Impedance modeling method and device of grid-connected converter system and grid-connected system

Abstract

The invention relates to an impedance modeling method and device of a grid-connected converter system, a grid-connected system, computer equipment and a computer readable storage medium. The grid-connected converter system comprises a converter and a filtering module which are connected, the converter is used for connecting a direct-current power supply end, and the filtering module is used for connecting a power grid; the method comprises the steps of injecting a disturbance signal corresponding to a target operation parameter into a grid-connected point in a process that a grid-connected converter system operates at the target operation parameter; the grid-connected point is a connection point of the filtering module and a power grid; obtaining measurement electrical parameters of the grid-connected converter system; determining a transfer function matrix of the converter according to the measured electrical parameters; and determining an impedance model of the grid-connected converter system based on the transfer function matrix of the converter. In the process of constructing the impedance model by adopting the method, the transfer function matrix of the converter is obtained by collecting the real electrical parameters of the grid-connected converter system during operation, and the impedance model of the grid-connected converter system obtained based on the transfer function matrix is more accurate and reliable.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and in particular to an impedance modeling method and device for a grid-connected converter system, a grid-connected system, a computer device, and a computer-readable storage medium. Background Art

[0002] Power systems are usually connected to the grid using grid-connected converters. Under weak grid conditions, the dynamic interaction between multiple power electronic converters and between power electronic converters and the AC grid can easily cause oscillations, which have a great impact on system stability. Therefore, it is necessary to analyze the stability of the power system in order to propose corresponding oscillation suppression strategies.

[0003] When analyzing the stability of the power system, it is necessary to establish an impedance model of the grid-connected converter system, determine the impedance of the grid-connected converter system, and use stability criteria such as the impedance ratio criterion for analysis.

[0004] At present, the impedance model of the grid-connected converter system is often established by impedance mechanism modeling based on theoretical derivation. Impedance mechanism modeling can clearly analyze and derive the impact of each link on the impedance of the grid-connected converter system. Since there are a large number of nonlinear relationships in the grid-connected converter system, it is not easy to analyze, so the mechanism modeling often ignores the influence of modulation. However, ignoring the modulation deviation will reduce the modeling accuracy, resulting in low evaluation reliability when evaluating system stability. Summary of the invention

[0005] Based on this, it is necessary to provide an impedance modeling method, device, grid-connected system, computer equipment and computer-readable storage medium for a grid-connected converter system, which can improve the impedance model accuracy of the grid-connected converter system in response to the above technical problems.

[0006] In a first aspect, the present application provides an impedance modeling method for a grid-connected converter system, wherein the grid-connected converter system comprises a converter and a filter module connected to each other, wherein the converter is used to connect to a DC power supply end, and the filter module is used to connect to a power grid; the method comprises:

[0007] In the process of the grid-connected converter system operating at the target operating parameters, a disturbance signal corresponding to the target operating parameters is injected into the grid-connected point; wherein the grid-connected point is the connection point between the filter module and the power grid;

[0008] Obtaining measured electrical parameters of the grid-connected converter system;

[0009] determining a transfer function matrix of the converter according to the measured electrical parameters;

[0010] An impedance model of the grid-connected converter system is determined based on a transfer function matrix of the converter.

[0011] In one embodiment, the number of the target operating parameters is multiple groups, and the measured electrical parameters include multiple groups of electrical parameters obtained based on each group of the target operating parameters; and determining the transfer function matrix of the converter according to the measured electrical parameters includes:

[0012] Determining a plurality of initial transfer function matrices of the converter according to each group of the measured electrical parameters;

[0013] A transfer function matrix of the converter is determined based on a plurality of the initial transfer function matrices.

[0014] In one embodiment, the number of the disturbance signals is multiple groups; the measured electrical parameters include multiple groups of electrical parameters obtained based on each group of the disturbance signals; and the transfer function matrix of the converter is determined according to the measured electrical parameters; including:

[0015] Screening and processing the measured electrical parameters of each group;

[0016] A transfer function matrix of the converter is determined based on the measured electrical parameters after screening.

[0017] In one embodiment, the method further comprises:

[0018] determining at least one frequency to be measured;

[0019] Determine a group of injection frequencies based on each of the frequencies to be measured and the preset fluctuation frequency value, wherein the group of injection frequencies includes at least two injection frequencies;

[0020] At least one group of disturbance signals is generated based on the injection frequency; the number of groups of disturbance signals is the same as the number of groups of injection frequencies, the number of disturbance signals in the group of disturbance signals is the same as the number of injection frequencies in the group of injection frequencies, and the frequency of each disturbance signal corresponds one-to-one to each injection frequency.

[0021] In one embodiment, the measured electrical parameters include the bridge arm voltage of the grid-connected point and the modulation voltage of the converter; and determining the transfer function matrix of the converter according to the measured electrical parameters includes:

[0022] Extracting the fundamental wave signal of the bridge arm voltage of the grid connection point, and determining the phase angle difference between the fundamental wave signal and the starting signal;

[0023] Using the phase angle difference as a reference angle, coordinate transformation is performed on the bridge arm voltage of the grid connection point and the modulation voltage of the converter;

[0024] The transfer function matrix of the converter is determined according to the coordinate transformation processing result and a preset transfer function matrix relationship.

[0025] In one embodiment, the method further comprises:

[0026] Inputting a plurality of preset groups of simulation operation parameters into the converter simulation model to obtain a plurality of groups of output results corresponding to each group of the simulation operation parameters; each group of the simulation operation parameters includes a load condition parameter and a power factor;

[0027] The output results of each group are analyzed and aggregated, and the simulation operation parameters that meet the requirements are determined as target operation parameters according to the processing results.

[0028] In a second aspect, the present application further provides an impedance modeling device for a grid-connected converter system, wherein the grid-connected converter system comprises a converter and a filter module connected to each other, wherein the converter is used to connect to a DC power supply end, and the filter module is used to connect to a power grid; the device comprises:

[0029] A disturbance injection module, used for injecting a disturbance signal corresponding to the target operating parameter into a grid connection point when the grid-connected converter system is operating at the target operating parameter; wherein the grid connection point is a connection point between the filter module and the power grid;

[0030] A parameter detection module, used to obtain measured electrical parameters of the grid-connected converter system;

[0031] A function confirmation module, used to determine a transfer function matrix of the converter according to the measured electrical parameters;

[0032] A model building module is used to determine the impedance model of the grid-connected converter system based on the transfer function matrix of the converter.

[0033] In the third aspect, the present application also provides a grid-connected system, including a grid-connected converter system and a grid-connected control system; the grid-connected converter system includes a converter and a filter module connected to each other, the converter is used to connect to a DC power supply end, and the filter module is used to connect to a power grid; the grid-connected control system is connected to the converter, and the grid-connected control system is used to determine the impedance model of the grid-connected converter system based on the method as described above.

[0034] In a fourth aspect, the present application further provides a computer device, comprising a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the following steps are implemented:

[0035] In the process of the grid-connected converter system operating at the target operating parameters, a disturbance signal corresponding to the target operating parameters is injected into the grid-connected point; wherein the grid-connected point is the connection point between the filter module and the power grid;

[0036] Obtaining measured electrical parameters of the grid-connected converter system;

[0037] determining a transfer function matrix of the converter according to the measured electrical parameters;

[0038] An impedance model of the grid-connected converter system is determined based on a transfer function matrix of the converter.

[0039] In a fifth aspect, the present application further provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the following steps are implemented:

[0040] In the process of the grid-connected converter system operating at the target operating parameters, a disturbance signal corresponding to the target operating parameters is injected into the grid-connected point; wherein the grid-connected point is the connection point between the filter module and the power grid;

[0041] Obtaining measured electrical parameters of the grid-connected converter system;

[0042] determining a transfer function matrix of the converter according to the measured electrical parameters;

[0043] An impedance model of the grid-connected converter system is determined based on a transfer function matrix of the converter.

[0044] The impedance modeling method, device, grid-connected system, computer equipment and computer-readable storage medium of the above-mentioned grid-connected converter system, the grid-connected converter system includes a connected converter and a filter module, the converter is used to connect to the DC power supply end, and the filter module is used to connect to the power grid; the impedance modeling method includes: in the process of the grid-connected converter system operating at the target operating parameters, injecting a disturbance signal corresponding to the target operating parameters into the grid-connected point; wherein the grid-connected point is the connection point between the filter module and the power grid; obtaining the measured electrical parameters of the grid-connected converter system; determining the transfer function matrix of the converter according to the measured electrical parameters; and determining the impedance model of the grid-connected converter system based on the transfer function matrix of the converter. Thus, in the process of constructing the impedance model, the transfer function matrix of the converter is obtained by collecting the real electrical parameters when the grid-connected converter system is running, and the transfer function matrix of the converter can accurately reflect the modulation state with high precision. The impedance model of the grid-connected converter system obtained based on this is more accurate and reliable. Furthermore, the stability analysis result of the grid-connected converter is more accurate, which is conducive to proposing more accurate impedance requirements for stable operation or oscillation suppression based on this, and is suitable for occasions with high precision requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the drawings required for use in the embodiments of the present application or related technical descriptions will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0046] Figure 1 A schematic diagram of a module of a grid-connected system in one embodiment;

[0047] Figure 2 A circuit topology diagram of a grid-connected converter system in one embodiment;

[0048] Figure 3 A schematic flow chart of an impedance modeling method for a grid-connected converter system in one embodiment;

[0049] Figure 4 A schematic diagram of operation control of a grid-connected control system in one embodiment;

[0050] Figure 5 A schematic diagram of a flow chart of determining a transfer function matrix of a converter according to measured electrical parameters in one embodiment;

[0051] Figure 6 A schematic diagram of the relationship of an impedance model of a grid-connected converter system in one embodiment;

[0052] Figure 7 A schematic diagram of a flow chart for measuring and calculating a transfer function matrix of a grid-connected converter system at a single frequency point in one embodiment;

[0053] Figure 8 A schematic diagram of a flow chart of measuring and calculating a transfer function matrix of a grid-connected converter system at multiple frequency points in one embodiment;

[0054] Fig. 9 is a simulation diagram of an impedance model of a grid-connected converter system in one embodiment;

[0055] Fig.10 is a structural block diagram of an impedance modeling device for a grid-connected converter system in one embodiment;

[0056] Fig.11 FIG. 4 is a diagram showing the internal structure of a computer device in one embodiment. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0058] The impedance modeling method of the grid-connected converter system provided in the embodiment of the present application can be applied to the grid-connected system. Figure 1 As shown, the grid-connected system includes a grid-connected converter system 100 and a grid-connected control system 200. The grid-connected converter system 100 includes a converter 110 and a filter module 120 connected to each other, the converter 110 is used to connect to the DC power supply end, and the filter module 120 is used to connect to the power grid. The grid-connected control system 200 is connected to the converter 110, and the grid-connected control system 200 is used to inject a disturbance signal corresponding to the target operating parameter into the grid-connected point during the operation of the grid-connected converter system at the target operating parameter; wherein the grid-connected point is the connection point between the filter module and the power grid; obtain the measured electrical parameters of the grid-connected converter system; determine the transfer function matrix of the converter according to the measured electrical parameters; and determine the impedance model of the grid-connected converter system based on the transfer function matrix of the converter.

[0059] The grid-connected control system 200 can be configured according to specific circumstances. For example, the grid-connected control system 200 can be a terminal or a server. The terminal can be, but is not limited to, various personal computers, laptops, tablet computers, etc. The server can be an independent physical server, or a server cluster or distributed system composed of multiple physical servers, or a cloud server that provides cloud computing services.

[0060] In one embodiment, Figure 2 As shown, the filter module 120 includes three-phase filter units A, B, and C respectively, and each filter unit includes an inductor L1, an inductor L2, and a capacitor Cf respectively. The inductor L1, the inductor L2, and the capacitor Cf form an LCL filter. Among them, the first end of the inductor L1 is used to connect to the power grid, the second end of the inductor L1 is connected to the first end of the inductor L2, the second end of the inductor L2 is connected to the converter 110, the first end of the capacitor Cf is connected to the common connection end of the inductor L1 and the inductor L2, and the second ends of the inductors and capacitors Cf in each filter unit are connected. It should be noted that Figure 2 The inductance Lg on the grid side represents the equivalent inductance on the grid side, and ega, egb, and egc represent the three-phase power on the grid side. The DC power supply Udc represents the power supply connected to the DC side, which is represented by an ideal current source in the figure. In actual applications, it can be the DC power provided by devices such as power conversion modules or capacitors.

[0061] In an exemplary embodiment, Figure 3 As shown in FIG. 1 , a method for modeling impedance of a grid-connected converter system is provided. The method is applied to Figure 1 The grid-connected control system 200 in FIG. 1 is taken as an example to illustrate the method, which includes the following steps 302 to 308. Among them:

[0062] Step 302: When the grid-connected converter system is operating at the target operating parameters, a disturbance signal corresponding to the target operating parameters is injected into the grid-connected point.

[0063] The grid connection point is the connection point between the filter module and the grid. Figure 2 In the illustrated embodiment, the connection point between the inductor L1 and the grid-side equivalent inductor Lg is the grid connection point, ie, the point of common coupling (PCC).

[0064] The target operating parameters may be predetermined parameters, such as operating parameters obtained in combination with a converter simulation model. In one embodiment, the target operating parameters include target load operating parameters and target power factor. When the grid-connected converter system stably operates at the target load operating parameters and target power factor, a corresponding disturbance signal is injected into the grid-connected point.

[0065] Among them, the disturbance signal is a small disturbance signal. In the power system, small disturbances have little impact on the system and usually do not cause large fluctuations or instability in the system, but can still be used to evaluate the stability and dynamic response characteristics of the system.

[0066] In this embodiment, while the grid-connected converter system is stably operating at the target load operating parameters and the target power factor, a corresponding small disturbance signal is injected into the grid connection point. This can prevent the system from experiencing excessive fluctuations or instability due to sudden changes, and can make the measurement of electrical parameters more accurate and reliable, thereby avoiding inaccurate measurements caused by unstable system operation.

[0067] Step 304, obtaining measured electrical parameters of the grid-connected converter system.

[0068] The measured electrical parameters include the bridge arm voltage at the grid connection point and the modulation voltage of the converter.

[0069] In some embodiments, the grid-connected system further comprises a detection module connected to the grid-connected control system, and the detection module is used to detect the bridge arm voltage of the grid-connected point and the modulation voltage of the converter.

[0070] In some embodiments, the detection module is used to detect the bridge arm voltage and bridge arm current (the current on the inductor L2) of the grid-connected point, and transmit them to the grid-connected control system. 2abc (including the bridge arm current i of the three phases A, B, and C 2a 、i 2b 、i 2c ) to transform the coordinates to obtain the current i in dq coordinates 2d 、i 2q At the same time, the grid-connected control system controls the bridge arm voltage u oabc(including the bridge arm voltage u of the three phases A, B, and C oa 、u ob 、u oc ) to transform the coordinates to obtain the voltage u in dq coordinates d and u q .

[0071] The grid-connected control system adopts Figure 4 The operation control logic shown in the figure is 2d 、i 2q and voltage u d 、u q Perform calculation to obtain the modulation voltage u dref and u qref . Among them, ω0 represents 50 Hz; L2 represents Figure 2 The inductance value of the inductor L2; H i represents the current loop controller, which is expressed as formula (1):

[0072] (1)

[0073] In formula (1), k ip Represents the current loop controller proportional coefficient, k ii represents the integral coefficient of the current loop controller, s represents the S domain, k ip and k ii Both can be given values.

[0074] Specifically, the current i 2d and a given reference current i 2d *After multiplication, the current loop controller H i After the operation, the first operation result is obtained; the current i 2q The second operation result is obtained by multiplying ω0 and the inductance value L2. The first operation result and the second operation result are multiplied by the voltage u d After multiplication, the modulation voltage u is obtained dref .

[0075] Current i 2q and a given reference current i 2q *After multiplication, the current loop controller H i After the operation, the third operation result is obtained; the current i 2d The fourth operation result is obtained by multiplying the third operation result and the fourth operation result with the voltage u q After multiplication, the modulation voltage u is obtained qref .

[0076] Step 306: Determine a transfer function matrix of the converter according to the measured electrical parameters.

[0077] like Figure 5As shown, determining the transfer function matrix of the converter according to the measured electrical parameters may include steps 502 to 506.

[0078] Step 502: extract the fundamental wave signal of the bridge arm voltage of the grid connection point, and determine the phase angle difference between the fundamental wave signal and the start signal.

[0079] Step 504: Using the phase angle difference as a reference angle, coordinate transformation is performed on the bridge arm voltage at the grid connection point and the modulation voltage of the converter.

[0080] The bridge arm voltage of the grid connection point includes the A-phase bridge arm voltage, the B-phase bridge arm voltage and the C-phase bridge arm voltage. When determining the reference angle, the bridge arm voltage of one of the phases can be used to determine it. Exemplarily, the phase angle difference θ of the A-phase fundamental voltage of the A-phase bridge arm voltage relative to the starting signal is extracted by Fourier decomposition, and this is used as the reference angle for abc / dq transformation. The starting signal is the signal when the system is running stably before the disturbance signal is injected.

[0081] Using the phase angle difference as the reference angle, the bridge arm voltage at the grid connection point is transformed by abc / dq to obtain the bridge arm voltage u in the dq coordinate system. od and u op .

[0082] Step 506: determine the transfer function matrix of the converter according to the coordinate transformation processing result and a preset transfer function matrix relationship.

[0083] The preset transfer function matrix relationship can be expressed as equation (2):

[0084] (2);

[0085] Among them, Δ represents the small signal amount, that is, the disturbance amount.

[0086] Thus, combined with the bridge arm voltage u in the dq coordinate system od and u op , modulation voltage u dref and uqref and equation (2) to obtain the converter transfer function matrix G PWM .

[0087] Step 308: Determine the impedance model of the grid-connected converter system based on the transfer function matrix of the converter.

[0088] For example, the grid-connected control system is based on the transfer function matrix G of the converter. PWM The transfer function matrix determined by the filter circuit is GL and YL, the transfer function matrix of the current loop controller is Gc, and the transfer function matrix G that characterizes the effect of the phase-locked error on the current positive conversion is i PLL, the transfer function matrix G that characterizes the effect of phase-locked error on the inverse transformation of voltage control quantity d PLL , and get Figure 6 The impedance model of the grid-connected converter system is shown.

[0089] It can be understood that the grid-connected control system includes a phase-locked loop control module, a current loop control module, and a modulation control module. The phase loop control module, the current loop control module, and the modulation control module can be implemented using a hardware module or a software module, and the specific implementation method does not need to be limited.

[0090] If the control mode of the grid-connected control system is single current loop control, the current loop command can be given according to actual requirements; if the control mode of the grid-connected control system is DC voltage outer loop and AC inner loop dual loop control or virtual synchronous machine control, the current loop command is the output of the outer loop control; the current loop command is used to control the current loop by taking the difference between the current loop command and the grid-connected point output current. That is, the input end of the current loop control module is the difference between the control command and the grid-connected point output current, and the output end is compared with the output end of the filter. The current loop controller expression of the current loop control module is formula (1).

[0091] The transfer function matrices determined by the filter circuit are GL and YL, where YL is the filter inductance admittance matrix and GL is the product of YL and the negative unit matrix;

[0092] (3)

[0093] Where Δ represents the small signal quantity, i.e., the disturbance quantity; the subscripts d and q represent the d-axis and q-axis components; I 2d ,I 2q Represents the component of the inductor L2 current in the dq coordinate system; I 1d ,I 1q represents the component of the inductor L1 current in the dq coordinate system; U d , U q Indicates the filter capacitor C f The components of the voltage in the dq coordinate system. ω represents the output angular frequency of the control system phase-locked loop; ω0 represents the angular frequency of the grid-connected converter system; L1 represents the inductance value of the inductor L1, C f Indicates capacitor filter capacitor C f The capacitance value of L2, L2 represents the inductance value of inductor L2; u pcc Indicates the voltage at the grid connection point.

[0094] The transfer function matrix determined by the current loop controller is Gc, which is expressed as formula (4):

[0095] (4).

[0096] The transfer function matrix that characterizes the influence of PLL phase-locking error on the control link is G PLL , which is expressed as formula (5):

[0097] (5);

[0098] Where Upccd represents the d-axis component of the common point voltage; T PLL represents the transfer function of the phase-locked loop PI controller, T PLL The expression of is formula (6):

[0099] (6);

[0100] Among them, k PLLp Represents the proportional coefficient of the phase-locked loop controller; k PLLi Represents the integral coefficient of the phase-locked loop controller.

[0101] The transfer function matrix that characterizes the effect of phase-locked error on current forward transformation is G i PLL The transfer function matrix that characterizes the effect of phase-locked error on the inverse transformation of voltage control quantity is G d PLL , the expressions are respectively:

[0102] (7);

[0103] (8);

[0104] Among them, I pccq ,I pccd Respectively represent the grid-connected current I pcc Components in the dq coordinate system.

[0105] Specifically, GL can be obtained according to equation (3), and the filter inductance admittance matrix YL can be obtained by inverting GL; the transfer function matrix G that represents the influence of PLL phase-locked error on the control link can be obtained through equations (5) and (6): PLL ; by G PLL , combined with equation (7) and equation (8), we can obtain the transfer function matrix G that characterizes the effect of phase-locked error on current forward transformation: i PLL The transfer function matrix G that characterizes the effect of phase-locked error on the inverse transformation of voltage control quantity d PLL ; The transfer function matrix G determined by the current loop controller can be obtained by formula (4) and formula (1): c ; Then get the small signal block diagram; Combined with the transfer function matrix G of the converter obtained based on the measured data PWM , and obtain the final impedance model of the grid-connected converter system.

[0106] Please refer again Figure 6 In the impedance model of the grid-connected converter system, the voltage small signal Δu PCCdq And the small signal of grid-connected current Δi PCCdq When voltage is used as excitation and current is used as response, the dq admittance of the converter system can be obtained through the impedance model of the grid-connected converter system; conversely, when current is used as excitation and voltage is used as response, the dq impedance of the converter system can be obtained. In this way, the impedance analysis of the converter system is realized.

[0107] In the impedance modeling method of the above-mentioned grid-connected converter system, during the process of constructing the impedance model, the transfer function matrix of the converter is obtained by collecting the real electrical parameters of the grid-connected converter system during operation. The transfer function matrix of the converter can accurately reflect the modulation state with high precision. The impedance model of the grid-connected converter system obtained based on this is more accurate and reliable. Furthermore, the impedance analysis results of the grid-connected converter are more reliable, and the stability analysis results are more accurate, which is conducive to proposing more precise impedance requirements for stable operation or oscillation suppression based on this, and is suitable for occasions with high precision requirements.

[0108] In one embodiment, the number of disturbance signals is one group; one group of disturbance signals includes two disturbance signals. The impedance modeling method of the grid-connected converter system also includes the following steps:

[0109] Step 1, determine the frequency to be tested;

[0110] Step 2, determining a group of injection frequencies based on the frequency to be measured and the preset fluctuation frequency value, wherein the group of injection frequencies includes two injection frequencies;

[0111] Step 3: Generate a set of disturbance signals based on the set of injection frequencies; the frequency of each disturbance signal corresponds to each injection frequency one by one.

[0112] Among them, the frequency to be measured and the preset fluctuation frequency value can be set according to the specific situation. The first injection frequency in a group of injection frequencies can be the sum of the frequency to be measured and the preset fluctuation frequency value, and the second injection frequency can be the difference between the frequency to be measured and the preset fluctuation frequency value.

[0113] For example, please refer to Figure 7 , determine the frequency to be measured is f m , the preset fluctuation frequency value is f0, then a set of injection frequencies f I The first injection frequency f i1 and the second injection frequency f i2 They are:

[0114]

[0115] A small disturbance signal with a frequency of the first injection frequency fi1 is determined as the first disturbance signal, and a small disturbance signal with a frequency of the second injection frequency fi2 is determined as the second disturbance signal.

[0116] Then, the first disturbance signal and the second disturbance signal in this group of disturbance signals are respectively injected into the grid-connected point of one phase, such as the grid-connected point of phase A, and the first measured electrical parameter of the grid-connected converter system after the injection of the first disturbance signal and the second measured electrical parameter after the injection of the second disturbance signal are obtained; the first measured electrical parameter and the second measured electrical parameter are saved.

[0117] The first measured electrical parameter and the second measured electrical parameter both include: a bridge arm voltage at the grid connection point and a modulation voltage. The bridge arm voltage at the grid connection point includes a bridge arm voltage U OA , B phase bridge arm voltage U OB and C phase bridge arm voltage U OC The modulation voltage of the converter includes the A phase modulation voltage U refa , B phase modulation voltage U refb and C phase modulation voltage U refc .

[0118] After determining the reference angle θ based on the A-phase bridge arm voltage, the first measured electrical parameter and the second electrical parameter are transformed into abc-dq coordinates. Then, the amplitude and phase transformation results of the bridge arm voltage and the modulation voltage at the measured frequency fm are extracted, and combined with the above formula (2), the transfer function matrix G of the converter at the measured frequency fm can be obtained: PWM .

[0119] This enables the measurement and calculation of the transfer function matrix (G PWM ), since the transfer function matrix G PWM It is obtained by collecting the real electrical parameters of the grid-connected converter system during operation, so it has high accuracy.

[0120] In one embodiment, the number of disturbance signals is multiple groups. The impedance modeling method of the grid-connected converter system also includes the following steps:

[0121] Step 1, determining at least one frequency to be measured;

[0122] Step 2, determining a group of injection frequencies based on each frequency to be measured and a preset fluctuation frequency value, wherein the group of injection frequencies includes at least two injection frequencies;

[0123] Step 3: generating at least one set of disturbance signals based on the injection frequency.

[0124] The number of disturbance signal groups is the same as the number of injection frequency groups, the number of disturbance signals in a disturbance signal group is the same as the number of injection frequencies in a injection frequency group, and the frequency of each disturbance signal corresponds to each injection frequency one by one.

[0125] Still taking the example that a group of injection frequencies determined by a frequency to be measured includes two injection frequencies, after determining that n (n is a positive integer) frequencies to be measured are obtained, n groups of injection frequencies can be obtained, each group of injection frequencies includes a first injection frequency and a second injection frequency, the first injection frequency is the sum of the frequency to be measured and the preset fluctuation frequency value, and the second injection frequency is the difference between the frequency to be measured and the preset fluctuation frequency value. Then, n groups of disturbance signals are obtained according to the n groups of injection frequencies.

[0126] The first disturbance signal and the second disturbance signal in the n groups of disturbance signals are injected into the grid connection point respectively, and the measured electrical parameters of the grid-connected converter system after the injection of 2n disturbance signals are obtained; after coordinate transformation of each measured electrical parameter, the amplitude and phase transformation results of each bridge arm voltage and modulation voltage are extracted, and combined with the above formula (2), the transfer function matrix G of the converter can be obtained: PWM .

[0127] Thus, the transfer function matrix (G PWM ), since the transfer function matrix G PWM It is calculated by collecting multiple sets of real electrical parameters when the grid-connected converter system is running, so it has high accuracy.

[0128] In some embodiments, please combine Figure 8 Among the n frequencies to be tested, the frequency difference between two adjacent frequencies to be tested is a preset fluctuation frequency value; after obtaining n groups of injection frequencies according to the n frequencies to be tested, the repeated frequencies in the n groups of injection frequencies can be deleted, and n+1 disturbance signals can be obtained based on the remaining n+1 injection frequencies.

[0129] The n+1 disturbance signals are respectively injected into the grid-connected point of phase A, and the measured electrical parameters of the grid-connected converter system are obtained after the injection of each disturbance signal.

[0130] After determining the reference angle θ based on the A-phase bridge arm voltage, perform abc-dq coordinate transformation on each data in the measured electrical parameters, and then extract the amplitude and phase transformation results of each bridge arm voltage and modulation voltage. Combined with the above formula (2), the transfer function matrix G of the converter can be obtained: PWM .

[0131] In this embodiment, by deleting repeated injection frequencies, repeated injection processes, repeated signal collection and calculation processes can be reduced, thereby improving the efficiency of model determination.

[0132] In some embodiments, when there are multiple groups of disturbance signals, measuring the electrical parameters includes multiple groups of electrical parameters obtained based on each group of disturbance signals; step 306 may include the following steps:

[0133] Step 1, screening and processing each group of measured electrical parameters;

[0134] Step 2: Determine the transfer function matrix of the converter based on the measured electrical parameters after screening.

[0135] Further, the process of screening each group of measured electrical parameters may include: using Z-Score standardization to standardize each group of measured electrical parameters, and calculating the Z score of each bridge arm voltage of each grid-connected point and the modulation voltage data point of the converter, and the expression of the Z score is:

[0136] ; Where x represents the data to be processed, μ represents the mean of the data, and σ represents the standard deviation.

[0137] If the absolute value of the bridge arm voltage at the grid connection point or the modulation voltage data point of the converter exceeds the preset threshold (such as 2 or 3), it is regarded as an abnormal value. Then the measured electrical parameter group where the abnormal value is located is deleted, which can reduce the subsequent calculation amount on the one hand, and on the other hand, the transfer function matrix obtained based on the screened data is more accurate and reliable.

[0138] Among them, the method for determining the transfer function matrix of the converter based on the measured electrical parameters after screening can refer to the above embodiment, firstly, coordinate transformation is performed on each group of measured electrical parameters after screening, and then the amplitude and phase transformation results of each bridge arm voltage and modulation voltage are extracted, and the transfer function matrix of the converter is obtained by combining formula (2).

[0139] Among them, the number of target operating parameters can be a group. When the grid-connected converter system stably operates within this group of target operating parameters, multiple frequency points can be used to measure and calculate the transfer function matrix of the grid-connected converter system, or a single frequency point can be used to measure and calculate the transfer function matrix of the grid-connected converter system. The specific design can be based on actual conditions.

[0140] In one embodiment, the number of target operating parameters is multiple groups, and the measured electrical parameters include multiple groups of electrical parameters obtained based on each group of target operating parameters. Step 306 may include the following steps:

[0141] Step 1, determining a plurality of initial transfer function matrices of the converter according to each group of measured electrical parameters;

[0142] Step 2: determining a transfer function matrix of the converter based on a plurality of initial transfer function matrices.

[0143] In actual implementation, when there are multiple groups of target operating parameters, when the grid-connected converter system is stably operating in each group of target operating parameters, a single frequency point can be used to measure and calculate the transfer function matrix of the grid-connected converter system to obtain multiple initial transfer function matrices corresponding to each group of target operating parameters, and then the transfer function matrix of the converter is determined based on the multiple initial transfer function matrices. Alternatively, multiple frequency points can be used to measure and calculate the transfer function matrix of the grid-connected converter system to obtain multiple initial transfer function matrices, and then the transfer function matrix of the converter is determined based on the multiple initial transfer function matrices.

[0144] In this embodiment, by operating the grid-connected converter system under multiple sets of target operating parameters to obtain multiple initial transfer function matrices, the accuracy of the final converter transfer function matrix can be improved.

[0145] In one embodiment, the impedance modeling method of the grid-connected converter system further includes the following steps:

[0146] Step 1, inputting a plurality of preset groups of simulation operation parameters into the converter simulation model, and obtaining a plurality of groups of output results corresponding to each group of simulation operation parameters;

[0147] Step 2: Analyze and aggregate the output results of each group, and determine the simulation operation parameters that meet the requirements as the target operation parameters based on the processing results.

[0148] Each set of simulation operation parameters includes load condition parameters and power factor. The load condition and power factor can be randomly generated or set by professionals based on experience. The preset multiple sets of simulation operation parameters can be a combination of different load conditions and power factors.

[0149] The converter simulation model can be a trained neural network. By inputting multiple preset sets of simulation operation parameters into the converter simulation model, the output results of the grid-connected converter corresponding to each set of simulation operation parameters can be obtained. Each set of output results can include parameters such as power, efficiency, and current waveform. The grid-connected control system stores the multiple sets of output results generated by the simulation for subsequent aggregate analysis.

[0150] When analyzing and aggregating each group of output results, a clustering algorithm can be used to analyze and aggregate the output results to find a combination of load conditions and power factors that meet the requirements, and use the combination as the target operating parameter. For example, if each parameter in multiple groups of output results meets a certain mathematical relationship, such as a linear relationship, it is determined that the simulation operating parameters corresponding to the multiple groups of output results meet the requirements.

[0151] In this embodiment, simulated operating parameters that meet the requirements are used as target operating parameters, so that the actual measured electrical parameters are more regular and the obtained transfer function matrix of the converter is more accurate.

[0152] In an optional embodiment, the process of constructing the converter simulation model may include the following steps:

[0153] Step 1, data preparation and simulation modeling: prepare the simulation data of the grid-connected converter system and define the load conditions and power factor.

[0154] Step 2, neural network training and generation: Use simulation data to train the neural network so that it can generate new load conditions and power factor combinations and predict output results.

[0155] Among them, the training and generation of neural networks include: defining the neural network structure, data training and verification, and neural network testing and tuning.

[0156] Regarding the definition of the neural network structure, it includes an input layer, a hidden layer, and an output layer. Specifically, the input layer: the characteristics of the load conditions (such as load type, load power, voltage and current, etc.); the range of the power factor (such as different factors such as 0.8, 0.9, 1, etc.). Hidden layer: The deep neural network (DNN) structure or the convolutional neural network (CNN) structure can be used to capture the complex nonlinear relationship of the input data. Two to three hidden layers can be selected according to the complexity. Output layer: The output results of the grid-connected converter system, such as power output, efficiency, current waveform, harmonic distortion, etc.

[0157] Regarding data training and verification, it includes: inputting existing simulation data (load conditions, power factor as input, and converter output as label) into the neural network for training; loss function: using mean square error (MSE) or other suitable loss functions to minimize the error between the results predicted by the neural network and the results of the simulation data; optimization algorithm: using the optimization algorithm to update the weights.

[0158] Regarding neural network testing and tuning, it includes: after training is completed, using a validation data set to evaluate the accuracy of the neural network, and tuning the network based on the test results to obtain a converter simulation model.

[0159] In order to better understand the above embodiment, a detailed explanation is given below in conjunction with an optional embodiment. Figure 2 The circuit topology shown, and Figure 4 The control strategy shown in the figure. Among them, the converter has no limit on level and structure; the inner loop of the control strategy adopts current loop control, and the outer loop control is not limited; the modulation strategy is not limited.

[0160] In actual implementation, the specific data may be a grid voltage of 110V, a DC side voltage of 200V, a grid side filter inductor of 5mH, a filter resistor of 2.9uF, a converter side filter inductor of 10mH, and a switching frequency of 10kHz.

[0161] By inputting a randomly generated combination of load condition parameters and power factor into the converter simulation model, multiple groups of output results corresponding to each group of simulated operating parameters are obtained; each group of output results is analyzed and aggregated, and multiple simulated operating parameters that meet the requirements are determined as multiple target operating parameters based on the processing results.

[0162] In the process of the grid-connected converter system operating at each set of target operating parameters, a transfer function matrix of the grid-connected converter system is measured and calculated using multiple frequency points. Specifically, after determining that n frequencies to be measured are obtained, n groups of injection frequencies are obtained according to the n frequencies to be measured, repeated frequencies in the n groups of injection frequencies are deleted, and n+1 disturbance signals are obtained based on the remaining n+1 injection frequencies.

[0163] The n+1 disturbance signals are respectively injected into the grid-connected point of phase A, and the measured electrical parameters of the grid-connected converter system after the injection of each disturbance signal (including the bridge arm voltage at the grid-connected point and the modulation voltage of the converter) are obtained.

[0164] Based on the A-phase bridge arm voltage, the reference angle θ is determined. The data in the measured electrical parameters are transformed into abc-dq coordinates. Then, the amplitude and phase transformation results of each bridge arm voltage and modulation voltage are extracted. Combined with the above formula (2), the transfer function matrix G of the converter is obtained: PWM .

[0165] According to equation (3), GL can be obtained. By inverting GL, the filter inductance admittance matrix YL can be obtained. By equations (5) and (6), the transfer function matrix G that represents the influence of PLL phase-locked error on the control link can be obtained. PLL ; by G PLL , combined with equation (7) and equation (8), we can obtain the transfer function matrix G that characterizes the effect of phase-locked error on current forward transformation: i PLL The transfer function matrix G that characterizes the effect of phase-locked error on the inverse transformation of voltage control quantity d PLL ; The transfer function matrix Gc determined by the current loop controller can be obtained by using equations (4) and (1); and then combined with the transfer function matrix Gc of the converter PWM , and obtain the final impedance model of the grid-connected converter system.

[0166] The impedance model of the grid-connected converter system is an impedance module obtained by hybrid modeling of grid-connected converter impedance experiment and mechanism considering modulation deviation. The impedance model obtained by the hybrid modeling and the detailed simulation results are shown in the figure below. Fig. 9 As shown in the figure, the goodness of fit under different working conditions is above 0.995.

[0167] The impedance modeling method of the above-mentioned grid-connected converter system considers modulation deviation and combines the grid-connected converter impedance experiment-mechanism modeling to obtain an impedance model. The impedance model retains the control mechanism and is convenient for oscillation analysis and suppression strategy research.

[0168] The impedance modeling method of the grid-connected converter system has high modeling accuracy, and the stability analysis result of the grid-connected converter is more accurate, which is conducive to proposing more accurate impedance requirements for stable operation or oscillation suppression based on this. It is suitable for occasions with high accuracy requirements.

[0169] It should be understood that, although the various steps in the flowcharts involved in the above-mentioned embodiments are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear explanation in this article, the execution of these steps does not have a strict order restriction, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above-mentioned embodiments can include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the steps or stages in other steps.

[0170] Based on the same inventive concept, the embodiment of the present application also provides an impedance modeling device for a grid-connected converter system for implementing the impedance modeling method for the grid-connected converter system involved above. The implementation scheme for solving the problem provided by the device is similar to the implementation scheme recorded in the above method, so the specific limitations in the embodiments of the impedance modeling device for one or more grid-connected converter systems provided below can refer to the limitations of the impedance modeling method for the grid-connected converter system above, and will not be repeated here.

[0171] In an exemplary embodiment, Fig.10 As shown, an impedance modeling device for a grid-connected converter system is provided, comprising: a disturbance injection module 602, a parameter detection module 604, a function confirmation module 606 and a model construction module 608, wherein:

[0172] The disturbance injection module 602 is used to inject a disturbance signal corresponding to the target operating parameter into the grid connection point when the grid-connected converter system is operating at the target operating parameter; wherein the grid connection point is the connection point between the filter module and the power grid;

[0173] The parameter detection module 604 is used to obtain the measured electrical parameters of the grid-connected converter system;

[0174] Function confirmation module 606, used to determine the transfer function matrix of the converter according to the measured electrical parameters;

[0175] The model building module 608 is used to determine the impedance model of the grid-connected converter system based on the transfer function matrix of the converter.

[0176] In one embodiment, the model building module 608 is further configured to determine a plurality of initial transfer function matrices of the converter according to each set of measured electrical parameters; and determine the transfer function matrix of the converter based on the plurality of initial transfer function matrices.

[0177] In one embodiment, the model building module 608 is further used to screen each group of measured electrical parameters; determine an initial transfer function matrix of the converter based on the screened measured electrical parameters; and determine a transfer function matrix of the converter based on the initial transfer function matrix.

[0178] In one embodiment, the model building module 608 is also used to determine at least one frequency to be measured; determine a group of injection frequencies based on each frequency to be measured and a preset fluctuation frequency value, wherein a group of injection frequencies includes at least two injection frequencies; generate at least one group of disturbance signals based on the injection frequencies; the number of groups of disturbance signals is the same as the number of groups of injection frequencies, the number of disturbance signals in a group of disturbance signals is the same as the number of injection frequencies in a group of injection frequencies, and the frequency of each disturbance signal corresponds one-to-one to each injection frequency.

[0179] In one embodiment, the model building module 608 is also used to extract the fundamental signal of the bridge arm voltage of the grid-connected point and determine the phase angle difference between the fundamental signal and the starting signal; using the phase angle difference as a reference angle, coordinate transformation is performed on the bridge arm voltage of the grid-connected point and the modulation voltage of the converter; and the transfer function matrix of the converter is determined according to the coordinate transformation processing result and a preset transfer function matrix relationship.

[0180] In one embodiment, the model building module 608 is also used to input multiple sets of preset simulation operating parameters into the converter simulation model to obtain multiple sets of output results corresponding to each set of simulation operating parameters; each set of simulation operating parameters includes load operating condition parameters and power factor; each set of output results is analyzed and aggregated, and the simulation operating parameters that meet the requirements are determined as target operating parameters based on the processing results.

[0181] Each module in the impedance modeling device of the above-mentioned grid-connected converter system can be implemented in whole or in part by software, hardware and a combination thereof. Each of the above-mentioned modules can be embedded in or independent of a processor in a computer device in the form of hardware, or can be stored in a memory in a computer device in the form of software, so that the processor can call and execute operations corresponding to each of the above modules.

[0182] In an exemplary embodiment, a grid-connected system is provided. Figure 1 The grid-connected system includes a grid-connected converter system 100 and a grid-connected control system 200. The grid-connected converter system 100 includes a converter 110 and a filter module 120 connected to each other. The converter 110 is used to connect to a DC power supply terminal, and the filter module is used to connect to a power grid. The grid-connected control system 200 is connected to the converter 110.

[0183] The grid-connected control system 200 can be configured according to specific circumstances. For example, the grid-connected control system 200 can be a terminal or a server. The terminal can be, but is not limited to, various personal computers, laptops, tablet computers, etc. The server can be an independent physical server, or a server cluster or distributed system composed of multiple physical servers, or a cloud server that provides cloud computing services.

[0184] In one embodiment, Figure 2 As shown, the filter module 120 includes three-phase filter units A, B, and C, and each filter unit includes an inductor L1, an inductor L2, and a capacitor Cf. The first end of the inductor L1 is used to connect to the power grid, the second end of the inductor L1 is connected to the first end of the inductor L2, the second end of the inductor L2 is connected to the converter 110, the first end of the capacitor Cf is connected to the common connection end of the inductor L1 and the inductor L2, and the second ends of the inductors and capacitors Cf in each filter unit are connected. It should be noted that Figure 2 The inductance Lg on the grid side represents the equivalent inductance on the grid side, and ega, egb, and egc represent the three-phase power on the grid side. The DC power supply Udc represents the power supply connected to the DC side, which is represented by an ideal current source in the figure. In actual applications, it can be the DC power provided by devices such as power conversion modules or capacitors.

[0185] The grid-connected control system 200 determines the impedance model of the grid-connected converter system based on the methods in the above-mentioned embodiments of the impedance modeling method for the grid-connected converter system.

[0186] In an exemplary embodiment, a computer device is provided. The computer device may be a server, and its internal structure diagram may be as shown in FIG. Fig.11As shown. The computer device includes a processor, a memory, an input / output interface (Input / Output, referred to as I / O) and a communication interface. Among them, the processor, the memory and the input / output interface are connected through a system bus, and the communication interface is connected to the system bus through the input / output interface. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the computer device is used to store relevant data. The input / output interface of the computer device is used to exchange information between the processor and an external device. The communication interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, an impedance modeling method of a grid-connected converter system is implemented.

[0187] Those skilled in the art will understand that Fig.11 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0188] In one embodiment, a computer device is further provided, including a memory and a processor, wherein a computer program is stored in the memory, and the processor implements the steps in the above-mentioned method embodiments when executing the computer program.

[0189] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps in the above-mentioned method embodiments are implemented.

[0190] A person of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment method can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to the memory, database or other medium used in the embodiments provided in the present application can include at least one of non-volatile memory and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. As an illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The database involved in each embodiment provided in this application may include at least one of a relational database and a non-relational database. Non-relational databases may include distributed databases based on blockchains, etc., but are not limited to this. The processor involved in each embodiment provided in this application may be a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, an artificial intelligence (AI) processor, etc., but are not limited to this.

[0191] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this application.

[0192] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. An impedance modeling method for a grid-connected converter system, characterized in that: The grid-connected converter system comprises a converter and a filter module connected to each other, wherein the converter is used to connect to a DC power supply terminal, and the filter module is used to connect to a power grid; the method comprises: In the process of the grid-connected converter system operating at the target operating parameters, a disturbance signal corresponding to the target operating parameters is injected into the grid-connected point; wherein the grid-connected point is the connection point between the filter module and the power grid; Obtaining measured electrical parameters of the grid-connected converter system; determining a transfer function matrix of the converter according to the measured electrical parameters; An impedance model of the grid-connected converter system is determined based on a transfer function matrix of the converter.

2. The method according to claim 1, characterized in that The number of the target operating parameters is multiple groups, and the measured electrical parameters include multiple groups of electrical parameters obtained based on each group of the target operating parameters; Determining the transfer function matrix of the converter according to the measured electrical parameters includes: Determining a plurality of initial transfer function matrices of the converter according to each group of the measured electrical parameters; A transfer function matrix of the converter is determined based on a plurality of the initial transfer function matrices.

3. The method according to claim 1, characterized in that The number of the disturbance signals is multiple groups; the measured electrical parameters include multiple groups of electrical parameters obtained based on each group of the disturbance signals; the transfer function matrix of the converter is determined according to the measured electrical parameters; including: Screening and processing the measured electrical parameters of each group; A transfer function matrix of the converter is determined based on the measured electrical parameters after screening.

4. The method according to claim 3, characterized in that The method further comprises: determining at least one frequency to be measured; Determine a group of injection frequencies based on each of the frequencies to be measured and the preset fluctuation frequency value, wherein the group of injection frequencies includes at least two injection frequencies; At least one group of disturbance signals is generated based on the injection frequency; the number of groups of disturbance signals is the same as the number of groups of injection frequencies, the number of disturbance signals in the group of disturbance signals is the same as the number of injection frequencies in the group of injection frequencies, and the frequency of each disturbance signal corresponds one-to-one to each injection frequency.

5. The method according to claim 1, characterized in that The measured electrical parameters include the bridge arm voltage of the grid-connected point and the modulation voltage of the converter; and determining the transfer function matrix of the converter according to the measured electrical parameters includes: Extracting the fundamental wave signal of the bridge arm voltage of the grid connection point, and determining the phase angle difference between the fundamental wave signal and the starting signal; Using the phase angle difference as a reference angle, coordinate transformation is performed on the bridge arm voltage of the grid connection point and the modulation voltage of the converter; The transfer function matrix of the converter is determined according to the coordinate transformation processing result and a preset transfer function matrix relationship.

6. The method according to claim 1, characterized in that; The method further comprises: Inputting a plurality of preset groups of simulation operation parameters into the converter simulation model to obtain a plurality of groups of output results corresponding to each group of the simulation operation parameters; each group of the simulation operation parameters includes a load condition parameter and a power factor; The output results of each group are analyzed and aggregated, and the simulation operation parameters that meet the requirements are determined as target operation parameters according to the processing results.

7. An impedance modeling device for a grid-connected converter system, characterized in that: The grid-connected converter system comprises a converter and a filter module connected to each other, wherein the converter is used to connect to a DC power supply terminal, and the filter module is used to connect to a power grid; the device comprises: A disturbance injection module, used for injecting a disturbance signal corresponding to the target operating parameter into a grid connection point when the grid-connected converter system is operating at the target operating parameter; wherein the grid connection point is a connection point between the filter module and the power grid; A parameter detection module, used to obtain measured electrical parameters of the grid-connected converter system; A function confirmation module, used to determine a transfer function matrix of the converter according to the measured electrical parameters; A model building module is used to determine the impedance model of the grid-connected converter system based on the transfer function matrix of the converter.

8. A grid-connected system, characterized in that: It includes a grid-connected converter system and a grid-connected control system; the grid-connected converter system includes a converter and a filter module connected to each other, the converter is used to connect to a DC power supply end, and the filter module is used to connect to a power grid; the grid-connected control system is connected to the converter, and the grid-connected control system is used to determine the impedance model of the grid-connected converter system based on the method described in any one of claims 1 to 6.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 6 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

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