Droop control inverter sequence impedance modeling method, system and server

Abstract

The embodiment of the invention relates to a droop control inverter sequence impedance modeling method and system and a server, and the modeling method comprises the steps: adding positive sequence small signal current disturbance with a preset frequency at a grid connection point between a droop control inverter and a power grid, and carrying out the modeling of a small signal in a current disturbance influence process, and then considering the influence of each control link and frequency coupling on the alternating current side impedance of the droop control inverter, so that a more accurate model can be established, and the modeling process is simple and convenient and easy to realize. According to the modeling method, the influence of each control link and the main circuit parameters on the stability of the inverter can be clearly known, and harmonic oscillation can be avoided by adjusting the main circuit and the control parameters of the droop control inverter.

Description

Technical Field

[0001] This application relates to the field of power electronic inverter system modeling technology, and in particular to a droop control inverter sequence impedance modeling method, system, and server. Background Technology

[0002] Due to pollution restrictions and increasingly severe energy shortages, the large-scale utilization of new energy sources such as wind and solar power has become an inevitable trend. Distributed generation is an important solution for achieving grid-connected power generation. Currently, most new energy power generation is connected to the grid through current-controlled power electronic devices. The large-scale integration of these devices weakens the inertia and damping effect of the grid system, increasing the difficulty of frequency and voltage regulation. Droop control, as one of the mainstream control strategies for distributed generation, can provide inertial damping for the system, improve the grid's frequency and voltage regulation capabilities, and provide support for the grid. Summary of the Invention

[0003] The purpose of this application is to provide a method, system, and server for modeling the sequence impedance of a droop control inverter.

[0004] To address the aforementioned technical problems, embodiments of this application provide a method for modeling the sequence impedance of a droop-controlled inverter considering frequency coupling, comprising: A state equation for the droop control inverter in the time domain is constructed. A Fourier transform is performed on the state equation to obtain the corresponding frequency domain expression. Based on the frequency domain expression and the positive-sequence small-signal current disturbance at a preset frequency at the grid connection point between the droop control inverter and the grid, the expression for the frequency domain small signal of the droop control inverter is obtained. The variables of the state equation include the three-phase grid connection point voltage, the three-phase grid connection point current, and the modulation signal. The frequency domain small signal corresponds to multiple different frequencies during the frequency coupling process. Based on the three-phase grid connection point voltage and three-phase grid connection point current, droop control is performed to obtain the frequency domain expression of the active power small signal of the droop control inverter. Combining the relationship between the active power small signal and the disturbance phase angle small signal, the phase angle frequency domain expression of the disturbance phase angle small signal considering the voltage small signal and the current small signal at different frequencies is obtained. Based on the phase angle frequency domain expression, calculate the first conduction duty cycle small signal expression of the voltage small signal and the current small signal after passing through the dq axis current loop at different frequencies; Based on the phase angle frequency domain expression, calculate the second conduction duty cycle small signal expression of the voltage small signal and the current small signal after passing through the dq axis voltage loop and the dq current loop at different frequencies; Based on the relationship between the reactive power droop control and voltage amplitude of the droop control inverter, and combined with the phase angle frequency domain expression, calculate the expression for the third conduction duty cycle small signal after the small signals of voltage and current at different frequencies pass through the reactive power loop, the d-axis voltage loop, and the current loop. Based on the phase angle frequency domain expression, calculate the expression for the fourth conduction duty cycle small signal generated by the inverse coordinate transformation of the dq axis steady-state component; Based on the expression for the frequency domain small signal, the expression for the first conduction duty cycle small signal, the expression for the second conduction duty cycle small signal, the expression for the third conduction duty cycle small signal, and the expression for the fourth conduction duty cycle small signal, the positive sequence self-impedance model, the positive sequence coupling impedance model, the negative sequence self-impedance model, and the negative sequence coupling impedance model of the droop control inverter are obtained.

[0005] Embodiments of this application also provide a droop-controlled inverter sequence impedance modeling system considering frequency coupling, comprising: The disturbance module is used to construct the state equation of the droop control inverter in the time domain, perform a Fourier transform on the state equation to obtain the corresponding frequency domain expression, and obtain the frequency domain expression of the droop control inverter based on the frequency domain expression and the positive sequence small-signal current disturbance at the preset frequency at the grid connection point between the droop control inverter and the grid. The variables of the state equation include the three-phase grid connection point voltage, the three-phase grid connection point current and the modulation signal, and the frequency domain small signal corresponds to multiple different frequencies during the frequency coupling process. The active power loop module is used to perform droop control based on the three-phase grid connection point voltage and the three-phase grid connection point current, to obtain the frequency domain expression of the active power small signal of the droop control inverter, and to obtain the phase angle frequency domain expression of the disturbance phase angle small signal considering the voltage small signal and the current small signal at different frequencies by combining the relationship between the active power small signal and the disturbance phase angle small signal. The current loop module is used to calculate the first duty cycle expression of the voltage small signal and the current small signal after passing through the dq axis current loop at different frequencies, based on the phase angle frequency domain expression. The voltage loop module is used to calculate the second conduction duty cycle small signal expression of the voltage small signal and the current small signal after passing through the dq axis voltage loop and the dq current loop at different frequencies, based on the phase angle frequency domain expression. The reactive power loop module is used to calculate the third conduction duty cycle small signal expression after passing through the reactive power loop, d-axis voltage loop and current loop, based on the relationship between the reactive power droop control and voltage amplitude of the droop control inverter and the phase angle frequency domain expression. The steady-state module is used to calculate the fourth conduction duty cycle small signal expression generated by the inverse coordinate transformation of the dq axis steady-state component based on the phase angle frequency domain expression. A complete modulation module is used to obtain the positive-sequence self-impedance model, positive-sequence coupling impedance model, negative-sequence self-impedance model, and negative-sequence coupling impedance model of the droop control inverter based on the expression of the frequency domain small signal, the expression of the first conduction duty cycle small signal, the expression of the second conduction duty cycle small signal, the expression of the third conduction duty cycle small signal, and the expression of the fourth conduction duty cycle small signal.

[0006] Embodiments of this application also provide a server, including: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the droop control inverter sequence impedance modeling method considering frequency coupling as described above.

[0007] Embodiments of this application also provide a computer-readable storage medium storing computer instructions that, when executed by a processor, implement the droop control inverter sequence impedance modeling method considering frequency coupling described in any of the preceding claims.

[0008] Embodiments of this application also provide a computer program product, including a computer program that, when executed by a processor, implements the steps of the droop control inverter sequence impedance modeling method considering frequency coupling described in any of the preceding claims.

[0009] In this embodiment, by introducing a positive-sequence small-signal current disturbance of a preset frequency at the grid connection point between the droop-controlled inverter and the grid, and considering the influence of various control loops and coupling frequencies, including active power loop control, voltage loop control, current loop control, reactive power loop control, and steady-state component control, on the AC side impedance of the droop-controlled inverter, a more accurate impedance model can be established. This impedance modeling process is clear, the derivation is simple, and the physical meaning of the impedance model is explicit. The influence of each parameter on the impedance can be determined through various expressions. The impedance model can also determine the relationship between current and voltage at each frequency, and the impedance model can be verified through measurement. The AC side impedance model of the droop-controlled inverter provides a theoretical basis for the design of droop-controlled inverters and a modeling foundation considering multiple factors for the AC side stability analysis of droop-controlled inverters.

[0010] Compared with simulation models, which cannot analyze the root cause of oscillations, the modeling in this application can clearly understand the impact of each control link and main circuit parameters on the stability of the inverter. Harmonic oscillations can be avoided by adjusting the main circuit parameters.

[0011] In this embodiment, after adding a positive-sequence small-signal current disturbance of a preset frequency, five different frequencies represented by a fifth-order vector are generated. By calculating the modulation signals at different frequencies, the positive-sequence self-impedance model, positive-sequence coupling impedance model, negative-sequence self-impedance model, and negative-sequence coupling impedance model of the droop control inverter are derived. Attached Figure Description

[0012] Figure 1 This is a flowchart illustrating a droop control inverter sequence impedance modeling method considering frequency coupling according to an embodiment of this application. Figure 2 This is the main circuit diagram of the droop control inverter according to an embodiment of this application; Figure 3 This is a control block diagram of the droop control inverter according to an embodiment of this application; Figure 4 This is a schematic block diagram of a droop control inverter sequence impedance modeling system considering frequency coupling, according to an embodiment of this application. Figure 5 This is a schematic block diagram of a server according to an embodiment of this application. Detailed Implementation

[0013] The inventors of this application have discovered that in current droop control processes, the inverter's line impedance when connected to the power grid is relatively high, making the interconnected system between the inverter and the power grid prone to harmonic oscillations, threatening its stable operation. Therefore, it is necessary to perform appropriate sequence impedance modeling on the droop control inverter, which can be used for stability analysis to avoid DC-side resonance problems.

[0014] This disclosure provides a method for modeling the sequence impedance of a droop control inverter considering frequency coupling. By adding a positive-sequence small-signal current disturbance of a preset frequency at the grid connection point between the droop control inverter and the grid, the small-signal model is performed during the frequency coupling process. Then, the influence of frequency coupling on the AC side impedance of the droop control inverter in each control loop is considered, which can establish a more accurate model. The modeling process is simple and easy to implement.

[0015] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the various embodiments of this application will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the various embodiments of this application to help readers better understand this application. However, the technical solutions claimed in this application can be implemented even without these technical details and various changes and modifications based on the following embodiments. The division of the various embodiments below is for the convenience of description and should not constitute any limitation on the specific implementation of this application. The various embodiments can be combined with and referenced by each other without contradiction.

[0016] Figure 1 The diagram shows a flowchart of a droop control inverter sequence impedance modeling method considering frequency coupling. This method is applied to the main circuit of a droop control inverter, and the topology of the main circuit is shown below. Figure 2 As shown, it includes a DC power supply (dc), an inverter bridge, and multiple inductors. L Multiple capacitors C ,in, V dc DC side voltage i dc This is the DC side current. i La , i Lb , i Lc for a , b , c Three-phase inductor current, i Ca , i Cb , i Cc for a , b , c Three-phase capacitor current, i a , i b , i c for a , b , c Three-phase grid connection point current, v a , v b , v c for a , b , c Three-phase grid connection point voltage, d a , d b , d c for a , b , c Three-phase duty cycle L For filtering inductors, C This is a filter capacitor.

[0017] The DC power supply (dc) can be a battery pack, a DC bus boosted by a photovoltaic array via a Boost circuit, a fuel cell, etc., and the voltage of the DC power supply (dc) is... Vdc .

[0018] An inverter bridge is a power conversion unit, typically consisting of multiple IGBTs or MOSFETs (and their anti-parallel diodes) forming a full-bridge circuit. By controlling the switching on and off of the transistors, direct current is "chopped" into high-frequency alternating current pulses.

[0019] inductance L Used to filter out high-frequency harmonic components near the switching frequency, making the output current waveform smooth.

[0020] capacitance C With inductance L Together, they form a low-pass filter, providing reactive power to the load and stabilizing the voltage waveform of the inverter output.

[0021] The main working principle of this main circuit is as follows: The droop control inverter generates a PWM signal to drive the switching transistors of the inverter bridge. By adjusting the duty cycle of the PWM, the width of the output AC pulse can be controlled, and then... LC After smoothing by the filter, a high-quality sinusoidal voltage is obtained. v a , v b , v c and a , b , c Three-phase grid connection point current i a , i b , i c It supplies power to the load or injects it into the power grid.

[0022] like Figure 3 As shown, Figure 3 This is the control block diagram for a droop-controlled inverter. Figure 3 middle, v d and v q for dq Grid connection point voltage, i Ld and i Lq for dq Shaft inductor current, P The active power of the inverter. Q The reactive power of the inverter. v dref for d Shaft voltage reference value, i Ldref and iLqref They are respectively d shaft and q D-axis current reference value. Control consists of power loop, voltage loop, and current loop. First, the phase angle is generated through the active power loop, and the d-axis voltage reference value is generated through the reactive power loop. Based on this, voltage control... H v ( s Based on the phase angle and amplitude commands, a current reference value is generated, and then the current controller... H i ( s Based on the phase angle and amplitude commands, a modulation wave is generated, and a modulation signal is generated through pulse width modulation to control the switching transistor to turn on and off.

[0023] Based on the main circuit and control block diagram of the droop-controlled inverter, this application provides a method for modeling the sequence impedance of a droop-controlled inverter considering frequency coupling, which includes steps S10 to S70.

[0024] S10: Construct the state equation of the droop control inverter in the time domain, perform a Fourier transform on the state equation to obtain the frequency domain expression corresponding to the state equation, and based on the frequency domain expression and the positive sequence small-signal current disturbance at the preset frequency at the grid connection point between the droop control inverter and the grid, obtain the expression of the frequency domain small signal of the droop control inverter. The variables of the state equation include the three-phase grid connection point voltage, the three-phase grid connection point current and the modulation signal, and the frequency domain small signal corresponds to multiple different frequencies during the frequency coupling process.

[0025] In some implementations, step S10 may include: Based on the main circuit of the droop control inverter, the state equation of the droop control inverter in the time domain is constructed and expressed by the following formulas 1 and 2: Formula 1; Formula 2; in, L This refers to the filter inductance of the main circuit. C This refers to the filter capacitor of the main circuit. Vdc This refers to the DC-side voltage of the main circuit. iLa , iLb , iLc They represent a , b , c Three-phase inductor current, ia , ib , ic They represent a , b , c Three-phase grid connection point current, va , vb , vc for a , b , c Three-phase grid connection point voltage, da , db , DC They represent a , b , c Three-phase duty cycle; Performing a Fourier transform on the state equation yields its frequency domain expression, which is represented by the following formulas 3 and 4: Formula 3; Formula 4; in, The inductor impedance matrix at different frequencies. For capacitor admittance matrices at different frequencies, express a Current at the parallel grid point; By subjecting the frequency domain expression to a positive-sequence small-signal current perturbation at the preset frequency, the frequency domain small-signal expression of the droop control inverter is obtained, expressed by the following formulas 5 and 6: Formula 5; Formula 6; in, This is the inductor impedance matrix at different frequencies after superimposing the perturbation. This represents the capacitance admittance matrix at different frequencies after superimposing the perturbation. and For the communication side a A matrix composed of small-signal voltage and small-signal current components at different frequencies at the phase-parallel grid points. for a The matrix of impedance components of the conduction duty cycle at different frequencies. For the communication side a A matrix composed of the voltage small-signal components and the current small-signal components of the phase inductor current at different frequencies.

[0026] By adding a positive-sequence small-signal disturbance of a preset frequency at the grid connection point between the droop control inverter and the grid, the inverter's dynamic response will be stimulated and oscillations will be triggered. This allows for analysis of the root cause of the oscillations, facilitating a clear understanding of the impact of each control link and main circuit parameters on the inverter's stability. Adjusting the parameters can avoid harmonic oscillations, measure impedance characteristics, and evaluate stability margins.

[0027] Since droop control affects the port voltage of the grid connection point, introducing a voltage disturbance at the connection point will impact its voltage, while introducing a current disturbance will not. Furthermore, introducing multiple positive-sequence small signals will affect measurement accuracy. Therefore, this application introduces a preset-frequency positive-sequence small-signal current disturbance at the grid connection point, which will not affect the port voltage or measurement accuracy. Moreover, the modeling method is simpler and the modeling process is more convenient.

[0028] In some implementations, the modulation signal is the final output of the calculations of all control loops of the droop control inverter, including the droop loop, voltage loop, and current loop. The modulation signal contains all the response information of the droop inverter controller to a positive-sequence small-signal disturbance of a preset frequency.

[0029] In some implementations, the variables of the frequency domain small signal are represented by a fifth-order vector, and the frequencies corresponding to each element of the vector are { f p 2 f 1, f p f 1, f p , f p + f 1, f p +2 f 1}, where, f p This refers to the preset frequency. f 1 represents the fundamental frequency of the power grid.

[0030] Specifically, the fundamental frequency of the power grid can be 50Hz. The preset frequency can be a low-frequency signal, such as close to the fundamental frequency of 50Hz, or a medium-frequency signal, such as 100Hz-1000Hz, or a high-frequency signal, such as higher than 1000Hz.

[0031] When a positive-sequence small-signal current disturbance of a preset frequency is encountered at the grid connection point between the droop control inverter and the grid, the resulting response frequencies are multiple, namely... f p 2 f 1, f p f 1, f p , f p +f 1, f p +2 f 1. Five different frequencies.

[0032] When a positive-sequence small-signal current disturbance of a preset frequency is added at the grid connection point between the droop control inverter and the grid, response components will be generated in these five different frequencies.

[0033] S20: Based on the three-phase grid-connected point voltage and three-phase grid-connected point current, droop control is performed to obtain the frequency domain expression of the active power small signal of the droop control inverter. Combining the relationship between the active power small signal and the disturbance phase angle small signal, the phase angle frequency domain expression of the disturbance phase angle small signal considering the voltage small signal and the current small signal at different frequencies is obtained.

[0034] Specifically, step S20 may include the following expression: Formula 9; in, Indicates the AC side of the main circuit a Different frequencies of parallel network points a Phase current small signal, This indicates the small signal of the disturbance phase angle. With the communication side a Different frequencies of parallel network points a Phase current small signal The transfer function matrix of the relation. This indicates the small signal of the disturbance phase angle. With the communication side a Different frequencies of parallel network points a Phase voltage small signal The transfer function matrix of the relationship.

[0035] Furthermore, firstly, based on the three-phase grid-connected point voltage and the three-phase grid-connected point current, droop control is performed to obtain the frequency domain expression of the active power small signal of the droop control inverter, which is represented by the following formula 7: Formula 7; in, This represents the small-signal components of active power at different frequencies. and This indicates the main circuit at different frequencies. dq Steady-state voltage at the grid connection point , This represents a matrix composed of small voltage signals at different frequencies at the grid connection point along the dq axis. , This represents the steady-state current at the grid connection point along the dq axis at different frequencies. , This represents a matrix composed of small current signals at different frequencies at the dq-axis grid connection point; The active power small signal The small signal of the disturbance phase angle is obtained through the active power loop of the droop control inverter. It can be represented by the following formula 8: Formula 8; in, This represents the small signal of the disturbance phase angle. This represents the open-loop transfer function matrix of the active power loop at different frequencies; Finally, using a Phase current represents the small signal of active power. Obtain the small signal of the perturbation phase angle The phase angle frequency domain expression is: Formula 9; By calculating the active power small signal, it is possible to calculate the disturbance phase angle small signal of voltage and current small signals at different frequencies, so as to facilitate the subsequent calculation of the influence of phase angle in coordinate transformation.

[0036] S30: Based on the phase angle frequency domain expression, calculate the first conduction duty cycle small signal expression of the voltage small signal and the current small signal after passing through the dq axis current loop at different frequencies.

[0037] In some implementations, step S30 may include: In the dq coordinate system, the small signal of the dq-axis inductor current... , After the current loop PI regulator and decoupling operation of the droop control inverter, the first harmonic vector expression of the modulated small signal dq axis is obtained. , It can be represented by the following formula 10: Formula 10; in, d-axis modulated wave Small signal of d-axis inductor current The transfer function matrix of the relation. d-axis modulated wave Small signal of q-axis inductor current The transfer function matrix of the relation. q-axis modulated wave Small signal of d-axis inductor current The transfer function matrix of the relation. q-axis modulated wave Small signal of q-axis inductor current The transfer function matrix of the relationship.

[0038] Based on the phase angle frequency domain expression, the first harmonic vector expression of the modulation small signal dq axis is... , After inverse transformation of the equal power coordinates, the conduction duty cycle is transformed into the abc coordinate system, and the small-signal expression of the first conduction duty cycle is obtained, which is represented by the following formula 11: Formula 11; in, The duty cycle of phase a current conduction and a Phase current small signal The transfer function matrix of the relationship, and related to the phase angle frequency domain expression. for a Phase current duty cycle Small signal of phase a voltage The transfer function matrix of the relationship, and is related to the phase angle frequency domain expression.

[0039] It is understood that the phase angle frequency domain expression is used for coordinate transformation and inverse coordinate transformation, and is related to the transfer function matrix. and transfer function matrix Related.

[0040] like Figure 3 As shown, the dq / abc module is used for coordinate transformation, and the input of the dq / abc module includes the phase angle. θ Therefore, it is necessary to calculate the first duty cycle expression of the voltage and current small signals after passing through the dq-axis current loop at different frequencies based on the phase angle frequency domain expression.

[0041] Calculating the small signal of the first conduction duty cycle facilitates the subsequent calculation of the positive-sequence self-impedance model, positive-sequence coupling impedance model, negative-sequence self-impedance model, and negative-sequence coupling impedance model of the droop control inverter.

[0042] S40: Based on the phase angle frequency domain expression, calculate the second conduction duty cycle small signal expression of the voltage small signal and the current small signal after passing through the dq axis voltage loop and the dq current loop at different frequencies.

[0043] Please see Figure 3 The input to the dq / abc module includes the phase angle. θ Therefore, it is necessary to calculate the expression for the second conduction duty cycle small signal after the voltage small signal and the current small signal pass through the dq axis voltage loop and dq current loop at different frequencies based on the phase angle frequency domain expression.

[0044] In some implementations, step S40 may include: In the dq coordinate system, after the voltage small signal passes through the voltage loop PI regulator and decoupling operation of the droop control inverter, and then through the current loop PI regulator and decoupling operation, the second harmonic vector expression of the modulated small signal along the dq axis is obtained. , ; expressed by the following formula 12: Formula 12; in, d-axis modulated wave Small signal of d-axis voltage The transfer function matrix of the relation. d-axis modulated wave With q-axis voltage small signal The transfer function matrix of the relation. q-axis modulated wave Small signal of d-axis inductor current The transfer function matrix of the relation. q-axis modulated wave Small signal of q-axis inductor current The transfer function matrix of the relation. This represents the small-signal voltage at different frequencies at the grid connection point along the d-axis. This represents the small voltage signal at different frequencies at the q-axis grid connection point.

[0045] Based on the phase angle frequency domain expression, the second harmonic vector expression of the modulation small signal dq axis is... , After the inverse transformation of the isopower coordinates, it is transformed into the abc coordinate system. a The phase conduction duty cycle is used to obtain the small-signal expression for the second duty cycle, which is represented by the following formula 13: Formula 13; in, For the a Phase voltage duty cycle With the a Phase current small signal The transfer function matrix of the relationship, and related to the phase angle frequency domain expression. For the a Phase voltage duty cycle With the a Phase voltage small signal The transfer function matrix of the relationship, and is related to the phase angle frequency domain expression.

[0046] It is understood that the phase angle frequency domain expression is used for coordinate transformation and inverse coordinate transformation, and is related to the transfer function matrix. and transfer function matrix Related.

[0047] Calculating the small signal of the second conduction duty cycle facilitates the subsequent calculation of the positive-sequence self-impedance model, positive-sequence coupling impedance model, negative-sequence self-impedance model, and negative-sequence coupling impedance model of the droop control inverter.

[0048] S50: Based on the relationship between the reactive power droop control and voltage amplitude of the droop control inverter, and combined with the phase angle frequency domain expression, calculate the expression for the third conduction duty cycle small signal of the voltage small signal and current small signal at different frequencies under the reactive power loop, the dq axis voltage loop and the dq axis current loop, and the abc coordinate after coordinate transformation.

[0049] Similarly, please refer to Figure 3 The input of the dq / abc module includes the phase angle θ. Therefore, it is necessary to calculate the expression of the third conduction duty cycle small signal after the voltage small signal and the current small signal pass through the reactive loop, the dq axis voltage loop and the dq current loop at different frequencies based on the phase angle frequency domain expression.

[0050] In some implementations, step S50 may include: Based on the three-phase grid-connected point voltage and three-phase grid-connected point current, droop control is performed to obtain the frequency domain expression of the reactive power small signal of the droop control inverter, which is expressed by the following formula 14: Formula 14; in, This indicates the small signal of reactive power; The reactive power small signal is passed through the reactive power loop, the dq-axis voltage loop, and the dq-axis current loop of the droop control inverter to obtain the d-axis modulated wave small signal. The third modulated wave small signal is represented by the following formula 15: Formula 15; in, Small signal of d-axis modulation wave With the small reactive power signal The transfer function matrix.

[0051] Using the above a Phase current expresses the small signal of reactive power. Then, based on the phase angle frequency domain expression, the third modulation wavelet small signal is... After inverse isopower coordinate transformation, it is converted to abc In coordinate system, obtain a q-axis conduction duty cycle It can be represented by the following formula 16: Formula 16; in, express a q-axis conduction duty cycle With the a Phase current small signal The transfer function matrix of the relationship, and related to the phase angle frequency domain expression. express a q-axis conduction duty cycle With the a Phase voltage small signal The transfer function matrix of the relationship, and is related to the phase angle frequency domain expression.

[0052] It is understood that the phase angle frequency domain expression is used for coordinate transformation and inverse coordinate transformation, and is related to the transfer function matrix. and transfer function matrix Related.

[0053] S60: Based on the phase angle frequency domain expression, calculate the expression for the fourth conduction duty cycle small signal generated by the inverse coordinate transformation of the dq axis steady-state component.

[0054] Similarly, please refer to Figure 3 The input to the dq / abc module includes the phase angle. θ Therefore, it is necessary to calculate the expression for the fourth conduction duty cycle small signal generated by the inverse coordinate transformation of the steady-state component of the dq axis based on the phase angle frequency domain expression.

[0055] In some implementations, step S60 may include: Based on the aforementioned phase angle frequency domain expression, the steady-state duty cycle of the dq-axis steady-state component after inverse coordinate transformation is expressed by the following formula 17: Formula 17; in, For steady-state conduction duty cycle With the a Phase current small signal The transfer function matrix of the relationship, and is related to the phase angle frequency domain expression; The steady-state duty cycle With the a Phase voltage small signal The transfer function matrix of the relationship, and is related to the phase angle frequency domain expression.

[0056] It is understood that the phase angle frequency domain expression is used for coordinate transformation and inverse coordinate transformation, and is related to the transfer function matrix. and transfer function matrix Related.

[0057] The steady-state component of the dq axis refers to the steady-state component of the fundamental frequency that appears as DC in the dq rotating coordinate system.

[0058] After the steady-state component of the dq axis undergoes inverse coordinate transformation, a fourth conduction duty cycle small-signal expression is generated. This fourth conduction duty cycle small-signal expression is used to calculate the positive-sequence self-impedance model, positive-sequence coupling impedance model, negative-sequence self-impedance model, and negative-sequence coupling impedance model of the droop control inverter.

[0059] S70: Based on the first conduction duty cycle small-signal expression, the second conduction duty cycle small-signal expression, the third conduction duty cycle small-signal expression, and the fourth conduction duty cycle small-signal expression, obtain the positive sequence self-impedance model, the positive sequence coupling impedance model, the negative sequence self-impedance model, and the negative sequence coupling impedance model of the droop control inverter.

[0060] Specifically, based on the expression for the frequency domain small signal, the expression for the first conduction duty cycle small signal, the expression for the second conduction duty cycle small signal, the expression for the third conduction duty cycle small signal, and the expression for the fourth conduction duty cycle small signal, the positive sequence impedance model and the positive sequence coupling impedance model of the droop control inverter are obtained, including: Using formulas 11, 13, and 15 to express formula 17, we obtain the following formula representation 18: Formula 18; Formulas 5 and 6 are expressions for small-signal signals in the frequency domain. Substituting Formula 6 and Formula 18 into Formula 5 specifically involves using Formula 6... Express, then use formula 18 And Formula 6 Substituting the expression into formula 5, we obtain the following formula 19: Formula 19: Where U represents a 5×5 identity matrix; To conduct duty cycle With the a Phase voltage small signal The transfer function matrix of the relation. To conduct duty cycle With the a Phase current small signal The transfer function matrix of the relationship.

[0061] Based on Equation 19, relevant frequencies are extracted and calculated to obtain the positive-sequence self-impedance model. The positive-sequence coupling impedance model Z pn ( sThe following formulas 20 and 21 are used to express this respectively: Formula 20; Formula 21; in, s=jω p , ω p The disturbance frequency is the angular frequency. ω p = 2 πf p , ω 1 represents the fundamental angular frequency. ω 1 = 2 πf 1, The disturbance frequency component of the grid connection point voltage. For the grid connection point voltage f p -2 f 1 frequency component, This represents the disturbance frequency component of the grid connection point current.

[0062] In some implementations, the positive-sequence self-impedance model is obtained based on Equation 19. Z pp ( s The positive-sequence coupling impedance model Z pn ( s Negative sequence self-impedance model and negative sequence coupling impedance model It can include: Based on the aforementioned formula 19, for the a Phase voltage small signal The positive-sequence self-impedance model is obtained by performing matrix operations on the relevant frequencies. Z pp ( s The positive-sequence coupling impedance model Z pn ( s Negative sequence self-impedance model and negative sequence coupling impedance model .

[0063] Specifically, in Formula 19 These are matrices of different frequencies. By performing matrix operations on the relevant frequencies, the positive-sequence self-impedance model can be obtained. Z pp ( s The positive-sequence coupling impedance model Z pn (s Negative sequence self-impedance model and negative sequence coupling impedance model .

[0064] It is obvious that in Formula 19 and It includes all the control parameters in Formula 18, namely: , , , , , , , By observing the influence of various control parameters on the inductor impedance, the relationship between voltage and current at each frequency can be seen, thus clarifying the physical meaning of the impedance model.

[0065] Next, based on the positive-sequence self-impedance model The positive-sequence coupling impedance model Obtain the negative-sequence self-impedance model and negative sequence coupling impedance model The negative-sequence self-impedance model and the negative-sequence coupled impedance model are expressed by the following formulas 22 and 23: Formula 22; Formula 23.

[0066] in, s=jω p , ω p The disturbance frequency is the angular frequency. ω p = 2 πf p , ω 1 represents the fundamental angular frequency. ω 1 = 2 πf 1.

[0067] Obtaining the positive-sequence self-impedance model Z pp ( s Positive sequence coupling impedance model Z pn ( s Negative sequence self-impedance model and negative sequence coupling impedance model Then, the modeling of the droop control inverter sequence impedance was completed.

[0068] It should be noted that steps S30, S40, S50, and S60 can be executed in parallel, and no restriction is imposed here.

[0069] The droop-controlled inverter sequence impedance modeling method of this application introduces a positive-sequence small-signal current disturbance of a preset frequency at the grid connection point between the droop-controlled inverter and the grid. Simultaneously, it considers the influence of various control loops and coupling frequencies, including active power loop control, voltage loop control, current loop control, reactive power loop control, and steady-state component control, on the AC side impedance of the droop-controlled inverter, thereby establishing a more accurate impedance model. This impedance modeling process is clear, the derivation is simple, and the physical meaning of the impedance model is explicit. The influence of each parameter on the impedance can be determined through various expressions. The impedance model can also determine the relationship between current and voltage at each frequency, and the impedance model can be verified through measurement. The AC side impedance model of the droop-controlled inverter provides a theoretical basis for the design of droop-controlled inverters and a modeling foundation that considers multiple factors for the AC side stability analysis of droop-controlled inverters.

[0070] Compared to simulation models, which cannot analyze the root cause of oscillations, the modeling in this application clearly shows the impact of each control element and main circuit parameter on inverter stability. This can be achieved by adjusting the main circuit parameters (inductance...) L and capacitor C )and Figure 3 The control parameters in each control link are adjusted to adjust the converter impedance, thereby avoiding harmonic oscillations.

[0071] Another embodiment of this application relates to a droop control inverter sequence impedance modeling system 400 that considers frequency coupling, such as... Figure 4 As shown, it includes: The disturbance module 401 is used to construct the state equation of the droop control inverter in the time domain, perform a Fourier transform on the state equation to obtain the frequency domain expression corresponding to the state equation, and obtain the frequency domain small signal expression of the droop control inverter based on the frequency domain expression and the positive sequence small signal current disturbance at the preset frequency at the grid connection point between the droop control inverter and the grid. The variables of the state equation include the three-phase grid connection point voltage, the three-phase grid connection point current and the modulation signal, and the frequency domain small signal corresponds to multiple different frequencies during the frequency coupling process. The active power loop module 402 is used to perform droop control based on the three-phase grid connection point voltage and the three-phase grid connection point current, to obtain the frequency domain expression of the active power small signal of the droop control inverter, and to obtain the phase angle frequency domain expression of the disturbance phase angle small signal considering the voltage small signal and the current small signal at different frequencies by combining the relationship between the active power small signal and the disturbance phase angle small signal. Current loop module 403 is used to calculate the first conduction duty cycle small signal expression of the voltage small signal and the current small signal after passing through the dq axis current loop at different frequencies based on the phase angle frequency domain expression; Voltage loop module 404 is used to calculate the second conduction duty cycle small signal expression of the voltage small signal and the current small signal after passing through the dq axis voltage loop and the dq current loop at different frequencies based on the phase angle frequency domain expression; The reactive power loop module 405 is used to calculate the expression of the third conduction duty cycle small signal after passing through the reactive power loop, d-axis voltage loop and current loop, based on the relationship between the reactive power droop control and voltage amplitude of the droop control inverter and the phase angle frequency domain expression. Steady-state module 406 is used to calculate the fourth conduction duty cycle small signal expression generated by the inverse coordinate transformation of the dq axis steady-state component based on the phase angle frequency domain expression; The complete modulation module 407 is used to obtain the positive-sequence self-impedance model, positive-sequence coupling impedance model, negative-sequence self-impedance model and negative-sequence coupling impedance model of the droop control inverter based on the expression of the frequency domain small signal, the expression of the first conduction duty cycle small signal, the expression of the second conduction duty cycle small signal, the expression of the third conduction duty cycle small signal and the expression of the fourth conduction duty cycle small signal.

[0072] Optionally, the variables of the frequency domain small signal are represented by a fifth-order vector, and the frequencies corresponding to each element of the vector are { f p 2 f 1, f p f 1, f p , f p + f 1, f p +2 f 1}, where, f p This refers to the preset frequency. f 1 represents the fundamental frequency of the power grid.

[0073] Optionally, the positive-sequence self-impedance model is represented by the following formula 20: Formula 20; The positive-sequence coupling impedance model is expressed by the following formula 21: Formula 21; The negative-sequence self-impedance model is expressed by the following formula 22: Formula 22; The negative-sequence coupling impedance model is expressed by the following formula 23: Formula 23; in, This represents the positive-sequence self-impedance model. This represents the positive-sequence coupling impedance model. This represents the negative-sequence self-impedance model. This represents the negative-order coupling impedance model; where, s=jω p , ω p The disturbance frequency is the angular frequency. ω p = 2 πf p , ω 1 represents the fundamental angular frequency. ω 1 = 2 πf 1, The disturbance frequency component of the grid connection point voltage. For the grid connection point voltage f p -2 f 1 frequency component, This represents the disturbance frequency component of the grid connection point current.

[0074] Optionally, the disturbance module 401 is also used for: Based on the main circuit of the droop control inverter, the state equation of the droop control inverter in the time domain is constructed and expressed by the following formulas 1 and 2: Formula 1; Formula 2; in, L This refers to the filter inductance of the main circuit. C This refers to the filter capacitor of the main circuit. V dc This refers to the DC-side voltage of the main circuit. i La , i Lb , i Lc They represent a , b , c Three-phase inductor current, i a , i b , i c They represent a , b , c Three-phase grid connection point current, va , v b , v c for a , b , c Three-phase grid connection point voltage, d a , d b , d c They represent a , b , c Three-phase duty cycle; Performing a Fourier transform on the state equation yields its frequency domain expression, which is represented by the following formulas 3 and 4: Formula 3; Formula 4; in, The inductor impedance matrix at different frequencies. For capacitor admittance matrices at different frequencies, i a express a Current at the parallel grid point; By subjecting the frequency domain expression to a positive-sequence small-signal current perturbation at the preset frequency, the frequency domain small-signal expression of the droop control inverter is obtained, expressed by the following formulas 5 and 6: Formula 5; Formula 6; in, This is the inductor impedance matrix at different frequencies after superimposing the perturbation. This represents the capacitance admittance matrix at different frequencies after superimposing the perturbation. and For the communication side a A matrix composed of small-signal voltage and small-signal current components at different frequencies at the phase-parallel grid points. for a The matrix of impedance components of the conduction duty cycle at different frequencies. For the communication side a A matrix composed of the voltage small-signal components and the current small-signal components of the phase inductor current at different frequencies.

[0075] Optionally, the active power loop module 402 is also used for: Based on the three-phase grid-connected point voltage and three-phase grid-connected point current, droop control is performed to obtain the frequency domain expression of the active power small signal of the droop control inverter, which is represented by the following formula 7: Formula 7; in, This represents the small-signal components of active power at different frequencies. and This indicates the main circuit at different frequencies. dq Steady-state voltage at the grid connection point , This represents a matrix composed of small voltage signals at different frequencies at the grid connection point along the dq axis. , This represents the steady-state current at the grid connection point along the dq axis at different frequencies. , This represents a matrix composed of small current signals at different frequencies at the dq-axis grid connection point; The active power small signal The small signal of the disturbance phase angle is obtained through the active power loop of the droop control inverter. It can be represented by the following formula 8: Formula 8; in, This represents the small signal of the perturbation phase angle at different frequencies. This represents the open-loop transfer function matrix of the active power loop at different frequencies; use a Phase current represents the small signal of active power. Obtain the small signal of the perturbation phase angle The phase angle frequency domain expression is: Formula 9; in, Indicates the AC side of the main circuit a Different frequencies of parallel network points a Phase current small signal, This indicates the small signal of the disturbance phase angle. With the communication side a Small current signals at different frequencies at parallel grid points The transfer function matrix of the relation. This indicates the small signal of the disturbance phase angle. With the communication side a Different frequencies of parallel network points a Phase voltage small signal The transfer function matrix of the relationship.

[0076] Optionally, the current loop module 403 is also used for: In the dq coordinate system, the small signal of the dq-axis inductor current... , After the current loop PI regulator and decoupling operation of the droop control inverter, the first harmonic vector expression of the modulated small signal dq axis is obtained. , ; Based on the phase angle frequency domain expression, the first harmonic vector expression of the modulation small signal dq axis is... , After the inverse transformation of the isopower coordinates, it is transformed into the abc coordinate system. a The phase conduction duty cycle is used to obtain the small-signal expression for the first conduction duty cycle, which is represented by the following formula 11: Formula 11; in, For the a Phase current duty cycle With the a Phase current small signal The transfer function matrix of the relationship, and is related to the phase angle frequency domain expression; For the a Phase current duty cycle With the a Phase voltage small signal The transfer function matrix of the relationship, and is related to the phase angle frequency domain expression.

[0077] Optionally, the voltage loop module 404 is also used for: In the dq coordinate system, after the voltage small signal passes through the voltage loop PI regulator and decoupling operation of the droop control inverter, and then through the current loop PI regulator and decoupling operation, the second harmonic vector expression of the modulated small signal along the dq axis is obtained. , ; Based on the phase angle frequency domain expression, the second harmonic vector expression of the modulation small signal dq axis is... , After inverse transformation of equal power coordinates, it is transformed to abc coordinate system a The phase conduction duty cycle is used to obtain the small-signal expression for the second conduction duty cycle, which is represented by the following formula 13: Formula 13; in, For the a Phase voltage duty cycle With the small signal of phase a current The transfer function matrix of the relationship, and is related to the phase angle frequency domain expression; The duty cycle of the voltage on phase a With the aPhase voltage small signal The transfer function matrix of the relationship, and is related to the phase angle frequency domain expression.

[0078] Optionally, the reactive power ring 505 is also used for: Based on the three-phase grid-connected point voltage and three-phase grid-connected point current, droop control is performed to obtain the frequency domain expression of the reactive power small signal of the droop control inverter, which is expressed by the following formula 14: Formula 14; in, This indicates the small signal of reactive power; The reactive power small signal is passed through the reactive power loop, the dq-axis voltage loop, and the dq-axis current loop of the droop control inverter to obtain the d-axis modulated wave small signal. The third modulated wave small signal is represented by the following formula 15: Formula 15; in, Small signal of d-axis modulation wave With the small reactive power signal The relationship.

[0079] Using the above a Phase current expresses the small signal of reactive power. Then, based on the phase angle frequency domain expression, the third modulation wavelet small signal is... After inverse transformation of the equal power coordinates, the system is transformed into the abc coordinate system to obtain... a q-axis conduction duty cycle It can be represented by the following formula 16: Formula 16; in, express a q-axis conduction duty cycle With the small signal of phase a current The transfer function matrix of the relationship, and is related to the phase angle frequency domain expression; express a q-axis conduction duty cycle With the small signal of phase a voltage The transfer function matrix of the relationship, and is related to the phase angle frequency domain expression.

[0080] Optionally, the steady-state module 406 is also used for: This can be expressed using the following formula 17: Formula 17; in, For steady-state conduction duty cycle With the a Phase current small signal The transfer function matrix of the relationship, and is related to the phase angle frequency domain expression; The steady-state duty cycle With the a Phase voltage small signal The transfer function matrix of the relationship, and is related to the phase angle frequency domain expression.

[0081] Optionally, the complete modulation module 407 is also used for: Using formulas 11, 13, and 15 to express formula 17, we obtain the following formula representation 18: Formula 18; Substituting Formula 6 and Formula 18 into Formula 5, we obtain the following Formula 19: Formula 19: Where U represents a 5×5 identity matrix, To conduct duty cycle With the a Phase voltage small signal The transfer function matrix of the relation. To conduct duty cycle With the a Phase current small signal The transfer function matrix of the relationship; Based on Equation 19, the positive-sequence self-impedance model is obtained. Z pp ( s The positive-sequence coupling impedance model Z pn ( s Negative sequence self-impedance model and negative sequence coupling impedance model .

[0082] Optionally, the complete modulation module 407 is also used for: Based on the aforementioned formula 19, for the a Phase voltage small signal The positive-sequence self-impedance model is obtained by performing matrix operations on the relevant frequencies. Zpp(s) The positive-sequence coupling impedance model Zpn(s) Negative sequence self-impedance model and negative sequence coupling impedance model .

[0083] Another embodiment of this application relates to a server, such as Figure 5As shown, it includes at least one processor 501; and a memory 502 communicatively connected to the at least one processor; wherein the memory 502 stores instructions executable by the at least one processor 501, the instructions being executed by the at least one processor 501 to enable the at least one processor 501 to perform the method described above.

[0084] The memory 502 and processor 501 are connected via a bus, which can include any number of interconnecting buses and bridges. The bus connects various circuits of one or more processors 501 and memory 502 together. The bus can also connect various other circuits, such as peripheral devices, voltage regulators, and power management circuits, which are well known in the art and therefore will not be described further herein. A bus interface provides an interface between the bus and the transceiver. The transceiver can be a single element or multiple elements, such as multiple receivers and transmitters, providing a unit for communicating with various other devices over a transmission medium. Data processed by processor 501 is transmitted over a wireless medium via an antenna, which further receives data and transmits it to processor 501.

[0085] Processor 501 is responsible for managing the bus and general processing, and can also provide various functions, including timing, peripheral interfaces, voltage regulation, power management, and other control functions. Memory 502 can be used to store data used by processor 501 during operation.

[0086] Another embodiment of this application relates to a computer-readable storage medium storing computer instructions that, when executed by a processor, implement the above-described method embodiments.

[0087] Another embodiment of this application relates to a computer program product, including a computer program that, when executed by a processor, implements the steps of the above-described method.

[0088] That is, those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware. This program is stored in a storage medium and includes several instructions to cause a device (which may be a microcontroller, chip, etc.) or processor to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as a USB flash drive, a portable hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0089] Those skilled in the art will understand that the above embodiments are specific embodiments for implementing this application, and in practical applications, various changes can be made to them in form and detail without departing from the spirit and scope of this application.

Claims

1. A method for modeling the sequence impedance of a droop-controlled inverter considering frequency coupling, characterized in that, include: A state equation for the droop control inverter in the time domain is constructed. A Fourier transform is performed on the state equation to obtain the corresponding frequency domain expression. Based on the frequency domain expression and the positive-sequence small-signal current disturbance at a preset frequency at the grid connection point between the droop control inverter and the grid, the expression for the frequency domain small signal of the droop control inverter is obtained. The variables of the state equation include the three-phase grid connection point voltage, the three-phase grid connection point current, and the modulation signal. The frequency domain small signal corresponds to multiple different frequencies during the frequency coupling process. Based on the three-phase grid connection point voltage and three-phase grid connection point current, droop control is performed to obtain the frequency domain expression of the active power small signal of the droop control inverter. Combining the relationship between the active power small signal and the disturbance phase angle small signal, the phase angle frequency domain expression of the disturbance phase angle small signal considering the voltage small signal and the current small signal at different frequencies is obtained. Based on the aforementioned phase angle frequency domain expression, the voltage small signal and the current small signal at different frequencies are calculated after passing through... dq Small-signal expression for the first conduction duty cycle after the shaft current loop; Based on the aforementioned phase angle frequency domain expression, the voltage small signal and the current small signal at different frequencies are calculated after passing through... dq Shaft voltage loop and the dq The small-signal expression for the second conduction duty cycle after the current loop; Based on the relationship between the reactive power droop control and voltage amplitude of the droop control inverter, and combined with the phase angle frequency domain expression, calculate the expression for the third conduction duty cycle small signal after the small signals of voltage and current at different frequencies pass through the reactive power loop, the d-axis voltage loop, and the current loop. Based on the aforementioned phase angle frequency domain expression, calculate dq The expression for the fourth conduction duty cycle small-signal generated by inverse coordinate transformation of the axis steady-state component; Based on the expression for the frequency domain small signal, the expression for the first conduction duty cycle small signal, the expression for the second conduction duty cycle small signal, the expression for the third conduction duty cycle small signal, and the expression for the fourth conduction duty cycle small signal, the positive sequence self-impedance model, the positive sequence coupling impedance model, the negative sequence self-impedance model, and the negative sequence coupling impedance model of the droop control inverter are obtained.

2. The method for modeling the sequence impedance of a droop-controlled inverter considering frequency coupling according to claim 1, characterized in that, The frequency domain small signal variables are represented by a fifth-order vector, and the frequencies corresponding to each element of the vector are { f p 2 f 1, f p f 1, f p , f p + f 1, f p +2 f 1}, where, f p This refers to the preset frequency. f 1 represents the fundamental frequency of the power grid.

3. The droop control inverter sequence impedance modeling method according to claim 2, characterized in that, The positive-sequence self-impedance model is expressed by the following formula 20: Official 20; The positive-sequence coupling impedance model is expressed by the following formula 21: Official 21; The negative-sequence self-impedance model is expressed by the following formula 22: Official 22; The negative-sequence coupling impedance model is expressed by the following formula 23: Official 23; in, This represents the positive-sequence self-impedance model. This represents the positive-sequence coupling impedance model. This represents the negative-sequence self-impedance model. This represents the negative-order coupling impedance model; s=jω p , ω p The disturbance frequency is the angular frequency. ω p = 2 πf p , ω 1 represents the fundamental angular frequency. ω 1 = 2 πf 1, The disturbance frequency component of the grid connection point voltage. For the grid connection point voltage ( f p -2 f 1) Frequency components, This represents the disturbance frequency component of the grid connection point current.

4. The method for modeling the sequence impedance of a droop-controlled inverter considering frequency coupling according to claim 1, characterized in that, The process involves constructing the state equation of the droop control inverter in the time domain, performing a Fourier transform on the state equation to obtain its corresponding frequency domain expression, and then, based on the frequency domain expression and the positive-sequence small-signal current disturbance at a preset frequency at the grid connection point between the droop control inverter and the grid, obtaining the frequency domain small-signal expression of the droop control inverter, including: Based on the main circuit of the droop control inverter, the state equation of the droop control inverter in the time domain is constructed and expressed by the following formulas 1 and 2: Official 1; Official 2; in, L This refers to the filter inductance of the main circuit. C This refers to the filter capacitor of the main circuit. Vdc This refers to the DC-side voltage of the main circuit. iLa , iLb , iLc They represent a , b , c Three-phase inductor current, ia , ib , ic They represent a , b , c Three-phase grid connection point current, va , vb , vc The voltage at the grid connection point of phases a, b, and c. da , db , DC These represent the duty cycles of phases a, b, and c, respectively. Performing a Fourier transform on the state equation yields its frequency domain expression, which is represented by the following formulas 3 and 4: Official 3; Official 4; in, The inductor impedance matrix at different frequencies. For capacitor admittance matrices at different frequencies, ia This represents the current at the grid connection point of phase a; By subjecting the frequency domain expression to a positive-sequence small-signal current perturbation at the preset frequency, the frequency domain small-signal expression of the droop control inverter is obtained, expressed by the following formulas 5 and 6: Official 5; Official 6; in, This is the inductor impedance matrix at different frequencies after superimposing the perturbation. This represents the capacitance admittance matrix at different frequencies after superimposing the perturbation. and For the communication side a The voltage small-signal component matrix and the current small-signal component matrix at different frequencies at the phase-parallel grid points. for a The matrix of conduction duty cycle quantities at different frequencies For the communication side a A matrix of small-signal components of the phase inductor current at different frequencies.

5. The droop control inverter sequence impedance modeling method considering frequency coupling according to claim 4, characterized in that, The droop control based on the three-phase grid-connected point voltage and current obtains the frequency domain expression of the active power small signal of the droop-controlled inverter. Combining the relationship between the active power small signal and the disturbance phase angle small signal, a phase angle frequency domain expression considering the voltage and current small signals at different frequencies is obtained, including: Based on the three-phase grid-connected point voltage and three-phase grid-connected point current, droop control is performed to obtain the frequency domain expression of the active power small signal of the droop control inverter, which is represented by the following formula 7: Official 7; in, This represents the small-signal components of active power at different frequencies. and This indicates the main circuit at different frequencies. dq Steady-state voltage at the grid connection point , This represents a matrix composed of small voltage signals at different frequencies at the grid connection point along the dq axis. , This represents the steady-state current at the grid connection point along the dq axis at different frequencies. , This represents a matrix composed of small current signals at different frequencies at the dq-axis grid connection point; The active power small signal The small signal of the disturbance phase angle is obtained through the active power loop of the droop control inverter. It can be represented by the following formula 8: Official 8; in, This represents the small signal of the perturbation phase angle at different frequencies. This represents the open-loop transfer function matrix of the active power loop at different frequencies; use a Phase current represents the small signal of active power. Obtain the small signal of the perturbation phase angle The phase angle frequency domain expression is: Official 9; in, Indicates the AC side of the main circuit a Different frequencies of parallel network points a Phase current small signal, This indicates the small signal of the disturbance phase angle. With the communication side a Small current signals at different frequencies at parallel grid points The transfer function matrix of the relation. This indicates the small signal of the disturbance phase angle. With the communication side a Different frequencies of parallel network points a Phase voltage small signal The transfer function matrix of the relationship.

6. The method for modeling the sequence impedance of a droop-controlled inverter considering frequency coupling according to claim 5, characterized in that, Based on the phase angle frequency domain expression, the voltage small signal and the current small signal at different frequencies are calculated. dq The small-signal expression for the first conduction duty cycle after the shaft current loop includes: exist dq In coordinate system, dq Small signal of shaft inductor current , After the current loop PI regulator and decoupling operation of the droop control inverter, a modulated small signal is obtained. dq First harmonic vector expression of the axis , ; Based on the phase angle frequency domain expression, the modulated small signal dq First harmonic vector expression of the axis , After the inverse transformation of the isopower coordinates, it is transformed into the abc coordinate system. a The phase conduction duty cycle is used to obtain the small-signal expression for the first conduction duty cycle, which is represented by the following formula 11: Official 11; in, For the a Phase current duty cycle With the a Phase current small signal The transfer function matrix of the relationship, and is related to the phase angle frequency domain expression; For the a Phase current duty cycle With the a Phase voltage small signal The transfer function matrix of the relationship, and is related to the phase angle frequency domain expression.

7. The method for modeling the sequence impedance of a droop-controlled inverter considering frequency coupling according to claim 6, characterized in that, Based on the phase angle frequency domain expression, the voltage small signal and the current small signal at different frequencies are calculated. dq Shaft voltage loop and the dq The small-signal expression for the second conduction duty cycle after the current loop includes: In the dq In the coordinate system, the voltage small signal, after passing through the voltage loop PI regulator and decoupling operation of the droop control inverter, and then through the current loop PI regulator and decoupling operation, obtains a modulated small signal. dq The second harmonic vector expression of the axis , ; Based on the phase angle frequency domain expression, the modulated small signal dq The second harmonic vector expression of the axis , After the inverse transformation of the isopower coordinates, it is transformed into the abc coordinate system. a The phase conduction duty cycle is used to obtain the small-signal expression for the second conduction duty cycle, which is represented by the following formula 13: Official 13; in, For the a Phase voltage duty cycle With the a Phase current small signal The transfer function matrix of the relationship, and related to the phase angle frequency domain expression. For the a Phase voltage duty cycle With the a Phase voltage small signal The transfer function matrix of the relationship, and is related to the phase angle frequency domain expression.

8. The method for modeling the sequence impedance of a droop-controlled inverter considering frequency coupling according to claim 7, characterized in that, Based on the relationship between the reactive power droop control and voltage amplitude of the droop control inverter, and combined with the phase angle frequency domain expression, the voltage small signal and current small signal at different frequencies are calculated after passing through the reactive power loop. dq Shaft voltage loop and the dq The small-signal expression for the third conduction duty cycle after the shaft current loop includes: Based on the three-phase grid-connected point voltage and three-phase grid-connected point current, droop control is performed to obtain the frequency domain expression of the reactive power small signal of the droop control inverter, which is expressed by the following formula 14: Official 14; in, This indicates the small signal of reactive power; The reactive power small signal is passed through the reactive power loop of the droop control inverter, and the... dq Shaft voltage loop and the dq Axial current loop to obtain d-axis modulated wavelet small signal The third modulated wave small signal is represented by the following formula 15: Official 15; in, Small signal of d-axis modulation wave With the small reactive power signal The transfer function matrix; Using the above a Phase current expresses the small signal of reactive power. Then, based on the phase angle frequency domain expression, the third modulation wavelet small signal is... After inverse isopower coordinate transformation, it is converted to abc In coordinate system, obtain a q-axis conduction duty cycle It can be represented by the following formula 16: Official 16; in, express a q-axis conduction duty cycle With the a Phase current small signal The transfer function matrix of the relationship, and is related to the phase angle frequency domain expression; express a q-axis conduction duty cycle With the a Phase voltage small signal The transfer function matrix of the relationship, and is related to the phase angle frequency domain expression.

9. The method for modeling the sequence impedance of a droop-controlled inverter considering frequency coupling according to claim 8, characterized in that, The expression for the fourth conduction duty cycle small signal generated by the inverse coordinate transformation of the dq axis steady-state component based on the phase angle frequency domain expression is expressed by the following formula 17: Official 17; in, For steady-state conduction duty cycle With the a Phase current small signal The transfer function matrix of the relationship, and is related to the phase angle frequency domain expression; The steady-state duty cycle With the a Phase voltage small signal The transfer function matrix of the relationship, and is related to the phase angle frequency domain expression.

10. The method for modeling the sequence impedance of a droop-controlled inverter considering frequency coupling according to claim 9, characterized in that, The positive-sequence self-impedance model, positive-sequence coupling impedance model, negative-sequence self-impedance model, and negative-sequence coupling impedance model of the droop control inverter are obtained based on the frequency domain small-signal expression, the first conduction duty cycle small-signal expression, the second conduction duty cycle small-signal expression, the third conduction duty cycle small-signal expression, and the fourth conduction duty cycle small-signal expression, including: Using formulas 11, 13, and 15 to express formula 17, we obtain the following formula representation 18: Official 18; Substituting Formula 6 and Formula 18 into Formula 5, we obtain the following Formula 19: Official 19: Where U represents a 5×5 identity matrix, To conduct duty cycle With the a Phase voltage small signal The transfer function matrix of the relation. To conduct duty cycle With the a Phase current small signal The transfer function matrix of the relationship; Based on Equation 19, the positive-sequence self-impedance model is obtained. Z pp ( s The positive-sequence coupling impedance model Z pn ( s Negative sequence self-impedance model and negative sequence coupling impedance model .

11. The method for modeling the sequence impedance of a droop-controlled inverter considering frequency coupling according to claim 10, characterized in that, Based on the aforementioned formula 19, the positive-sequence self-impedance model is obtained. Z pp ( s The positive-sequence coupling impedance model Z pn ( s Negative sequence self-impedance model and negative sequence coupling impedance model ,include: Based on the aforementioned formula 19, for the a Phase voltage small signal The positive-sequence self-impedance model is obtained by performing matrix operations on the relevant frequencies. Zpp(s) The positive-sequence coupling impedance model Zpn(s) Negative sequence self-impedance model and negative sequence coupling impedance model .

12. A droop-controlled inverter sequence impedance modeling system considering frequency coupling, characterized in that, include: The disturbance module is used to construct the state equation of the droop control inverter in the time domain, perform a Fourier transform on the state equation to obtain the corresponding frequency domain expression, and obtain the frequency domain expression of the droop control inverter based on the frequency domain expression and the positive sequence small-signal current disturbance at the preset frequency at the grid connection point between the droop control inverter and the grid. The variables of the state equation include the three-phase grid connection point voltage, the three-phase grid connection point current and the modulation signal, and the frequency domain small signal corresponds to multiple different frequencies during the frequency coupling process. The active power loop module is used to perform droop control based on the three-phase grid connection point voltage and the three-phase grid connection point current, to obtain the frequency domain expression of the active power small signal of the droop control inverter, and to obtain the phase angle frequency domain expression of the disturbance phase angle small signal considering the voltage small signal and the current small signal at different frequencies by combining the relationship between the active power small signal and the disturbance phase angle small signal. The current loop module is used to calculate the first duty cycle expression of the voltage small signal and the current small signal after passing through the dq axis current loop at different frequencies, based on the phase angle frequency domain expression. The voltage loop module is used to calculate the second conduction duty cycle small signal expression of the voltage small signal and the current small signal after passing through the dq axis voltage loop and the dq current loop at different frequencies, based on the phase angle frequency domain expression. The reactive power loop module is used to calculate the third conduction duty cycle small signal expression after passing through the reactive power loop, d-axis voltage loop and current loop, based on the relationship between the reactive power droop control and voltage amplitude of the droop control inverter and the phase angle frequency domain expression. The steady-state module is used to calculate the fourth conduction duty cycle small signal expression generated by the inverse coordinate transformation of the dq axis steady-state component based on the phase angle frequency domain expression. A complete modulation module is used to obtain the positive-sequence self-impedance model, positive-sequence coupling impedance model, negative-sequence self-impedance model, and negative-sequence coupling impedance model of the droop control inverter based on the expression of the frequency domain small signal, the expression of the first conduction duty cycle small signal, the expression of the second conduction duty cycle small signal, the expression of the third conduction duty cycle small signal, and the expression of the fourth conduction duty cycle small signal.

13. A server, characterized in that, include: At least one processor; as well as, A memory communicatively connected to the at least one processor; wherein, The memory stores instructions executable by the at least one processor, which, when executed by the at least one processor, enables the at least one processor to perform the droop control inverter sequence impedance modeling method considering frequency coupling as described in any one of claims 1 to 11.

14. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions that, when executed by a processor, implement the droop control inverter sequence impedance modeling method considering frequency coupling as described in any one of claims 1 to 11.

15. A computer program product, comprising a computer program, characterized in that, When executed by a processor, the computer program implements the steps of the droop control inverter sequence impedance modeling method considering frequency coupling as described in any one of claims 1 to 11.

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