A balanced coordination control method and system for improving small signal stability and voltage support capability of distributed wind-solar new energy grid-connected

Abstract

The application belongs to the field of power system control, and relates to a balanced and coordinated control method for improving small signal stability and voltage support capability of a distributed wind-solar new energy grid-connected system, characterized by the following steps: S1: frequency domain modeling is performed by using a sequence admittance modeling method for the distributed wind-solar power generation system; S2: source side and network side impedance matching calculation is performed to calculate the stability margin at the intersection point; S3: a consistency index for measuring the voltage state is added; S4: a distributed control scheme is adopted, and a distributed collaborative control algorithm is constructed based on the consistency factor of the whole system voltage to keep the bus voltage of each unit within a feasible range; and S5: the damping margin is compensated to the voltage support control. The application can ensure small signal stability, support voltage as much as possible, avoid oscillation and overvoltage instability problems of the distributed wind-solar photovoltaic grid-connected system, and promote efficient consumption of renewable energy.

Description

Technical Field

[0001] This invention belongs to the field of power system control, and more specifically, relates to a balanced and coordinated control method and system for improving the small-signal stability and voltage support capability of distributed wind and solar renewable energy grid connection. Background Technology

[0002] The large-scale grid connection of new energy sources, such as distributed wind power and photovoltaics, via power electronic converters is characterized by weak disturbance rejection and weak reactive power support, profoundly altering the system dynamics. Under this transformation, the system's small-signal stability and voltage support capability have become the core contradictions constrained by each other. In the Spanish blackout of 2025, measures such as strengthening the grid mesh structure and reducing power transmission through tie lines were initially taken to suppress the observed 0.64Hz low-frequency oscillation. While this temporarily suppressed the oscillation, it raised the overall system voltage level, creating a potential trigger for voltage instability. This incident demonstrates that under a high proportion of new energy grid connection, the insufficient broadband damping and inadequate dynamic reactive power support capability of the system are coupled, and their dynamic conflict ultimately leads to a cascading collapse. Therefore, it is urgent to improve the active support capability of distributed new energy sources while ensuring their small-signal stability.

[0003] To address the aforementioned challenges, current research primarily follows two relatively independent paths: small-signal frequency domain stability and voltage support. Regarding small-signal stability, research methods mainly fall into two categories: state-space methods and impedance methods. State-space methods require complete system transparency and known parameters. However, with the increasing scale of distributed renewable energy systems, this method suffers from the curse of dimensionality. To solve this problem, impedance modeling has proven to be an effective solution, which can be divided into dq impedance methods and sequence impedance methods. dq impedance is limited in its application because it cannot be directly measured in engineering, making it difficult to directly reveal the mechanism. Sequence impedance methods, developed based on a stationary coordinate system, have the advantages of being measurable in engineering and providing intuitive mechanism revelation. However, this method is based on overall matrix modeling and cannot independently reveal the effects of frequency coupling and AC / DC coupling. The matrix size based on matrix stability analysis also increases with system scale, leading to the complexity of solving for right-half-plane poles, making it unsuitable for the analysis and application of distributed renewable energy grid-connected systems. Therefore, this method is limited in both modeling accuracy and criterion efficiency. Sequence impedance methods, on the other hand, are a new method developed based on sequence impedance methods, integrating the concepts of impedance and admittance. This method offers advantages in modular modeling and efficient stability analysis. This method has the potential to efficiently reveal the stability mechanism of distributed renewable energy grid connection.

[0004] Regarding voltage support, existing research typically treats renewable energy aggregation as equivalent and designs coordinated control strategies based on the port bus voltage of the renewable energy source. Among these, reactive power-based voltage feedforward compensation control can enable renewable energy to output reactive power in response to grid voltage changes under quasi-steady-state conditions, ensuring voltage safety at the point of common coupling (PCC). Further evaluation of the reactive power output capacity of renewable energy sources and calculation of reference values ​​using voltage and system impedance parameters are conducted to achieve precise PCC voltage regulation. Other studies have further considered the constraints between port voltage and power factor, proposing a coordinated control strategy to balance the two. Furthermore, existing research suggests employing a distributed voltage control scheme to coordinate the reactive power output of doubly-fed induction generators and static synchronous compensators. This method keeps the voltage of all bus terminals in the wind farm within a feasible range, achieving coordinated voltage control. While these efforts have made progress, a fundamental challenge is increasingly apparent: there is often a profound contradiction between voltage support capability and small-signal stability. Existing methods design and optimize these two as independent objectives, without systematically balancing and coordinating them. Therefore, an effective control method to coordinate these two aspects is urgently needed. Summary of the Invention

[0005] The purpose of this invention is to provide a balanced and coordinated control method and system for improving the small-signal stability and voltage support capability of distributed wind and solar power grid connection. This aims to avoid the problem of small-signal instability caused by voltage rise. Furthermore, by coordinating with the distributed wind and solar grid connection system (a distributed wind and solar grid connection system refers to an existing engineering grid connection scenario; coordinating the distributed wind and solar grid connection system means coordinating and controlling the existing engineering system; the proposed balanced and coordinated control is a control strategy that optimizes the design of the existing engineering system), the small-signal stability is globally improved. This ensures small-signal stability while consistently supporting the voltage, avoiding oscillations and overvoltage instability in the distributed wind and solar grid connection system, and promoting the efficient consumption of renewable energy.

[0006] To achieve the above objectives, the technical solution adopted by this invention is a balanced and coordinated control method for improving the small-signal stability and voltage support capability of distributed wind and solar renewable energy grid connection, characterized by the following steps: S1: Frequency domain modeling is performed on the distributed wind and solar power generation system using the sequential impedance modeling method. Based on the harmonic linearization method, the control equations and port equations of the AC subsystem and DC subsystem are derived. The frequency domain model is constructed after considering the frequency and AC-DC coupling of the system. S2: Based on S1, perform source-side and grid-side impedance matching calculations, calculate the stability margin at the intersection point of the two, and obtain the small-signal stability margin of the distributed wind power photovoltaic grid-connected system under different average voltages. S3: Based on S2, and taking into account the contradictory mechanism between small-signal stability and voltage active support capability, a consistency index that can measure voltage state is added, thereby realizing leaderless interaction of global information. S4: Based on S3, and taking into account the characteristics of distributed new energy, a distributed control scheme is adopted. A distributed collaborative control algorithm is constructed based on the consistency factor of the entire system voltage to keep the bus voltage of each unit within a feasible range, thereby achieving voltage collaborative control. S5: Based on S2 and S4, and considering the conflicting constraints between small-signal stability and active voltage support capability, the damping margin is compensated into the voltage support control based on the small-signal damping margin of the theoretical model of each unit under different operating conditions, thereby achieving a localized dynamic balance between small-signal stability and voltage support.

[0007] Further, in step S1, the frequency domain modeling of the distributed wind and solar power generation system using the sequential impedance modeling method can be calculated as follows: The steady-state operating point of the modulation signal is denoted as . ; , and These represent the disturbance vectors of alternating current, alternating voltage, and direct current voltage, respectively. , and This is the system small-signal matrix corresponding to the disturbance current, voltage, and DC voltage; the scalar value of the DC voltage is represented by... express; The admittance diagonal matrix of the distributed photovoltaic grid-connected port; For the communication side; DC side; This is the steady-state matrix of the modulated signal; The per-unit factor for the disturbance voltage; To represent the amplitude of the disturbance voltage signal; The complex phase angle of the disturbance voltage; the corrected admittance matrix is ​​expressed as... , and , Add or subtract the correction frequency at the fundamental frequency to the disturbance frequency. For the perturbation frequency, The imaginary unit, The fundamental frequency, Add or subtract a correction frequency of twice the fundamental frequency to the disturbance frequency. It is twice the fundamental frequency; similarly, the complex frequency domain relation is defined as and , The perturbation frequency is a complex variable added to or subtracted from the fundamental frequency. For complex variables, For the perturbation frequency plus or minus twice the fundamental frequency, it is a complex variable; , These represent the amplitude and phase of the disturbance voltage signal, respectively. There is a coupling relationship between the AC and DC sides of a distributed wind and solar power generation system. Therefore, it is necessary to precisely define the relationship between the AC and DC voltages: in, and These correspond to the DC bus voltage and the AC side voltage, respectively. Describe the effect of the positive-sequence AC component on the DC side; the inherent capacitance and impedance of the DC circuit are denoted as... ; It has DC self-admittance; Alternating current; and These are the positive-sequence admittance from DC to AC and the positive-sequence self-admittance from AC, respectively.

[0008] Frequency coupling originates from the closed-loop feedback interaction between distributed renewable energy systems and the AC grid. For grid-connected units, while the basic feedback mechanism is similar to the aforementioned AC-DC coupling process, the interaction path differs fundamentally: frequency coupling primarily involves the external AC grid network, while AC-DC coupling is an internal process between the AC and DC sides of the unit. Therefore, this frequency coupling effect can be quantitatively modeled and incorporated into the system analysis as an equivalent additional impedance term. in, This is the equivalent coupling admittance; and These represent negative-order coupling admittance and negative-order self-admittance, respectively. This is the equivalent negative sequence grid admittance; This is the transfer admittance at the coupling frequency.

[0009] Furthermore, in step S2, the source-side and grid-side impedance matching calculations are performed, and the stability margin at their intersection point is calculated. The small-signal stability margin under different system average voltages can be calculated as follows: in, and The impedance and equivalent impedance of each distributed renewable energy unit; R g and L g The equivalent resistance and inductance on the grid side are... For complex variables, For is the imaginary unit, This is the phasor of the steady-state voltage. and These are DC voltage and AC inductance, respectively. and These represent the current loop and the voltage loop, respectively. , and These are the feedback coefficients, phase-locked loop function, and voltage feedforward equation, respectively. The specific value range is 1-100). and It is a steady-state complex quantity. For small signal phase margin, For the actual stable phase, This is the standard stable phase.

[0010] Furthermore, in step S3, based on the contradictory mechanism between small-signal stability and active voltage support capability, a consistency index that can measure the voltage state is added and can be calculated as follows: in, The consistency coefficient, The specific value range is 0-1; , and These are the steady-state voltage, the actual voltage, and the maximum voltage, respectively.

[0011] Furthermore, in step S4, a distributed control scheme is adopted. The distributed cooperative control algorithm constructed based on the consistency factor of the entire system voltage can be calculated as follows: in, This is the voltage value after active voltage control. This is the voltage reference value for the distributed renewable energy unit. Let be the voltage reference value for the i-th distributed renewable energy unit. and For distributed control PI parameters ( and The specific values ​​are 0-10 and 0-100 respectively. For complex variables, For virtual part units, The consistency coefficient of the i-th distributed wind and solar unit ( (Specific value is 0-1) For the j-th distributed wind and solar unit ( The specific value is 0-1).

[0012] Furthermore, in step S5, based on the small-signal damping margin of each unit's theoretical model under different operating conditions, the damping margin is compensated to the voltage support control calculation as follows: in, To correct the steady-state value of the voltage after applying active voltage support control; For phase transfer coefficient, The specific value range is 0-10. For complex variables, For virtual part units, The consistency coefficient of the i-th distributed wind and solar unit ( (Specific value is 0-1) For the j-th distributed wind and solar unit ( The specific value is 0-1). For the actual stable phase, For standard stable phase, and For distributed control PI parameters ( and The specific values ​​are 0-10 and 0-100, respectively.

[0013] Furthermore, the balanced and coordinated control system for improving the small-signal stability and voltage support capability of distributed wind and solar renewable energy grid connection, as described above, is characterized by comprising: The transmission module is used to calculate the parameters based on the parameters from the voltage operation status detection stage during the additional active voltage support control stage, and input the parameters into the controllers of each distributed control system to realize the parameter adjustment of the controllers. The PMU module is used to collect signals such as AC current and AC voltage of distributed renewable energy grid connection, so as to calculate stability constraint relationship and voltage operating point, and detect the real-time changes of grid connection frequency and voltage. The detection module is used to compare the grid-connected voltage and current data collected by the PMU module with the real-time change range of the detection voltage calculated by the calculation module, so as to detect whether a start signal is output. The calculation module is used to calculate the control margin of the active power and reactive power of the converter based on the distributed new energy grid-connected AC current, AC voltage and other signals obtained by the PMU module. The control module is used to apply feedback voltage supplementary control to the stability margin of the distributed new energy source, thereby taking into account the small-signal stability supplementary control in the control process.

[0014] Compared with the prior art, the above-described technical solutions conceived in this invention can achieve the following beneficial effects: This invention characterizes the contradictory mechanism between small-signal stability and voltage support capability. Based on this mechanism, a distributed balance coordination control strategy based on a consensus algorithm and small-signal damping margin compensation is proposed. Compared with existing decentralized and distributed control, this invention can support voltage as consistently as possible while ensuring small-signal stability. It avoids the over-limit problem and local oscillation problem caused by local voltage rise, further improving the overall voltage coordination capability and small-signal stability of the distributed renewable energy grid-connected system. It also prevents distributed renewable energy units from entering the low-voltage ride-through process due to voltage drops, further improving the system's voltage support capability. Attached Figure Description

[0015] Figure 1 This is a flowchart of a balanced and coordinated control method for improving the small-signal stability and voltage support capability of distributed wind and solar new energy grid connection, provided in the embodiment.

[0016] Figure 2 This is a diagram illustrating a balanced and coordinated control method for improving the small-signal stability and voltage support capability of distributed wind and solar new energy grid connection, as provided in the embodiment.

[0017] Figure 3 The figure shows a comparison of voltage support and small-signal stability of different control methods in a distributed voltage regulation system; (a) distributed voltage results of decentralized control, (b) distributed voltage results of the proposed control, (c) voltage regulation effect of different voltage references under the proposed control, and (d) comparison of voltage support capabilities between the proposed control and distributed control.

[0018] Figure 4 This is a comparison chart of different control methods in distributed power grids in terms of voltage support and small-signal stability; (a) overall voltage results under different average voltages, (b) distributed voltage results of decentralized control when the voltage of a certain plug-in grid connection point rises to 1.1 times the rated voltage, (c) distributed voltage results of the proposed control when the voltage of a certain plug-in grid connection point rises to 1.2 times the rated voltage, and (d) comparison of voltage support capabilities of different methods. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0020] See Figure 1 This invention provides a balanced and coordinated control method for improving the small-signal stability and voltage support capability of distributed wind and solar renewable energy grid connection, comprising the following steps: S1: Frequency domain modeling is performed on the distributed wind and solar power generation system using the sequential impedance modeling method. Based on the harmonic linearization method, the control equations and port equations of the AC subsystem and DC subsystem are derived. The frequency domain model is constructed after considering the frequency and AC-DC coupling of the system. Specifically, in step S1, the frequency domain modeling of the distributed wind and solar power generation system using the sequential impedance modeling method can be calculated as follows: The steady-state operating point of the modulation signal is denoted as . ; , and These represent the disturbance vectors of alternating current, alternating voltage, and direct current voltage, respectively. , and This is the system small-signal matrix corresponding to the disturbance current, voltage, and DC voltage; the scalar value of the DC voltage is represented by... express The admittance diagonal matrix of the distributed photovoltaic grid-connected port; For the communication side; DC side; This is the steady-state matrix of the modulated signal; The per-unit factor for the disturbance voltage; To represent the amplitude of the disturbance voltage signal; The complex phase angle of the disturbance voltage; the corrected admittance matrix is ​​expressed as... , and , Add or subtract the correction frequency at the fundamental frequency to the disturbance frequency. For the perturbation frequency, The imaginary unit, The fundamental frequency, Add or subtract a correction frequency of twice the fundamental frequency to the disturbance frequency. It is twice the fundamental frequency; similarly, the complex frequency domain relation is defined as and , The perturbation frequency is a complex variable added to or subtracted from the fundamental frequency. For complex variables, For the perturbation frequency plus or minus twice the fundamental frequency, it is a complex variable; , These represent the amplitude and phase of the disturbance voltage signal, respectively. There is a coupling relationship between the AC and DC sides of a distributed wind and solar power generation system. Therefore, it is necessary to precisely define the relationship between the AC and DC voltages: in, and These correspond to the DC bus voltage and the AC side voltage, respectively. Describe the effect of the positive-sequence AC component on the DC side; the inherent capacitance and impedance of the DC circuit are denoted as... ; It has DC self-admittance; Alternating current; and These are the positive-sequence admittance from DC to AC and the positive-sequence self-admittance from AC, respectively.

[0021] Frequency coupling originates from the closed-loop feedback interaction between distributed renewable energy systems and the AC grid. For grid-connected units, while the basic feedback mechanism is similar to the aforementioned AC-DC coupling process, the interaction path differs fundamentally: frequency coupling primarily involves the external AC grid network, while AC-DC coupling is an internal process between the AC and DC sides of the unit. Therefore, this frequency coupling effect can be quantitatively modeled and incorporated into the system analysis as an equivalent additional impedance term. in, This is the equivalent coupling admittance; and These represent negative-order coupling admittance and negative-order self-admittance, respectively. This is the equivalent negative sequence grid admittance; This is the transfer admittance at the coupling frequency.

[0022] S2: Based on S1, perform source-side and grid-side impedance matching calculations, calculate the stability margin at the intersection point of the two, and obtain the small-signal stability margin of the wind and solar new energy grid-connected system under different average voltages. Specifically, in step S2, source-side and grid-side impedance matching calculations are performed, and the stability margin at their intersection point is calculated. The small-signal stability margin under different system average voltages can be calculated as follows: in, and The impedance and equivalent impedance of each distributed renewable energy unit; R g and L g The equivalent resistance and inductance on the grid side are... For complex variables, For is the imaginary unit, This is the phasor of the steady-state voltage. and These are DC voltage and AC inductance, respectively. and These represent the current loop and the voltage loop, respectively. , and These are the feedback coefficients, phase-locked loop function, and voltage feedforward equation, respectively. The specific value range is 1-100). and It is a steady-state complex quantity. For small signal phase margin, For the actual stable phase, This is the standard stable phase.

[0023] S3: Based on S2, and taking into account the contradictory mechanism between small-signal stability and voltage active support capability, a consistency index that can measure voltage state is added, thereby realizing leaderless interaction of global information. Specifically, in step S3, based on the contradictory mechanism between small-signal stability and active voltage support capability, a consistency index that can measure the voltage state is added and can be calculated as follows: in, The consistency coefficient, The specific value is 0-1; , and These are the steady-state voltage, the actual voltage, and the maximum voltage, respectively.

[0024] S4: Based on S3, and taking into account the characteristics of distributed new energy, a distributed control scheme is adopted. A distributed collaborative control algorithm is constructed based on the consistency factor of the entire system voltage to keep the bus voltage of each unit within a feasible range, thereby achieving voltage collaborative control. Specifically, in step S4, a distributed control scheme is adopted. The distributed cooperative control algorithm constructed based on the consistency factor of the entire system voltage can be calculated as follows: in, This is the voltage value after active voltage control. This is the voltage reference value for the distributed renewable energy unit. Let be the voltage reference value for the i-th distributed renewable energy unit. and For distributed control PI parameters ( and The specific values ​​are 0-10 and 0-100 respectively. For complex variables, For virtual part units, The consistency coefficient of the i-th distributed wind and solar unit ( The specific value is 0-1). For the j-th distributed wind and solar unit, The specific value is 0-1.

[0025] S5: Based on S2 and S4, and considering the conflicting constraints between small-signal stability and active voltage support capability, the damping margin is compensated into the voltage support control based on the small-signal damping margin of the theoretical model of each unit under different operating conditions, thereby achieving a localized dynamic balance between small-signal stability and voltage support.

[0026] Specifically, in step S5, based on the small-signal damping margin of each unit's theoretical model under different operating conditions, the damping margin is compensated to the voltage support control calculation as follows: in, To correct the steady-state value of the voltage after applying active voltage support control; For phase transfer coefficient, The specific value is 0-10. For complex variables, For virtual part units, The consistency coefficient of the i-th distributed wind and solar unit ( (Specific value is 0-1) For the j-th distributed wind and solar unit ( The specific value is 0-1). For the actual stable phase, For standard stable phase, and For distributed control PI parameters ( and The specific values ​​are 0-10 and 0-100, respectively.

[0027] The above-mentioned method enables a balanced and coordinated control system for improving the small-signal stability and voltage support capability of distributed wind and solar renewable energy grid connection, including: The transmission module is used to calculate the parameters based on the parameters from the voltage operation status detection stage during the additional active voltage support control stage, and input the parameters into the controllers of each distributed control system to realize the parameter adjustment of the controllers. The PMU module is used to collect signals such as AC current and AC voltage of distributed renewable energy grid connection, so as to calculate stability constraint relationship and voltage operating point, and detect the real-time changes of grid connection frequency and voltage. The detection module is used to compare the grid-connected voltage and current data collected by the PMU module with the real-time change range of the detection voltage calculated by the calculation module, so as to detect whether a start signal is output. The calculation module is used to calculate the control margin of the active power and reactive power of the converter based on the distributed new energy grid-connected AC current, AC voltage and other signals obtained by the PMU module. The control module is used to apply feedback voltage supplementary control to the stability margin of the distributed new energy source, thereby taking into account the small-signal stability supplementary control in the control process.

[0028] The division of modules in the above-described balanced and coordinated control method for improving the small-signal stability and voltage support capability of distributed wind and solar energy grid connection is only for illustrative purposes. In other embodiments, the balanced and coordinated control method for improving the small-signal stability and voltage support capability of distributed wind and solar energy grid connection can be divided into different modules as needed to complete all or part of the functions of the above-described balanced and coordinated control method for improving the small-signal stability and voltage support capability of distributed wind and solar energy grid connection.

[0029] To verify the practicality of this invention, simulation experiments were conducted under different frequency voltage drops in this embodiment. The simulation results are as follows: Figure 3 , Figure 4 The above, wherein, Figure 3 A comparison of the voltage support and small-signal stability of different control methods in a distributed voltage regulation system; Figure 4 A comparison of different control methods in distributed power grids in terms of voltage support and small-signal stability; from Figures 3-4 It is evident that by employing the balanced and coordinated control method proposed in this invention to improve the small-signal stability and voltage support capability of distributed wind and solar renewable energy grid connection, the voltage is supported as consistently as possible while ensuring small-signal stability. This avoids the problem of exceeding limits and local oscillations caused by local voltage rises, further enhancing the overall voltage coordination capability and small-signal stability of the distributed renewable energy grid-connected system. It also prevents distributed renewable energy units from entering the low-voltage ride-through process due to voltage drops, further improving the system's voltage support capability.

[0030] 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.

[0031] 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 this application. 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.

[0032] The aforementioned computer program instructions may also be stored in a computer-readable storage medium capable of directing a computer or other programmable data processing device to operate 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.

[0033] 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.

[0034] 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 balanced and coordinated control method for improving the small-signal stability and voltage support capability of distributed wind and solar renewable energy grid connection, characterized in that... Includes the following steps: S1: Frequency domain modeling is performed on the distributed wind and solar power generation system using the sequential impedance modeling method. Based on the harmonic linearization method, the control equations and port equations of the AC subsystem and DC subsystem are derived. The frequency domain model is constructed after considering the frequency and AC-DC coupling of the system. S2: Based on S1, perform source-side and grid-side impedance matching calculations, calculate the stability margin at the intersection point of the two, and obtain the small-signal stability margin of the distributed wind power photovoltaic grid-connected system under different average voltages. S3: Based on S2, and taking into account the contradictory mechanism between small-signal stability and voltage active support capability, a consistency index that can measure voltage state is added, thereby realizing leaderless interaction of global information. S4: Based on S3, and taking into account the characteristics of distributed new energy, a distributed control scheme is adopted. A distributed collaborative control algorithm is constructed based on the consistency factor of the entire system voltage to keep the bus voltage of each unit within a feasible range, thereby achieving voltage collaborative control. S5: Based on S2 and S4, and considering the conflicting constraints between small-signal stability and active voltage support capability, the damping margin is compensated into the voltage support control based on the small-signal damping margin of the theoretical model of each unit under different operating conditions, thereby achieving a localized dynamic balance between small-signal stability and voltage support.

2. The balanced and coordinated control method for improving the small-signal stability and voltage support capability of distributed wind and solar new energy grid connection according to claim 1, characterized in that... In step S1, the frequency domain modeling of the distributed wind and solar power generation system using the sequential impedance modeling method can be calculated as follows: The steady-state operating point of the modulation signal is denoted as . ; , and These represent the disturbance vectors of alternating current, alternating voltage, and direct current voltage, respectively. , and This is the system small-signal matrix corresponding to the disturbance current, voltage, and DC voltage; the scalar value of the DC voltage is represented by... express; The admittance diagonal matrix of the distributed photovoltaic grid-connected port; For the communication side; DC side; This is the steady-state matrix of the modulated signal; This is the per-unit factor for the disturbance voltage; To represent the amplitude of the disturbance voltage signal; The complex phase angle of the disturbance voltage; the corrected admittance matrix is ​​expressed as... , and , Add or subtract the correction frequency at the fundamental frequency to the disturbance frequency. For the perturbation frequency, The imaginary unit, The fundamental frequency, Add or subtract a correction frequency of twice the fundamental frequency to the disturbance frequency. It is twice the fundamental frequency; similarly, the complex frequency domain relation is defined as and , The perturbation frequency is a complex variable added to or subtracted from the fundamental frequency. For complex variables, For the perturbation frequency plus or minus twice the fundamental frequency, it is a complex variable; , These represent the amplitude and phase of the disturbance voltage signal, respectively; there is a coupling relationship between the AC and DC sides of a distributed wind and solar power generation system; therefore, it is necessary to accurately define the relationship between the AC and DC voltages. in, and These correspond to the DC bus voltage and the AC side voltage, respectively. Describe the effect of the positive-sequence AC component on the DC side; the inherent capacitance and impedance of the DC circuit are denoted as... ; It has DC self-admittance; Alternating current; and These are the positive-sequence admittance from DC to AC and the positive-sequence self-admittance from AC, respectively. Frequency coupling originates from the closed-loop feedback interaction between distributed renewable energy systems and the AC grid. For grid-connected units, although their basic feedback mechanism is similar to the aforementioned AC-DC coupling process, the interaction path is fundamentally different: frequency coupling mainly involves the external AC grid network, while AC-DC coupling is an internal process between the AC and DC sides of the unit. Therefore, this frequency coupling effect can be handled through quantitative modeling and incorporated into the system analysis as an equivalent additional impedance term. in, This is the equivalent coupling admittance; and These represent negative-order coupling admittance and negative-order self-admittance, respectively. This is the equivalent negative sequence grid admittance; This is the transfer admittance at the coupling frequency.

3. The balanced and coordinated control method for improving the small-signal stability and voltage support capability of distributed wind and solar new energy grid connection according to claim 1, characterized in that... In step S2, the source-side and grid-side impedance matching calculations are performed, and the stability margin at their intersection point is calculated. The small-signal stability margin under different system average voltages can be calculated as follows: in, and The impedance and equivalent impedance of each distributed renewable energy unit; R g and L g The equivalent resistance and inductance on the grid side are... For complex variables, For is the imaginary unit, The phasor of the steady-state voltage; and These are DC voltage and AC inductance, respectively. and These represent the current loop and the voltage loop, respectively. , and These are the feedback coefficients, phase-locked loop function, and voltage feedforward equation, respectively. The specific value range is 1-100; and For steady-state complex quantities; For small signal phase margin, For the actual stable phase, This is the standard stable phase.

4. The balanced and coordinated control method for improving the small-signal stability and voltage support capability of distributed wind and solar new energy grid connection according to claim 1, characterized in that... In step S3, based on the contradictory mechanism between small-signal stability and active voltage support capability, a consistency index that can measure the voltage state is added and can be calculated as follows: in, The consistency coefficient, The specific value range is 0-1; , and These are the steady-state voltage, the actual voltage, and the maximum voltage, respectively.

5. The balanced and coordinated control method for improving the small-signal stability and voltage support capability of distributed wind and solar new energy grid connection according to claim 1, characterized in that... In step S4, a distributed control scheme is adopted. Based on the consistency factor of the entire system voltage, a distributed cooperative control algorithm is constructed, which can be calculated as follows: in, This is the voltage value after active voltage control. This is the voltage reference value for the distributed renewable energy unit. Let be the voltage reference value for the i-th distributed renewable energy unit. and For PI parameters in distributed control, and The specific values ​​are 0-10 and 0-100 respectively; For complex variables, For virtual part units, Let be the consistency coefficient of the i-th distributed wind-solar unit. The specific value is 0-1; For the j-th distributed wind and solar unit, The specific value is 0-1.

6. The balanced and coordinated control method for improving the small-signal stability and voltage support capability of distributed wind and solar new energy grid connection according to claim 1, characterized in that... In step S5, based on the small-signal damping margin of each unit's theoretical model under different operating conditions, the damping margin is compensated to the voltage support control calculation as follows: in, To correct the steady-state value of the voltage after applying active voltage support control; For phase transfer coefficient, The specific value range is 0-10. For complex variables, For virtual part units, Let be the consistency coefficient of the i-th distributed wind-solar unit. The specific value is 0-1; For the j-th distributed wind and solar unit, The specific value is 0-1. For the actual stable phase, For standard stable phase, and For PI parameters in distributed control, and The specific values ​​are 0-10 and 0-100, respectively.

7. A balanced and coordinated control system for improving the small-signal stability and voltage support capability of distributed wind and solar renewable energy grid connection, as described above, is characterized in that... include: The transmission module is used to calculate the parameters based on the parameters from the voltage operation status detection stage during the additional active voltage support control stage, and input the parameters into the controllers of each distributed control system to realize the parameter adjustment of the controllers. The PMU module is used to collect signals such as AC current and AC voltage of distributed renewable energy grid connection, so as to calculate stability constraint relationship and voltage operating point, and detect the real-time changes of grid connection frequency and voltage. The detection module is used to compare the grid-connected voltage and current data collected by the PMU module with the real-time change range of the detection voltage calculated by the calculation module, so as to detect whether a start signal is output. The calculation module is used to calculate the control margin of the active power and reactive power of the converter based on the distributed new energy grid-connected AC current, AC voltage and other signals obtained by the PMU module. The control module is used to apply feedback voltage supplementary control to the stability margin of the distributed new energy source, thereby taking into account the small-signal stability supplementary control in the control process.

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