Impedance modeling method and device and computer equipment

Abstract

The invention relates to an impedance modeling method and device and computer equipment. Comprising the steps that disturbance voltage is injected to the alternating current side of a main circuit, a first relation between a modulation small signal and an alternating current small signal is obtained through alternating current control topology, the disturbance voltage and a phase angle small signal are correlated through a phase-locked loop, and a second relation between the modulation small signal and an alternating voltage small signal is determined; injecting disturbance voltage to the direct current side of the main circuit, and determining a third relationship between the modulation small signal and the alternating current small signal and a fourth relationship between the direct current small signals based on the alternating current control topology and the direct current control topology; and finally, impedance modeling is carried out in combination with a frequency small-signal model, so that self-impedance and coupling impedance characteristics of an alternating current side and a direct current side can be accurately reflected, and a basis is provided for analyzing system stability and optimizing a control strategy.

Description

Technical Field

[0001] This application relates to the field of smart grid control technology, and in particular to an impedance modeling method, apparatus and computer equipment. Background Technology

[0002] Achieving stable power output and grid compatibility is a core requirement in power grid control. Two-level voltage source converters, with their precise control over output voltage amplitude, frequency, and phase, can effectively mitigate power fluctuations from renewable energy generation, ensuring power quality meets grid connection standards.

[0003] However, the impedance modeling process of traditional two-level voltage source converters (VSCs) typically uses a second-order transfer function matrix to describe only the AC side impedance characteristics, which has the following problems: it does not consider the impact of DC bus voltage fluctuations on the AC side, especially under weak grid conditions, the error is significant; the coupling is simplified, only assuming that the AC side dq axis is completely decoupled, but in reality, the coupling effect is obvious in the high-frequency band; and it cannot analyze the DC side stability, such as the DC bus resonance problem in photovoltaic grid-connected systems. Summary of the Invention

[0004] Based on this, the purpose of this application is to provide an impedance modeling method, apparatus, and computer device that can achieve precise power control under unbalanced power grids, so as to solve the technical problems mentioned in the background art.

[0005] Firstly, this application provides an impedance modeling method. Applied to a two-level voltage source converter, including the main circuit, AC control topology, and phase-locked loop, wherein: When a disturbance voltage is injected into the AC side of the main circuit, the first frequency small-signal model in the AC loop is determined. The first relationship between the modulated small signal and the alternating current small signal is determined based on the AC control topology. Based on the phase-locked loop association of the disturbance voltage and phase angle small signal, a second relationship is determined between the modulation small signal and the AC voltage small signal; Impedance modeling is performed based on the first relationship, the second relationship, and the first frequency small-signal model.

[0006] In one embodiment, the AC control topology includes a proportional-integral (PI) regulator and a decoupling module; the modulation small signal includes a first modulation small signal; determining the first relationship between the modulation small signal and the AC current small signal based on the AC control topology includes: performing a Parker transform on the AC current small signal according to the fundamental voltage phase; processing the transformed AC current small signal through the PPI regulator and the decoupling module to obtain an initial modulation small signal; performing an inverse Parker transform on the initial modulation small signal to obtain the first modulation small signal, and converting it into the first relationship between the first modulation small signal and the AC current small signal.

[0007] In one embodiment, the step of associating the disturbance voltage and the small phase angle signal based on the phase-locked loop includes: determining the AC voltage after the disturbance voltage undergoes a Parker transformation; determining the relationship between the AC voltage and the small phase angle signal based on the fundamental frequency voltage amplitude and the fundamental voltage phase; and associating the disturbance voltage and the small phase angle signal based on the transfer function of the phase-locked loop and the relationship between the AC voltage and the small phase angle signal.

[0008] In one embodiment, the modulation small signal includes a second modulation small signal; determining the second relationship between the modulation small signal and the AC voltage small signal includes: superimposing a phase angle small signal associated with the disturbance voltage onto the AC control topology; performing a Parker transform on the AC current small signal superimposed with the phase angle small signal until a candidate modulation small signal is determined through the proportional-integral regulator and decoupling module in the AC control topology; performing an inverse Parker transform on the candidate modulation small signal superimposed with the phase angle small signal to obtain the second modulation small signal, and converting it into the second relationship between the second modulation small signal and the AC voltage small signal.

[0009] In one embodiment, the two-level voltage source converter further includes a DC control topology, and the above method further includes: when injecting a disturbance voltage to the DC side of the main circuit, determining a second frequency small-signal model in the AC loop; determining a third relationship between the modulation small signal and the AC current small signal based on the AC control topology; determining a fourth relationship between the modulation small signal and the DC voltage small signal based on the DC control topology; and performing impedance modeling based on the third relationship, the fourth relationship, and the second frequency small-signal model.

[0010] In one embodiment, the modulation small signal further includes a third modulation small signal; determining the fourth relationship between the modulation small signal and the DC voltage small signal based on the DC control topology includes: determining an initial current based on the transfer function of the DC voltage small signal and the DC control topology; determining a target modulation small signal based on the initial current and the transfer function of the AC control topology; performing an inverse Park transform on the target modulation small signal to obtain a third modulation small signal, and converting it into a fourth relationship between the third modulation small signal and the DC current small signal.

[0011] Secondly, this application also provides an impedance modeling device. Applied to a two-level voltage source converter, it includes a main circuit, an AC control topology, and a phase-locked loop, wherein: The first relationship determination module is used to determine the first frequency small-signal model in the AC loop when a disturbance voltage is injected into the AC side of the main circuit; and to determine the first relationship between the modulation small signal and the AC current small signal based on the AC control topology. The second relationship determination module is used to associate the disturbance voltage and phase angle small signal based on the phase-locked loop, and determine the second relationship between the modulation small signal and the AC voltage small signal; and to perform impedance modeling based on the first relationship, the second relationship and the first frequency small signal model.

[0012] In one embodiment, the two-level voltage source converter further includes a DC control topology, and the above-mentioned device further includes: The third relationship determination module is used to determine the second frequency small-signal model in the AC loop when a disturbance voltage is injected into the DC side of the main circuit; and to determine the third relationship between the modulation small signal and the AC current small signal based on the AC control topology. The fourth relationship determination module is used to determine the fourth relationship between the modulation small signal and the DC current small signal based on the DC control topology; and to perform impedance modeling based on the third relationship, the fourth relationship and the second frequency small signal model.

[0013] Thirdly, this application also provides a computer device. The computer device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the steps of the impedance modeling method described above.

[0014] Fourthly, this application also provides a computer-readable storage medium. The computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of the above impedance modeling method.

[0015] The aforementioned impedance modeling method, apparatus, computer equipment, and readable storage medium inject a disturbance voltage into the AC side of the main circuit to determine the first frequency small-signal model of the AC loop; by using the AC control topology, the first relationship between modulation and AC current small-signal is obtained; by using a phase-locked loop to correlate the disturbance voltage and phase angle small-signal, the second relationship between modulation and AC voltage small-signal is determined; by combining the three to model, the impedance characteristics of the AC side can be accurately reflected, providing a basis for analyzing system stability and optimizing control strategies. Attached Figure Description

[0016] Figure 1 This is a main circuit topology diagram of a two-level voltage source converter in one embodiment; Figure 2This is a flowchart illustrating an impedance modeling method in one embodiment; Figure 3 Here is an AC control topology diagram for one embodiment; Figure 4 This is a topology diagram of phase-locked loop control in one embodiment; Figure 5 This is a flowchart illustrating the impedance modeling method in another embodiment; Figure 6 This is a DC control topology diagram in one embodiment; Figure 7 This is a schematic diagram illustrating the impedance definition and distribution in one embodiment; Figure 8 This is a flowchart illustrating the impedance modeling method in another embodiment; Figure 9 This is an internal structural diagram of a computer device in one embodiment; Figure 1 middle, This indicates the three-phase current at the AC port. This indicates the three-phase voltage at the AC port. Indicates the DC side current. Indicates the DC port voltage. This represents the equivalent output current of the converter bridge arm. L Indicates the filter inductance. C dc Indicates capacitance; Figure 3 middle, This indicates the three-phase current at the AC port. This represents the current component in the dq coordinate system after the Park transformation. This represents the modulation signal in the dq coordinate system. This represents the three-phase modulated signal after the inverse Parker transform. Indicates the phase angle of the phase-locked loop. This represents the d-axis reference current in the dq coordinate system. This represents the q-axis reference current in the dq coordinate system. Indicates the decoupling gain. This represents the transfer function of the current PI control. Figure 4 middle, This indicates the three-phase voltage at the AC port. This represents the voltage components in the dq coordinate system after the Park transformation. Indicates the phase angle of the phase-locked loop. This represents the transfer function of the phase-locked loop (PLL) PI control. Indicates the angular frequency correction value. Indicates the rated angular frequency; Figure 6 middle, Indicates the DC port voltage. Indicates the DC voltage reference value. This represents the d-axis reference current in the dq coordinate system. This represents the DC voltage PI control transfer function. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0018] The impedance modeling method provided in this application can be applied to two-level voltage source converters, such as... Figure 1 As shown, Figure 1 This is a main circuit topology diagram of a two-level voltage source converter. It consists of a three-phase full-bridge circuit, with each phase including two IGBTs with anti-parallel diodes, for a total of six switching devices. The DC side is supported by a capacitor for stable voltage, while the AC side outputs a controllable AC voltage through PWM modulation. It supports decoupled control of active and reactive power, making it suitable for applications requiring flexible power adjustment. The self-admittance and coupling admittance obtained through impedance modeling serve as the frequency domain identifier of the two-level voltage source converter. They can be used in fields such as new energy grid-connected inverters, static synchronous compensators, energy storage, and high-voltage DC transmission. With these, wideband stability margins can be calculated in seconds, oscillation sources can be locked, PLL and voltage loop gains can be optimized, and feedforward cancellers can be designed. Furthermore, LC filters can be quantitatively added, grid short-circuit ratios can be evaluated, high-frequency protection thresholds can be set, and a closed-loop system can be implemented for the entire lifecycle of equipment grid-connected design, operation and maintenance, and upgrades.

[0019] In one embodiment, such as Figure 2 As shown, an impedance modeling method is provided, applied to a two-level voltage source converter, including the main circuit, AC control topology, and phase-locked loop, comprising the following steps: In step S202, when injecting a disturbance voltage to the AC side of the main circuit, the first frequency small-signal model in the AC loop is determined.

[0020] In this application, the small-signal representation only retains the small perturbation amount that deviates from the steady-state operating point, and does not consider the signal quantity when higher-order nonlinear terms are not considered.

[0021] Specifically, when a disturbance voltage is injected at the AC side port of the main circuit and there is no disturbance voltage at the DC side port, the current response data sequence is simultaneously acquired. At this time, the time-domain model of the main circuit is transformed into a first frequency-domain small-signal model under the AC loop. For example, using... Figure 1 Taking phase a as an example, the small-signal model of the first frequency is determined as follows: .in, This represents the small-signal component of the phase a current in the three-phase AC current. Indicates the DC bus voltage. This represents the small-signal component modulated by phase a. Y represents the small-signal component of phase a voltage. lp This represents a diagonal admittance matrix.

[0022] In one embodiment, the determination is made based on the AC side port response data sequence at the disturbance frequency. At this point, all three phase responses are zero sequence. The diagonal element at the corresponding position is 0, as shown below: ; in, L Indicates the filter inductance. The imaginary unit, , , , , This is the fundamental frequency.

[0023] Step S204: Determine the first relationship between the modulated small signal and the AC current small signal based on the AC control topology.

[0024] Specifically, such as Figure 3 The AC control topology diagram is shown. After the small AC current signal is input to the AC control topology, it undergoes Parker transformation and small-signal linearization to obtain the small current signal in dq coordinates. Then, this small current signal in dq coordinates is passed through a regulator and decoupling circuit to obtain the initial modulated small signal (m). d m q Finally, the initial modulation signal is subjected to an inverse Parker transform to obtain the modulation signal (m) in the three-phase stationary coordinate system. a m b m c This leads to the determination of the first relationship Q between the modulation small signal and the AC current small signal. The Q matrix represents the dependence of the modulation signal on the AC side port current, determined by the current control of the two-level voltage source converter.

[0025] Step S206: Based on the phase-locked loop correlation of disturbance voltage and phase angle small signal, determine the second relationship between modulation small signal and AC voltage small signal.

[0026] Specifically, such as Figure 4The diagram shows a phase-locked loop (PLL) control topology. When a disturbance voltage is input to the PLL, it undergoes Parker transformation and PLL transfer function processing sequentially, yielding the harmonic vector relationship between the input disturbance voltage and the output phase angle small signal. However, when considering the effects of a non-ideal PLL, the grid current in the AC control topology, after coordinate transformation, interacts with the harmonic vector of the phase angle small signal, generating additional harmonic components. Therefore, refer to... Figure 3 As shown, the phase angle small signal also needs to be... This is superimposed onto the AC control topology to further consider the second relationship P between the modulated small signal and the AC voltage small signal corresponding to the disturbance voltage. The P matrix represents the dependence of the modulated small signal on the AC side port voltage, and is jointly determined by the phase-locked loop and the current control of the two-level voltage source converter.

[0027] Step S208: Impedance modeling is performed based on the first relation, the second relation, and the first frequency small-signal model.

[0028] When a positive sequence voltage disturbance is applied to the AC side port At that time, the AC side port of the two-level voltage source converter generates a frequency of The positive sequence current, the positive sequence self-admittance is The DC-side port generates a frequency of... The current, i.e., the coupling admittance. The frequency generated by the AC side port is The negative sequence current, i.e., the coupling admittance. When a negative sequence voltage disturbance is applied to the AC side port At that time, the AC side port of the two-level voltage source converter generates a frequency of The negative sequence current, the negative sequence self-admittance is The DC-side port generates a frequency of... The current, i.e., the coupling admittance. The frequency generated by the AC side port is The positive sequence current, i.e., the coupling admittance. .

[0029] Specifically, by combining the first relationship between the modulation small signal and the AC current small signal, and the second relationship between the modulation small signal and the AC voltage small signal, the modulation small model m is determined. a With alternating current small signal i a AC voltage small signal v a The first objective relationship is: Substituting the first objective relationship into the first frequency small-signal model and simplifying by rearranging terms, the harmonic component relationship between the AC current small-signal and the AC voltage small-signal is obtained, so as to determine the self-admittance and coupling admittance corresponding to different disturbances based on the harmonic component relationship.

[0030] In the above impedance modeling method, a disturbance voltage is injected into the AC side of the main circuit to determine the first frequency small-signal model of the AC loop; the first relationship between modulation and AC current small signal is obtained by using the AC control topology; the second relationship between modulation and AC voltage small signal is determined by associating the disturbance voltage and phase angle small signal through a phase-locked loop; the combination of these three models can accurately reflect the AC side impedance characteristics, providing a basis for analyzing system stability and optimizing control strategies.

[0031] In one embodiment, such as Figure 5 As shown, Figure 5 A flowchart illustrating the impedance modeling method when injecting disturbance voltage into the AC side is shown. It includes: transforming the time-domain model of the main circuit into a first frequency-domain small-signal model under the AC loop; calculating the expression of the modulation small signal with respect to the AC current small signal based on AC port current control, i.e., determining the first relationship between the modulation small signal and the AC current small signal; calculating the expression of the modulation small signal with respect to the AC voltage small signal based on the phase-locked loop and AC port current control, i.e., determining the second relationship between the modulation small signal and the AC voltage small signal; and substituting the expression related to the modulation small signal into the first frequency-domain small-signal model to obtain the impedance modeling result for the AC side.

[0032] Among the relevant parameters mentioned in this application are the fundamental frequency current amplitude. Fundamental frequency current amplitude Fundamental voltage phase (e.g., 30°), fundamental current phase (e.g., 15°), DC bus voltage Integral coefficient of current PI control Phase-locked loop PI control proportional coefficient and integral coefficient Voltage PI control proportional coefficient and integral coefficient Decoupling gain Modulator gain Disturbance frequency Fundamental frequency .

[0033] In one embodiment, determining the first relationship between the modulation small signal and the AC current small signal based on the AC control topology includes: performing a Parker transformation on the AC current small signal according to the fundamental voltage phase; processing the transformed AC current small signal through a proportional-integral regulator and a decoupling module to obtain an initial modulation small signal; performing an inverse Parker transformation on the initial modulation small signal to obtain a first modulation small signal, and converting it into the first relationship between the first modulation small signal and the AC current small signal.

[0034] The AC control topology includes a proportional-integral regulator and a decoupling module; the modulated small signal includes a first modulated small signal.

[0035] Specifically, refer to Figure 3 As shown, after performing a Parker transform on the small AC current signal, the small current signal in the dq coordinate system is obtained as follows: ;

[0036] in, , The phase of the fundamental voltage. This represents the small-signal component of the three-phase current at the AC port. This represents the small-signal components of the current along the d-axis and q-axis in the dq coordinate system. The coordinate transformation matrix is: ;

[0037] Then, after the small current signal in the dq coordinate system passes through the proportional-integral regulator and the decoupling module, the initial modulated small signal obtained is: ;

[0038] in, This represents the transfer function of the proportional-integral controller. This represents the decoupling gain. Finally, after inverse Parker transformation to a three-phase stationary coordinate system, the expression for the harmonic vector of the first modulated small signal is: ;

[0039] The simplified first relationship Q between the first modulation small signal and the alternating current small signal is: ; in This indicates the modulator gain.

[0040] In this embodiment, the small AC current signal is first converted to DC by Parker transformation based on the phase of the fundamental voltage; then the initial modulation signal is obtained by processing the proportional-integral regulator and the decoupling module; finally, the first modulation signal is obtained by inverse Parker transformation, and then the first relationship between it and the original small AC current signal is determined, avoiding the problem of oversimplification of coupling, laying the foundation for precise current control, and improving regulation efficiency and accuracy.

[0041] In one embodiment, when a positive-sequence voltage disturbance is injected: ;

[0042] in: ;

[0043] In one embodiment, associating a disturbance voltage and a small phase angle signal based on a phase-locked loop includes: determining the AC voltage after Parker transformation of the disturbance voltage; determining the relationship between the AC voltage and the small phase angle signal based on the fundamental frequency voltage amplitude and the fundamental voltage phase; and associating the disturbance voltage and the small phase angle signal based on the transfer function of the phase-locked loop and the relationship between the AC voltage and the small phase angle signal.

[0044] Specifically, when considering the small phase angle signal present in the phase-locked loop, the new coordinate transformation matrix is: ;

[0045] After the disturbance voltage undergoes a Park transformation using the new coordinate transformation matrix, the output AC voltage in the dq coordinate system is obtained as follows: ;

[0046] After simplification, the relationship between AC voltage and small-signal phase angle is as follows: ;

[0047] in, Given a 5×5 matrix, the elements at positions (2, 1), (2, 3), and (5, 4) are respectively... , and All other elements are 0. This is combined with the transfer function in the phase-locked loop control block diagram. The harmonic vector expression for the small-signal output phase angle of the phase-locked loop when the input positive-sequence voltage disturbance is obtained is as follows: ;

[0048] In this embodiment, the AC voltage after the Parker transformation of the disturbance voltage is first determined to provide a basis for subsequent correlation; then, the relationship between the AC voltage and the small phase angle signal is clarified by combining the amplitude of the fundamental frequency voltage and the phase phase voltage; finally, the disturbance voltage and the small phase angle signal are correlated by using the phase-locked loop transfer function, providing a basis for accurately analyzing the impact of the disturbance on the phase angle and optimizing the phase-locked loop control.

[0049] In one embodiment, the relationship between AC voltage and small-signal phase angle can be obtained as follows: ;

[0050] Among them, let , ;

[0051] In one embodiment, determining the second relationship between the modulation small signal and the AC voltage small signal includes: superimposing the phase angle small signal associated with the disturbance voltage onto the AC control topology; performing a Parker transform on the AC current small signal superimposed with the phase angle small signal until a candidate modulation small signal is determined through the proportional-integral regulator and decoupling module in the AC control topology; performing an inverse Parker transform on the candidate modulation small signal superimposed with the phase angle small signal to obtain the second modulation small signal, and converting it into the second relationship between the second modulation small signal and the AC voltage small signal.

[0052] Among them, the modulated small signal includes the second modulated small signal.

[0053] Specifically, refer to Figure 3 The phase angle small signal has been included. The input is fed into the AC control topology. Therefore, after the AC current small signal superimposed with the phase angle small signal undergoes the Park transform, a new current small signal with the steady-state term eliminated is obtained as follows: ;

[0054] Next, after the new small current signal in the dq coordinate system passes through the proportional-integral regulator and the decoupling module, a candidate modulation small signal is obtained; the small signal superimposed with the phase angle small signal is then... The candidate modulation small signal, after undergoing inverse Parker transformation to a three-phase stationary coordinate system, yields the second modulation small signal with the steady-state term eliminated: ;

[0055] The final relationship P between the second modulated small signal and the AC voltage small signal is: ; ;

[0056] In this matrix, all elements except those in (1, 3) and (3, 3) are 0. , Indicates the phase of the modulated signal. This represents the decoupling gain.

[0057] In this embodiment, the phase angle small signal is superimposed on the AC control topology, and a candidate modulation small signal is obtained through Parker transformation, regulator and decoupling module; then the candidate signal superimposed with the phase angle small signal is inversely Parker transformed to obtain the second modulation small signal and determine its second relationship with the AC voltage small signal, which provides a basis for analyzing the impact of disturbances and optimizing control, and improves the system's disturbance immunity.

[0058] In one embodiment, the method further includes: when injecting a disturbance voltage to the DC side of the main circuit, determining a second frequency small-signal model in the AC loop; determining a third relationship between the modulation small signal and the AC current small signal based on the AC control topology; determining a fourth relationship between the modulation small signal and the DC voltage small signal based on the DC control topology; and performing impedance modeling based on the third relationship, the fourth relationship, and the second frequency small-signal model.

[0059] Among them, the two-level voltage source converter also includes a DC control topology, which allows for the application of voltage disturbances to the DC side port. At that time, the DC-side port of the two-level voltage source converter generates a frequency of... The current, the self-admittance is The frequency generated by the AC side port is The positive sequence current, i.e., the coupling admittance. The frequency generated by the AC side port is The negative sequence current, i.e., the coupling admittance. The specific impedance definition and distribution are as follows: Figure 7 As shown.

[0060] Specifically, when a disturbance voltage is injected at the DC side port of the main circuit and there is no disturbance voltage at the AC side port, the current response data sequence is simultaneously acquired. At this time, the time-domain model of the main circuit is transformed into a second frequency-domain small-signal model under the AC loop. For example, using... Figure 1 Taking phase a as an example, the small-signal model of the second frequency is determined as follows: Similarly, referring to step S204 above, a third relationship Q between the modulation small signal and the AC current small signal can be determined based on the AC control topology. Then, the DC voltage small signal corresponding to the disturbance voltage is input to the DC control topology to obtain the initial current. After the initial current is further input to the AC control topology, a fourth relationship E between the modulation small signal and the DC voltage small signal is obtained. Here, the E matrix represents the dependence of the modulation small signal on the DC bus voltage, which is determined by the DC bus voltage control.

[0061] Finally, based on the third relationship between the modulation small signal and the AC current small signal, and the fourth relationship between the modulation small signal and the DC voltage small signal, the modulation small model m is determined. a With alternating current small signal i a DC voltage small signal v dc The second objective relationship is: Substituting the second objective relationship into the second frequency small-signal model and simplifying by rearranging terms, the harmonic component relationship between the AC current small-signal and the DC voltage small-signal is obtained. Based on the harmonic component relationship, the self-admittance and coupling admittance under the applied disturbance voltage at the DC side port are determined.

[0062] In this embodiment, after injecting a disturbance voltage to the DC side of the main circuit, the second frequency small-signal model of the AC loop is determined, providing a basis for impedance modeling. The influence of DC bus voltage fluctuations on the AC side is fully considered. The third relationship between modulation and AC current small-signal is determined by the AC control topology, and the fourth relationship between the two is determined by the DC control topology. Finally, the modeling is performed by combining the third and fourth relationships with the second frequency small-signal model, which can accurately reflect the system impedance characteristics and provide a basis for analyzing DC side stability and optimizing control strategies.

[0063] In one embodiment, the determination is made based on the AC side port response data sequence at the disturbance frequency. At this point, all three phase responses are zero sequence. The corresponding diagonal element is 0, as shown below: ;

[0064] In one embodiment, such as Figure 8 As shown, Figure 8 A flowchart illustrating the impedance modeling method when injecting disturbance voltage into the DC side is shown. It includes: transforming the time-domain model of the main circuit into a second-frequency-domain small-signal model under AC loop conditions; calculating the expression of the modulation small signal with respect to the AC current small signal based on AC port current control, i.e., determining the third relationship between the modulation small signal and the AC current small signal; calculating the expression of the modulation small signal with respect to the DC voltage small signal based on DC control topology control, i.e., determining the fourth relationship between the modulation small signal and the DC voltage small signal; and substituting the expression related to the modulation small signal into the second-frequency-domain small-signal model to obtain the impedance modeling result on the DC side.

[0065] therefore, Figure 5 and Figure 8 The impedance modeling process can accurately reflect the self-impedance and coupling impedance characteristics of the AC and DC sides, providing a basis for analyzing system stability and optimizing control strategies.

[0066] In one embodiment, determining the fourth relationship between the modulation small signal and the DC current small signal based on the DC control topology includes: determining the initial current based on the DC voltage small signal and the transfer function of the DC control topology; determining the target modulation small signal based on the initial current and the transfer function of the AC control topology; performing an inverse Park transform on the target modulation small signal to obtain a third modulation small signal, and converting it into the fourth relationship between the third modulation small signal and the DC current small signal.

[0067] The modulated small signal also includes a third modulated small signal.

[0068] Specifically, DC-side port voltage disturbances do not generate small-signal harmonic components of the phase-locked loop (PLL), but only cause disturbances in the d-axis reference current, thereby affecting the target modulation small-signal. At the same frequency The following disturbance is generated: ;

[0069] in This represents the transfer function of the DC control topology. Therefore, after determining the initial current based on the small DC voltage signal corresponding to the disturbance voltage and the transfer function of the DC control topology, the target modulation signal can be determined based on the initial current and the transfer function of the AC control topology. Finally, the target modulation signal is transformed by inverse dq coordinates to obtain the third modulation signal, which is then converted into a fourth relationship E between the third modulation signal and the DC current signal: ;

[0070] In this embodiment, the initial current is first determined by the disturbance voltage and the DC control topology transfer function; then, the target modulation small signal is obtained by combining the AC control topology transfer function; the third modulation small signal is obtained by inverse Park transform, and then the fourth relationship between it and the DC current small signal is determined, which provides a basis for analyzing the AC-DC side coupling characteristics and optimizing system control.

[0071] In one embodiment, the frequency domain small-signal model of the DC bus in the DC control topology is as follows: ;

[0072] in, This indicates the three-phase current at the AC side port. Indicates the amplitude of the three-phase current. This indicates the three-phase voltage at the AC side port. This indicates a three-phase modulated small signal. This indicates the amplitude of the three-phase modulated signal. Indicates the DC side current. This represents the common-mode voltage, typically under positive-sequence perturbations: The cross product of two vectors is transformed into the dot product of the Toplitz matrix and the vector. , Toplitz matrix: ;

[0073] in, , This indicates the phase of the modulated signal. , Indicates the phase of the phase current. Asterisk (*) Indicates complex conjugation.

[0074] In one embodiment, after substituting the first objective relationship into the first frequency small-signal model and simplifying by rearranging terms, the harmonic component relationship between the AC current small-signal and the AC voltage small-signal is obtained as follows: ;

[0075] From the above, we can determine the following in the impedance modeling results: ; ;

[0076] in , Furthermore, it can be based on Design a negative-sequence current compensator to achieve precise power control under unbalanced power grid conditions. Calculate the coupling admittance on the DC side under positive-sequence voltage disturbances on the AC side using a small-signal frequency domain model of the DC bus. This application will not elaborate further.

[0077] By using the positive-sequence and negative-sequence related self-admittance and transferred admittance, the self-admittance of the AC side when a negative-sequence disturbance is injected can be determined. Coupling admittance and DC-side coupling admittance .

[0078] ;

[0079] In one embodiment, after substituting the second objective relationship into the second frequency small-signal model and simplifying by rearranging terms, the harmonic component relationship between the AC current small-signal and the DC voltage small-signal is obtained as follows: ;

[0080] The impedance modeling results can be determined from the above equation as follows: ; ;

[0081] in , Furthermore, the self-admittance can be calculated based on a small-signal model in the frequency domain combined with the DC bus. It identifies the DC bus resonance point and uses stability analysis and other methods to identify the resonance frequency domain point, thereby suppressing oscillations through path blocking, enhanced damping, and other methods.

[0082] In summary, this application, based on the frequency-domain small-signal model of the main circuit, derives the current response of the AC port and the DC port by performing frequency-domain small-signal modeling of the AC control topology and the phase-locked loop when a disturbance voltage is injected into the AC port. Similarly, by performing frequency-domain small-signal modeling of the AC and DC control topologies when a disturbance voltage is injected into the DC port, the current response of the DC port and the AC port are derived. Therefore, compared to traditional impedance models that neglect the influence of AC-side voltage disturbances on the DC-side current response, this application establishes the coupled admittance of the DC-side current response corresponding to AC-side voltage disturbances and the AC-side current response corresponding to DC-side voltage disturbances, thus improving the accuracy of stability analysis. Furthermore, compared to traditional impedance models based on the dq coordinate system that do not consider negative-sequence voltage disturbances, this application simultaneously considers the self-admittance and coupled admittance of the current response under both positive-sequence and negative-sequence voltage disturbances.

[0083] It should be understood that although the steps in the flowcharts of the above embodiments are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the above embodiments may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0084] Based on the same inventive concept, this application also provides an impedance modeling apparatus for implementing the impedance modeling method described above. The solution provided by this apparatus is similar to the implementation scheme described in the above method; therefore, the specific limitations in one or more impedance modeling apparatus embodiments provided below can be found in the limitations of the impedance modeling method described above, and will not be repeated here.

[0085] In one embodiment, an impedance modeling apparatus is provided for a two-level voltage source converter, including a main circuit, an AC control topology, and a phase-locked loop, comprising: a first relationship determination module and a second relationship determination module, wherein: The first relationship determination module is used to inject a disturbance voltage into the AC side of the main circuit to determine the first frequency small-signal model in the AC loop; and to determine the first relationship between the modulation small signal and the AC current small signal based on the AC control topology. The second relationship determination module is used to determine the second relationship between the modulation small signal and the AC voltage small signal based on the phase-locked loop correlation disturbance voltage and phase angle small signal; and to perform impedance modeling based on the first relationship, the second relationship and the first frequency small signal model.

[0086] In one embodiment, the two-level voltage source converter further includes a DC control topology, and the above-mentioned device further includes a third relationship determination module and a fourth relationship determination module, wherein: The third relationship determination module is used to determine the second frequency small-signal model in the AC loop when a disturbance voltage is injected into the DC side of the main circuit; and to determine the third relationship between the modulation small signal and the AC current small signal based on the AC control topology.

[0087] The fourth relationship determination module is used to determine the fourth relationship between the modulated small signal and the DC current small signal based on the DC control topology; and to perform impedance modeling based on the third relationship, the fourth relationship and the second frequency small signal model.

[0088] The various modules in the impedance modeling described above can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in the processor of a computer device in hardware form or independent of it, or they can be stored in the memory of a computer device in software form, so that the processor can call and execute the operations corresponding to each module.

[0089] In one embodiment, a computer device is provided, which may be a server, and its internal structure diagram may be as follows: Figure 9 As shown, this computer device includes a processor, memory, input / output (I / O) interfaces, and a communication interface. The processor, memory, and I / O interfaces are connected via a system bus, and the communication interface is also connected to the system bus via the I / O interfaces. The processor provides computational and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system, computer programs, and a database. The internal memory provides the environment for the operating system and computer programs stored in the non-volatile storage media. The database stores time-domain equations and frequency-domain small-signal equations. The I / O interfaces are used for exchanging information between the processor and external devices. The communication interface is used for communication with external terminals via a network connection. When executed by the processor, the computer program implements an impedance modeling method.

[0090] Those skilled in the art will understand that Figure 9The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0091] In one embodiment, a computer device is also provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps in the above method embodiments.

[0092] In one embodiment, a computer-readable storage medium is provided storing a computer program that, when executed by a processor, implements the steps in the above method embodiments.

[0093] In one embodiment, a computer program product or computer program is provided, the computer program product or computer program including computer instructions stored in a computer-readable storage medium. A processor of a computer device reads the computer instructions from the computer-readable storage medium, and executes the computer instructions, causing the computer device to perform the steps in the above method embodiments.

[0094] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments of the above methods. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile 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. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0095] The technical features of the above embodiments can be combined in any way. For the sake of brevity, 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 specification.

[0096] The above embodiments are merely illustrative of several implementation methods of this application, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. An impedance modeling method, characterized in that, Applied to a two-level voltage source converter, including the main circuit, AC control topology, and phase-locked loop, wherein: When a disturbance voltage is injected into the AC side of the main circuit, the first frequency small-signal model in the AC loop is determined. The first relationship between the modulated small signal and the alternating current small signal is determined based on the AC control topology. Based on the phase-locked loop association of the disturbance voltage and phase angle small signal, a second relationship is determined between the modulation small signal and the AC voltage small signal; Impedance modeling is performed based on the first relationship, the second relationship, and the first frequency small-signal model.

2. The method according to claim 1, characterized in that, The AC control topology includes a proportional-integral regulator and a decoupling module; The modulated small signal includes a first modulated small signal; The determination of the first relationship between the modulated small signal and the AC current small signal based on the AC control topology includes: The small AC current signal is subjected to Parker transformation based on the phase of the fundamental voltage. The transformed AC current small signal is processed by a proportional-integral regulator and a decoupling module to obtain the initial modulation small signal; The initial modulation signal is subjected to an inverse Parker transform to obtain a first modulation signal, which is then converted into a first relationship between the first modulation signal and the alternating current signal.

3. The method according to claim 1, characterized in that, The method of associating the disturbance voltage and phase angle small signal based on the phase-locked loop includes: Determine the AC voltage after the disturbance voltage undergoes Parker transformation; The relationship between the AC voltage and the phase angle small signal is determined based on the fundamental frequency voltage amplitude and the fundamental voltage phase. The disturbance voltage and the small phase angle signal are correlated based on the transfer function of the phase-locked loop and the relationship between the AC voltage and the small phase angle signal.

4. The method according to claim 1 or 3, characterized in that, The modulated small signal includes a second modulated small signal; determining the second relationship between the modulated small signal and the AC voltage small signal includes: The phase angle small signal associated with the disturbance voltage is superimposed onto the AC control topology; The small AC current signal superimposed with the phase angle small signal is subjected to Parker transformation until the candidate modulation small signal is determined through the proportional-integral regulator and decoupling module in the AC control topology. The candidate modulation signal with superimposed phase angle small signal is subjected to inverse Park transform to obtain the second modulation small signal, and then transformed into a second relationship between the second modulation small signal and the AC voltage small signal.

5. The method according to claim 1, characterized in that, The two-level voltage source converter also includes a DC control topology, and the above method further includes: When a disturbance voltage is injected into the DC side of the main circuit, the second frequency small-signal model in the AC loop is determined. A third relationship between the modulated small signal and the alternating current small signal is determined based on the AC control topology. A fourth relationship between the modulated small signal and the DC voltage small signal is determined based on the DC control topology. Impedance modeling is performed based on the third relation, the fourth relation, and the second frequency small-signal model.

6. The method according to claim 5, characterized in that, The modulated small signal further includes a third modulated small signal; the determination of the fourth relationship between the modulated small signal and the DC voltage small signal based on the DC control topology includes: The initial current is determined based on the small-signal DC voltage and the transfer function of the DC control topology; The target modulation small signal is determined based on the initial current and the transfer function of the AC control topology; The target modulation signal is subjected to an inverse Parker transform to obtain a third modulation signal, which is then converted into a fourth relationship between the third modulation signal and the DC voltage signal.

7. An impedance modeling device, characterized in that, This is applied to a two-level voltage source converter, which includes a main circuit, an AC control topology, and a phase-locked loop, wherein: The first relationship determination module is used to determine the first frequency small-signal model in the AC loop when a disturbance voltage is injected into the AC side of the main circuit; and to determine the first relationship between the modulation small signal and the AC current small signal based on the AC control topology. The second relationship determination module is used to associate the disturbance voltage and phase angle small signal based on the phase-locked loop, and determine the second relationship between the modulation small signal and the AC voltage small signal; and to perform impedance modeling based on the first relationship, the second relationship and the first frequency small signal model.

8. The apparatus according to claim 7, characterized in that, The two-level voltage source converter also includes a DC control topology, and the above-mentioned device also includes: The third relationship determination module is used to determine the second frequency small-signal model in the AC loop when a disturbance voltage is injected into the DC side of the main circuit; and to determine the third relationship between the modulation small signal and the AC current small signal based on the AC control topology. The fourth relationship determination module is used to determine the fourth relationship between the modulation small signal and the DC current small signal based on the DC control topology; and to perform impedance modeling based on the third relationship, the fourth relationship and the second frequency small signal model.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 6.

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

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