A positive and negative sequence four-port impedance modeling method and device for a hybrid power transmission system

Abstract

The application provides a positive and negative sequence four-port impedance modeling method and device of a mixed frequency power transmission system, and relates to the technical field of impedance modeling. The method comprises the following steps: obtaining a positive and negative sequence voltage coupling matrix according to a power frequency side PCC steady-state q-axis voltage, a frequency division side PCC steady-state q-axis voltage, a power frequency side PLL transfer function and a frequency division side PLL transfer function; obtaining the positive and negative sequence four-port impedance according to a pre-obtained power frequency side current inner loop controller matrix, a frequency division side current inner loop controller matrix, a power frequency side voltage outer loop controller matrix, a frequency division side voltage outer loop controller matrix, a power frequency side decoupling matrix, a frequency division side decoupling matrix, a voltage calculation matrix, a current calculation matrix and the positive and negative sequence voltage coupling matrix. The method and device provided in the application embodiment can improve the modeling accuracy of the positive and negative sequence four-port impedance of the mixed frequency power transmission system.

Description

Technical Field

[0001] This invention relates to the field of impedance modeling technology, specifically to a positive and negative sequence four-port impedance modeling method and apparatus for a mixed-frequency transmission system. Background Technology

[0002] In recent years, frequency-division transmission technology has been widely used in large-scale offshore wind power grid connection and other fields. The coexistence of frequency-division systems and power frequency systems makes the dynamic interaction between power electronic equipment and the power grid more complex, and the resulting wide-frequency domain stability problem urgently needs to be solved. As the core converter connecting the power frequency grid and the frequency-division wind power system, the impedance characteristics of the AC-AC converter have a decisive impact on the stable operation of the entire mixed-frequency transmission system.

[0003] In the field of impedance modeling for power electronic devices, harmonic linearization methods, by injecting small-signal perturbations and establishing a linear relationship between voltage and current, have become an effective means of analyzing the dynamic characteristics of systems. This method, based on the system's circuit parameters and control structure, obtains impedance characteristics through frequency domain scanning, providing a theoretical basis for stability assessment. However, with the increasing complexity of mixed-frequency transmission systems, existing modeling methods face numerous challenges in handling multi-frequency coupling problems.

[0004] In the harmonic impedance modeling of AC-AC frequency converters, the existing technology has the following main drawbacks:

[0005] 1) Insufficient characterization of frequency coupling effect: Traditional single-sequence impedance model cannot accurately describe the dynamic coupling between positive and negative sequence components, and ignores the energy interaction mechanism between different frequency ports, resulting in limited model accuracy.

[0006] 2) Inadequate consideration of dynamic response of control system: Existing methods oversimplify the dynamic characteristics of phase-locked loop and the frequency coupling effect it causes, and fail to establish a complete mathematical description of the control system in positive and negative sequence coordinate systems.

[0007] 3) Lack of complete model structure: Conventional modeling schemes simplify the mixed frequency transmission system into independent ports for analysis, lacking a unified modeling framework that can simultaneously characterize the impedance characteristics of power frequency and frequency division systems, making it difficult to fully reflect the dynamic behavior of the system. Summary of the Invention

[0008] To address the problems in the prior art, embodiments of the present invention provide a method and apparatus for modeling positive and negative sequence four-port impedances of a mixed-frequency transmission system, which can at least partially solve the problems existing in the prior art.

[0009] On the one hand, this invention proposes a positive and negative sequence four-port impedance modeling method for a mixed-frequency transmission system, including:

[0010] The positive and negative sequence voltage coupling matrix is ​​obtained based on the steady-state q-axis voltage of the PCC on the power frequency side, the steady-state q-axis voltage of the PCC on the frequency division side, the transfer function of the PLL on the power frequency side, and the transfer function of the PLL on the frequency division side.

[0011] The positive and negative sequence four-port impedances are obtained based on the pre-obtained power frequency side current inner loop controller matrix, frequency division side current inner loop controller matrix, power frequency side voltage outer loop controller matrix, frequency division side voltage outer loop controller matrix, power frequency side decoupling matrix, frequency division side decoupling matrix, voltage calculation matrix, current calculation matrix, and the positive and negative sequence voltage coupling matrix.

[0012] The step of obtaining the positive and negative sequence voltage coupling matrix based on the steady-state q-axis voltage of the PCC on the power frequency side, the steady-state q-axis voltage of the PCC on the frequency division side, the transfer function of the PLL on the power frequency side, and the transfer function of the PLL on the frequency division side includes:

[0013] The positive and negative sequence voltage coupling matrix is ​​calculated according to the following formula. :

[0014] ;

[0015] in, The steady-state q-axis voltage of the PCC on the power frequency side. The steady-state q-axis voltage of the PCC on the frequency divider side is... The transfer function of the power frequency side PLL. This is the transfer function of the frequency division side PLL.

[0016] The power frequency side PLL transfer function is expressed according to the following formula:

[0017] ;

[0018] in, The steady-state d-axis voltage of the PCC on the power frequency side. This is the proportional gain of the power frequency side phase-locked loop. The integral time constant of the phase-locked loop on the power frequency side;

[0019] The transfer function of the frequency division side PLL is expressed by the following formula:

[0020] ;

[0021] in, The steady-state d-axis voltage of the PCC on the frequency divider side. This is the proportional gain of the phase-locked loop on the frequency division side. This is the integral time constant of the phase-locked loop on the frequency division side.

[0022] The acquisition of the power frequency side current inner loop controller matrix and the frequency division side current inner loop controller matrix includes:

[0023] The matrix of the power frequency side current inner loop PI controller is obtained based on the proportional gain of the power frequency side current inner loop PI controller and the integral time constant of the power frequency side current inner loop PI controller.

[0024] The matrix of the frequency divider current inner loop controller is obtained based on the proportional gain of the frequency divider current inner loop PI controller and the integral time constant of the frequency divider current inner loop PI controller.

[0025] The acquisition of the power frequency side voltage outer loop controller matrix and the frequency division side voltage outer loop controller matrix includes:

[0026] The power frequency side voltage outer loop controller matrix is ​​obtained based on the proportional gain of the power frequency side outer loop control DC voltage PI controller, the proportional gain of the power frequency side outer loop control reactive power PI controller, the integral time constant of the power frequency side outer loop control DC voltage PI controller, and the integral time constant of the power frequency side outer loop control reactive power PI controller.

[0027] The outer loop controller matrix of the frequency divider voltage is obtained based on the proportional gain of the DC voltage PI controller on the outer loop control of the frequency divider side and the integral time constant of the DC voltage PI controller on the outer loop control of the frequency divider side.

[0028] The acquisition of the power frequency side decoupling matrix and the frequency division side decoupling matrix includes:

[0029] The power frequency side decoupling matrix is ​​obtained based on the power frequency side filter and the power frequency side frequency;

[0030] The frequency division decoupling matrix is ​​obtained based on the frequency division side filter and the frequency division side frequency.

[0031] On one hand, this invention proposes a positive and negative sequence four-port impedance modeling device for a mixed-frequency transmission system, comprising:

[0032] The first acquisition unit is used to acquire the positive and negative sequence voltage coupling matrix based on the steady-state q-axis voltage of the PCC on the power frequency side, the steady-state q-axis voltage of the PCC on the frequency division side, the transfer function of the PLL on the power frequency side, and the transfer function of the PLL on the frequency division side.

[0033] The second acquisition unit is used to acquire the positive and negative sequence four-port impedance based on the pre-acquired power frequency side current inner loop controller matrix, frequency division side current inner loop controller matrix, power frequency side voltage outer loop controller matrix, frequency division side voltage outer loop controller matrix, power frequency side decoupling matrix, frequency division side decoupling matrix, voltage calculation matrix, current calculation matrix, and the positive and negative sequence voltage coupling matrix.

[0034] In another aspect, embodiments of the present invention provide a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the following method:

[0035] The positive and negative sequence voltage coupling matrix is ​​obtained based on the steady-state q-axis voltage of the PCC on the power frequency side, the steady-state q-axis voltage of the PCC on the frequency division side, the transfer function of the PLL on the power frequency side, and the transfer function of the PLL on the frequency division side.

[0036] The positive and negative sequence four-port impedances are obtained based on the pre-obtained power frequency side current inner loop controller matrix, frequency division side current inner loop controller matrix, power frequency side voltage outer loop controller matrix, frequency division side voltage outer loop controller matrix, power frequency side decoupling matrix, frequency division side decoupling matrix, voltage calculation matrix, current calculation matrix, and the positive and negative sequence voltage coupling matrix.

[0037] This invention provides a computer-readable storage medium, comprising:

[0038] The computer-readable storage medium stores a computer program that, when executed by a processor, implements the following method:

[0039] The positive and negative sequence voltage coupling matrix is ​​obtained based on the steady-state q-axis voltage of the PCC on the power frequency side, the steady-state q-axis voltage of the PCC on the frequency division side, the transfer function of the PLL on the power frequency side, and the transfer function of the PLL on the frequency division side.

[0040] The positive and negative sequence four-port impedances are obtained based on the pre-obtained power frequency side current inner loop controller matrix, frequency division side current inner loop controller matrix, power frequency side voltage outer loop controller matrix, frequency division side voltage outer loop controller matrix, power frequency side decoupling matrix, frequency division side decoupling matrix, voltage calculation matrix, current calculation matrix, and the positive and negative sequence voltage coupling matrix.

[0041] This invention also provides a computer program product, which includes a computer program that, when executed by a processor, implements the following method:

[0042] The positive and negative sequence voltage coupling matrix is ​​obtained based on the steady-state q-axis voltage of the PCC on the power frequency side, the steady-state q-axis voltage of the PCC on the frequency division side, the transfer function of the PLL on the power frequency side, and the transfer function of the PLL on the frequency division side.

[0043] The positive and negative sequence four-port impedances are obtained based on the pre-obtained power frequency side current inner loop controller matrix, frequency division side current inner loop controller matrix, power frequency side voltage outer loop controller matrix, frequency division side voltage outer loop controller matrix, power frequency side decoupling matrix, frequency division side decoupling matrix, voltage calculation matrix, current calculation matrix, and the positive and negative sequence voltage coupling matrix.

[0044] The positive and negative sequence four-port impedance modeling method and apparatus for mixed-frequency transmission systems provided in this invention obtains the positive and negative sequence voltage coupling matrix based on the steady-state q-axis voltage of the power frequency side PCC, the steady-state q-axis voltage of the frequency division side PCC, the power frequency side PLL transfer function, and the frequency division side PLL transfer function; and obtains the positive and negative sequence four-port impedance based on the pre-obtained power frequency side current inner loop controller matrix, frequency division side current inner loop controller matrix, power frequency side voltage outer loop controller matrix, frequency division side voltage outer loop controller matrix, power frequency side decoupling matrix, frequency division side decoupling matrix, voltage calculation matrix, current calculation matrix, and the positive and negative sequence voltage coupling matrix, which can improve the modeling accuracy of the positive and negative sequence four-port impedance of the mixed-frequency transmission system. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:

[0046] Figure 1 This is a flowchart illustrating a positive and negative sequence four-port impedance modeling method for a mixed-frequency transmission system provided in an embodiment of the present invention.

[0047] Figure 2 This is a schematic diagram of the equivalent topology of the AC-AC frequency converter provided in an embodiment of the present invention.

[0048] Figure 3 This is a schematic diagram of the structure of a positive and negative sequence four-port impedance modeling device for a mixed-frequency power transmission system provided in an embodiment of the present invention.

[0049] Figure 4 This is a schematic diagram of the physical structure of a computer device provided in an embodiment of the present invention. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Here, the illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other.

[0051] Figure 1 This is a flowchart illustrating a positive and negative sequence four-port impedance modeling method for a mixed-frequency transmission system provided in an embodiment of the present invention, as shown below. Figure 1 As shown, the positive and negative sequence four-port impedance modeling method for a mixed-frequency transmission system provided in this embodiment of the invention includes:

[0052] Step S1: Obtain the positive and negative sequence voltage coupling matrix based on the steady-state q-axis voltage of the PCC on the power frequency side, the steady-state q-axis voltage of the PCC on the frequency division side, the transfer function of the PLL on the power frequency side, and the transfer function of the PLL on the frequency division side.

[0053] Step S2: Obtain the positive and negative sequence four-port impedance based on the pre-obtained power frequency side current inner loop controller matrix, frequency division side current inner loop controller matrix, power frequency side voltage outer loop controller matrix, frequency division side voltage outer loop controller matrix, power frequency side decoupling matrix, frequency division side decoupling matrix, voltage calculation matrix, current calculation matrix, and the positive and negative sequence voltage coupling matrix.

[0054] In step S1 above, the device obtains the positive and negative sequence voltage coupling matrix based on the steady-state q-axis voltage of the PCC on the power frequency side, the steady-state q-axis voltage of the PCC on the frequency divider side, the transfer function of the PLL on the power frequency side, and the transfer function of the PLL on the frequency divider side. The device can be a computer device that executes this method. The acquisition, storage, use, and processing of data in the technical solution of this application all comply with relevant regulations.

[0055] In step S2 above, the device obtains the positive and negative sequence four-port impedance based on the pre-obtained power frequency side current inner loop controller matrix, frequency division side current inner loop controller matrix, power frequency side voltage outer loop controller matrix, frequency division side voltage outer loop controller matrix, power frequency side decoupling matrix, frequency division side decoupling matrix, voltage calculation matrix, current calculation matrix, and the positive and negative sequence voltage coupling matrix.

[0056] As a key component of mixed-frequency power transmission systems, the AC-AC converter has the following topology: Figure 2 As shown, the system includes a power frequency converter, a frequency divider converter, and a DC link. The power frequency side is connected to a 50Hz power grid, and the frequency divider side is connected to a 50 / 3Hz power grid, with the two sides coupled via DC capacitors. Traditional modeling methods analyze the system in the dq coordinate system, but this makes it difficult to directly characterize the frequency coupling effect. This invention uses positive and negative sequence impedance modeling, dividing the system into four ports: power frequency positive sequence, power frequency negative sequence, frequency divider positive sequence, and frequency divider negative sequence, to fully describe the dynamic interaction between different frequency systems.

[0057] Positive-negative sequence transformation is the core of analyzing asymmetric systems. For a three-phase equilibrium system, the phasor transformation formula is as follows:

[0058]

[0059] in, , and These are the positive-sequence and negative-sequence components, respectively. The positive-sequence component corresponds to the frequency... The frequency corresponding to the negative order component In mixed-frequency transmission systems, conversion needs to be applied separately on the power frequency side and the frequency division side, with the power frequency side frequency... Frequency division side Harmonic injection is achieved by applying a small-signal voltage disturbance to the port, for example, injecting a frequency of [frequency value missing] into the positive-sequence port at the power frequency. The disturbance is measured, and the response current is measured to calculate the impedance.

[0060] The main circuit modeling is explained as follows:

[0061] The main circuit includes L-filters on the power frequency side and the frequency divider side, as well as a DC link. The three-phase voltage equations on the power frequency side are:

[0062]

[0063] in, For current vectors, This is the converter output voltage. Let L1 be the power frequency PCC point voltage. Through positive-to-negative sequence transformation, L1 is the power frequency side filter, and R1 is the power frequency side resistor. The power frequency side positive-sequence equation (frequency) is... )for:

[0064]

[0065] in, This represents the positive-sequence component of the output voltage of the power frequency side converter. This is the positive sequence voltage at the power frequency PCC point. This represents the positive sequence current on the power frequency side. The negative sequence equation on the power frequency side (frequency) is... )for:

[0066]

[0067] in, This represents the negative sequence component of the output voltage of the power frequency side converter. The negative sequence voltage at the power frequency PCC point. This is the negative sequence current on the power frequency side. The positive sequence equation on the frequency divider side (frequency) )for:

[0068]

[0069] in, This represents the positive-sequence component of the output voltage of the frequency divider converter. The positive sequence voltage at the PCC point of the frequency division. This represents the positive-sequence current on the frequency divider side. The negative-sequence equation on the frequency divider side (frequency) )for:

[0070]

[0071] in, This represents the negative sequence component of the output voltage of the frequency divider converter. The negative sequence voltage at the PCC point of the frequency division. This is the negative sequence current on the frequency divider side. The dynamics of the DC link are determined by the power balance.

[0072]

[0073] in and For the instantaneous power on the power frequency side and the frequency division side, DC voltage For DC capacitors. After small-signal linearization, the admittance matrix of the main circuit is initially in diagonal form:

[0074]

[0075] This matrix indicates that there is no coupling between positive and negative sequences when there is no control, but DC power balancing will introduce inter-port interaction.

[0076] The impact on phase-locked loops is explained below:

[0077] Phase-locked loops (PLLs) are used to connect synchronous converters to the grid voltage; their dynamic process introduces positive and negative sequence coupling. The phase deviation of the PLL on the power frequency side... Related to negative sequence voltage:

[0078]

[0079] in Transfer function for the power frequency side PLL:

[0080]

[0081] The steady-state d-axis voltage of the PCC on the power frequency side. This is the proportional gain of the power frequency side phase-locked loop. This is the integral time constant of the power frequency side phase-locked loop.

[0082] Similarly, the phase deviation of the PLL on the frequency divider side With the negative sequence voltage of the PCC on the frequency divider side Related.

[0083]

[0084]

[0085] For the frequency divider side PLL transfer function, The steady-state d-axis voltage of the PCC on the frequency divider side. This is the proportional gain of the phase-locked loop on the frequency division side. This is the integral time constant of the phase-locked loop on the frequency division side.

[0086] The PLL causes the control coordinate system to rotate, affecting the voltage and current relationship. After linearization, the positive and negative sequence voltage coupling matrices are:

[0087]

[0088] in, The steady-state q-axis voltage of the PCC on the power frequency side. The steady-state q-axis voltage of the PCC on the frequency divider side is... The transfer function of the power frequency side PLL. Let be the transfer function of the frequency-division side PLL. This formula quantifies the positive and negative sequence coupling mechanism dynamically introduced by the phase-locked loop, explicitly representing the frequency coupling effect in matrix form, and solving the problem of neglecting sequence interaction in traditional models.

[0089] The modeling of the control module is explained as follows:

[0090] The control module includes an inner current loop, an outer voltage loop, and a modulation process.

[0091] Inner current loop:

[0092] The power frequency side current controller outputs a modulated voltage in both positive and negative sequences:

[0093]

[0094] in This is the inner loop controller matrix for the power frequency side current. The proportional gain of the inner loop PI controller for the power frequency side current. The integral time constant of the inner loop PI controller for the power frequency side current is given. This is the decoupling matrix for the power frequency side. The same applies to the frequency divider side, with parameters corresponding to the frequency divider frequency.

[0095] Voltage inner loop:

[0096] The outer loop control of the power frequency side controls the DC voltage and reactive power, and the reference value for the output current is as follows:

[0097]

[0098] in, This is the outer loop controller matrix for the power frequency side voltage. The proportional gain of the DC voltage PI controller is used for the outer loop control of the power frequency side. The proportional gain of the reactive power PI controller for the outer loop control on the power frequency side. The integral time constant of the DC voltage PI controller for the outer loop control on the power frequency side. The integral time constant of the reactive power PI controller for the outer loop control on the power frequency side is denoted as . This is the reference value for the positive sequence current on the power frequency side. This is the reference value for the negative sequence current on the power frequency side. DC voltage This is the DC voltage reference value. For the reactive power control of the outer loop on the power frequency side, The reference values ​​for reactive power control on the power frequency side outer loop and AC voltage and output current on the frequency divider side outer loop are as follows:

[0099]

[0100] in, This is the outer loop controller matrix for the frequency division side voltage. The proportional gain of the DC voltage PI controller is used for the outer loop control of the frequency divider side. The integral time constant of the DC voltage PI controller on the frequency divider side outer loop control. This is the reference value for the positive sequence current on the frequency divider side. This is the reference value for the negative sequence current on the frequency division side. The positive sequence voltage at the PCC point of the frequency division. This is the reference value for the positive sequence voltage at the frequency division PCC point. The negative sequence voltage at the PCC point of the frequency division. This is the reference value for the negative sequence voltage at the frequency division PCC point.

[0101] The modulation process is explained as follows:

[0102] The relationship between the converter output voltage and the modulation signal is as follows:

[0103]

[0104] in, This is the positive sequence component of the modulated signal. For the negative sequence component of the modulated signal, the small-signal change in DC voltage is derived from power balance:

[0105]

[0106] in, ( (indicating conjugation) This represents the steady-state value of the positive sequence voltage on the power frequency side. This represents the steady-state value of the positive sequence current on the power frequency side. This represents the small-signal change in the positive-sequence voltage on the power frequency side. This represents the small-signal change in the positive-sequence current on the power frequency side. This represents the steady-state value of the negative sequence voltage on the power frequency side. This represents the steady-state value of the negative sequence current on the power frequency side. This refers to the small-signal change in the negative sequence voltage on the power frequency side. This represents the small-signal change in the negative sequence current on the power frequency side. Similar calculations.

[0107] This formula, by linearizing the power perturbation equation, derives the contribution of the DC link dynamics to the coupling between ports, providing a quantitative basis for the energy interaction path in the four-port impedance model.

[0108] Positive and negative sequence four-port impedance:

[0109] The main circuit, phase-locked loop, and control module are integrated, and the four-port impedance matrix is ​​obtained through matrix operations. The system equations are defined as follows:

[0110]

[0111] Total admittance matrix The calculation is as follows:

[0112]

[0113] This formula integrates the main circuit and control module through matrix operations, constructs the basis of the four-port admittance model, and realizes a unified mathematical description of the dynamic interaction between power frequency and frequency division systems.

[0114] The positive and negative sequence four-port impedances are:

[0115]

[0116] in, , , . For voltage calculation matrix, The current calculation matrix is ​​obtained by linearizing the power balance equation. This positive and negative sequence four-port impedance matrix fully describes the dynamic interaction between the power frequency and frequency division systems, including sequence coupling and frequency coupling. It is an identity matrix.

[0117] This formula transforms the dynamic response of the control system in the positive and negative sequence domains into impedance form, fully reflecting the frequency coupling and sequence coupling caused by the controller.

[0118] The positive and negative sequence four-port impedance model constructed in this invention accurately describes the energy transfer paths between ports of different frequencies in a mixed-frequency transmission system: the coupling between the positive and negative sequence ports of the power frequency reflects the energy redistribution during asymmetrical grid operation; the coupling between the positive and negative sequence ports of the frequency division reflects the imbalance characteristics within the frequency division system; and the interaction between the power frequency and frequency division ports realizes energy transfer between different frequency systems through DC link power balancing. From a dynamic perspective, the positive and negative sequence coupling introduced by the phase-locked loop reveals the response mechanism of the control system to grid asymmetry, while the controller matrix quantifies the system's dynamic adjustment capability to disturbances. The four-port impedance characterization not only provides a quantitative analysis tool for system stability but also reveals the intrinsic mechanism of frequency coupling and sequence interaction in the mixed-frequency system from a physical perspective, laying a theoretical foundation for system optimization design.

[0119] By constructing a positive and negative sequence four-port impedance model, a complete mathematical description of the dynamic interaction between power frequency and frequency division ports in a mixed-frequency transmission system is achieved for the first time, breaking through the limitations of traditional single-frequency impedance models. This model not only accurately characterizes the frequency coupling effect caused by the phase-locked loop and control module, but also quantifies the energy interaction mechanism between positive and negative sequence components through a matrix method, providing a high-precision theoretical basis for system stability analysis. At the same time, this modeling method has clear physical meaning and engineering applicability, and can be directly applied to impedance measurement and controller parameter optimization in actual systems, significantly improving the stability margin and control performance of mixed-frequency transmission systems.

[0120] The positive and negative sequence four-port impedance modeling method for mixed-frequency transmission systems provided in this invention describes the dynamic characteristics of AC-AC converters in mixed-frequency systems by establishing a four-port impedance matrix that includes power frequency positive sequence, power frequency negative sequence, sub-frequency positive sequence, and sub-frequency negative sequence. This modeling method innovatively introduces a frequency coupling matrix and a positive and negative sequence domain representation of the control system, providing a new technical approach for the stability analysis and control design of mixed-frequency transmission systems.

[0121] The positive and negative sequence four-port impedance modeling method for mixed-frequency transmission systems provided in this invention obtains the positive and negative sequence voltage coupling matrix based on the steady-state q-axis voltage of the power frequency side PCC, the steady-state q-axis voltage of the frequency division side PCC, the power frequency side PLL transfer function, and the frequency division side PLL transfer function; and obtains the positive and negative sequence four-port impedance based on the pre-obtained power frequency side current inner loop controller matrix, frequency division side current inner loop controller matrix, power frequency side voltage outer loop controller matrix, frequency division side voltage outer loop controller matrix, power frequency side decoupling matrix, frequency division side decoupling matrix, voltage calculation matrix, current calculation matrix, and the positive and negative sequence voltage coupling matrix, which can improve the modeling accuracy of the positive and negative sequence four-port impedance of the mixed-frequency transmission system.

[0122] In the above optional embodiments, obtaining the positive and negative sequence voltage coupling matrix based on the steady-state q-axis voltage of the power frequency side PCC, the steady-state q-axis voltage of the frequency division side PCC, the power frequency side PLL transfer function, and the frequency division side PLL transfer function includes:

[0123] The positive and negative sequence voltage coupling matrix is ​​calculated according to the following formula. :

[0124] ;

[0125] in, The steady-state q-axis voltage of the PCC on the power frequency side. The steady-state q-axis voltage of the PCC on the frequency divider side is... The transfer function of the power frequency side PLL. This refers to the transfer function of the frequency division side PLL. Refer to the above embodiments for further details; no further repetition is necessary.

[0126] In the above optional embodiments, the power frequency side PLL transfer function is expressed according to the following formula:

[0127] ;

[0128] in, The steady-state d-axis voltage of the PCC on the power frequency side. This is the proportional gain of the power frequency side phase-locked loop. This is the integral time constant of the power frequency side phase-locked loop; please refer to the above embodiments for explanation, and it will not be repeated here.

[0129] The transfer function of the frequency division side PLL is expressed by the following formula:

[0130] ;

[0131] in, The steady-state d-axis voltage of the PCC on the frequency divider side. This is the proportional gain of the phase-locked loop on the frequency division side. This is the integration time constant of the phase-locked loop on the frequency division side. Refer to the above embodiments for further details; further explanation is unnecessary.

[0132] In the above optional embodiments, obtaining the power frequency side current inner loop controller matrix and the frequency division side current inner loop controller matrix includes:

[0133] The power frequency side current inner loop controller matrix is ​​obtained based on the proportional gain and integral time constant of the power frequency side current inner loop PI controller; this can be referred to the above embodiment for explanation, and will not be repeated here.

[0134] The frequency-division side current inner loop controller matrix is ​​obtained based on the proportional gain and integral time constant of the frequency-division side current inner loop PI controller. This can be referred to the above embodiment for explanation, and will not be repeated here.

[0135] In the above optional embodiments, obtaining the power frequency side voltage outer loop controller matrix and the frequency division side voltage outer loop controller matrix includes:

[0136] The power frequency side voltage outer loop controller matrix is ​​obtained based on the proportional gain of the power frequency side outer loop control DC voltage PI controller, the proportional gain of the power frequency side outer loop control reactive power PI controller, the integral time constant of the power frequency side outer loop control DC voltage PI controller, and the integral time constant of the power frequency side outer loop control reactive power PI controller; this can be referred to the above embodiment for explanation, and will not be repeated here.

[0137] The frequency divider voltage outer loop controller matrix is ​​obtained based on the proportional gain and integral time constant of the frequency divider side outer loop control DC voltage PI controller. This can be referred to the above embodiment for explanation, and will not be repeated here.

[0138] In the above optional embodiments, obtaining the power frequency side decoupling matrix and the frequency division side decoupling matrix includes:

[0139] The power frequency side decoupling matrix is ​​obtained based on the power frequency side filter and the power frequency side frequency; this can be referred to the above embodiment for explanation, and will not be repeated here.

[0140] The frequency division decoupling matrix is ​​obtained based on the frequency division side filter and the frequency division side frequency. This can be referred to the above embodiment for explanation, and will not be repeated here.

[0141] Figure 3 This is a schematic diagram of the structure of a positive and negative sequence four-port impedance modeling device for a frequency mixing transmission system provided in an embodiment of the present invention, as shown below. Figure 3 As shown, the positive and negative sequence four-port impedance modeling device for a mixed-frequency transmission system provided in this embodiment of the invention includes a first acquisition unit 301 and a second acquisition unit 302, wherein:

[0142] The first acquisition unit 301 is used to acquire the positive and negative sequence voltage coupling matrix based on the steady-state q-axis voltage of the PCC on the power frequency side, the steady-state q-axis voltage of the PCC on the frequency division side, the transfer function of the PLL on the power frequency side, and the transfer function of the PLL on the frequency division side; the second acquisition unit 302 is used to acquire the positive and negative sequence four-port impedance based on the pre-obtained power frequency side current inner loop controller matrix, frequency division side current inner loop controller matrix, power frequency side voltage outer loop controller matrix, frequency division side voltage outer loop controller matrix, power frequency side decoupling matrix, frequency division side decoupling matrix, voltage calculation matrix, current calculation matrix, and the positive and negative sequence voltage coupling matrix.

[0143] Specifically, the first acquisition unit 301 in the device is used to acquire the positive and negative sequence voltage coupling matrix based on the steady-state q-axis voltage of the PCC on the power frequency side, the steady-state q-axis voltage of the PCC on the frequency division side, the transfer function of the PLL on the power frequency side, and the transfer function of the PLL on the frequency division side; the second acquisition unit 302 is used to acquire the positive and negative sequence four-port impedance based on the pre-obtained power frequency side current inner loop controller matrix, frequency division side current inner loop controller matrix, power frequency side voltage outer loop controller matrix, frequency division side voltage outer loop controller matrix, power frequency side decoupling matrix, frequency division side decoupling matrix, voltage calculation matrix, current calculation matrix, and the positive and negative sequence voltage coupling matrix.

[0144] The positive and negative sequence four-port impedance modeling device for a mixed-frequency transmission system provided in this invention obtains the positive and negative sequence voltage coupling matrix based on the steady-state q-axis voltage of the power frequency side PCC, the steady-state q-axis voltage of the frequency division side PCC, the power frequency side PLL transfer function, and the frequency division side PLL transfer function; and obtains the positive and negative sequence four-port impedance based on the pre-obtained power frequency side current inner loop controller matrix, frequency division side current inner loop controller matrix, power frequency side voltage outer loop controller matrix, frequency division side voltage outer loop controller matrix, power frequency side decoupling matrix, frequency division side decoupling matrix, voltage calculation matrix, current calculation matrix, and the positive and negative sequence voltage coupling matrix, thereby improving the modeling accuracy of the positive and negative sequence four-port impedance of the mixed-frequency transmission system.

[0145] The embodiments of the present invention provide a positive and negative sequence four-port impedance modeling device for a mixed frequency transmission system, which can be used to execute the processing flow of the above-described method embodiments. Its functions will not be repeated here, but can be referred to the detailed description of the above-described method embodiments.

[0146] Figure 4 This is a schematic diagram of the physical structure of a computer device provided in an embodiment of the present invention, such as... Figure 4 As shown, the computer device includes: a memory 401, a processor 402, and a computer program stored in the memory 401 and executable on the processor 402. When the processor 402 executes the computer program, it implements the following method:

[0147] The positive and negative sequence voltage coupling matrix is ​​obtained based on the steady-state q-axis voltage of the PCC on the power frequency side, the steady-state q-axis voltage of the PCC on the frequency division side, the transfer function of the PLL on the power frequency side, and the transfer function of the PLL on the frequency division side.

[0148] The positive and negative sequence four-port impedances are obtained based on the pre-obtained power frequency side current inner loop controller matrix, frequency division side current inner loop controller matrix, power frequency side voltage outer loop controller matrix, frequency division side voltage outer loop controller matrix, power frequency side decoupling matrix, frequency division side decoupling matrix, voltage calculation matrix, current calculation matrix, and the positive and negative sequence voltage coupling matrix.

[0149] This embodiment discloses a computer program product, which includes a computer program that, when executed by a processor, implements the following method:

[0150] The positive and negative sequence voltage coupling matrix is ​​obtained based on the steady-state q-axis voltage of the PCC on the power frequency side, the steady-state q-axis voltage of the PCC on the frequency division side, the transfer function of the PLL on the power frequency side, and the transfer function of the PLL on the frequency division side.

[0151] The positive and negative sequence four-port impedances are obtained based on the pre-obtained power frequency side current inner loop controller matrix, frequency division side current inner loop controller matrix, power frequency side voltage outer loop controller matrix, frequency division side voltage outer loop controller matrix, power frequency side decoupling matrix, frequency division side decoupling matrix, voltage calculation matrix, current calculation matrix, and the positive and negative sequence voltage coupling matrix.

[0152] This embodiment provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the following method:

[0153] The positive and negative sequence voltage coupling matrix is ​​obtained based on the steady-state q-axis voltage of the PCC on the power frequency side, the steady-state q-axis voltage of the PCC on the frequency division side, the transfer function of the PLL on the power frequency side, and the transfer function of the PLL on the frequency division side.

[0154] The positive and negative sequence four-port impedances are obtained based on the pre-obtained power frequency side current inner loop controller matrix, frequency division side current inner loop controller matrix, power frequency side voltage outer loop controller matrix, frequency division side voltage outer loop controller matrix, power frequency side decoupling matrix, frequency division side decoupling matrix, voltage calculation matrix, current calculation matrix, and the positive and negative sequence voltage coupling matrix.

[0155] Compared with existing technical solutions, the positive and negative sequence four-port impedance modeling method for mixed-frequency transmission systems provided in this invention obtains the positive and negative sequence voltage coupling matrix based on the steady-state q-axis voltage of the power frequency side PCC, the steady-state q-axis voltage of the frequency division side PCC, the power frequency side PLL transfer function, and the frequency division side PLL transfer function; and obtains the positive and negative sequence four-port impedance based on the pre-obtained power frequency side current inner loop controller matrix, frequency division side current inner loop controller matrix, power frequency side voltage outer loop controller matrix, frequency division side voltage outer loop controller matrix, power frequency side decoupling matrix, frequency division side decoupling matrix, voltage calculation matrix, current calculation matrix, and the positive and negative sequence voltage coupling matrix, thereby improving the modeling accuracy of the positive and negative sequence four-port impedance of the mixed-frequency transmission system.

[0156] 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.

[0157] 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 will 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.

[0158] 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.

[0159] 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.

[0160] In the description of this specification, the references to terms such as "an embodiment," "a specific embodiment," "some embodiments," "for example," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0161] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for modeling the positive and negative sequence four-port impedance of a mixed-frequency transmission system, characterized in that, include: The positive and negative sequence voltage coupling matrix is ​​obtained based on the steady-state q-axis voltage of the PCC on the power frequency side, the steady-state q-axis voltage of the PCC on the frequency division side, the transfer function of the PLL on the power frequency side, and the transfer function of the PLL on the frequency division side. The positive and negative sequence four-port impedances are obtained based on the pre-obtained power frequency side current inner loop controller matrix, frequency division side current inner loop controller matrix, power frequency side voltage outer loop controller matrix, frequency division side voltage outer loop controller matrix, power frequency side decoupling matrix, frequency division side decoupling matrix, voltage calculation matrix, current calculation matrix, and the positive and negative sequence voltage coupling matrix.

2. The positive and negative sequence four-port impedance modeling method for a mixed-frequency transmission system according to claim 1, characterized in that, The step of obtaining the positive and negative sequence voltage coupling matrix based on the steady-state q-axis voltage of the PCC on the power frequency side, the steady-state q-axis voltage of the PCC on the frequency division side, the transfer function of the PLL on the power frequency side, and the transfer function of the PLL on the frequency division side includes: The positive and negative sequence voltage coupling matrix is ​​calculated according to the following formula. : ； in, The steady-state q-axis voltage of the PCC on the power frequency side. The steady-state q-axis voltage of the PCC on the frequency divider side is... The transfer function of the power frequency side PLL. This is the transfer function of the frequency division side PLL.

3. The positive and negative sequence four-port impedance modeling method for a mixed-frequency transmission system according to claim 2, characterized in that, The power frequency side PLL transfer function is expressed by the following formula: ； in, The steady-state d-axis voltage of the PCC on the power frequency side. This is the proportional gain of the power frequency side phase-locked loop. The integral time constant of the phase-locked loop on the power frequency side; The transfer function of the frequency division side PLL is expressed by the following formula: ； in, The steady-state d-axis voltage of the PCC on the frequency divider side. This is the proportional gain of the phase-locked loop on the frequency division side. This is the integral time constant of the phase-locked loop on the frequency division side.

4. The positive and negative sequence four-port impedance modeling method for a mixed-frequency transmission system according to claim 1, characterized in that, Obtaining the power frequency side current inner loop controller matrix and the frequency division side current inner loop controller matrix includes: The matrix of the power frequency side current inner loop PI controller is obtained based on the proportional gain of the power frequency side current inner loop PI controller and the integral time constant of the power frequency side current inner loop PI controller. The matrix of the frequency divider current inner loop controller is obtained based on the proportional gain of the frequency divider current inner loop PI controller and the integral time constant of the frequency divider current inner loop PI controller.

5. The positive and negative sequence four-port impedance modeling method for a mixed-frequency transmission system according to claim 1, characterized in that, Obtaining the power frequency side voltage outer loop controller matrix and the frequency division side voltage outer loop controller matrix includes: The power frequency side voltage outer loop controller matrix is ​​obtained based on the proportional gain of the power frequency side outer loop control DC voltage PI controller, the proportional gain of the power frequency side outer loop control reactive power PI controller, the integral time constant of the power frequency side outer loop control DC voltage PI controller, and the integral time constant of the power frequency side outer loop control reactive power PI controller. The outer loop controller matrix of the frequency divider voltage is obtained based on the proportional gain of the DC voltage PI controller on the outer loop control of the frequency divider side and the integral time constant of the DC voltage PI controller on the outer loop control of the frequency divider side.

6. The positive and negative sequence four-port impedance modeling method for a mixed-frequency transmission system according to claim 1, characterized in that, Obtaining the power frequency side decoupling matrix and the frequency division side decoupling matrix includes: The power frequency side decoupling matrix is ​​obtained based on the power frequency side filter and the power frequency side frequency; The frequency division decoupling matrix is ​​obtained based on the frequency division side filter and the frequency division side frequency.

7. A positive and negative sequence four-port impedance modeling device for a mixed-frequency transmission system, characterized in that, include: The first acquisition unit is used to acquire the positive and negative sequence voltage coupling matrix based on the steady-state q-axis voltage of the PCC on the power frequency side, the steady-state q-axis voltage of the PCC on the frequency division side, the transfer function of the PLL on the power frequency side, and the transfer function of the PLL on the frequency division side. The second acquisition unit is used to acquire the positive and negative sequence four-port impedance based on the pre-acquired power frequency side current inner loop controller matrix, frequency division side current inner loop controller matrix, power frequency side voltage outer loop controller matrix, frequency division side voltage outer loop controller matrix, power frequency side decoupling matrix, frequency division side decoupling matrix, voltage calculation matrix, current calculation matrix, and the positive and negative sequence voltage coupling matrix.

8. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the method of any one of claims 1 to 6.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the method of any one of claims 1 to 6.

10. A computer program product, characterized in that, The computer program product includes a computer program that, when executed by a processor, implements the method of any one of claims 1 to 6.

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