Modular multilevel converter impedance modeling method, system, equipment and medium

Abstract

A modular multilevel converter impedance modeling method, system, device and medium belong to the technical field of flexible DC power transmission, and the method comprises the following steps: constructing a multi-frequency mapping relation between a DC power transmission network port voltage and a current small signal; constructing a direct-current voltage synchronous control loop small-signal multi-frequency mapping relation by considering a direct-current power transmission network multi-frequency mapping relation; building a modular multilevel converter control loop multi-frequency mapping relation by considering AC voltage, current and circulation control; constructing a modular multilevel converter bridge arm power path multi-frequency mapping relation under the action of the control loop; and constructing an impedance analytical model of the modular multilevel converter in a direct-current voltage synchronous control mode by combining the constructed multi-frequency mapping relationships, and completing impedance modeling of the modular multilevel converter. According to the method, the impedance analysis model of the modular multilevel converter can be obtained through accurate analysis, and technical support is provided for new energy and flexible direct current broadband oscillation analysis and solution in a weak synchronous power supply support scene.

Description

Technical Field

[0001] This invention belongs to the field of flexible DC transmission technology, specifically relating to a modular multilevel converter impedance modeling method, system, equipment, and medium. Background Technology

[0002] As new energy development expands into deserts, Gobi, wastelands, and deep-sea areas, flexible DC transmission of new energy has become the dominant form of large-scale new energy development in my country. These remote areas face the challenge of weak synchronous power supply support, urgently requiring modular multilevel converters used in flexible DC transmission to provide voltage support to the AC grid.

[0003] In recent years, broadband oscillation accidents have occurred frequently in new energy and flexible DC islanded systems, seriously affecting the safe and stable operation of the systems. In scenarios supported by weak synchronous power sources, the system stability is simultaneously affected by the dynamic interaction of new energy converters, modular multilevel converters, and the AC power grid, making the broadband oscillation characteristics more complex and the oscillation risk more prominent.

[0004] Impedance modeling of renewable energy converters and modular multilevel converters (MMCs) is a key technology for analyzing and solving broadband oscillations. Existing impedance modeling methods for renewable energy converters are increasingly mature and sound. For MMCs supported by weak synchronous power sources, impedance modeling methods primarily focus on virtual synchronous machine control. However, for MMCs that need to establish DC voltage for the DC system, conventional virtual synchronous machine control is insufficient to maintain DC voltage stability. In this case, MMCs require DC voltage synchronization control to both construct DC voltage and provide voltage frequency support to the AC grid. However, the broadband oscillation risks of MMCs under DC voltage synchronization control in relation to renewable energy converters and weak grids remain unclear. Existing methods have not yet addressed impedance modeling of MMCs under DC voltage synchronization control, making it difficult to analyze the broadband oscillation problem of renewable energy and flexible DC power sources in weak synchronous power source scenarios. Summary of the Invention

[0005] The purpose of this invention is to address the problems in the prior art by providing a modular multilevel converter impedance modeling method, system, device, and medium. By characterizing the multi-frequency mapping relationship between the DC transmission network and the DC voltage synchronization control loop, and considering the influence of voltage, current, circulating current control loop, and bridge arm power path, the impedance analytical model of the modular multilevel converter under DC voltage synchronization control mode is accurately obtained. This provides key technical support for the analysis and solution of new energy and flexible DC broadband oscillation in scenarios supported by weak synchronous power sources.

[0006] To achieve the above objectives, the present invention provides the following technical solution: Firstly, a modular multilevel converter impedance modeling method is provided, including: Construct a multi-frequency mapping relationship between small-signal voltage and current at the port of a DC transmission network; Taking into account the multi-frequency mapping relationship of DC transmission network, a small-signal multi-frequency mapping relationship of DC voltage synchronization control loop is constructed; Taking into account AC voltage, current and circulating current control, a multi-frequency mapping relationship for the control loop of a modular multilevel converter is constructed; Constructing the multi-frequency mapping relationship of the power path of the modular multilevel converter bridge arm under the action of the control loop; By combining the multi-frequency mapping relationship between the small signals of the DC transmission network port voltage and current, the multi-frequency mapping relationship of the small signals of the DC voltage synchronization control loop, the multi-frequency mapping relationship of the modular multilevel converter control loop, and the multi-frequency mapping relationship of the modular multilevel converter bridge arm power path under the action of the control loop, an analytical impedance model of the modular multilevel converter under the DC voltage synchronization control mode is constructed, and the impedance modeling of the modular multilevel converter is completed.

[0007] As a preferred embodiment, the topology of the modular multilevel converter includes a cascaded submodule series, bridge arm resistors and inductors, a-phase lower bridge arm, b-phase upper bridge arm, b-phase lower bridge arm, c-phase upper bridge arm, c-phase lower bridge arm, DC side wiring, and AC side wiring. The lower end of the cascaded submodule series is connected to the upper end of the bridge arm resistors and inductors, together forming the a-phase upper bridge arm. The cascaded submodule series consists of Nf cascaded submodules. The a-phase lower bridge arm and a-phase upper bridge arm are centrally symmetrical, and the b-phase upper bridge arm and c-phase upper bridge arm have the same configuration as the a-phase upper bridge arm. The b-phase lower bridge arm and c-phase lower bridge arm have the same configuration as the a-phase lower bridge arm. Wherein, a-phase... The lower end of the upper bridge arm is connected to the upper end of the lower bridge arm of phase a. The upper end of the upper bridge arm of phase a is connected to the upper end of the upper bridge arm of phase b, and then connected to the upper end of the upper bridge arm of phase c. The lower end of the lower bridge arm of phase a is connected to the lower end of the lower bridge arm of phase b, and then connected to the lower end of the lower bridge arm of phase c. The lower end of the upper bridge arm of phase b is connected to the upper end of the lower bridge arm of phase b, and the lower end of the upper bridge arm of phase c is connected to the upper end of the lower bridge arm of phase c. The upper end of the upper bridge arm of phase c and the lower end of the lower bridge arm of phase c are connected to the DC side wiring. The connection points between the lower end of the upper bridge arm of phase a and the upper end of the lower bridge arm of phase a, the lower end of the upper bridge arm of phase b and the upper end of the lower bridge arm of phase b, and the lower end of the upper bridge arm of phase c and the upper end of the lower bridge arm of phase c are connected to the AC side wiring.

[0008] As a preferred embodiment, in the step of constructing the multi-frequency mapping relationship between the port voltage and current small signals of the DC transmission network, the DC transmission network adopts... n Festival Equivalent circuit representation, each section The equivalent circuit includes the equivalent resistance. Equivalent inductance With equivalent capacitance Among them, equivalent resistance With equivalent inductance This forms an RL series branch, connecting the two equivalent capacitors. Parallel connection is formed on both sides of the RL series branch. Type equivalent circuit; Small signal voltage at the remote port of DC transmission network Small signal of remote port current The multi-frequency mapping relationship between them conforms to the following expression:

[0009] In the formula, The mathematical expression for the far-end multi-frequency mapped impedance matrix is:

[0010] Each element in the matrix represents a small-signal mapping relationship between any two frequencies of current and voltage, and the subscript indicates the frequency conversion relationship. For example, express small frequency current signal to Frequency-voltage small-signal mapping relationship ( For the perturbation frequency, (where the base frequency is used), and other elements follow the same logic; Each section of the DC transmission network Equivalent resistance and impedance matrix of type circuit Equivalent inductance-impedance matrix With equivalent capacitance and impedance matrix It conforms to the following expression:

[0011] In the formula, diag[] denotes a diagonal matrix function. The largest integer multiple of the impedance matrix is ​​considered. It is the identity matrix; Modular multilevel converter DC port voltage small signal Small signal with DC port current The multi-frequency mapping relationship between them conforms to the following expression:

[0012] In the formula, This refers to the multi-frequency mapped impedance matrix of a DC transmission network; the multi-frequency mapped impedance matrix of the DC transmission network From the far-end multi-frequency mapped impedance matrix and each section Equivalent resistance and impedance matrix of type circuit Equivalent inductance-impedance matrix and equivalent capacitance-impedance matrix The solution is obtained using the following recursive formula:

[0013] In the formula, || represents parallel operation. For consideration Festival The equivalent circuit multi-frequency mapped impedance matrix, For consideration Festival The equivalent circuit multi-frequency mapped impedance matrix, for The initial term.

[0014] As a preferred embodiment, in the step of constructing the small-signal multi-frequency mapping relationship of the DC voltage synchronization control loop, taking into account the multi-frequency mapping relationship of the DC transmission network, the impedance matrix of the DC transmission network multi-frequency mapping is used. Under the action of the modular multilevel converter, the small signal of the DC port voltage With DC voltage reference command After the difference is calculated, it is controlled by advance compensation. Inertial control Damping control Function: To adjust the fundamental angular frequency. Then integrate to obtain the reference angle. Reference angle small signal Small signal of DC port voltage of modular multilevel converter The multi-frequency mapping relationship between them conforms to the following expression:

[0015] In the formula, For inertial damping control multi-frequency mapping matrix, For advanced compensation control multi-frequency mapping matrix; , The expressions are as follows:

[0016]

[0017] In the formula, The active-frequency moment of inertia, This is the frequency-active power damping coefficient. This is the proportional coefficient for advance compensation control. To proactively compensate for controlled bandwidth; Reactive power small signal via inertial control and damping control Function: To generate AC voltage d-axis reference command small signal AC voltage d-axis reference command small signal Small signal of bridge arm current AC voltage small signal The multi-frequency mapping relationship between them conforms to the following expression:

[0018] In the formula, The amplitude of the fundamental frequency component of the AC voltage. This is the voltage-reactive power damping coefficient. , These are the d-axis and q-axis multi-frequency mapped AC current matrices, respectively. For reactive power synchronous control multi-frequency mapping matrix, It is a differential mode multi-frequency mapping matrix. , These are the Park transform d-axis and q-axis multi-frequency mapping matrices, respectively. The expression is:

[0019] In the formula, The reactive power-voltage rotational inertia; The expression is:

[0020] , All The matrix, except for the following elements, has all elements as 0:

[0021]

[0022] In the formula, In order to be in ~ Integers that change between intervals. The phase of the fundamental frequency component of the AC voltage; | represents taking the absolute value; mod() represents the modulo operation.

[0023] As a preferred embodiment, in the step of constructing the multi-frequency mapping relationship of the control loop of the modular multilevel converter, taking into account AC voltage, current, and circulating current control, the AC voltage d-axis reference command small signal AC voltage control generates small AC current d-axis and q-axis reference command signals. , In AC current control and reference angle small signal Under the combined effect, a small signal of AC modulation is generated. The small signal of the bridge arm current; Through circulating current control and reference angle small signal Under the influence of the current, a small signal of circulating current modulation is generated. AC modulated signal small signal and circulating modulation signal small signal Together they constitute the small signal of the bridge arm modulation signal Bridge arm modulation signal small signal AC voltage d-axis reference command small signal Reference angle small signal Small signal of bridge arm current AC voltage small signal The multi-frequency mapping relationship between them conforms to the following expression:

[0024] In the formula, The decoupling coefficient is the AC current control coefficient. The decoupling coefficient for circulating control is... , These are the AC modulation signal matrices for the d-axis and q-axis multi-frequency mapped bridge arms, respectively. , These are the d-axis and q-axis multi-frequency mapped bridge arm circulating current modulation signal matrices, respectively. For common-mode multi-frequency mapping matrix, , These are the Park inverse transform d-axis and q-axis multi-frequency mapping matrices, respectively. , These are the negative-order second-harmonic Park transform d-axis and q-axis multi-frequency mapping matrices, respectively. , These are the negative-order second-harmonic Park inverse transform d-axis and q-axis multi-frequency mapping matrices, respectively. For AC current control of multi-frequency mapping matrix, For circulating current control multi-frequency mapping matrix, This is an AC voltage-controlled multi-frequency mapping matrix; The expression is:

[0025] , , , , , The expressions are as follows:

[0026] , , The expressions are as follows:

[0027] In the formula, The transfer function for AC current PI control. This is the transfer function for the circulating current PI control. This is the transfer function for AC voltage PI control.

[0028] As a preferred embodiment, in the step of constructing the multi-frequency mapping relationship of the modular multilevel converter arm power path under the action of the control loop, the small signal of the arm current is obtained according to the Kirchhoff voltage relationship and Kirchhoff current relationship of the arm power path. Small signal of bridge arm modulation signal DC port voltage small signal AC voltage small signal The multi-frequency mapping relationship between them is expressed as follows:

[0029] In the formula, , , These are the multi-frequency mapped bridge arm current, bridge arm capacitor voltage, and bridge arm modulation signal matrix, respectively. This is the multi-frequency mapped impedance matrix of the bridge arm capacitor. The impedance matrix of the bridge arm inductor is a multi-frequency mapped impedance matrix. , The expression is:

[0030] In the formula, For the number of bridge arm sub-modules, The capacitance value of the submodule. , These are the bridge arm inductance and the bridge arm resistance, respectively.

[0031] As a preferred approach, in the step of constructing an analytical impedance model of the modular multilevel converter under DC voltage synchronization control by combining the multi-frequency mapping relationships between the small-signal voltage and current of the DC transmission network port, the multi-frequency mapping relationships of the small-signal voltage synchronization control loop, the multi-frequency mapping relationships of the modular multilevel converter control loop, and the multi-frequency mapping relationships of the modular multilevel converter arm power paths under the control loop, and completing the impedance modeling of the modular multilevel converter, the admittance matrix of the modular multilevel converter under DC voltage synchronization control is obtained. The expression is as follows:

[0032] In the formula, the superscript -1 indicates the operation of finding the inverse matrix. This is the multi-frequency mapping matrix for the power path of the bridge arm capacitor. This is the multi-frequency mapping matrix for the power path of the bridge arm inductor. For the multi-frequency mapping matrix of the circulating control action, This is the multi-frequency mapping matrix for steady-state circulating current modulation. For AC current control, a multi-frequency mapping matrix is ​​used. This is the steady-state AC current multi-frequency mapping matrix. For AC voltage control, a multi-frequency mapping matrix is ​​used. This is the steady-state AC voltage multi-frequency mapping matrix. This is the multi-frequency mapping matrix for reactive voltage inertial control. This is the multi-frequency mapping matrix for reactive current inertial control. For DC voltage synchronization control, a multi-frequency mapping matrix is ​​used. The dynamic multi-frequency mapping matrix of the DC transmission network is expressed as follows:

[0033] In the formula, The common-mode zero-sequence multi-frequency mapping matrix is ​​expressed as follows:

[0034] The impedance analytical model of the modular multilevel converter based on DC voltage synchronous control is obtained, and its expression is as follows:

[0035] In the formula, For the positive sequence impedance of the modular multilevel converter, For the positive sequence coupling impedance of the modular multilevel converter, For the negative sequence impedance of the modular multilevel converter, For the negative sequence coupling impedance of modular multilevel converters, For matrix The line, number Column elements; For matrix The line, number Column elements; For matrix The line, number Column elements; For matrix The line, number The elements of the column.

[0036] Secondly, a modular multilevel converter impedance modeling system is provided, including: The first multi-frequency mapping relationship construction module is used to construct the multi-frequency mapping relationship between the small signals of voltage and current at the DC transmission network port. The second multi-frequency mapping relationship construction module is used to take into account the multi-frequency mapping relationship of the DC transmission network and construct the small-signal multi-frequency mapping relationship of the DC voltage synchronization control loop. The third multi-frequency mapping relationship construction module is used to take into account AC voltage, current and circulating current control, and to construct the multi-frequency mapping relationship of the modular multilevel converter control loop. The fourth multi-frequency mapping relationship construction module is used to construct the multi-frequency mapping relationship of the power path of the modular multilevel converter bridge arm under the action of the control loop; The impedance analysis model construction module is used to combine the multi-frequency mapping relationship between the small signals of DC transmission network port voltage and current, the multi-frequency mapping relationship of the small signals of DC voltage synchronization control loop, the multi-frequency mapping relationship of the modular multilevel converter control loop, and the multi-frequency mapping relationship of the modular multilevel converter bridge arm power path under the action of the control loop to construct the impedance analysis model of the modular multilevel converter under DC voltage synchronization control mode, and complete the impedance modeling of the modular multilevel converter.

[0037] As a preferred embodiment, when constructing the multi-frequency mapping relationship between the port voltage and current small signals of the DC transmission network, the first multi-frequency mapping relationship construction module uses the DC transmission network as... n Festival Equivalent circuit representation, each section The equivalent circuit includes the equivalent resistance. Equivalent inductance With equivalent capacitance Among them, equivalent resistance With equivalent inductance This forms an RL series branch, connecting the two equivalent capacitors. Parallel connection is formed on both sides of the RL series branch. Type equivalent circuit; Small signal voltage at the remote port of DC transmission network Small signal of remote port current The multi-frequency mapping relationship between them conforms to the following expression:

[0038] In the formula, The mathematical expression for the far-end multi-frequency mapped impedance matrix is:

[0039] Each element in the matrix represents a small-signal mapping relationship between any two frequencies of current and voltage, and the subscript indicates the frequency conversion relationship. For example, express small frequency current signal to Frequency-voltage small-signal mapping relationship ( For the perturbation frequency, (where the base frequency is used), and other elements follow the same logic; Each section of the DC transmission network Equivalent resistance and impedance matrix of type circuit Equivalent inductance-impedance matrix With equivalent capacitance and impedance matrix It conforms to the following expression:

[0040] In the formula, diag[] represents a diagonal matrix function. The largest integer multiple of the impedance matrix is ​​considered. It is the identity matrix; Modular multilevel converter DC port voltage small signal Small signal with DC port current The multi-frequency mapping relationship between them conforms to the following expression:

[0041] In the formula, This refers to the multi-frequency mapped impedance matrix of a DC transmission network. From the far-end multi-frequency mapped impedance matrix and each section Equivalent resistance and impedance matrix of type circuit Equivalent inductance-impedance matrix and equivalent capacitance-impedance matrix The solution is obtained using the following recursive formula:

[0042] In the formula, || represents parallel operation. For consideration Festival The equivalent circuit multi-frequency mapped impedance matrix, For consideration Festival The equivalent circuit multi-frequency mapped impedance matrix, for The initial term.

[0043] As a preferred embodiment, the second multi-frequency mapping relationship construction module, when constructing the small-signal multi-frequency mapping relationship of the DC voltage synchronization control loop, uses the multi-frequency mapping impedance matrix of the DC transmission network. Under the action of the modular multilevel converter, the small signal of the DC port voltage With DC voltage reference command After the difference is calculated, it is controlled by advance compensation. Inertial control Damping control Function: To adjust the fundamental angular frequency. Then integrate to obtain the reference angle. Reference angle small signal Small signal of DC port voltage of modular multilevel converter The multi-frequency mapping relationship between them conforms to the following expression:

[0044] In the formula, For inertial damping control multi-frequency mapping matrix, For advanced compensation control multi-frequency mapping matrix; , The expressions are as follows:

[0045]

[0046] In the formula, The active-frequency moment of inertia, This is the frequency-active power damping coefficient. This is the proportional coefficient for advance compensation control. To proactively compensate for controlled bandwidth; Reactive power small signal via inertial control and damping control Function: To generate AC voltage d-axis reference command small signal AC voltage d-axis reference command small signal Small signal of bridge arm current AC voltage small signal The multi-frequency mapping relationship between them conforms to the following expression:

[0047] In the formula, The amplitude of the fundamental frequency component of the AC voltage. This is the voltage-reactive power damping coefficient. , These are the d-axis and q-axis multi-frequency mapped AC current matrices, respectively. For reactive power synchronous control multi-frequency mapping matrix, It is a differential mode multi-frequency mapping matrix. , These are the Park transform d-axis and q-axis multi-frequency mapping matrices, respectively. The expression is:

[0048] In the formula, The reactive power-voltage rotational inertia; The expression is:

[0049] , All The matrix, except for the following elements, has all elements as 0:

[0050]

[0051] In the formula, In order to be in ~ Integers that change between intervals. The phase of the fundamental frequency component of the AC voltage; | represents taking the absolute value; mod() represents the modulo operation.

[0052] As a preferred embodiment, the third multi-frequency mapping relationship construction module, when constructing the multi-frequency mapping relationship of the modular multilevel converter control loop, uses the AC voltage d-axis reference command small signal. AC voltage control generates small AC current d-axis and q-axis reference command signals. , In AC current control and reference angle small signal Under the combined effect, a small signal of AC modulation is generated. The small signal of the bridge arm current; Through circulating current control and reference angle small signal Under the influence of the current, a small signal of circulating current modulation is generated. AC modulated signal small signal and circulating modulation signal small signal Together they constitute the small signal of the bridge arm modulation signal Bridge arm modulation signal small signal AC voltage d-axis reference command small signal Reference angle small signal Small signal of bridge arm current AC voltage small signal The multi-frequency mapping relationship between them conforms to the following expression:

[0053] In the formula, The decoupling coefficient is the AC current control coefficient. The decoupling coefficient for circulating control is... , These are the AC modulation signal matrices for the d-axis and q-axis multi-frequency mapped bridge arms, respectively. , These are the d-axis and q-axis multi-frequency mapped bridge arm circulating current modulation signal matrices, respectively. For common-mode multi-frequency mapping matrix, , These are the Park inverse transform d-axis and q-axis multi-frequency mapping matrices, respectively. , These are the negative-order second-harmonic Park transform d-axis and q-axis multi-frequency mapping matrices, respectively. , These are the negative-order second-harmonic Park inverse transform d-axis and q-axis multi-frequency mapping matrices, respectively. For AC current control of multi-frequency mapping matrix, For circulating current control multi-frequency mapping matrix, This is an AC voltage-controlled multi-frequency mapping matrix; The expression is:

[0054] , , , , , The expressions are as follows:

[0055] , , The expressions are as follows:

[0056] In the formula, The transfer function for AC current PI control. This is the transfer function for the circulating current PI control. This is the transfer function for AC voltage PI control.

[0057] As a preferred embodiment, when constructing the multi-frequency mapping relationship of the modular multilevel converter arm power path under the action of the control loop, the fourth multi-frequency mapping relationship construction module obtains the small signal of the arm current based on the Kirchhoff voltage relationship and Kirchhoff current relationship of the arm power path. Small signal of bridge arm modulation signal DC port voltage small signal AC voltage small signal The multi-frequency mapping relationship between them is expressed as follows:

[0058] In the formula, , , These are the multi-frequency mapped bridge arm current, bridge arm capacitor voltage, and bridge arm modulation signal matrix, respectively. This is the multi-frequency mapped impedance matrix of the bridge arm capacitor. The impedance matrix of the bridge arm inductor is a multi-frequency mapped impedance matrix. , The expression is:

[0059] In the formula, For the number of bridge arm sub-modules, The capacitance value of the submodule. , These are the bridge arm inductance and the bridge arm resistance, respectively.

[0060] As a preferred embodiment, the impedance analysis model construction module obtains the admittance matrix of the modular multilevel converter under DC voltage synchronous control. The expression is as follows:

[0061] In the formula, the superscript -1 indicates the operation of finding the inverse matrix. This is the multi-frequency mapping matrix for the power path of the bridge arm capacitor. This is the multi-frequency mapping matrix for the power path of the bridge arm inductor. For the multi-frequency mapping matrix of the circulating control action, This is the multi-frequency mapping matrix for steady-state circulating current modulation. For AC current control, a multi-frequency mapping matrix is ​​used. This is the steady-state AC current multi-frequency mapping matrix. For AC voltage control, a multi-frequency mapping matrix is ​​used. This is the steady-state AC voltage multi-frequency mapping matrix. This is the multi-frequency mapping matrix for reactive voltage inertial control. This is the multi-frequency mapping matrix for reactive current inertial control. For DC voltage synchronization control, a multi-frequency mapping matrix is ​​used. The dynamic multi-frequency mapping matrix of the DC transmission network is expressed as follows:

[0062] In the formula, The common-mode zero-sequence multi-frequency mapping matrix is ​​expressed as follows:

[0063] The impedance analytical model of the modular multilevel converter based on DC voltage synchronous control is obtained, and its expression is as follows:

[0064] In the formula, For the positive sequence impedance of the modular multilevel converter, For the positive sequence coupling impedance of the modular multilevel converter, For the negative sequence impedance of the modular multilevel converter, For the negative sequence coupling impedance of modular multilevel converters, For matrix The line, number Column elements; For matrix The line, number Column elements; For matrix The line, number Column elements; For matrix The line, number The elements of the column.

[0065] Thirdly, an electronic device is provided, including a processor and a memory, the processor being used to execute a computer program stored in the memory to implement the modular multilevel converter impedance modeling method described above.

[0066] Fourthly, a computer-readable storage medium is provided, the computer-readable storage medium storing at least one instruction, which, when executed by a processor, implements the modular multilevel converter impedance modeling method.

[0067] Compared with the prior art, the first aspect of the present invention has at least the following beneficial effects: To address the challenge of impedance modeling for modular multilevel converters (MMBDCs) that require simultaneous DC voltage construction and AC voltage support, this invention proposes a method that characterizes the multi-frequency mapping relationship between the DC transmission network and the voltage and current at the remote ports on the dynamic characteristics of the MMBDC voltage. This allows the model to more realistically and accurately reflect the dynamic characteristics of the converter's DC voltage at different frequencies, improving the overall accuracy of the model. Furthermore, the invention fully considers the effects of the DC voltage synchronization control loop, AC voltage, current, and circulating current control loop, as well as the influence of the arm power path. In actual MMBDC operation, these factors are intertwined and interact, significantly impacting converter performance. By comprehensively considering these factors and analyzing and modeling their influence on converter impedance, this invention provides a more complete description of the converter's behavior under complex operating conditions, offering strong support for accurate converter performance analysis. This invention accurately establishes an analytical impedance model for modular multilevel converters under DC voltage synchronous control. This model boasts high accuracy and reliability, accurately predicting the converter's impedance characteristics under different operating conditions. It provides crucial technical support for the analysis and resolution of broadband oscillations in new energy converters, modular multilevel converters, and weak grids. In the new energy field, such as wind power and photovoltaic power generation, converters are core equipment. Accurately understanding the converter's impedance characteristics is essential for improving the stability and efficiency of new energy power generation systems. The analytical impedance model established in this invention helps engineers deeply analyze the impedance changes of new energy converters under different operating conditions, thereby optimizing converter design and control strategies, and improving the reliability and power quality of new energy power generation systems. Modular multilevel converters, as advanced power electronic devices, have broad application prospects in high-voltage DC transmission and flexible AC transmission. The analytical impedance model established in this invention provides important theoretical basis and technical support for the research and engineering application of modular multilevel converters. Through this model, the dynamic characteristics of the converter can be better understood, its control algorithm optimized, and the converter's performance and operating efficiency improved, promoting the further development of modular multilevel converter technology. In weak power grid environments, due to the grid's low inertia and damping, broadband oscillations are prone to occur, severely impacting the safe and stable operation of the power system. The impedance analysis model established in this invention can be used to analyze the interaction between the weak power grid and the modular multilevel converter, accurately identifying the generation mechanism and influencing factors of broadband oscillations. Based on this, effective suppression measures can be formulated, such as adjusting the converter's control parameters and adding damping devices, thereby effectively solving the broadband oscillation problem in weak power grids and ensuring the safe and stable operation of the power system.

[0068] It is understood that the beneficial effects of the second to fourth aspects mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here. Attached Figure Description

[0069] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0070] Figure 1 A schematic diagram of the topology of the modular multilevel converter according to an embodiment of the present invention; Figure 2 A schematic diagram of the topology of a DC transmission network according to an embodiment of the present invention; Figure 3 A schematic diagram of the DC voltage synchronization control loop structure in an embodiment of the present invention; Figure 4 A schematic diagram of the control loop structure of the modular multilevel converter according to an embodiment of the present invention; Figure 5 Flowchart of the modular multilevel converter impedance modeling method according to an embodiment of the present invention; Figure 6(a) shows the verification results of the positive sequence impedance and positive sequence coupling impedance of the modular multilevel converter impedance analytical model based on DC voltage synchronous control in this embodiment of the invention; Figure 6(b) shows the verification results of the negative sequence impedance and negative sequence coupling impedance of the modular multilevel converter impedance analysis model based on DC voltage synchronous control in this embodiment of the invention. Detailed Implementation

[0071] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of this application with unnecessary detail. Flowcharts are used in the embodiments of this application to illustrate the operations performed by the apparatus according to the embodiments of this application. It should be understood that the preceding or following operations are not necessarily performed in exact order. Instead, various steps may be processed in reverse order or simultaneously as needed. Furthermore, other operations may be added to these processes, or one or more steps may be removed from these processes.

[0072] Please see Figure 5 This invention proposes a modular multilevel converter impedance modeling method based on DC voltage synchronization control to improve the broadband oscillation analysis technology for flexible DC transmission. Specifically, it mainly includes the following steps: S1. Construct a multi-frequency mapping relationship between the small signals of voltage and current at the port of the DC transmission network; S2. Taking into account the multi-frequency mapping relationship of DC transmission network, construct the small-signal multi-frequency mapping relationship of DC voltage synchronization control loop; S3. Taking into account AC voltage, current and circulating current control, construct a multi-frequency mapping relationship for the control loop of a modular multilevel converter; S4. Construct the multi-frequency mapping relationship of the power path of the modular multilevel converter bridge arm under the action of the control loop; S5. Combining the multi-frequency mapping relationship between the small signals of the DC transmission network port voltage and current, the multi-frequency mapping relationship of the small signals of the DC voltage synchronization control loop, the multi-frequency mapping relationship of the modular multilevel converter control loop, and the multi-frequency mapping relationship of the modular multilevel converter bridge arm power path under the action of the control loop, construct the impedance analytical model of the modular multilevel converter under the DC voltage synchronization control mode, and complete the impedance modeling of the modular multilevel converter.

[0073] Please see Figure 1 The topology of the modular multilevel converter described in this embodiment includes a submodule cascade series 1, a bridge arm resistor and inductor 2, a-phase lower bridge arm 3, a-phase upper bridge arm 4, a-phase lower bridge arm 5, a-phase upper bridge arm 6, a-phase lower bridge arm 7, a DC side connection 8, and an AC side connection 9. The lower end of the submodule cascade series 1 is connected to the upper end of the bridge arm resistor and inductor 2, together forming the a-phase upper bridge arm. The submodule cascade series 1 is composed of Nf cascaded submodules. Furthermore, the a-phase lower bridge arm 3 and the a-phase upper bridge arm are centrally symmetrical; the b-phase upper bridge arm 4 and the c-phase upper bridge arm 6 have the same configuration as the a-phase upper bridge arm; and the b-phase lower bridge arm 5 and the c-phase lower bridge arm 7 have the same configuration as the a-phase lower bridge arm 3. Furthermore, the lower end of the upper bridge arm of phase a is connected to the upper end of the lower bridge arm 3 of phase a; the upper end of the upper bridge arm of phase a is connected to the upper end of the upper bridge arm 4 of phase b, and then connected to the upper end of the upper bridge arm 6 of phase c; the lower end of the lower bridge arm 3 of phase a is connected to the lower end of the lower bridge arm 5 of phase b, and then connected to the lower end of the lower bridge arm 7 of phase c; the lower end of the upper bridge arm 4 of phase b is connected to the upper end of the lower bridge arm 5 of phase b, and the lower end of the upper bridge arm 6 of phase c is connected to the upper end of the lower bridge arm 7 of phase c; the upper end of the upper bridge arm 6 of phase c and the lower end of the lower bridge arm 7 of phase c are connected to the DC side wiring 8; the connection point between the lower end of the upper bridge arm of phase a and the upper end of the lower bridge arm 3 of phase a, the connection point between the lower end of the upper bridge arm of phase b and the upper end of the lower bridge arm 5 of phase b, and the connection point between the lower end of the upper bridge arm of phase c and the upper end of the lower bridge arm 7 of phase c are connected to the AC side wiring 9.

[0074] In one possible implementation, in step S1, please refer to Figure 2 DC transmission networks adopt n Festival Equivalent circuit representation, each section The equivalent circuit includes the equivalent resistance. Equivalent inductance With equivalent capacitance Among them, equivalent resistance With equivalent inductance This forms an RL series branch, connecting the two equivalent capacitors. Parallel connection is formed on both sides of the RL series branch. Type equivalent circuit; Small signal voltage at the remote port of DC transmission network Small signal of remote port current The multi-frequency mapping relationship between them conforms to the following expression:

[0075] In the formula, The mathematical expression for the far-end multi-frequency mapped impedance matrix is:

[0076] Each element in the matrix represents a small-signal mapping relationship between any two frequencies of current and voltage, and the subscript indicates the frequency conversion relationship. For example, express small frequency current signal to Frequency-voltage small-signal mapping relationship ( For the perturbation frequency, (where the base frequency is used), and other elements follow the same logic; When the far end of the DC transmission network is a linear element, the far end multi-frequency mapped impedance matrix It is a diagonal matrix, with off-diagonal elements equal to 0; when the far end of the DC transmission network contains nonlinear components, such as power electronic devices, the far-end multi-frequency mapped impedance matrix... It is a non-diagonal matrix, and not all of its non-diagonal elements are 0.

[0077] Each section of the DC transmission network Equivalent resistance and impedance matrix of type circuit Equivalent inductance-impedance matrix With equivalent capacitance and impedance matrix It conforms to the following expression:

[0078] In the formula, diag[] denotes a diagonal matrix function. The largest integer multiple of the impedance matrix is ​​considered. It is the identity matrix; Modular multilevel converter DC port voltage small signal Small signal with DC port current The multi-frequency mapping relationship between them conforms to the following expression:

[0079] In the formula, Multi-frequency mapped impedance matrix of DC transmission network; Multi-frequency mapped impedance matrix of DC transmission network From the far-end multi-frequency mapped impedance matrix and each section Equivalent resistance and impedance matrix of type circuit Equivalent inductance-impedance matrix and equivalent capacitance-impedance matrix The solution is obtained using the following recursive formula:

[0080] In the formula, || represents parallel operation. For consideration Festival The equivalent circuit multi-frequency mapped impedance matrix, For consideration Festival The equivalent circuit multi-frequency mapped impedance matrix, for The initial term.

[0081] In one possible implementation, in step S2, please refer to Figure 3 The impedance matrix of the DC transmission network is mapped to multiple frequencies. Under the action of the modular multilevel converter, the small signal of the DC port voltage With DC voltage reference command After the difference is calculated, it is controlled by advance compensation. Inertial control Damping control Function: To adjust the fundamental angular frequency. Then integrate to obtain the reference angle. Reference angle small signal Small signal of DC port voltage of modular multilevel converter The multi-frequency mapping relationship between them conforms to the following expression:

[0082] In the formula, For inertial damping control multi-frequency mapping matrix, For advanced compensation control multi-frequency mapping matrix; , The expressions are as follows:

[0083]

[0084] In the formula, The active-frequency moment of inertia, This is the frequency-active power damping coefficient. This is the proportional coefficient for advance compensation control. To proactively compensate for controlled bandwidth; Reactive power small signal via inertial control and damping control Function: To generate AC voltage d-axis reference command small signal AC voltage d-axis reference command small signal Small signal of bridge arm current AC voltage small signal The multi-frequency mapping relationship between them conforms to the following expression:

[0085] In the formula, The amplitude of the fundamental frequency component of the AC voltage. This is the voltage-reactive power damping coefficient. , These are the d-axis and q-axis multi-frequency mapped AC current matrices, respectively. For reactive power synchronous control multi-frequency mapping matrix, It is a differential mode multi-frequency mapping matrix. , These are the Park transform d-axis and q-axis multi-frequency mapping matrices, respectively. The expression is:

[0086] In the formula, The reactive power-voltage rotational inertia; The expression is:

[0087] , All The matrix, except for the following elements, has all elements as 0:

[0088]

[0089] In the formula, In order to be in ~ Integers that change between intervals. The phase of the fundamental frequency component of the AC voltage; | represents taking the absolute value; mod() represents the modulo operation.

[0090] In one possible implementation, in step S3, please refer to Figure 4 AC voltage d-axis reference command small signal AC voltage control generates small AC current d-axis and q-axis reference command signals. , In AC current control and reference angle small signal Under the combined effect, a small signal of AC modulation is generated. The small signal of the bridge arm current; Through circulating current control and reference angle small signal Under the influence of the current, a small signal of circulating current modulation is generated. AC modulated signal small signal and circulating modulation signal small signal Together they constitute the small signal of the bridge arm modulation signal Bridge arm modulation signal small signal AC voltage d-axis reference command small signal Reference angle small signal Small signal of bridge arm current AC voltage small signal The multi-frequency mapping relationship between them conforms to the following expression:

[0091] In the formula, The decoupling coefficient is the AC current control coefficient. The decoupling coefficient for circulating control is... , These are the AC modulation signal matrices for the d-axis and q-axis multi-frequency mapped bridge arms, respectively. , These are the d-axis and q-axis multi-frequency mapped bridge arm circulating current modulation signal matrices, respectively. For common-mode multi-frequency mapping matrix, , These are the Park inverse transform d-axis and q-axis multi-frequency mapping matrices, respectively. , These are the negative-order second-harmonic Park transform d-axis and q-axis multi-frequency mapping matrices, respectively. , These are the negative-order second-harmonic Park inverse transform d-axis and q-axis multi-frequency mapping matrices, respectively. For AC current control of multi-frequency mapping matrix, For circulating current control multi-frequency mapping matrix, This is an AC voltage-controlled multi-frequency mapping matrix; The expression is:

[0092] , , , , , The expressions are as follows:

[0093] , , The expressions are as follows:

[0094] In the formula, The transfer function for AC current PI control. This is the transfer function for the circulating current PI control. This is the transfer function for AC voltage PI control.

[0095] In one possible implementation, in step S4, the small signal of the bridge arm current is obtained based on the Kirchhoff voltage relationship and the Kirchhoff current relationship of the bridge arm power path. Small signal of bridge arm modulation signal DC port voltage small signal AC voltage small signal The multi-frequency mapping relationship between them is expressed as follows:

[0096] In the formula, , , These are the multi-frequency mapped bridge arm current, bridge arm capacitor voltage, and bridge arm modulation signal matrix, respectively. This is the multi-frequency mapped impedance matrix of the bridge arm capacitor. The impedance matrix of the bridge arm inductor is a multi-frequency mapped impedance matrix. , The expression is:

[0097] In the formula, For the number of bridge arm sub-modules, The capacitance value of the submodule. , These are the bridge arm inductance and the bridge arm resistance, respectively.

[0098] In one possible implementation, in step S5, the admittance matrix of the modular multilevel converter under DC voltage synchronous control mode is obtained. The expression is as follows:

[0099] In the formula, the superscript -1 indicates the operation of finding the inverse matrix. This is the multi-frequency mapping matrix for the power path of the bridge arm capacitor. This is the multi-frequency mapping matrix for the power path of the bridge arm inductor. For the multi-frequency mapping matrix of the circulating control action, This is the multi-frequency mapping matrix for steady-state circulating current modulation. For AC current control, a multi-frequency mapping matrix is ​​used. This is the steady-state AC current multi-frequency mapping matrix. For AC voltage control, a multi-frequency mapping matrix is ​​used. This is the steady-state AC voltage multi-frequency mapping matrix. This is the multi-frequency mapping matrix for reactive voltage inertial control. This is the multi-frequency mapping matrix for reactive current inertial control. For DC voltage synchronization control, a multi-frequency mapping matrix is ​​used. The dynamic multi-frequency mapping matrix of the DC transmission network is expressed as follows:

[0100] In the formula, The common-mode zero-sequence multi-frequency mapping matrix is ​​expressed as follows:

[0101] The impedance analytical model of the modular multilevel converter based on DC voltage synchronous control is obtained, and its expression is as follows:

[0102] In the formula, For the positive sequence impedance of the modular multilevel converter, For the positive sequence coupling impedance of the modular multilevel converter, For the negative sequence impedance of the modular multilevel converter, For the negative sequence coupling impedance of modular multilevel converters, For matrix The line, number Column elements; For matrix The line, number Column elements; For matrix The line, number Column elements; For matrix The line, number The elements of the column.

[0103] In a specific application example, for Figure 1 Electromagnetic transient simulation impedance sweep frequency verification was performed on the modular multilevel converter shown. The modular multilevel converter in this embodiment has a rated power of 4000MW and a DC voltage of... The voltage is 800kV, the grid short-circuit ratio is 2.5, and the amplitude of the fundamental frequency component of the AC voltage is... For 327kV, the number of bridge arm sub-modules The capacitance value of the submodule is 320. The bridge arm inductance is 21.2mF. The resistance of the bridge arm is 50mH. The resistance is 0.5Ω. The proportional gain for advance compensation control is... Advanced compensation control bandwidth The active-frequency moment of inertia are 39 and 1.1427, respectively. Frequency-active damping coefficient They are 5627×10 4 447800, reactive power-voltage moment of inertia Voltage-reactive damping coefficient The values ​​are 17678 and 140 respectively. The proportional and integral coefficients of the AC voltage controller are 0.0500 and 0.1000 respectively, and the proportional and integral coefficients of the AC current controller are 2.7676 × 10⁻⁶. -5 0.0095, AC current control decoupling coefficient It is 9.8175×10 -6 The proportional and integral coefficients of the circulating controller are 5.5536 × 10⁻⁶. -6 0.0007, decoupling coefficient for circulating control 3.9270×10 -5 .

[0104] Following steps S1 to S5 of the modular multilevel converter impedance modeling method in this embodiment of the invention, an analytical impedance model of the modular multilevel converter based on DC voltage synchronous control is constructed, and impedance sweep frequency verification is performed using MATLAB / SIMULINK simulation tools. The verification results of the analytical impedance model of the modular multilevel converter based on DC voltage synchronous control are shown in Figures 6(a) and 6(b), where the solid line represents the analytical result, and the discrete points represent the simulation sweep frequency result. The results show that the analytical and simulation sweep results agree well, verifying the accuracy of the analytical impedance modeling of the modular multilevel converter based on DC voltage synchronous control described in this embodiment of the invention.

[0105] Another embodiment of the present invention also proposes a modular multilevel converter impedance modeling system, comprising: The first multi-frequency mapping relationship construction module is used to construct the multi-frequency mapping relationship between the small signals of voltage and current at the DC transmission network port. The second multi-frequency mapping relationship construction module is used to take into account the multi-frequency mapping relationship of the DC transmission network and construct the small-signal multi-frequency mapping relationship of the DC voltage synchronization control loop. The third multi-frequency mapping relationship construction module is used to take into account AC voltage, current and circulating current control, and to construct the multi-frequency mapping relationship of the modular multilevel converter control loop. The fourth multi-frequency mapping relationship construction module is used to construct the multi-frequency mapping relationship of the power path of the modular multilevel converter bridge arm under the action of the control loop; The impedance analysis model construction module is used to combine the multi-frequency mapping relationship between the small signals of DC transmission network port voltage and current, the multi-frequency mapping relationship of the small signals of DC voltage synchronization control loop, the multi-frequency mapping relationship of the modular multilevel converter control loop, and the multi-frequency mapping relationship of the modular multilevel converter bridge arm power path under the action of the control loop to construct the impedance analysis model of the modular multilevel converter under DC voltage synchronization control mode, and complete the impedance modeling of the modular multilevel converter.

[0106] In one possible implementation, when the first multi-frequency mapping relationship construction module constructs the multi-frequency mapping relationship between the small signals of voltage and current at the DC transmission network port, the DC transmission network adopts... n Festival Equivalent circuit representation, each section The equivalent circuit includes the equivalent resistance. Equivalent inductance With equivalent capacitance Among them, equivalent resistance With equivalent inductance This forms an RL series branch, connecting the two equivalent capacitors. Parallel connection is formed on both sides of the RL series branch. Type equivalent circuit; Small signal voltage at the remote port of DC transmission network Small signal of remote port current The multi-frequency mapping relationship between them conforms to the following expression:

[0107] In the formula, The mathematical expression for the far-end multi-frequency mapped impedance matrix is:

[0108] Each element in the matrix represents a small-signal mapping relationship between any two frequencies of current and voltage, and the subscript indicates the frequency conversion relationship. For example, express small frequency current signal to Frequency-voltage small-signal mapping relationship ( For the perturbation frequency, (where the base frequency is used), and other elements follow the same logic; Each section of the DC transmission network Equivalent resistance and impedance matrix of type circuit Equivalent inductance-impedance matrix With equivalent capacitance and impedance matrix It conforms to the following expression:

[0109] In the formula, diag[] denotes a diagonal matrix function. The largest integer multiple of the impedance matrix is ​​considered. It is the identity matrix; Modular multilevel converter DC port voltage small signal Small signal with DC port current The multi-frequency mapping relationship between them conforms to the following expression:

[0110] In the formula, This refers to the multi-frequency mapped impedance matrix of a DC transmission network; the multi-frequency mapped impedance matrix of the DC transmission network From the far-end multi-frequency mapped impedance matrix and each section Equivalent resistance and impedance matrix of type circuit Equivalent inductance-impedance matrix and equivalent capacitance-impedance matrix The solution is obtained using the following recursive formula:

[0111] In the formula, || represents parallel operation. For consideration Festival The equivalent circuit multi-frequency mapped impedance matrix, For consideration Festival The equivalent circuit multi-frequency mapped impedance matrix, for The initial term.

[0112] In one possible implementation, when constructing the small-signal multi-frequency mapping relationship of the DC voltage synchronization control loop, the second multi-frequency mapping relationship construction module uses the multi-frequency mapping impedance matrix of the DC transmission network. Under the action of the modular multilevel converter, the small signal of the DC port voltage With DC voltage reference command After the difference is calculated, it is controlled by advance compensation. Inertial control Damping control Function: To adjust the fundamental angular frequency. Then integrate to obtain the reference angle. Reference angle small signal Small signal of DC port voltage of modular multilevel converter The multi-frequency mapping relationship between them conforms to the following expression:

[0113] In the formula, For inertial damping control multi-frequency mapping matrix, For advanced compensation control multi-frequency mapping matrix; , The expressions are as follows:

[0114]

[0115] In the formula, The active-frequency moment of inertia, This is the frequency-active power damping coefficient. This is the proportional coefficient for advance compensation control. To proactively compensate for controlled bandwidth; Reactive power small signal via inertial control and damping control Function: To generate AC voltage d-axis reference command small signal AC voltage d-axis reference command small signal Small signal of bridge arm current AC voltage small signal The multi-frequency mapping relationship between them conforms to the following expression:

[0116] In the formula, The amplitude of the fundamental frequency component of the AC voltage. This is the voltage-reactive power damping coefficient. , These are the d-axis and q-axis multi-frequency mapped AC current matrices, respectively. For reactive power synchronous control multi-frequency mapping matrix, It is a differential mode multi-frequency mapping matrix. , These are the Park transform d-axis and q-axis multi-frequency mapping matrices, respectively. The expression is:

[0117] In the formula, The reactive power-voltage rotational inertia; The expression is:

[0118] , All The matrix, except for the following elements, has all elements as 0:

[0119]

[0120] In the formula, In order to be in ~ Integers that change between intervals. The phase of the fundamental frequency component of the AC voltage; | represents taking the absolute value; mod() represents the modulo operation.

[0121] In one possible implementation, when constructing the multi-frequency mapping relationship of the modular multilevel converter control loop, the third multi-frequency mapping relationship construction module uses the AC voltage d-axis reference command small signal. AC voltage control generates small AC current d-axis and q-axis reference command signals. , In AC current control and reference angle small signal Under the combined effect, a small signal of AC modulation is generated. The small signal of the bridge arm current; Through circulating current control and reference angle small signal Under the influence of the current, a small signal of circulating current modulation is generated. AC modulated signal small signal and circulating modulation signal small signal Together they constitute the small signal of the bridge arm modulation signal Bridge arm modulation signal small signal AC voltage d-axis reference command small signal Reference angle small signal Small signal of bridge arm current AC voltage small signal The multi-frequency mapping relationship between them conforms to the following expression:

[0122] In the formula, The decoupling coefficient is the AC current control coefficient. The decoupling coefficient for circulating control is... , These are the AC modulation signal matrices for the d-axis and q-axis multi-frequency mapped bridge arms, respectively. , These are the d-axis and q-axis multi-frequency mapped bridge arm circulating current modulation signal matrices, respectively. For common-mode multi-frequency mapping matrix, , These are the Park inverse transform d-axis and q-axis multi-frequency mapping matrices, respectively. , These are the negative-order second-harmonic Park transform d-axis and q-axis multi-frequency mapping matrices, respectively. , These are the negative-order second-harmonic Park inverse transform d-axis and q-axis multi-frequency mapping matrices, respectively. For AC current control of multi-frequency mapping matrix, For circulating current control multi-frequency mapping matrix, This is an AC voltage-controlled multi-frequency mapping matrix; The expression is:

[0123] , , , , , The expressions are as follows:

[0124] , , The expressions are as follows:

[0125] In the formula, The transfer function for AC current PI control. This is the transfer function for the circulating current PI control. This is the transfer function for AC voltage PI control.

[0126] In one possible implementation, when the fourth multi-frequency mapping relationship construction module constructs the multi-frequency mapping relationship of the modular multilevel converter arm power path under the action of the control loop, it obtains the small signal of the arm current based on the Kirchhoff voltage relationship and Kirchhoff current relationship of the arm power path. Small signal of bridge arm modulation signal DC port voltage small signal AC voltage small signal The multi-frequency mapping relationship between them is expressed as follows:

[0127] In the formula, , , These are the multi-frequency mapped bridge arm current, bridge arm capacitor voltage, and bridge arm modulation signal matrix, respectively. This is the multi-frequency mapped impedance matrix of the bridge arm capacitor. The impedance matrix of the bridge arm inductor is a multi-frequency mapped impedance matrix. , The expression is:

[0128] In the formula, For the number of bridge arm sub-modules, The capacitance value of the submodule. , These are the bridge arm inductance and the bridge arm resistance, respectively.

[0129] In one possible implementation, the impedance analysis model building module obtains the admittance matrix of the modular multilevel converter under DC voltage synchronous control. The expression is as follows:

[0130] In the formula, the superscript -1 indicates the operation of finding the inverse matrix. This is the multi-frequency mapping matrix for the power path of the bridge arm capacitor. This is the multi-frequency mapping matrix for the power path of the bridge arm inductor. For the multi-frequency mapping matrix of the circulating control action, This is the multi-frequency mapping matrix for steady-state circulating current modulation. For AC current control, a multi-frequency mapping matrix is ​​used. This is the steady-state AC current multi-frequency mapping matrix. For AC voltage control, a multi-frequency mapping matrix is ​​used. This is the steady-state AC voltage multi-frequency mapping matrix. This is the multi-frequency mapping matrix for reactive voltage inertial control. This is the multi-frequency mapping matrix for reactive current inertial control. For DC voltage synchronization control, a multi-frequency mapping matrix is ​​used. The dynamic multi-frequency mapping matrix of the DC transmission network is expressed as follows:

[0131] In the formula, The common-mode zero-sequence multi-frequency mapping matrix is ​​expressed as follows:

[0132] The impedance analytical model of the modular multilevel converter based on DC voltage synchronous control is obtained, and its expression is as follows:

[0133] In the formula, For the positive sequence impedance of the modular multilevel converter, For the positive sequence coupling impedance of the modular multilevel converter, For the negative sequence impedance of the modular multilevel converter, For the negative sequence coupling impedance of modular multilevel converters, For matrix The line, number Column elements; For matrix The line, number Column elements; For matrix The line, number Column elements; For matrix The line, number The elements of the column.

[0134] Another embodiment of the present invention also proposes an electronic device including a processor and a memory, the processor being used to execute a computer program stored in the memory to implement the modular multilevel converter impedance modeling method described above.

[0135] Another embodiment of the present invention also proposes a computer-readable storage medium storing at least one instruction that, when executed by a processor, implements the modular multilevel converter impedance modeling method described above.

[0136] The computer program includes computer program code, which can be in the form of source code, object code, executable file, or some intermediate form. The computer-readable storage medium can include any entity or device capable of carrying the computer program code, a medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory, a random access memory, an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc. It should be noted that the content included in the computer-readable medium can be appropriately added or removed according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the computer-readable medium does not include electrical carrier signals and telecommunication signals. For ease of explanation, the above content only shows the parts related to the embodiments of the present invention; for specific technical details not disclosed, please refer to the method section of the embodiments of the present invention. This computer-readable storage medium is non-transitory and can be stored in storage devices formed by various electronic devices, enabling the execution process described in the method of the embodiments of the present invention.

[0137] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0138] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0139] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0140] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0141] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A modular multilevel converter impedance modeling method, characterized in that, include: Construct a multi-frequency mapping relationship between small-signal voltage and current at the port of a DC transmission network; Taking into account the multi-frequency mapping relationship of DC transmission network, a small-signal multi-frequency mapping relationship of DC voltage synchronization control loop is constructed; Taking into account AC voltage, current and circulating current control, a multi-frequency mapping relationship for the control loop of a modular multilevel converter is constructed; Constructing the multi-frequency mapping relationship of the power path of the modular multilevel converter bridge arm under the action of the control loop; By combining the multi-frequency mapping relationship between the small signals of the DC transmission network port voltage and current, the multi-frequency mapping relationship of the small signals of the DC voltage synchronization control loop, the multi-frequency mapping relationship of the modular multilevel converter control loop, and the multi-frequency mapping relationship of the modular multilevel converter bridge arm power path under the action of the control loop, an analytical impedance model of the modular multilevel converter under the DC voltage synchronization control mode is constructed, and the impedance modeling of the modular multilevel converter is completed.

2. The modular multilevel converter impedance modeling method according to claim 1, characterized in that, The topology of the modular multilevel converter includes a cascaded submodule series (1), a bridge arm resistor and inductor (2), a-phase lower bridge arm (3), b-phase upper bridge arm (4), b-phase lower bridge arm (5), c-phase upper bridge arm (6), c-phase lower bridge arm (7), DC side wiring (8), and AC side wiring (9); the lower end of the cascaded submodule series (1) is connected to the upper end of the bridge arm resistor and inductor (2), together forming the a-phase upper bridge arm; the cascaded submodule series (1) is composed of Nf cascaded submodules; The lower bridge arm (3) of phase a and the upper bridge arm of phase a are symmetrically arranged at the top and bottom. The upper bridge arm (4) of phase b and the upper bridge arm (6) of phase c are arranged in the same way as the upper bridge arm of phase a. The lower bridge arm (5) of phase b and the lower bridge arm (7) of phase c are arranged in the same way as the lower bridge arm (3) of phase a. The lower end of the upper bridge arm of phase a is connected to the upper end of the lower bridge arm (3) of phase a. The upper end of the upper bridge arm of phase a is connected to the upper end of the upper bridge arm (4) of phase b, and then connected to the upper end of the upper bridge arm (6) of phase c. The lower end of the lower bridge arm (3) of phase a is connected to the lower end of the lower bridge arm (5) of phase b, and then connected to the upper end of the lower bridge arm (6). The lower end of the c-phase lower bridge arm (7) is connected to the lower end of the b-phase upper bridge arm (4); the lower end of the b-phase upper bridge arm (4) is connected to the upper end of the b-phase lower bridge arm (5); the lower end of the c-phase upper bridge arm (6) is connected to the upper end of the c-phase lower bridge arm (7); the upper end of the c-phase upper bridge arm (6) and the lower end of the c-phase lower bridge arm (7) are connected to the DC side wiring (8); the lower end of the a-phase upper bridge arm and the upper end of the a-phase lower bridge arm (3), the lower end of the b-phase upper bridge arm (4) and the upper end of the b-phase lower bridge arm (5), and the lower end of the c-phase upper bridge arm (6) and the upper end of the c-phase lower bridge arm (7) are connected to the AC side wiring (9).

3. The modular multilevel converter impedance modeling method according to claim 1, characterized in that, In the step of constructing the multi-frequency mapping relationship between the port voltage and current small signals of the DC transmission network, the DC transmission network adopts... n Festival Equivalent circuit representation, each section The equivalent circuit includes the equivalent resistance. Equivalent inductance With equivalent capacitance Among them, equivalent resistance With equivalent inductance This forms an RL series branch, connecting the two equivalent capacitors. Parallel connection is formed on both sides of the RL series branch. Type equivalent circuit; Small signal voltage at the remote port of DC transmission network Small signal of remote port current The multi-frequency mapping relationship between them conforms to the following expression: In the formula, The mathematical expression for the far-end multi-frequency mapped impedance matrix is: In the formula, each element of the matrix represents the small-signal mapping relationship between any two frequencies of current and voltage, and the subscript indicates the frequency conversion relationship; Each section of the DC transmission network Equivalent resistance and impedance matrix of type circuit Equivalent inductance-impedance matrix With equivalent capacitance and impedance matrix It conforms to the following expression: In the formula, diag[] denotes a diagonal matrix function. The largest integer multiple of the impedance matrix is ​​considered. It is the identity matrix; Modular multilevel converter DC port voltage small signal Small signal with DC port current The multi-frequency mapping relationship between them conforms to the following expression: In the formula, This refers to the multi-frequency mapped impedance matrix of a DC transmission network; the multi-frequency mapped impedance matrix of the DC transmission network From the far-end multi-frequency mapped impedance matrix and each section Equivalent resistance and impedance matrix of type circuit Equivalent inductance-impedance matrix and equivalent capacitance-impedance matrix The solution is obtained using the following recursive formula: In the formula, || represents parallel operation. For consideration Festival The equivalent circuit multi-frequency mapped impedance matrix, For consideration Festival The equivalent circuit multi-frequency mapped impedance matrix, for The initial term.

4. The modular multilevel converter impedance modeling method according to claim 3, characterized in that, In the step of constructing the small-signal multi-frequency mapping relationship of the DC voltage synchronization control loop, taking into account the multi-frequency mapping relationship of the DC transmission network, the impedance matrix of the DC transmission network multi-frequency mapping is used. Under the action of the modular multilevel converter, the small signal of the DC port voltage With DC voltage reference command After the difference is calculated, it is controlled by advance compensation. Inertial control Damping control Function: To adjust the fundamental angular frequency. Then integrate to obtain the reference angle. Reference angle small signal Small signal of DC port voltage of modular multilevel converter The multi-frequency mapping relationship between them conforms to the following expression: In the formula, For inertial damping control multi-frequency mapping matrix, For advanced compensation control multi-frequency mapping matrix; , The expressions are as follows: In the formula, The active-frequency moment of inertia, This is the frequency-active power damping coefficient. This is the proportional coefficient for advance compensation control. To proactively compensate for controlled bandwidth; Reactive power small signal via inertial control and damping control Function: To generate AC voltage d-axis reference command small signal AC voltage d-axis reference command small signal Small signal of bridge arm current AC voltage small signal The multi-frequency mapping relationship between them conforms to the following expression: In the formula, The amplitude of the fundamental frequency component of the AC voltage. This is the voltage-reactive power damping coefficient. , These are the d-axis and q-axis multi-frequency mapped AC current matrices, respectively. For reactive power synchronous control multi-frequency mapping matrix, It is a differential mode multi-frequency mapping matrix. , These are the Park transform d-axis and q-axis multi-frequency mapping matrices, respectively. The expression is: In the formula, The reactive power-voltage rotational inertia; The expression is: , All The matrix, except for the following elements, has all elements as 0: In the formula, In order to be in ~ Integers that change between intervals. The phase of the fundamental frequency component of the AC voltage; | represents taking the absolute value; mod() represents the modulo operation.

5. The modular multilevel converter impedance modeling method according to claim 4, characterized in that, In the step of constructing a multi-frequency mapping relationship for the control loop of a modular multilevel converter, taking into account AC voltage, current, and circulating current control, the AC voltage d-axis reference command small signal... AC voltage control generates small AC current d-axis and q-axis reference command signals. , In AC current control and reference angle small signal Under the combined effect, a small signal of AC modulation is generated. The small signal of the bridge arm current; Through circulating current control and reference angle small signal Under the influence of the current, a small signal of circulating current modulation is generated. AC modulated signal small signal and circulating modulation signal small signal Together they constitute the small signal of the bridge arm modulation signal Bridge arm modulation signal small signal AC voltage d-axis reference command small signal Reference angle small signal Small signal of bridge arm current AC voltage small signal The multi-frequency mapping relationship between them conforms to the following expression: In the formula, The decoupling coefficient is the AC current control coefficient. The decoupling coefficient for circulating control is... , These are the AC modulation signal matrices for the d-axis and q-axis multi-frequency mapped bridge arms, respectively. , These are the d-axis and q-axis multi-frequency mapped bridge arm circulating current modulation signal matrices, respectively. For common-mode multi-frequency mapping matrix, , These are the Park inverse transform d-axis and q-axis multi-frequency mapping matrices, respectively. , These are the negative-order second-harmonic Park transform d-axis and q-axis multi-frequency mapping matrices, respectively. , These are the negative-order second-harmonic Park inverse transform d-axis and q-axis multi-frequency mapping matrices, respectively. For AC current control of multi-frequency mapping matrix, For circulating current control multi-frequency mapping matrix, This is an AC voltage-controlled multi-frequency mapping matrix; The expression is: , , , , , The expressions are as follows: , , The expressions are as follows: In the formula, The transfer function for AC current PI control. This is the transfer function for the circulating current PI control. This is the transfer function for AC voltage PI control.

6. The modular multilevel converter impedance modeling method according to claim 5, characterized in that, In the step of constructing the multi-frequency mapping relationship of the modular multilevel converter arm power path under the action of the control loop, the small signal of the arm current is obtained according to the Kirchhoff voltage relationship and Kirchhoff current relationship of the arm power path. Small signal of bridge arm modulation signal DC port voltage small signal AC voltage small signal The multi-frequency mapping relationship between them is expressed as follows: In the formula, , , These are the multi-frequency mapped bridge arm current, bridge arm capacitor voltage, and bridge arm modulation signal matrix, respectively. This is the multi-frequency mapped impedance matrix of the bridge arm capacitor. The impedance matrix of the bridge arm inductor is a multi-frequency mapped impedance matrix. , The expression is: In the formula, For the number of bridge arm sub-modules, The capacitance value of the submodule. , These are the bridge arm inductance and the bridge arm resistance, respectively.

7. The modular multilevel converter impedance modeling method according to claim 6, characterized in that, In the step of constructing an analytical impedance model of the modular multilevel converter under DC voltage synchronization control, by combining the multi-frequency mapping relationships between the small-signal voltage and current of the DC transmission network port, the multi-frequency mapping relationships of the small-signal small-signal of the DC voltage synchronization control loop, the multi-frequency mapping relationships of the modular multilevel converter control loop, and the multi-frequency mapping relationships of the modular multilevel converter arm power path under the action of the control loop, the admittance matrix of the modular multilevel converter under DC voltage synchronization control is obtained. The expression is as follows: In the formula, the superscript -1 indicates the operation of finding the inverse matrix. This is the multi-frequency mapping matrix for the power path of the bridge arm capacitor. This is the multi-frequency mapping matrix for the power path of the bridge arm inductor. For the multi-frequency mapping matrix of the circulating control action, This is the multi-frequency mapping matrix for steady-state circulating current modulation. For AC current control, a multi-frequency mapping matrix is ​​used. This is the steady-state AC current multi-frequency mapping matrix. For AC voltage control, a multi-frequency mapping matrix is ​​used. This is the steady-state AC voltage multi-frequency mapping matrix. This is the multi-frequency mapping matrix for reactive voltage inertial control. This is the multi-frequency mapping matrix for reactive current inertial control. For DC voltage synchronization control, a multi-frequency mapping matrix is ​​used. The dynamic multi-frequency mapping matrix of the DC transmission network is expressed as follows: In the formula, The common-mode zero-sequence multi-frequency mapping matrix is ​​expressed as follows: The impedance analytical model of the modular multilevel converter based on DC voltage synchronous control is obtained, and its expression is as follows: In the formula, For the positive sequence impedance of the modular multilevel converter, For the positive sequence coupling impedance of the modular multilevel converter, For the negative sequence impedance of the modular multilevel converter, For the negative sequence coupling impedance of modular multilevel converters, For matrix The line, number Column elements; For matrix The line, number Column elements; For matrix The line, number Column elements; For matrix The line, number The elements of the column.

8. A modular multilevel converter impedance modeling system, characterized in that, include: The first multi-frequency mapping relationship construction module is used to construct the multi-frequency mapping relationship between the small signals of voltage and current at the DC transmission network port. The second multi-frequency mapping relationship construction module is used to take into account the multi-frequency mapping relationship of the DC transmission network and construct the small-signal multi-frequency mapping relationship of the DC voltage synchronization control loop. The third multi-frequency mapping relationship construction module is used to take into account AC voltage, current and circulating current control, and to construct the multi-frequency mapping relationship of the modular multilevel converter control loop. The fourth multi-frequency mapping relationship construction module is used to construct the multi-frequency mapping relationship of the power path of the modular multilevel converter bridge arm under the action of the control loop; The impedance analysis model construction module is used to combine the multi-frequency mapping relationship between the small signals of DC transmission network port voltage and current, the multi-frequency mapping relationship of the small signals of DC voltage synchronization control loop, the multi-frequency mapping relationship of the modular multilevel converter control loop, and the multi-frequency mapping relationship of the modular multilevel converter bridge arm power path under the action of the control loop to construct the impedance analysis model of the modular multilevel converter under DC voltage synchronization control mode, and complete the impedance modeling of the modular multilevel converter.

9. The modular multilevel converter impedance modeling system according to claim 8, characterized in that, When constructing the multi-frequency mapping relationship between the port voltage and current small signals of the DC transmission network, the first multi-frequency mapping relationship construction module uses the DC transmission network as an example. n Festival Equivalent circuit representation, each section The equivalent circuit includes the equivalent resistance. Equivalent inductance With equivalent capacitance Among them, equivalent resistance With equivalent inductance This forms an RL series branch, connecting the two equivalent capacitors. Parallel connection is formed on both sides of the RL series branch. Type equivalent circuit; Small signal voltage at the remote port of DC transmission network Small signal of remote port current The multi-frequency mapping relationship between them conforms to the following expression: In the formula, The mathematical expression for the far-end multi-frequency mapped impedance matrix is: In the formula, each element of the matrix represents the small-signal mapping relationship between any two frequencies of current and voltage, and the subscript indicates the frequency conversion relationship; Each section of the DC transmission network Equivalent resistance and impedance matrix of type circuit Equivalent inductance-impedance matrix With equivalent capacitance and impedance matrix It conforms to the following expression: In the formula, diag[] denotes a diagonal matrix function. The largest integer multiple of the impedance matrix is ​​considered. It is the identity matrix; Modular multilevel converter DC port voltage small signal Small signal with DC port current The multi-frequency mapping relationship between them conforms to the following expression: In the formula, This refers to the multi-frequency mapped impedance matrix of a DC transmission network; the multi-frequency mapped impedance matrix of the DC transmission network From the far-end multi-frequency mapped impedance matrix and each section Equivalent resistance and impedance matrix of type circuit Equivalent inductance-impedance matrix and equivalent capacitance-impedance matrix The solution is obtained using the following recursive formula: In the formula, || represents parallel operation. For consideration Festival The equivalent circuit multi-frequency mapped impedance matrix, For consideration Festival The equivalent circuit multi-frequency mapped impedance matrix, for The initial term.

10. The modular multilevel converter impedance modeling system according to claim 9, characterized in that, When constructing the small-signal multi-frequency mapping relationship of the DC voltage synchronization control loop, the second multi-frequency mapping relationship construction module uses the multi-frequency mapping impedance matrix of the DC transmission network. Under the action of the modular multilevel converter, the small signal of the DC port voltage With DC voltage reference command After the difference is calculated, it is controlled by advance compensation. Inertial control Damping control Function: To adjust the fundamental angular frequency. Then integrate to obtain the reference angle. Reference angle small signal Small signal of DC port voltage of modular multilevel converter The multi-frequency mapping relationship between them conforms to the following expression: In the formula, For inertial damping control multi-frequency mapping matrix, For advanced compensation control multi-frequency mapping matrix; , The expressions are as follows: In the formula, The active-frequency moment of inertia, This is the frequency-active power damping coefficient. This is the proportional coefficient for advance compensation control. To proactively compensate for controlled bandwidth; Reactive power small signal via inertial control and damping control Function: To generate AC voltage d-axis reference command small signal AC voltage d-axis reference command small signal Small signal of bridge arm current AC voltage small signal The multi-frequency mapping relationship between them conforms to the following expression: In the formula, The amplitude of the fundamental frequency component of the AC voltage. This is the voltage-reactive power damping coefficient. , These are the d-axis and q-axis multi-frequency mapped AC current matrices, respectively. For reactive power synchronous control multi-frequency mapping matrix, It is a differential mode multi-frequency mapping matrix. , These are the Park transform d-axis and q-axis multi-frequency mapping matrices, respectively. The expression is: In the formula, The reactive power-voltage rotational inertia; The expression is: , All The matrix, except for the following elements, has all elements as 0: In the formula, In order to be in ~ Integers that change between intervals. The phase of the fundamental frequency component of the AC voltage; | represents taking the absolute value; mod() represents the modulo operation.

11. The modular multilevel converter impedance modeling system according to claim 10, characterized in that, When constructing the multi-frequency mapping relationship of the modular multilevel converter control loop, the third multi-frequency mapping relationship construction module uses the AC voltage d-axis reference command small signal. AC voltage control generates small AC current d-axis and q-axis reference command signals. , In AC current control and reference angle small signal Under the combined effect, a small signal of AC modulation is generated. The small signal of the bridge arm current; Through circulating current control and reference angle small signal Under the influence of the current, a small signal of circulating current modulation is generated. AC modulated signal small signal and circulating modulation signal small signal Together they constitute the small signal of the bridge arm modulation signal Bridge arm modulation signal small signal AC voltage d-axis reference command small signal Reference angle small signal Small signal of bridge arm current AC voltage small signal The multi-frequency mapping relationship between them conforms to the following expression: In the formula, The decoupling coefficient is the AC current control coefficient. The decoupling coefficient for circulating control is... , These are the AC modulation signal matrices for the d-axis and q-axis multi-frequency mapped bridge arms, respectively. , These are the d-axis and q-axis multi-frequency mapped bridge arm circulating current modulation signal matrices, respectively. For common-mode multi-frequency mapping matrix, , These are the Park inverse transform d-axis and q-axis multi-frequency mapping matrices, respectively. , These are the negative-order second-harmonic Park transform d-axis and q-axis multi-frequency mapping matrices, respectively. , These are the negative-order second-harmonic Park inverse transform d-axis and q-axis multi-frequency mapping matrices, respectively. For AC current control of multi-frequency mapping matrix, For circulating current control multi-frequency mapping matrix, This is an AC voltage-controlled multi-frequency mapping matrix; The expression is: , , , , , The expressions are as follows: , , The expressions are as follows: In the formula, The transfer function for AC current PI control. This is the transfer function for the circulating current PI control. This is the transfer function for AC voltage PI control.

12. The modular multilevel converter impedance modeling system according to claim 11, characterized in that, When constructing the multi-frequency mapping relationship of the modular multilevel converter arm power path under the action of the control loop, the fourth multi-frequency mapping relationship construction module obtains the small signal of the arm current based on the Kirchhoff voltage relationship and Kirchhoff current relationship of the arm power path. Small signal of bridge arm modulation signal DC port voltage small signal AC voltage small signal The multi-frequency mapping relationship between them is expressed as follows: In the formula, , , These are the multi-frequency mapped bridge arm current, bridge arm capacitor voltage, and bridge arm modulation signal matrix, respectively. This is the multi-frequency mapped impedance matrix of the bridge arm capacitor. The impedance matrix of the bridge arm inductor is a multi-frequency mapped impedance matrix. , The expression is: In the formula, For the number of bridge arm sub-modules, The capacitance value of the submodule. , These are the bridge arm inductance and the bridge arm resistance, respectively.

13. The modular multilevel converter impedance modeling system according to claim 12, characterized in that, The impedance analysis model construction module obtains the admittance matrix of the modular multilevel converter under DC voltage synchronous control. The expression is as follows: In the formula, the superscript -1 indicates the operation of finding the inverse matrix. This is the multi-frequency mapping matrix for the power path of the bridge arm capacitor. This is the multi-frequency mapping matrix for the power path of the bridge arm inductor. For the multi-frequency mapping matrix of the circulating control action, This is the multi-frequency mapping matrix for steady-state circulating current modulation. For AC current control, a multi-frequency mapping matrix is ​​used. This is the steady-state AC current multi-frequency mapping matrix. For AC voltage control, a multi-frequency mapping matrix is ​​used. This is the steady-state AC voltage multi-frequency mapping matrix. This is the multi-frequency mapping matrix for reactive voltage inertial control. This is the multi-frequency mapping matrix for reactive current inertial control. For DC voltage synchronization control, a multi-frequency mapping matrix is ​​used. The dynamic multi-frequency mapping matrix of the DC transmission network is expressed as follows: In the formula, The common-mode zero-sequence multi-frequency mapping matrix is ​​expressed as follows: The impedance analytical model of the modular multilevel converter based on DC voltage synchronous control is obtained, and its expression is as follows: In the formula, For the positive sequence impedance of the modular multilevel converter, For the positive sequence coupling impedance of the modular multilevel converter, For the negative sequence impedance of the modular multilevel converter, For the negative sequence coupling impedance of modular multilevel converters, For matrix The line, number Column elements; For matrix The line, number Column elements; For matrix The line, number Column elements; For matrix The line, number The elements of the column.

14. An electronic device, characterized in that, It includes a processor and a memory, the processor being used to execute a computer program stored in the memory to implement the modular multilevel converter impedance modeling method as described in any one of claims 1 to 7.

15. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores at least one instruction that, when executed by a processor, implements the modular multilevel converter impedance modeling method as described in any one of claims 1 to 7.

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