multi-inverter system of the new energy station.

[0011] Furthermore, the method for obtaining the impedance transfer function of a single inverter from output current to grid connection point voltage in a unified coordinate system based on the established linearized mathematical model of the new energy grid-connected inverter includes:

[0012] Establish mathematical model of new energy grid-connected inverter;

[0013] The mathematical model is linearized to obtain the relationship between the grid connection point voltage and the grid-connected inverter output current of a single inverter in a dq synchronous rotating coordinate system;

[0014] The infinite power grid is selected as the unified coordinate system, and the relationship between the grid connection point voltage and the inverter output current of a single inverter in the dq synchronous rotating coordinate system is transformed into the unified coordinate system.

[0015] Furthermore, the method of determining the inverter coherence criterion based on the impedance transfer function, calculating the difference of the amplitude-frequency characteristics of n inverters, and performing coherence grouping on the n inverters includes:

[0016] Establish inverter coherence criterion based on frequency domain transfer function;

[0017] Based on the amplitude-frequency characteristics of the impedance transfer function, the inverter synchronization criterion is simplified to obtain the impedance transfer function Z xx Practical criterion for the amplitude-frequency characteristic response of

[0018] Defining the difference of the inverters according to the practical coherence criterion;

[0019] The difference between every two inverters is calculated in turn, and the inverters are synchronously identified and grouped according to the difference and the selected allowable error.

[0020] Furthermore, the difference of the inverter is:

[0021] ε ij =|G i (Z xxi (s))-G j (Z xxj (s))|

[0022] In the formula, ε ij is the difference of the inverter; Z xxi (s) and Zxxj (s) are the impedance transfer functions from the x-axis output current change to the x-axis grid-connected point voltage change of the i-th inverter and the j-th inverter in the unified coordinate system.

[0023] Furthermore, when calculating the aggregation parameters of the inverters in each synchronization group based on the inverter grouping results, it includes: aggregation of circuit structure parameters and aggregation of control system parameters, and the aggregation of control system parameters includes aggregation of phase-locked loop control parameters and aggregation of current loop control parameters.

[0024] Furthermore, the aggregation of the circuit structure parameters is:

[0025] L f,eq =L f1 / / L f2 / / … / / L fn

[0026] Where, L f,eq is the filter inductance of the equivalent model, L f1 , L f2 , ...L fn They respectively represent the filter inductance of the 1st to nth grid-connected inverters in a certain synchronization group.

[0027] Further, the aggregation method of the phase-locked loop control parameters is:

[0028]

[0029] In the formula, k pPLL,eq and k iPLL,eq are the proportional coefficient and integral coefficient of the phase-locked loop of the equivalent system respectively; k pPLLi and k iPLLi are the proportional coefficient and integral coefficient of the phase-locked loop of the i-th inverter, c i is the weight coefficient of the i-th inverter;

[0030] The aggregation method of current loop control parameters is:

[0031]

[0032] In the formula, k pi,eq and k ii,eq are the current loop proportional coefficient and integral coefficient of the equivalent system respectively; k pij and k iij are the proportional coefficient and integral coefficient of the current loop of the jth inverter, c j is the weight coefficient of the jth inverter.

[0033] In a second aspect, the present invention provides a small signal equivalent modeling system for a new energy grid-connected inverter, comprising:

[0034] The impedance transfer function determination module is used to obtain the impedance transfer function of a single inverter from output current to grid connection point voltage in a unified coordinate system based on the established linearized mathematical model of the new energy grid-connected inverter;

[0035] A synchronization grouping module is used to determine the synchronization criteria of the inverter based on the impedance transfer function, calculate the difference of the amplitude-frequency characteristics of n inverters, and perform synchronization grouping on the n inverters;

[0036] The aggregation parameter calculation module is used to calculate the aggregation parameters of the inverters in each synchronization group based on the inverter grouping results, obtain the synchronization equivalent model of the multi-inverter system, and simulate and analyze the multi-inverter system of the new energy station.

[0037] In a third aspect, the present invention provides a processing device, which includes at least a processor and a memory, wherein a computer program is stored in the memory, and when the processor runs the computer program, the steps of the small signal equivalent modeling method of the new energy grid-connected inverter are executed to implement the computer program.

[0038] In a fourth aspect, the present invention provides a computer storage medium having computer-readable instructions stored thereon, wherein the computer-readable instructions can be executed by a processor to implement the steps of the small signal equivalent modeling method of the new energy grid-connected inverter.

[0039] Due to the adoption of the above technical solution, the present invention has the following advantages: the present invention performs synchronization grouping of the multi-inverter grid-connected system by the synchronization criterion based on the inverter frequency domain transfer function, thereby overcoming the disadvantage of the large equivalent error of the traditional single machine, and at the same time overcoming the disadvantage that the existing multi-machine synchronization criterion depends on the measured data of the new energy station, and performs equivalent aggregation of the system based on the inverter linearization model, thereby improving the accuracy of the multi-machine aggregation model and the efficiency of the simulation operation. Therefore, it can be widely used in the field of power electronics technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Throughout the accompanying drawings, the same reference numerals are used to represent the same components. In the accompanying drawings:

[0041] Figure 1 This is a flow chart of the small signal equivalent modeling method of the new energy grid-connected inverter in the present invention;

[0042] Figure 2 It is a schematic diagram of the structure and control system of a single inverter in the present invention;

[0043] Figure 3A schematic diagram of the relationship between each inverter and the unified coordinate system in the present invention;

[0044] Figure 4 This is a structural diagram of a system of five new energy grid-connected inverters according to a specific implementation scheme of the present invention;

[0045] Figure 5 is an amplitude-frequency characteristic curve diagram of the impedance transfer function Zxx of the five inverters in the present invention;

[0046] Figure 6 Comparison of active power waveforms before and after grouping equal values ​​based on the frequency domain transfer function coherence criterion in the present invention;

[0047] Figure 7 This is a comparison diagram of the active power waveforms before and after the single-machine equivalent of 5 new energy grid-connected inverters in the present invention. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0049] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0050] When modeling and analyzing large-scale renewable energy (wind power, photovoltaic) sites, due to the large number of renewable energy grid-connected inverters and complex control methods, if each power generation unit in the entire system is modeled in detail, the system order will be too high, which can easily cause "dimensionality disaster" and greatly increase the difficulty of simulation analysis.

[0051] In order to overcome the shortcomings of the existing dynamic equivalent modeling methods for new energy inverters, the present invention proposes a small signal equivalent modeling method for new energy grid-connected inverters based on frequency domain transfer function. The grouping index does not rely on the real data in the actual operation of the inverter, but performs equivalent aggregation on the multi-inverter grid-connected system based on the linearization model of the grid-connected inverter, thereby improving the accuracy of the multi-machine aggregation model. Under the premise of ensuring the accuracy of the equivalent model, the order of the model is effectively reduced, and the simulation operation time of the multi-inverter grid-connected system is shortened.

[0052] Correspondingly, in some other embodiments of the present invention, a new energy grid-connected inverter small signal equivalent modeling system, device and medium are also provided.

[0053] Example 1

[0054] like Figure 1 As shown, this embodiment provides a small signal equivalent modeling method for a new energy grid-connected inverter. Starting from the linearized model of the new energy grid-connected inverter, a grid-connected inverter synchronization criterion based on the frequency domain transfer function is proposed, which no longer relies on the monitoring data of the actual grid-connected operation of the grid-connected inverter, effectively reduces the order of the system, and has the advantages of being simple, practical, and having high model accuracy. Specifically, the following steps are included:

[0055] Step 1: Based on the established linearized mathematical model of the new energy grid-connected inverter, the impedance transfer function from the output current to the grid-connected point voltage of a single inverter in a unified coordinate system is obtained.

[0056] Specifically, the above step 1 can be implemented by the following steps:

[0057] Step 1.1: Establish a mathematical model of the new energy grid-connected inverter.

[0058] like Figure 2 The figure shows the structure and control system of a single inverter. The mathematical model includes a grid-connected inverter controlled by a phase-locked loop and a current loop, a filter, and a weak power grid. f is the filter inductor, L g is the equivalent inductance of the weak grid, G pll and H i They are PI controllers for phase-locked loop and current loop respectively; I dref and I qref are given reference values ​​for the d-axis and q-axis currents of the current loop, U dref and U qref They are the reference values ​​of the d-axis and q-axis voltages output by the current loop respectively.

[0059] Step 1.2: Linearize the mathematical model to obtain the relationship between the grid-connected point voltage and the grid-connected inverter output current of a single inverter in the dq synchronous rotating coordinate system.

[0060] Specifically, the mathematical model is linearized, that is, a small disturbance increment is applied at the equilibrium point of the system mathematical model, and the increment of higher-order terms is ignored, and the relationship between the grid-connected point voltage and the inverter output current in the dq synchronous rotating coordinate system is obtained, which is expressed as:

[0061]

[0062] In formula (1), all variables are based on the dq synchronous rotating coordinate system of each inverter, Δupccd and Δu pccq They represent the change of the grid connection point voltage in the dq synchronous rotating coordinate system; Δi d and Δi q They represent the changes of the inverter output current in the dq synchronous rotating coordinate system; Z dd (s), Z qd (s), Z dq (s) and Z qq (s) are the four impedance transfer functions in the dq synchronous rotating coordinate system.

[0063] Step 1.3: Select the infinite grid as the unified coordinate system, and transform the relationship between the grid connection point voltage and the inverter output current of the single inverter in the dq synchronous rotating coordinate system obtained in step 1.2 into the unified coordinate system.

[0064] like Figure 3 As shown in the figure, it is a schematic diagram of coordinate transformation, and the coordinate transformation relationship is:

[0065]

[0066] In the formula, f di and f qi is the grid connection point voltage or inverter current of the i-th inverter in its own dq coordinate system; f xi and f yi is the grid-connected point voltage or inverter current of the i-th inverter in the unified coordinate system; θ i is the phase angle difference between the dq coordinate system of the i-th inverter and the unified coordinate system.

[0067] Linearizing (2) yields:

[0068]

[0069] Where Δf di and Δf qi is the change in the grid connection point voltage or inverter current of the i-th inverter in its own dq coordinate system; Δf xi and Δf yi is the change in the grid connection point voltage or inverter current of the i-th inverter in the unified coordinate system; θ i0 is the phase angle difference between the dq coordinate system of the i-th inverter and the unified coordinate system at the steady-state operating point; f qi0 and f di0 are respectively the steady-state operating points of the grid-connected point voltage or inverter current of the i-th inverter in its own dq coordinate system.

[0070] Combining equation (1) and equation (3), we can get:

[0071]

[0072] In formula (4), the coordinate system is based on the selected unified coordinate system, and Δu pccx and Δu pccy They represent the change of the grid connection point voltage in the unified coordinate system; Δi xi and Δi yi They represent the changes of the inverter output current in the unified coordinate system; Z xx (s), Z yx (s), Z xy (s) and Z yy (s) are the four impedance transfer functions in the same coordinate system.

[0073] Step 2: Determine the inverter synchronization criterion based on the impedance transfer function, calculate the difference of the amplitude-frequency characteristics of n inverters, and perform synchronization grouping on the n inverters.

[0074] like Figure 3 As shown, the implementation process of the homology equivalent modeling method in the present invention includes the following steps:

[0075] Step 2.1: Establish the inverter synchronization criterion based on the frequency domain transfer function.

[0076] If the difference between the amplitude-frequency characteristic response and the phase-frequency characteristic response of the frequency domain transfer function of the two inverters is not greater than the allowable error δ in the entire frequency band (i.e., a wider frequency band including the power frequency), it can be determined that the two grid-connected inverters are synchronized, which can be expressed as:

[0077]

[0078] Where, |G1(s)| and |G2(s)| represent the amplitude-frequency characteristics of the two inverters, ∠G1(s) and ∠G2(s) represent the phase-frequency characteristics, and δ1 and δ2 represent the allowable errors corresponding to the amplitude-frequency characteristics and the phase-frequency characteristics, respectively.

[0079] Step 2.2: Based on the amplitude-frequency characteristics of the impedance transfer function, the inverter synchronization criterion in step 2.1 is simplified to obtain the inverter synchronization criterion based on the impedance transfer function Z xx Practical criterion for the amplitude-frequency characteristic response of.

[0080] According to the above, the linearized mathematical model of each inverter is a 2*2 matrix, Z xx (s), Z xy (s), Z yx (s), Z yy(s) correspond to four transfer functions respectively. If the four transfer functions of the two inverters all meet the given criterion, the inverters are strictly synchronized. However, if the amplitude-frequency characteristic curve of each transfer function is judged, the workload of synchronization judgment is greatly increased. Therefore, in order to make the synchronization criterion practical, this embodiment selects one of the transfer functions Z xx (s); that is, if the impedance transfer function Z of the two grid-connected inverters xx If the amplitude-frequency characteristic curve of is not greater than a given error δ at any frequency, it can be determined that the two grid-connected inverters are synchronized, that is,

[0081] ||G1(s)|-|G2(s)||≤δ (6)

[0082] Where δ is the allowable error corresponding to the amplitude-frequency characteristics of the two inverters.

[0083] Step 2.3: Define the difference between the inverters according to the practical coherence criterion obtained in step 2.2:

[0084] ε ij =|G i (Z xxi (s))-G j (Z xxj (s))| (7)

[0085] In the formula, ε ij is the difference of the inverter; Z xxi (s) and Z xxj (s) are the impedance transfer functions from the x-axis output current change to the x-axis grid-connected point voltage change of the i-th inverter and the j-th inverter in the unified coordinate system.

[0086] Step 2.4: Calculate the difference between every two inverters in turn, and perform synchronization identification and grouping of the inverters based on the difference and the selected allowable error.

[0087] Step 3: Based on the inverter grouping results, calculate the aggregation parameters of the inverters in each synchronization group to obtain the synchronization equivalent model of the multi-inverter system, so as to simulate and analyze the multi-inverter system of the new energy station.

[0088] The aggregation parameters include the aggregation of circuit structure parameters and the aggregation of control system parameters, and the aggregation of control system parameters includes the aggregation of phase-locked loop control parameters and the aggregation of current loop control parameters.

[0089] Specifically, the aggregation method of each parameter is:

[0090] Step 3.1: The aggregation method of circuit structure parameters is:

[0091] L f,eq =Lf1 / / L f2 / / … / / L fn (8)

[0092] Where, L f,eq is the filter inductance of the equivalent model, L f1 , L f2 , ...L fn They respectively represent the filter inductance of the 1st to nth grid-connected inverters in a certain synchronization group.

[0093] Step 3.2: The aggregation method of the phase-locked loop control parameters is:

[0094]

[0095] In the formula, k pPLL,eq and k iPLL,eq are the proportional coefficient and integral coefficient of the phase-locked loop of the equivalent system respectively; k pPLLi and k iPLLi are the proportional coefficient and integral coefficient of the phase-locked loop of the i-th inverter, c i is the weight coefficient of the i-th inverter, which is equivalent to the d-axis current reference value of the i-th inverter in the present invention.

[0096] Step 3.3: The aggregation method of current loop control parameters is:

[0097]

[0098] In the formula, k pi,eq and k ii,eq are the current loop proportional coefficient and integral coefficient of the equivalent system respectively; k pij and k iij are the proportional coefficient and integral coefficient of the phase-locked loop of the jth inverter, c j is the weight coefficient of the j-th inverter, which is equivalent to the d-axis current reference value of the j-th inverter in the present invention, and n is the number of inverters in the same synchronization group.

[0099] Example 2

[0100] This embodiment uses Figure 4 The present invention is further introduced by taking the five new energy grid-connected inverter systems shown as an example.

[0101] First, establish the dq impedance transfer function of each grid-connected inverter in a unified coordinate system and plot the impedance Z of the five grid-connected inverters. xx The amplitude-frequency characteristic curve of Figure 5 shown.

[0102] Then, the difference between every two inverters is calculated according to the difference defined in the present invention, and the difference calculation results are shown in Table 1.

[0103] Table 1 Difference calculation results

[0104] No. 1 2 3 4 5 1 0 6.0210 9.5433 8.0807 12.0418 2 — 0 7.5258 4.0035 8.3903 3 — — 0 3.5235 2.4991 4 — — — 0 6.2015 5 — — — — 0

[0105] If the allowable error is 5dB, it can be seen from Table 1 that the difference between grid-connected inverters No. 2 and No. 4 is small, and the difference between grid-connected inverters No. 3, No. 4, and No. 5 is small, so the grouping result is that No. 2-5 is a synchronization group. However, it can be observed from Table 1 that the difference between grid-connected inverters No. 4 and No. 5 is large. In order to ensure the rigor of the grouping result, No. 2 and No. 4 are divided into a synchronization group, and No. 3 and No. 5 are divided into a synchronization group. Therefore, in this example, the five grid-connected inverters are divided into three synchronization groups, namely 1; 2 and 4; 3 and 5.

[0106] Figure 6 is a comparison diagram of the active power of the equivalent model obtained by aggregation according to the equivalent modeling method of the present invention and the active power of the detailed model, Figure 7 The figure shows the comparison of active power between the single machine equivalent method and the detailed model. Figure 6 It can be seen that the equivalent model obtained by clustering the coherence criterion proposed in the present invention is basically consistent with the dynamic response of the detailed model. Figure 7 It can be seen that the dynamic process of the single-machine equivalent model cannot match the detailed model. Figure 6 and Figure 7 The comparison verifies the effectiveness of the equivalent modeling method proposed in this invention.

[0107] Example 3

[0108] The above-mentioned embodiment 1 provides a new energy grid-connected inverter small signal equivalent modeling method, and correspondingly, this embodiment provides a new energy grid-connected inverter small signal equivalent modeling system. The system provided in this embodiment can implement a new energy grid-connected inverter small signal equivalent modeling method of embodiment 1, and the system can be implemented by software, hardware, or a combination of software and hardware. For example, the system may include integrated or separate functional modules or functional units to execute the corresponding steps in each method of embodiment 1. Since the system of this embodiment is basically similar to the method embodiment, the description process of this embodiment is relatively simple, and the relevant parts can refer to the partial description of embodiment 1. The embodiment of the system provided in this embodiment is only schematic.

[0109] This embodiment provides a new energy grid-connected inverter small signal equivalent modeling system, including:

[0110] The impedance transfer function determination module is used to obtain the impedance transfer function of a single inverter from output current to grid connection point voltage in a unified coordinate system based on the established linearized mathematical model of the new energy grid-connected inverter;

[0111] A synchronization grouping module is used to determine the synchronization criteria of the inverter based on the impedance transfer function, calculate the difference of the amplitude-frequency characteristics of n inverters, and perform synchronization grouping on the n inverters;

[0112] The aggregation parameter calculation module is used to calculate the aggregation parameters of the inverters in each synchronization group based on the inverter grouping results, and obtain the synchronization equivalent model of the multi-inverter system to simulate and analyze the multi-inverter system of the new energy station.

[0113] Example 4

[0114] This embodiment provides a processing device corresponding to the small signal equivalent modeling method of a new energy grid-connected inverter provided in this embodiment 1. The processing device can be a processing device for a client, such as a mobile phone, a laptop computer, a tablet computer, a desktop computer, etc., to execute the method of embodiment 1.

[0115] The processing device includes a processor, a memory, a communication interface and a bus, and the processor, the memory and the communication interface are connected through the bus to complete mutual communication. The memory stores a computer program that can be run on the processor, and the processor executes a new energy grid-connected inverter small signal equivalent modeling method provided in this embodiment 1 when running the computer program.

[0116] In some embodiments, the memory may be a high-speed random access memory (RAM), and may also include a non-volatile memory, such as at least one disk memory.

[0117] In other embodiments, the processor may be a central processing unit (CPU), a digital signal processor (DSP), or other general-purpose processors of various types, which are not limited herein.

[0118] Example 5

[0119] A new energy grid-connected inverter small signal equivalent modeling method of this embodiment 1 can be specifically implemented as a computer program product, which may include a computer-readable storage medium carrying computer-readable program instructions for executing the new energy grid-connected inverter small signal equivalent modeling method described in this embodiment 1.

[0120] Computer readable storage media can be tangible devices that hold and store instructions used by instruction execution devices. Computer readable storage media can be, for example, but not limited to, electronic storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any combination thereof.

[0121] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A small signal equivalent modeling method for a new energy grid-connected inverter, characterized in that: The following steps are involved: Based on the established linearized mathematical model of the new energy grid-connected inverter, the impedance transfer function from the output current to the grid-connected point voltage of a single inverter in a unified coordinate system is obtained; Determining the inverter coherence criterion based on the impedance transfer function, calculating the difference of the amplitude-frequency characteristics of n inverters, and performing coherence grouping on the n inverters; Based on the inverter grouping results, the aggregation parameters of the inverters in each synchronization group are calculated to obtain the synchronization equivalent model of the multi-inverter system, which is used to simulate and analyze the multi-inverter system of the new energy station; The method of determining the inverter coherence criterion based on the impedance transfer function, calculating the difference of the amplitude-frequency characteristics of n inverters, and performing coherence grouping on the n inverters includes: Establish inverter coherence criterion based on frequency domain transfer function; The inverter synchronization criterion is: if the difference between the amplitude-frequency characteristic response and the phase-frequency characteristic response of the frequency domain transfer function of the two inverters is not greater than the allowable error within the entire frequency band, then the two grid-connected inverters are judged to be synchronized, which is expressed as: In the formula, and Respectively represent the amplitude-frequency characteristics of the two inverters, and Respectively represent the phase-frequency characteristics of the two inverters; and Respectively represent the allowable errors corresponding to the amplitude-frequency characteristic and the phase-frequency characteristic; Based on the amplitude-frequency characteristics of the impedance transfer function, the inverter synchronization criterion is simplified to obtain the impedance transfer function Z xx Practical criterion for the amplitude-frequency characteristic response of The practical criterion is: if the impedance transfer function Z of the two grid-connected inverters xx If the amplitude-frequency characteristic curve of is not greater than a given error at any frequency, then the two grid-connected inverters are considered to be synchronized, that is: In the formula, δ is the allowable error corresponding to the amplitude-frequency characteristics of the two inverters; Defining the difference of the inverter according to the practical criterion; The difference of the inverter is: In the formula, is the difference of the inverter; and They are respectively i Inverter and j The impedance transfer function from the x-axis output current change of the inverter to the x-axis grid connection point voltage change; Calculate the difference between every two inverters in turn, and perform synchronization identification and grouping of the inverters based on the difference and the selected allowable error; The calculation of the aggregate parameters of the inverters in each synchronization group based on the inverter grouping result includes: aggregation of circuit structure parameters and aggregation of control system parameters, wherein the aggregation of control system parameters includes aggregation of phase-locked loop control parameters and aggregation of current loop control parameters; The aggregation of the circuit structure parameters is: Where, L f,eq is the filter inductance of the equivalent model, L f1 , L f2 , ...L fn They represent the filter inductance of the 1st to nth grid-connected inverters in a certain synchronization group respectively; The aggregation method of the phase-locked loop control parameters is: In the formula, and are the proportional coefficient and integral coefficient of the phase-locked loop of the equivalent system respectively; and are the proportional coefficient and integral coefficient of the phase-locked loop of the i-th inverter, is the weight coefficient of the i-th inverter; The aggregation method of current loop control parameters is: In the formula, and They are the current loop proportional coefficient and integral coefficient of the equivalent system respectively; and are the proportional coefficient and integral coefficient of the current loop of the jth inverter, is the weight coefficient of the jth inverter.

2. A small signal equivalent modeling method for a new energy grid-connected inverter as claimed in claim 1, characterized in that: The method for obtaining the impedance transfer function of a single inverter from output current to grid connection point voltage in a unified coordinate system based on the established linearized mathematical model of the new energy grid-connected inverter includes: Establish mathematical model of new energy grid-connected inverter; The mathematical model is linearized to obtain the relationship between the grid connection point voltage and the grid-connected inverter output current of a single inverter in a dq synchronous rotating coordinate system; The infinite power grid is selected as the unified coordinate system, and the relationship between the grid connection point voltage and the inverter output current of a single inverter in the dq synchronous rotating coordinate system is transformed into the unified coordinate system.

3. A small signal equivalent modeling system for a new energy grid-connected inverter, characterized in that: include: The impedance transfer function determination module is used to obtain the impedance transfer function of a single inverter from output current to grid connection point voltage in a unified coordinate system based on the established linearized mathematical model of the new energy grid-connected inverter; A synchronization grouping module is used to determine the synchronization criteria of the inverter based on the impedance transfer function, calculate the difference of the amplitude-frequency characteristics of n inverters, and perform synchronization grouping on the n inverters; The aggregation parameter calculation module is used to calculate the aggregation parameters of the inverters in each synchronization group based on the inverter grouping results, obtain the synchronization equivalent model of the multi-inverter system, and perform simulation analysis on the multi-inverter system of the new energy station; The method of determining the inverter coherence criterion based on the impedance transfer function, calculating the difference of the amplitude-frequency characteristics of n inverters, and performing coherence grouping on the n inverters includes: Establish inverter coherence criterion based on frequency domain transfer function; The inverter synchronization criterion is: if the difference between the amplitude-frequency characteristic response and the phase-frequency characteristic response of the frequency domain transfer function of the two inverters is not greater than the allowable error within the entire frequency band, then the two grid-connected inverters are judged to be synchronized, which is expressed as: In the formula, and Respectively represent the amplitude-frequency characteristics of the two inverters, and Respectively represent the phase-frequency characteristics of the two inverters; and Respectively represent the allowable errors corresponding to the amplitude-frequency characteristic and the phase-frequency characteristic; Based on the amplitude-frequency characteristics of the impedance transfer function, the inverter synchronization criterion is simplified to obtain the impedance transfer function Z xx Practical criterion for the amplitude-frequency characteristic response of The practical criterion is: if the impedance transfer function Z of the two grid-connected inverters xx If the amplitude-frequency characteristic curve of is not greater than a given error at any frequency, then the two grid-connected inverters are considered to be synchronized, that is: In the formula, δ is the allowable error corresponding to the amplitude-frequency characteristics of the two inverters; Defining the difference of the inverter according to the practical criterion; The difference of the inverter is: In the formula, is the difference of the inverter; and They are respectively i Inverter and j The impedance transfer function from the x-axis output current change of the inverter to the x-axis grid connection point voltage change; Calculate the difference between every two inverters in turn, and perform synchronization identification and grouping of the inverters based on the difference and the selected allowable error; The calculation of the aggregate parameters of the inverters in each synchronization group based on the inverter grouping result includes: aggregation of circuit structure parameters and aggregation of control system parameters, wherein the aggregation of control system parameters includes aggregation of phase-locked loop control parameters and aggregation of current loop control parameters; The aggregation of the circuit structure parameters is: Where, L f,eq is the filter inductance of the equivalent model, L f1 , L f2 , ...L fn They represent the filter inductance of the 1st to nth grid-connected inverters in a certain synchronization group respectively; The aggregation method of the phase-locked loop control parameters is: In the formula, and are the proportional coefficient and integral coefficient of the phase-locked loop of the equivalent system respectively; and are the proportional coefficient and integral coefficient of the phase-locked loop of the i-th inverter, is the weight coefficient of the i-th inverter; The aggregation method of current loop control parameters is: In the formula, and They are the current loop proportional coefficient and integral coefficient of the equivalent system respectively; and are the proportional coefficient and integral coefficient of the current loop of the jth inverter, is the weight coefficient of the jth inverter.

4. A processing device, the processing device comprising at least a processor and a memory, the memory storing a computer program, characterized in that: When the processor runs the computer program, the processor executes the steps of the method for small signal equivalent modeling of the new energy grid-connected inverter as described in any one of claims 1 to 2.

5. A computer storage medium, characterized in that: Computer-readable instructions are stored thereon, and the computer-readable instructions can be executed by a processor to implement the steps of the small signal equivalent modeling method for a new energy grid-connected inverter according to any one of claims 1 to 2.

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