A method and device for determining complex impedance of a point of common coupling, electronic equipment and medium

Abstract

The application discloses a kind of grid-connected point complex impedance determination method, device, electronic equipment and medium, it is related to grid-connected inverter system control technical field, first according to the target voltage coefficient matrix of phase-locked loop of the preset small signal model of inverter corresponding direct axis power grid information and phase-locked loop, second grid-connected voltage matrix and first grid-connected current matrix are determined based on the target current coefficient matrix of phase-locked loop corresponding to target voltage coefficient matrix and inductance, then according to target voltage coefficient matrix and target current coefficient matrix determine second grid-connected voltage matrix and second grid-connected current matrix, finally based on the complex impedance of the grid-connected point of inverter determined by first grid-connected voltage matrix, first grid-connected current matrix, second grid-connected voltage matrix and second grid-connected current matrix, the scheme introduces the direct axis power grid information corresponding to inverter, complements the missing phase information in preset small signal model, overcomes frequency coupling effect, accurately obtains the complex impedance of inverter grid-connected point.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of grid-connected inverter system control, and particularly relates to a grid-connected point complex impedance determination method and device, electronic equipment and medium. BACKGROUND

[0002] With the increasing proportion of new energy in the power system, the grid-connected converter as the interface between new energy and the power grid is often connected to the power grid through a long line and a transformer, thereby reducing the stability of the PCC (Point of Common Coupling).

[0003] The common current-controlled grid-connected inverter impedance matrix is mainly asymmetric due to the asymmetry of the phase-locked loop. Because the common grid-connected inverter phase-locked loop only contains the information of the quadrature axis and ignores the information of the direct axis, the phase information on the direct axis in the synchronous rotating coordinate system is missing, thereby causing the impedance matrix to be asymmetric, eventually exhibiting frequency coupling effect, and thus the complex impedance value of the grid-connected point of the inverter cannot be accurately obtained. SUMMARY

[0004] The purpose of the present application is to provide a grid-connected point complex impedance determination method, device, electronic equipment and medium. The present application introduces the direct-axis grid information corresponding to the inverter, and determines the target voltage coefficient matrix of the phase-locked loop according to the direct-axis grid information and the preset small signal model of the phase-locked loop corresponding to the inverter, thereby complementing the missing phase information in the preset small signal model, overcoming the frequency coupling effect, and accurately obtaining the complex impedance of the grid-connected point of the inverter.

[0005] To solve the above technical problems, the present application provides a grid-connected point complex impedance determination method, comprising:

[0006] determining a target voltage coefficient matrix of the phase-locked loop according to the direct-axis grid information corresponding to the inverter and a preset small signal model of the phase-locked loop corresponding to the inverter;

[0007] determining the inductance corresponding to the inverter;

[0008] determining a first grid-connected voltage matrix and a first grid-connected current matrix based on a target current coefficient matrix of the phase-locked loop corresponding to the target voltage coefficient matrix and the inductance;

[0009] determining a second grid-connected voltage matrix and a second grid-connected current matrix according to the target voltage coefficient matrix and the target current coefficient matrix;

[0010] determining the complex impedance of the grid-connected point of the inverter based on the first grid-connected voltage matrix, the first grid-connected current matrix, the second grid-connected voltage matrix and the second grid-connected current matrix.

[0011] Optionally, the target voltage coefficient matrix of the phase-locked loop is determined according to the direct-axis power grid information corresponding to the inverter and the preset small-signal model of the phase-locked loop corresponding to the inverter, and the target voltage coefficient matrix comprises:

[0012] The d-axis complex phase and the q-axis complex phase of the phase-locked loop are determined.

[0013] The target voltage coefficient matrix is determined according to the d-axis complex phase, the q-axis complex phase, the direct-axis power grid information and the preset small-signal model.

[0014] Optionally, the target voltage coefficient matrix is determined according to the d-axis complex phase, the q-axis complex phase, the direct-axis power grid information and the preset small-signal model, and the target voltage coefficient matrix comprises:

[0015] The d-axis voltage, the q-axis voltage, the d-axis grid-connected voltage disturbance and the q-axis grid-connected voltage disturbance of the inverter corresponding to the direct-axis power grid information are determined according to the direct-axis power grid information.

[0016] The target voltage coefficient matrix is determined according to the d-axis complex phase, the q-axis complex phase, the d-axis voltage, the q-axis voltage, the d-axis grid-connected voltage disturbance, the q-axis grid-connected voltage disturbance and the preset small-signal model.

[0017] The preset small-signal model is: Δθ is the complex phase of the phase-locked loop.

[0018] The target voltage coefficient matrix is: Wherein, Δθ d is the d-axis complex phase, Δθ q is the q-axis complex phase, G pll (s) is the first transfer function of the phase-locked loop, V d is the d-axis voltage, V q is the q-axis voltage, ΔV d is the d-axis grid-connected voltage disturbance, and ΔV q is the q-axis grid-connected voltage disturbance.

[0019] Optionally, the first grid-connected voltage matrix and the first grid-connected current matrix are determined based on the target current coefficient matrix of the phase-locked loop corresponding to the target voltage coefficient matrix and the inductance, and the first grid-connected voltage matrix and the first grid-connected current matrix comprise:

[0020] The first transfer function of the phase-locked loop and the second transfer function of the current loop corresponding to the inverter are determined.

[0021] The d-axis grid-connected current and the q-axis grid-connected current of the inverter are determined.

[0022] determine the first grid-connected voltage matrix and the first grid-connected current matrix according to the d-axis grid-connected current, the q-axis grid-connected current, the target current coefficient matrix, the first transfer function, the second transfer function, the inductance, a first grid-connected voltage matrix determination formula and a first grid-connected current matrix determination formula;

[0023] The first grid-connected voltage matrix determination formula is: T V-i G pll (s) is the first transfer function, G i (s) is the second transfer function, is the target current coefficient matrix, I d is the d-axis grid-connected current, I q is the q-axis grid-connected current;

[0024] The first grid-connected current matrix determination formula is: I-i = [G i (s) + sL]E; wherein T I-i is the first grid-connected current matrix, s is a preset order, L is the inductance, and E is a second-order unit matrix.

[0025] Optionally, the second grid-connected voltage matrix and the second grid-connected current matrix are determined according to the target voltage coefficient matrix and the target current coefficient matrix, and the method comprises:

[0026] determining a d-axis grid-connected current disturbance and a q-axis grid-connected current disturbance of the inverter;

[0027] converting an initial transient power small signal model into a target transient power small signal model based on a preset symmetrization operation, the d-axis grid-connected current disturbance, the q-axis grid-connected current disturbance, the target voltage coefficient matrix and the target current coefficient matrix;

[0028] determining the second grid-connected voltage matrix and the second grid-connected current matrix according to the target transient power small signal model;

[0029] The initial transient power small signal model is: ΔP is a first power disturbance of the inverter, ΔQ is a second power disturbance of the inverter, is the target voltage coefficient matrix;

[0030] The target transient power small signal model is: ΔP ′ is a third power disturbance of the inverter, and ΔQ ′a fourth power disturbance quantity of the inverter, a target current coefficient matrix after the preset symmetrization operation, a target voltage coefficient matrix after the preset symmetrization operation, ΔI d a d-axis grid-connected current disturbance quantity, ΔI q a q-axis grid-connected current disturbance quantity.

[0031] Optionally, the second grid-connected voltage matrix and the second grid-connected current matrix are determined according to the target instantaneous power small signal model, and the method comprises:

[0032] the target current coefficient matrix after the preset symmetrization operation is determined based on the target instantaneous power small signal model;

[0033] the second grid-connected voltage matrix and the second grid-connected current matrix are determined according to a grid-connected point voltage of the inverter, the target current coefficient matrix after the preset symmetrization operation, a first transfer function of the phase-locked loop, a second transfer function of a current loop corresponding to the inverter, a third transfer function of a power loop corresponding to the inverter, a second grid-connected voltage matrix determination formula, and a second grid-connected current matrix determination formula;

[0034] wherein the second grid-connected voltage matrix determination formula is: T V-c the second grid-connected voltage matrix, V m the grid-connected point voltage, G pll (s) is the first transfer function, G i (s) is the second transfer function, G c (s) is the third transfer function, the target current coefficient matrix after the preset symmetrization operation;

[0035] the second grid-connected current matrix determination formula is: T I-c = [1.5V m G c (s)G i (s)]E; T I-c the second grid-connected current matrix, and E is a second-order unit matrix.

[0036] Optionally, the complex impedance of the grid-connected point of the inverter is determined based on the first grid-connected voltage matrix, the first grid-connected current matrix, the second grid-connected voltage matrix, and the second grid-connected current matrix, and the method comprises:

[0037] d-axis grid-connection current perturbation quantity, a q-axis grid-connection current perturbation quantity, a d-axis grid-connection voltage perturbation quantity, a q-axis grid-connection voltage perturbation quantity and a grid-connection point voltage of the inverter;

[0038] constructing an impedance equation based on the grid-connection point voltage, the d-axis grid-connection current perturbation quantity, the q-axis grid-connection current perturbation quantity, the d-axis grid-connection voltage perturbation quantity, the q-axis grid-connection voltage perturbation quantity, the first grid-connection voltage matrix, the first grid-connection current matrix, the second grid-connection voltage matrix and the second grid-connection current matrix, so as to determine the complex impedance according to a solution of the impedance equation;

[0039] wherein the impedance equation is:

[0040] the solution of the impedance equation is:

[0041] wherein, is the complex impedance, j is a preset parameter, is a grid-connection point voltage complex vector of the inverter, is a grid-connection point current complex vector of the inverter.

[0042] To solve the above technical problems, the application further provides a grid-connection point complex impedance determination device, comprising:

[0043] a first determination unit configured to determine a target voltage coefficient matrix of a phase-locked loop of the inverter according to direct-axis grid information corresponding to the inverter and a preset small signal model of the phase-locked loop corresponding to the inverter;

[0044] a second determination unit configured to determine an inductance corresponding to the inverter;

[0045] a third determination unit configured to determine a first grid-connection voltage matrix and a first grid-connection current matrix based on a target current coefficient matrix of the phase-locked loop corresponding to the target voltage coefficient matrix and the inductance;

[0046] a fourth determination unit configured to determine a second grid-connection voltage matrix and a second grid-connection current matrix according to the target voltage coefficient matrix and the target current coefficient matrix;

[0047] a fifth determination unit configured to determine a complex impedance of a grid-connection point of the inverter based on the first grid-connection voltage matrix, the first grid-connection current matrix, the second grid-connection voltage matrix and the second grid-connection current matrix.

[0048] To solve the above technical problems, the application further provides an electronic device, comprising:

[0049] a memory configured to store a computer program;

[0050] A processor is configured to implement the steps of the grid point complex impedance determination method when executing the computer program.

[0051] To solve the above technical problems, the application further provides a computer readable storage medium, wherein the computer readable storage medium stores a computer program, and the computer program is configured to implement the steps of the grid point complex impedance determination method when executed by a processor.

[0052] The application aims to provide a grid point complex impedance determination method, device, electronic equipment and medium, which determines a target voltage coefficient matrix of a phase-locked loop according to direct-axis grid information corresponding to an inverter and a preset small signal model of the phase-locked loop, determines a first grid voltage matrix and a first grid current matrix based on a target current coefficient matrix of the phase-locked loop corresponding to the target voltage coefficient matrix and an inductance, determines a second grid voltage matrix and a second grid current matrix according to the target voltage coefficient matrix and the target current coefficient matrix, and finally determines a complex impedance of a grid point of the inverter based on the determined first grid voltage matrix, first grid current matrix, second grid voltage matrix and second grid current matrix. The application introduces the direct-axis grid information corresponding to the inverter, complements the missing phase information in the preset small signal model, overcomes the frequency coupling effect, and accurately obtains the complex impedance of the grid point of the inverter. BRIEF DESCRIPTION OF DRAWINGS

[0053] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of the provided drawings.

[0054] Figure 1 A process flow chart of a grid point complex impedance determination method provided by the present application;

[0055] Figure 2 A process flow chart of another grid point complex impedance determination method provided by the present application;

[0056] Figure 3 A topology structure diagram of a three-phase inverter provided by the present application;

[0057] Figure 4 A small signal model diagram of a three-phase inverter provided by the present application;

[0058] Figure 5a A diagram showing the influence of the present method on the frequency coupling effect;

[0059] Figure 5bAnother method provided by the present application for providing a graph of the influence of the frequency coupling effect;

[0060] Figure 5c Another method provided by the present application for providing a graph of the influence of the frequency coupling effect;

[0061] Figure 6 A complex impedance theory / frequency sweep Bode diagram provided by the present application;

[0062] Figure 7 A structure diagram of a grid connection point complex impedance determination device provided by the present application;

[0063] Figure 8 A structure diagram of an electronic device provided by the present application. DETAILED DESCRIPTION

[0064] The core of the present application is to provide a grid connection point complex impedance determination method, device, electronic device and medium, the present application introduces the direct axis grid information corresponding to the inverter, and determines the target voltage coefficient matrix according to the direct axis grid information and the existing preset small signal model of the phase-locked loop corresponding to the inverter, completes the missing phase information in the preset small signal model, overcomes the frequency coupling effect, and accurately obtains the complex impedance of the grid connection point of the inverter.

[0065] Please refer to Figure 1 , Figure 1 A process flow chart of a grid connection point complex impedance determination method provided by the present application. The method comprises:

[0066] S11: determining the target voltage coefficient matrix of the phase-locked loop according to the direct axis grid information corresponding to the inverter and the preset small signal model of the phase-locked loop corresponding to the inverter;

[0067] S12: determining the inductance corresponding to the inverter;

[0068] S13: determining the first grid connection voltage matrix and the first grid connection current matrix based on the target current coefficient matrix of the phase-locked loop corresponding to the target voltage coefficient matrix and the inductance;

[0069] S14: determining the second grid connection voltage matrix and the second grid connection current matrix according to the target voltage coefficient matrix and the target current coefficient matrix;

[0070] S15: determining the complex impedance of the grid connection point of the inverter based on the first grid connection voltage matrix, the first grid connection current matrix, the second grid connection voltage matrix and the second grid connection current matrix.

[0071] In the present application, in order to overcome the problem of asymmetry of the impedance matrix of the grid-connected inverter in common current control, the corresponding direct-axis grid information of the inverter is introduced first, and the target voltage coefficient matrix of the phase-locked loop is determined according to the corresponding direct-axis grid information of the inverter and the preset small signal model of the corresponding phase-locked loop of the inverter, then the first grid-connected voltage matrix and the first grid-connected current matrix are determined based on the determined inductance and the target current coefficient matrix of the corresponding phase-locked loop of the target voltage coefficient matrix, and the second grid-connected voltage matrix and the second grid-connected current matrix are determined according to the determined target voltage coefficient matrix and the target current coefficient matrix, and finally the complex impedance of the grid-connected point of the inverter can be determined based on the first grid-connected voltage matrix, the first grid-connected current matrix, the second grid-connected voltage matrix and the second grid-connected current matrix, the missing phase information in the preset small signal model is completed, the frequency coupling effect is overcome, and the complex impedance of the grid-connected point of the inverter is accurately obtained.

[0072] It should be noted that in a weak grid, the traditional grid-connected converter has a frequency coupling problem, which results in the impedance in the synchronous rotating coordinate system needing to be represented by a second-order multiple-input multiple-output (MIMO, Multiple-Input Multiple-Output) matrix, increasing the complexity of the impedance. For a MIMO system, the stability judgment method is the generalized Nyquist criterion, which cannot give a clear physical meaning when evaluating the stability of the system, and can only qualitatively analyze how physical quantities affect stability. With the proposal of the unified impedance modeling theory, when the MIMO impedance matrix of the system is a symmetric matrix, the negative sequence impedance is equivalent to zero, that is, for a single ω s frequency voltage disturbance, only the current response of ω s frequency will be generated, while the current response of the coupled frequency of 2ω0-ω s is suppressed to zero. Thus, the impedance matrix of the system can be reduced from the MIMO matrix to a single-input single-output (SISO, Single-Input Single-Output) complex matrix, and for the SISO matrix, there are various criteria for stability judgment, and the influence and sensitivity of various physical quantities on the impedance can be analyzed, thereby more clearly showing the influence of various physical quantities on stability. The asymmetry of the impedance matrix of the common current-controlled grid-connected inverter is mainly caused by the asymmetry of the phase-locked loop, because the common grid-connected inverter only contains the cross-axis information of the phase-locked loop and ignores the direct-axis information, resulting in the loss of phase information in the direct-axis in the synchronous rotating coordinate system, thereby causing the asymmetry of the impedance matrix and finally exhibiting the frequency coupling effect. In today's power system with high new energy penetration, grid-connected inverters using direct power control are gradually increasing. Such converters realize direct power control through a power loop based on a phase-locked loop and a current loop, but because the small signal model of the power calculation formula is asymmetric, it becomes more difficult to suppress the frequency coupling, and also makes the stability analysis of such devices complex.

[0073] It also needs to be explained that in the process of determining the complex impedance of the grid-connected point, the first step is to model the small signal of the symmetrical phase-locked loop to obtain the coupling relationship between the physical quantities in the controller, the real physical quantities and the phase: ΔX ipll = ΔX i -jX i Δθ, where Δθ is the complex phase obtained by the symmetrical phase-locked loop. ΔX ipll is the small disturbance quantity of the physical quantity in the controller, ΔX i is the small disturbance quantity of the corresponding real physical quantity, X i is the working point value of the small signal model of the physical quantity, where Δθ is the complex phase obtained by the symmetrical phase-locked loop. In fact, the symmetrical phase-locked loop also includes the information of the direct-axis grid into the control loop, so that the phase of the controller changes from one-dimensional phase to two-dimensional complex phase. Due to the lack of dimension of the classical three-phase synchronous phase-locked loop, the coefficient matrix of ΔV d , ΔV q in the preset small signal model is not symmetrical, which leads to the asymmetry of the MIMO matrix of the grid-connected impedance, and finally causes the frequency coupling effect. Therefore, the symmetrical phase-locked loop supplements the dimension by introducing the direct-axis voltage into the control loop, which can compensate the coefficient matrix of the voltage small disturbance to be symmetrical, and finally realizes the suppression of frequency coupling based on the symmetrical phase-locked loop and the current loop.

[0074] It also needs to be explained that in the process of determining the complex impedance of the grid-connected point, the second step is to model the small signal of the current loop and the L-type inductive filter to obtain the SISO small signal matrix T V-i , T I-i about the grid-connected voltage and the grid-connected current in the dq coordinate system based on the current loop and the symmetrical phase-locked loop.

[0075] It also needs to be explained that in the process of determining the complex impedance of the grid-connected point, the third step is to realize the symmetry of the small signal model of the instantaneous power by modifying the power calculation formula without affecting the steady-state power control, so as to obtain the SISO small signal matrix T V-c , T I-c about the grid-connected voltage and the grid-connected current in the synchronous rotating coordinate system by modeling the impedance of the power loop. In the small signal model of the classical instantaneous power formula, the coefficient matrix of ΔV d , ΔV q is not symmetrical, which directly leads to the asymmetry of the MIMO grid-connected impedance matrix, and finally causes the frequency coupling effect. The small signal model of the modified instantaneous power formula has symmetry, which can keep the part of the grid-connected impedance coefficient matrix containing the power loop symmetrical, and finally realize the suppression of frequency coupling on the basis of keeping the symmetrical phase-locked loop and the current loop symmetrical.

[0076] It is also necessary to explain that the T V-i , T I-i and T V-c , T I-c column write synchronous rotating coordinate system inverter impedance equation, the solution of equivalent PCC point SISO complex impedance Z pcc , and the grid point complex impedance determination process is shown in Figure 2 .

[0077] It is also necessary to explain that considering the coupling of the phase-locked loop and the weak grid, the voltage disturbance of the PCC point will enter the controller system through the phase-locked loop, thereby affecting the system stability, so it is necessary to consider the inverter impedance under the coupling of the phase-locked loop and the weak grid. Among them, Figure 3 is the topology structure diagram of the three-phase inverter, and the method in this paper is suitable for the three-phase grid-connected inverter system shown in Figure 3 , in which Figure 3 , V A , V B , V C are the three-phase PCC point voltages, I A , I B , I C are the three-phase grid-connected currents, V ga , V gb , V gc are the three-phase grid voltages, Z L is the line impedance, L is the inverter side filter, V DC is the inverter DC side voltage, G pll (s) is the phase-locked loop transfer function, G c (s) is the power loop transfer function, G i (s) is the current loop transfer function, V dq is the PCC point voltage in the synchronous rotating coordinate system, I dq is the grid-connected current in the synchronous rotating coordinate system, I dqref is the reference grid-connected current in the synchronous rotating coordinate system, V invdq is the inverter side output voltage in the synchronous rotating coordinate system, D abc is the modulation ratio, and the system small signal model considering the power loop, the symmetric phase-locked loop and the current loop is shown in Figure 4 .

[0078] It is also necessary to explain that Fig. 5 is a diagram showing the influence of the method on the frequency coupling effect. It mainly includes three FFT (Fast Fourier Transform) analyses of adding 370Hz voltage disturbance, which are:

[0079] 1) FFT analysis including only the current loop and the symmetric phase-locked loop, as shown in Figure 5a ;

[0080] 2) FFT analysis with power loop added but without modified power calculation formula as shown in Figure 5b .

[0081] 3) FFT analysis with power loop added and with modified power calculation formula as shown in Figure 5c .

[0082] It can be seen from Figure 5a that, for the inverter model containing only current loop and symmetrical phase-locked loop, after adding 370Hz voltage disturbance, the grid-connected current only produces 370Hz response, and the frequency coupling phenomenon does not occur. It is proved that the two-dimensional MIMO impedance can be reduced to SISO complex impedance. It can be seen from Figure 5b that, in the case of using the classical power calculation formula for direct power control, after adding 370Hz voltage disturbance to the PCC point, the grid-connected current responds to 370Hz and 270Hz two frequencies, and the frequency coupling phenomenon occurs, at this time the two-dimensional MIMO impedance cannot be reduced to SISO complex impedance. As Figure 5b a comparison, Figure 5c it is shown that, after modifying the power calculation formula, under 370Hz voltage disturbance, the 270Hz current response is almost zero, and the frequency coupling effect is almost completely suppressed. It is proved that using the modified instantaneous power calculation formula in direct power control can realize the reduction of the grid-connected impedance of the inverter.

[0083] It should also be noted that, Figure 6 the theoretical / frequency sweep Bode diagram of complex impedance, from Figure 6 it can be seen that the theoretical impedance model and the impedance model obtained by frequency sweep are almost consistent, verifying the correctness of the small signal model, and finally the system stability can be determined by using the SISO complex impedance model.

[0084] The embodiment provides a grid-connected point complex impedance determination method, first, target voltage coefficient matrices of a phase-locked loop are determined according to corresponding direct-axis grid information of an inverter and a preset small signal model of the phase-locked loop, then first grid-connected voltage matrices and first grid-connected current matrices are determined based on target current coefficient matrices of the phase-locked loop corresponding to the target voltage coefficient matrices and inductances, then second grid-connected voltage matrices and second grid-connected current matrices are determined according to the target voltage coefficient matrices and the target current coefficient matrices, and finally a complex impedance of a grid-connected point of the inverter is determined based on the determined first grid-connected voltage matrices, the first grid-connected current matrices, the second grid-connected voltage matrices and the second grid-connected current matrices. The scheme introduces the corresponding direct-axis grid information of the inverter, complements the missing phase information in the preset small signal model, overcomes the frequency coupling effect, and accurately obtains the complex impedance of the grid-connected point of the inverter.

[0085] On the basis of the above embodiment:

[0086] As an optional embodiment, the target voltage coefficient matrix of the phase-locked loop is determined according to the direct-axis grid information corresponding to the inverter and a preset small signal model of the phase-locked loop corresponding to the inverter, and the target voltage coefficient matrix is determined according to the d-axis complex phase and the q-axis complex phase of the phase-locked loop, the direct-axis grid information, and the preset small signal model.

[0087] The d-axis complex phase and the q-axis complex phase of the phase-locked loop are determined.

[0088] The target voltage coefficient matrix is determined according to the d-axis complex phase, the q-axis complex phase, the direct-axis grid information, and the preset small signal model.

[0089] In the application, the specific process of determining the target voltage coefficient matrix of the phase-locked loop according to the direct-axis grid information corresponding to the inverter and the preset small signal model of the phase-locked loop corresponding to the inverter is that the d-axis complex phase and the q-axis complex phase of the phase-locked loop are first determined, and then the target voltage coefficient matrix is determined according to the d-axis complex phase, the q-axis complex phase, the direct-axis grid information, and the preset small signal model, thereby improving the reliability of the process of determining the target voltage coefficient matrix.

[0090] As an optional embodiment, the target voltage coefficient matrix is determined according to the d-axis complex phase, the q-axis complex phase, the direct-axis grid information, and the preset small signal model, and the target voltage coefficient matrix is determined according to the d-axis complex phase, the q-axis complex phase, the direct-axis grid information, and the preset small signal model.

[0091] The d-axis voltage, the q-axis voltage, the d-axis grid-connected voltage disturbance, and the q-axis grid-connected voltage disturbance of the inverter corresponding to the direct-axis grid information are determined according to the direct-axis grid information.

[0092] The target voltage coefficient matrix is determined according to the d-axis complex phase, the q-axis complex phase, the d-axis voltage, the q-axis voltage, the d-axis grid-connected voltage disturbance, the q-axis grid-connected voltage disturbance, and the preset small signal model.

[0093] The preset small signal model is as follows: Δθ is the complex phase of the phase-locked loop.

[0094] The target voltage coefficient matrix is as follows: Δθ d is the d-axis complex phase, Δθ q is the q-axis complex phase, G pll (s) is the first transfer function of the phase-locked loop, V d is the d-axis voltage, V q is the q-axis voltage, ΔV d is the d-axis grid-connected voltage disturbance, and ΔV q is the q-axis grid-connected voltage disturbance.

[0095] In the application, the specific process of determining the target voltage coefficient matrix according to the d-axis complex phase, the q-axis complex phase, the direct-axis grid information and the preset small signal model is as follows: first, the d-axis voltage, the q-axis voltage, the d-axis grid voltage disturbance and the q-axis grid voltage disturbance of the inverter corresponding to the direct-axis grid information are determined according to the direct-axis grid information, and then the target voltage coefficient matrix is determined according to the d-axis complex phase, the q-axis complex phase, the d-axis voltage, the q-axis voltage, the d-axis grid voltage disturbance, the q-axis grid voltage disturbance and the preset small signal model, so that the target voltage coefficient matrix can be accurately determined.

[0096] As an optional embodiment, the first grid-connected voltage matrix and the first grid-connected current matrix are determined based on the target current coefficient matrix corresponding to the phase-locked loop of the target voltage coefficient matrix and the inductance, and the first grid-connected voltage matrix and the first grid-connected current matrix are determined based on the target current coefficient matrix corresponding to the phase-locked loop of the target voltage coefficient matrix and the inductance, including:

[0097] determining the first transfer function of the phase-locked loop and the second transfer function of the current loop corresponding to the inverter;

[0098] determining the d-axis grid-connected current and the q-axis grid-connected current of the inverter;

[0099] determining the first grid-connected voltage matrix and the first grid-connected current matrix according to the d-axis grid-connected current, the q-axis grid-connected current, the target current coefficient matrix, the first transfer function, the second transfer function, the inductance, the first grid-connected voltage matrix determination formula and the first grid-connected current matrix determination formula;

[0100] wherein the first grid-connected voltage matrix determination formula is: T V-i (s) is the first transfer function, G pll (s) is the second transfer function, i is the target current coefficient matrix, I d is the d-axis grid-connected current, I q is the q-axis grid-connected current;

[0101] the first grid-connected current matrix determination formula is: I-i T i (s)+sL]E; wherein T I-i is the first grid-connected current matrix, s is a preset order, L is the inductance, and E is a second-order unit matrix.

[0102] ​In the application, the specific process for determining the first grid-connected voltage matrix and the first grid-connected current matrix based on the target current coefficient matrix corresponding to the phase-locked loop of the target voltage coefficient matrix and the inductance is as follows: first, determining the first transfer function of the phase-locked loop and the second transfer function of the current loop corresponding to the inverter, then determining the d-axis grid-connected current and the q-axis grid-connected current of the inverter, and finally bringing the determined d-axis grid-connected current, q-axis grid-connected current, target current coefficient matrix, first transfer function, second transfer function, inductance into the first grid-connected voltage matrix determination formula and the first grid-connected current matrix determination formula, so that the first grid-connected voltage matrix and the first grid-connected current matrix can be accurately determined.

[0103] As an optional embodiment, the second grid-connected voltage matrix and the second grid-connected current matrix are determined according to the target voltage coefficient matrix and the target current coefficient matrix, comprising:

[0104] determining the d-axis grid-connected current disturbance and the q-axis grid-connected current disturbance of the inverter;

[0105] converting an initial instantaneous power small signal model into a target instantaneous power small signal model based on a preset symmetrization operation, the d-axis grid-connected current disturbance, the q-axis grid-connected current disturbance, the target voltage coefficient matrix and the target current coefficient matrix;

[0106] determining the second grid-connected voltage matrix and the second grid-connected current matrix according to the target instantaneous power small signal model;

[0107] wherein, the initial instantaneous power small signal model is: ΔP is the first power disturbance of the inverter, ΔQ is the second power disturbance of the inverter, is the target voltage coefficient matrix;

[0108] the target instantaneous power small signal model is: wherein, ΔP ′ is the third power disturbance of the inverter, ΔQ ′ is the fourth power disturbance of the inverter, is the target current coefficient matrix after the preset symmetrization operation, is the target voltage coefficient matrix after the preset symmetrization operation, ΔI d is the d-axis grid-connected current disturbance, ΔI q is the q-axis grid-connected current disturbance.

[0109] In the application, the specific process for determining the second grid-connected voltage matrix and the second grid-connected current matrix according to the target voltage coefficient matrix and the target current coefficient matrix is as follows: first, determining the d-axis grid-connected current disturbance and the q-axis grid-connected current disturbance of the inverter, then converting the initial instantaneous power small signal model into a target instantaneous power small signal model based on the preset symmetrization operation, the d-axis grid-connected current disturbance, the q-axis grid-connected current disturbance, the target voltage coefficient matrix and the target current coefficient matrix, and finally determining the second grid-connected voltage matrix and the second grid-connected current matrix according to the target instantaneous power small signal model, thereby improving the accuracy of the process for determining the second grid-connected voltage matrix and the second grid-connected current matrix.

[0110] As an optional embodiment, the process for determining the second grid-connected voltage matrix and the second grid-connected current matrix according to the target instantaneous power small signal model comprises:

[0111] determining the target current coefficient matrix after the preset symmetrization operation based on the target instantaneous power small signal model;

[0112] determining the second grid-connected voltage matrix and the second grid-connected current matrix according to the grid-connected point voltage of the inverter, the target current coefficient matrix after the preset symmetrization operation, the first transfer function of the phase-locked loop, the second transfer function of the current loop corresponding to the inverter, the third transfer function of the power loop corresponding to the inverter, the second grid-connected voltage matrix determination formula and the second grid-connected current matrix determination formula;

[0113] wherein the second grid-connected voltage matrix determination formula is: T V-c is the second grid-connected voltage matrix, V m is the grid-connected point voltage, G pll (s) is the first transfer function, G i (s) is the second transfer function, G c (s) is the third transfer function, is the target current coefficient matrix after the preset symmetrization operation;

[0114] the second grid-connected current matrix determination formula is: I-c T m = [1.5V c G i (s)G I-c (s)]E; T I-c is the second grid-connected current matrix, and E is a second-order unit matrix.

[0115] In the application, the specific process for determining the second grid-connected voltage matrix and the second grid-connected current matrix according to the target instantaneous power small signal model is as follows: first, the target current coefficient matrix after preset symmetrization operation is determined based on the target instantaneous power small signal model, and then the grid-connected point voltage of the inverter, the target current coefficient matrix after preset symmetrization operation, the first transfer function of the phase-locked loop, the second transfer function of the current loop corresponding to the inverter, the third transfer function of the power loop corresponding to the inverter are brought into the second grid-connected voltage matrix determination formula and the second grid-connected current matrix determination formula, so that the second grid-connected voltage matrix and the second grid-connected current matrix can be accurately determined.

[0116] It should be noted that V m is the PCC grid-connected point voltage, and in the numerical value V m ≈V d , G i (s), G c (s) and G pll (s) are respectively the current loop transfer function, the power loop transfer function and the phase-locked loop transfer function in the Laplace domain.

[0117] As an optional embodiment, the complex impedance of the grid-connected point of the inverter is determined based on the first grid-connected voltage matrix, the first grid-connected current matrix, the second grid-connected voltage matrix and the second grid-connected current matrix, and the method comprises the steps of:

[0118] determining the d-axis grid-connected current disturbance, the q-axis grid-connected current disturbance, the d-axis grid-connected voltage disturbance, the q-axis grid-connected voltage disturbance and the grid-connected point voltage of the inverter;

[0119] constructing an impedance equation based on the grid-connected point voltage, the d-axis grid-connected current disturbance, the q-axis grid-connected current disturbance, the d-axis grid-connected voltage disturbance, the q-axis grid-connected voltage disturbance, the first grid-connected voltage matrix, the first grid-connected current matrix, the second grid-connected voltage matrix and the second grid-connected current matrix, so as to determine the complex impedance according to the solution of the impedance equation;

[0120] wherein the impedance equation is:

[0121] the solution of the impedance equation is:

[0122] wherein, is the complex impedance, j is a preset parameter, is the grid-connected point voltage complex vector of the inverter, is the grid-connected point current complex vector of the inverter.

[0123] In the application, the specific process of determining the complex impedance of the grid-connected point of the inverter based on the first grid-connected voltage matrix, the first grid-connected current matrix, the second grid-connected voltage matrix and the second grid-connected current matrix is that: the d-axis grid-connected current disturbance, the q-axis grid-connected current disturbance, the d-axis grid-connected voltage disturbance, the q-axis grid-connected voltage disturbance and the grid-connected point voltage are determined first, and then the complex impedance is determined according to the determined grid-connected point voltage, the d-axis grid-connected current disturbance, the q-axis grid-connected current disturbance, the d-axis grid-connected voltage disturbance, the q-axis grid-connected voltage disturbance, the first grid-connected voltage matrix, the first grid-connected current matrix, the second grid-connected voltage matrix and the second grid-connected current matrix, so that the accuracy of the complex impedance determination process is improved.

[0124] It should be noted that, and The expression of Where V d (s) is the corrected grid-connected voltage, I d (s) is the corrected grid-connected current.

[0125] It should also be noted that the active power and the reactive power calculated by the classical instantaneous power formula have

[0126] Where is the angle of current leading voltage, V m , I m are the voltage amplitude and the current amplitude of the PCC point respectively.

[0127] The active power and the reactive power calculated by the corrected instantaneous power formula have:

[0128] From the above two formulas, P=P' and Q=-Q' can be obtained. Therefore, the difference between the corrected instantaneous power formula and the classical instantaneous power formula is that the reactive power is the opposite number of each other. It is proved that the corrected instantaneous power formula is feasible in direct power control. In addition, when using the corrected instantaneous power formula, the reactive power reference value in the controller needs to take the opposite number of the actual value.

[0129] Please refer to Figure 7 , Figure 7 The structure diagram of a grid-connected point complex impedance determination device provided by the application is shown in the figure. The device comprises:

[0130] The first determination unit 11 is configured to determine the target voltage coefficient matrix of the phase-locked loop according to the direct-axis grid information corresponding to the inverter and the preset small signal model of the phase-locked loop corresponding to the inverter.

[0131] The second determination unit 12 is configured to determine the inductance corresponding to the inverter.

[0132] The third determination unit 13 is configured to determine the first grid-connected voltage matrix and the first grid-connected current matrix based on the target current coefficient matrix of the phase-locked loop corresponding to the target voltage coefficient matrix and the inductance.

[0133] The fourth determination unit 14 is configured to determine the second grid-connected voltage matrix and the second grid-connected current matrix according to the target voltage coefficient matrix and the target current coefficient matrix.

[0134] The fifth determination unit 15 is configured to determine the complex impedance of the grid-connected point of the inverter based on the first grid-connected voltage matrix, the first grid-connected current matrix, the second grid-connected voltage matrix and the second grid-connected current matrix.

[0135] The grid-connected point complex impedance determination device provided in the embodiment has the same beneficial effects as the method, and thus the description of the embodiments of the grid-connected point complex impedance determination device can refer to the description of the embodiments of the method, which will not be repeated here.

[0136] It should be noted that the application realizes the order reduction of the grid-connected impedance of the grid-connected inverter to SISO complex impedance by modifying the instantaneous power formula without affecting the normal direct power control, and simplifies the system stability analysis process. The application has wide application range and strong universality. The method can obtain the corresponding SISO grid-connected complex impedance of the direct power control type grid-connected inverter under different working conditions and different control parameters. The relationship between the SISO complex impedance and each real physical quantity can be quantified.

[0137] Please refer to Figure 8 , Figure 8 A structural schematic diagram of an electronic device provided by the application is shown in FIG. 1. The electronic device comprises:

[0138] The memory 20 is configured to store a computer program.

[0139] The processor is configured to implement the steps 21 of the grid-connected point complex impedance determination method when executing the computer program.

[0140] The electronic device provided in the embodiment can include but is not limited to a smart phone, a tablet computer, a notebook computer or a desktop computer, etc.

[0141] The processor 21 may include one or more processing cores, such as a quad-core processor or an octa-core processor. The processor 21 may be implemented using at least one of the following hardware forms: Digital Signal Processor (DSP), Field-Programmable Gate Array (FPGA), or Programmable Logic Array (PLA). The processor 21 may also include a main processor and a coprocessor. The main processor, also known as the Central Processing Unit (CPU), is used to process data in the wake-up state; the coprocessor is a low-power processor used to process data in the standby state. In some embodiments, the processor 21 may integrate a Graphics Processing Unit (GPU), which is responsible for rendering and drawing the content to be displayed on the screen. In some embodiments, the processor 21 may also include an Artificial Intelligence (AI) processor, which is used to handle computational operations related to machine learning.

[0142] The memory 20 may include one or more computer-readable storage media, which may be non-transitory. The memory 20 may also include high-speed random access memory and non-volatile memory, such as one or more disk storage devices or flash memory devices. In this embodiment, the memory 20 is used to store at least the following computer program 201, which, after being loaded and executed by the processor 21, is capable of implementing the relevant steps of the grid connection point complex impedance determination method disclosed in any of the foregoing embodiments. In addition, the resources stored in the memory 20 may also include an operating system 202 and data 203, and the storage method may be temporary or permanent storage. The operating system 202 may include Windows, Unix, Linux, etc. The data 203 may include, but is not limited to, the grid connection point complex impedance determination method.

[0143] In some embodiments, the electronic device may further include a display screen 22, an input / output interface 23, a communication interface 24, a power supply 25, and a communication bus 26.

[0144] Those skilled in the art will understand that Figure 8 The structures shown do not constitute a limitation on electronic devices and may include more or fewer components than those shown.

[0145] The embodiment is aimed to provide an electronic device, wherein the memory 20 is used to store a computer program, and the processor 21 is used to execute the computer program to realize the steps of the grid connection point complex impedance determination method, so that the process is more efficient and accurate.

[0146] The embodiment also provides a computer readable storage medium corresponding embodiment, and the computer readable storage medium stores a computer program, and the computer program is executed by the processor to realize the steps of the grid connection point complex impedance determination method.

[0147] It can be understood that if the method in the above embodiment is realized in the form of a software function unit and sold or used as an independent product, it can be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the present application essentially or the part that contributes to the prior art or the whole or part of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium, and executes all or part of the steps of the method of each embodiment of the present application. The foregoing storage medium includes: a U disk, a mobile hard disk, a read-only memory (Read-Only Memory, ROM), a random access memory (Random Access Memory, RAM), a magnetic disk or an optical disk, and various media that can store program codes.

[0148] The computer readable storage medium provided by the embodiment corresponds to the above method, and has the same beneficial effects as the above method. Therefore, the embodiments of the computer readable storage medium part are described with reference to the embodiments of the method part, and will not be described here.

[0149] It should be noted that in the specification, the relationship terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or device. Without more limitations, the element defined by the statement "including a" does not exclude the presence of another identical element in the process, method, article or device including the element.

[0150] The foregoing description of the disclosed embodiments enables a person skilled in the art to make or use the application. Modifications of these embodiments will occur to persons of skill in the art, and that the appended claims are intended to cover all such modifications that do not depart from the true spirit and scope of the application. Therefore, the application is not limited to the embodiments shown but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for determining the complex impedance of a grid connection point, characterized in that, The method comprises the following steps: determining a target voltage coefficient matrix of a phase-locked loop corresponding to the inverter according to the direct-axis grid information corresponding to the inverter and a preset small signal model of the phase-locked loop corresponding to the inverter; determining an inductance corresponding to the inverter; determining a first grid-connected voltage matrix and a first grid-connected current matrix based on a target current coefficient matrix of the phase-locked loop corresponding to the target voltage coefficient matrix and the inductance; determining a second grid-connected voltage matrix and a second grid-connected current matrix according to the target voltage coefficient matrix and the target current coefficient matrix; determining a complex impedance of a grid-connected point of the inverter based on the first grid-connected voltage matrix, the first grid-connected current matrix, the second grid-connected voltage matrix and the second grid-connected current matrix.

2. The point of common coupling complex impedance determination method as claimed in claim 1, wherein, The method comprises the following steps: determining a d-axis complex phase and a q-axis complex phase of the phase-locked loop; determining the target voltage coefficient matrix according to the d-axis complex phase, the q-axis complex phase, the direct-axis grid information and the preset small signal model.

3. The point of common coupling complex impedance determination method as claimed in claim 2, wherein, The method comprises the following steps: determining a d-axis voltage, a q-axis voltage, a d-axis grid-connected voltage disturbance and a q-axis grid-connected voltage disturbance of the inverter corresponding to the direct-axis grid information according to the direct-axis grid information; determining the target voltage coefficient matrix according to the d-axis complex phase, the q-axis complex phase, the d-axis voltage, the q-axis voltage, the d-axis grid-connected voltage disturbance, the q-axis grid-connected voltage disturbance and the preset small signal model. The preset small signal model is: = ; is a complex phase of the phase-locked loop. The target voltage coefficient matrix is: = ; wherein, is the d-axis complex phase, is the q-axis complex phase, is the first transfer function of the phase-locked loop, is the d-axis voltage, is the q-axis voltage, is the d-axis grid-connected voltage disturbance amount, is the q-axis grid-connected voltage disturbance amount.

4. The point of common coupling complex impedance determination method as claimed in claim 1, wherein, The method comprises the following steps: determining a first transfer function of the phase-locked loop and a second transfer function of a current loop corresponding to the inverter; determining a d-axis grid-connected current and a q-axis grid-connected current of the inverter; determining the first grid-connected voltage matrix and the first grid-connected current matrix according to the d-axis grid-connected current, the q-axis grid-connected current, the target current coefficient matrix, the first transfer function, the second transfer function, the inductance, a first grid-connected voltage matrix determination formula and a first grid-connected current matrix determination formula; The first grid-connected voltage matrix determination formula is: ; The first grid-connected voltage matrix is The first transfer function is The second transfer function is The target current coefficient matrix is The d-axis grid-connected current is The q-axis grid-connected current is The first grid-connected current matrix determination formula is: ; wherein, is the first grid-connected current matrix, is a preset order, is the inductance, is a second-order unit matrix.

5. The point of common coupling complex impedance determination method as claimed in claim 1, wherein, The method comprises the following steps: determining a d-axis grid-connected current disturbance and a q-axis grid-connected current disturbance of the inverter; converting an initial instantaneous power small signal model into a target instantaneous power small signal model based on a preset symmetrization operation, the d-axis grid-connected current disturbance, the q-axis grid-connected current disturbance, the target voltage coefficient matrix and the target current coefficient matrix; determining the second grid-connected voltage matrix and the second grid-connected current matrix according to the target instantaneous power small signal model; The initial instantaneous power small signal model is: = ; is the first power disturbance quantity of the inverter, is the second power disturbance quantity of the inverter, is the target voltage coefficient matrix; The target instantaneous power small signal model is: = + ; wherein, is a third power disturbance quantity of the inverter, is a fourth power disturbance quantity of the inverter, is the target current coefficient matrix after the preset symmetrization operation, is the target voltage coefficient matrix after the preset symmetrization operation, is a d-axis grid-connected current disturbance quantity, is a q-axis grid-connected current disturbance quantity.

6. The point of common coupling complex impedance determination method as claimed in claim 5, wherein, The method comprises the following steps: determine the target current coefficient matrix after the preset symmetrization operation based on the target instantaneous power small signal model; determine the second grid-connected voltage matrix and the second grid-connected current matrix according to the grid-connected point voltage of the inverter, the target current coefficient matrix after the preset symmetrization operation, the first transfer function of the phase-locked loop, the second transfer function of the current loop corresponding to the inverter, the third transfer function of the power loop corresponding to the inverter, a second grid-connected voltage matrix determination formula and a second grid-connected current matrix determination formula; The second grid-connected voltage matrix determination formula is: ; The second grid-connected voltage matrix is The grid point voltage is The first transfer function is The second transfer function is The third transfer function is The target current coefficient matrix after the preset symmetrization operation is The second grid-connected current matrix determination formula is: ; is the second grid-connected current matrix, is a second-order unit matrix.

7. The point of common coupling complex impedance determination method according to any one of claims 1 to 6, wherein, the determination of the complex impedance of the grid-connected point of the inverter based on the first grid-connected voltage matrix, the first grid-connected current matrix, the second grid-connected voltage matrix and the second grid-connected current matrix comprises: determine the d-axis grid-connected current disturbance, the q-axis grid-connected current disturbance, the d-axis grid-connected voltage disturbance, the q-axis grid-connected voltage disturbance and the grid-connected point voltage; construct an impedance equation based on the grid-connected point voltage, the d-axis grid-connected current disturbance, the q-axis grid-connected current disturbance, the d-axis grid-connected voltage disturbance, the q-axis grid-connected voltage disturbance, the first grid-connected voltage matrix, the first grid-connected current matrix, the second grid-connected voltage matrix and the second grid-connected current matrix, so as to determine the complex impedance according to the solution of the impedance equation; The impedance equation is: ; The solution of the impedance equation is: ; wherein, is the d-axis grid voltage disturbance quantity, is the q-axis grid voltage disturbance quantity, is the first grid voltage matrix, is a first transfer function, is a second transfer function, is the d-axis grid current, is the q-axis grid current, is the first grid current matrix, is the inductance, is the d-axis grid current disturbance quantity, is the q-axis grid current disturbance quantity, is the second grid voltage matrix, is the grid point voltage, is a third transfer function, is the second grid current matrix, is the complex impedance, j is a preset parameter, is a grid point voltage complex vector of the inverter, is a grid point current complex vector of the inverter.

8. A point of common coupling complex impedance determination apparatus characterized by, comprise: a first determination unit configured to determine a target voltage coefficient matrix of the phase-locked loop according to the direct-axis grid information corresponding to the inverter and a preset small signal model of the phase-locked loop corresponding to the inverter; a second determination unit configured to determine the inductance corresponding to the inverter; a third determination unit configured to determine a first grid-connected voltage matrix and a first grid-connected current matrix based on a target current coefficient matrix of the phase-locked loop corresponding to the target voltage coefficient matrix and the inductance; a fourth determination unit configured to determine a second grid-connected voltage matrix and a second grid-connected current matrix according to the target voltage coefficient matrix and the target current coefficient matrix; a fifth determination unit configured to determine the complex impedance of the grid-connected point of the inverter based on the first grid-connected voltage matrix, the first grid-connected current matrix, the second grid-connected voltage matrix and the second grid-connected current matrix.

9. An electronic device, comprising: comprise: a memory configured to store a computer program; a processor configured to implement the steps of the grid-connected point complex impedance determination method according to any one of claims 1 to 7 when the computer program is executed.

10. A computer-readable storage medium, characterized in that, The computer program is stored on the computer readable storage medium and is executed by the processor to implement the steps of the grid-connected point complex impedance determination method according to any one of claims 1 to 7.

Images