Distributed-consensus-based unbalanced voltage compensation method and system for microgrid

Abstract

The application discloses a micro-grid unbalanced voltage compensation method and system based on distributed consistency, and belongs to the technical field of micro-grid control, and comprises the following steps: constructing an island micro-grid model, the island micro-grid model is used for controlling inverters through one-to-one virtual synchronous machines; a distributed negative sequence voltage compensator is constructed; whether the voltage imbalance coefficient at the corresponding moment exceeds the preset threshold is judged, if yes, the distributed negative sequence voltage compensator is triggered to control the inverters one by one for secondary control, otherwise, the distributed negative sequence voltage compensator is not triggered, and only the virtual synchronous machine is used to control the corresponding inverters for primary control to complete the active compensation of the unbalanced voltage of all distributed power supplies. The application realizes the rapid detection of unbalanced disturbance, the collaborative compensation adjustment among multiple nodes, and good output symmetry and system stability are maintained.

Description

Technical Field

[0001] This invention belongs to the field of microgrid control technology, specifically relating to a method and system for unbalanced voltage compensation in microgrids based on distributed consensus. Background Technology

[0002] With the continuous increase in the proportion of new energy sources, building flexible, efficient, and intelligent power systems has become an important direction for future development. As a small autonomous system integrating renewable energy, power conversion equipment, energy storage devices, and loads, microgrids possess characteristics such as self-control, self-healing, and self-sufficiency. They can operate independently or in parallel with the main grid and are an important support for achieving coordinated optimization of multiple energy sources.

[0003] In isolated environments, distributed generation (DG) sources in microgrids are often connected to the power system via inverters. To support voltage, regulate frequency, and maintain stable operation, grid-connected inverters have gradually become the mainstream development direction. Grid-connected inverters provide inertia support and primary frequency regulation capabilities by simulating the rotor motion equations of synchronous generators using a Virtual Synchronous Generator (VSG). Specifically, the VSG control strategy simulates the electrical and mechanical characteristics of synchronous generators, giving the inverter physical properties such as inertial response and damping regulation, providing a superior modeling framework for grid-connected control. The VSG scheme not only facilitates the coordinated operation of the power system and the traditional grid but also improves the dynamic response performance of the power system in the early stages of disturbances, demonstrating broad engineering application prospects.

[0004] However, due to various factors, voltage imbalance often occurs during microgrid operation, mainly including: unbalanced loads, inconsistent inverter control, asymmetrical impedance of distribution lines, grid connection faults, and switching disturbances. This imbalance can lead to excessive negative sequence current, causing a series of problems such as equipment overheating, motor vibration, protection malfunctions, and harmonic distortion, thereby significantly reducing power supply quality and system stability.

[0005] Existing methods for suppressing voltage imbalance mainly include the following categories: (1) Physically correcting the imbalance source through three-phase load optimization or reactive power compensation equipment, but this increases equipment costs and is not economical; (2) Calculating and issuing compensation tasks for each DG through centralized monitoring and centralized controller, but this is highly dependent on the communication system and is easily affected by link interruption or main controller failure; (3) Performing negative sequence voltage detection and rapid injection compensation locally on the inverter based on dq decoupling control or instantaneous power theory, but the local independent compensation method cannot achieve multi-node collaborative optimization control, and is prone to redundant compensation or control conflicts. At the same time, the traditional dq decoupling control or instantaneous power decomposition method is prone to detection delay or filtering error under low-voltage weak grid and dynamic disturbance conditions, thus affecting control accuracy. In view of this, a microgrid unbalanced voltage compensation scheme based on distributed consistency is proposed. Summary of the Invention

[0006] The purpose of this invention is to address the above-mentioned problems by proposing a microgrid unbalanced voltage compensation method and system based on distributed consistency, aiming to achieve rapid detection of unbalanced disturbances, coordinated compensation and adjustment among multiple nodes, and maintain good output symmetry and system stability.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] The microgrid unbalanced voltage compensation method based on distributed consensus proposed in this invention is applied to including An islanded microgrid with distributed power sources, where each distributed power source is connected to an inverter, includes the following steps:

[0009] S1. Construct an islanded microgrid model. The islanded microgrid model is used to control the inverter through a one-to-one corresponding virtual synchronous machine, that is, to construct the rotor motion equation of each virtual synchronous machine and obtain the reference voltage control signal of each virtual synchronous machine at the corresponding time.

[0010] S2. Construct a distributed negative-sequence voltage compensator to perform the following operations:

[0011] S21. Perform positive and negative sequence decomposition on the three-phase voltage of the islanded microgrid at the current moment to obtain the voltage imbalance coefficient at the corresponding moment.

[0012] S22. Treat a distributed power source as a node to construct an undirected graph, and use the distributed consensus algorithm to calculate the negative sequence compensation voltage command of each distributed power source at the corresponding time according to the undirected graph.

[0013] S23. Add the reference voltage control signal of the virtual synchronous machine at the corresponding time and the negative sequence compensation voltage command of the distributed power source at the corresponding time to obtain the final control signal of the corresponding distributed power source at the corresponding time.

[0014] S3. Determine whether the voltage imbalance coefficient at the corresponding moment exceeds the preset threshold. If so, trigger the distributed negative sequence voltage compensator to perform secondary control on each inverter. That is, input the final control signal of each distributed power source at the corresponding moment into the corresponding inverter to complete the active compensation of the unbalanced voltage of all distributed power sources. Otherwise, do not trigger the distributed negative sequence voltage compensator, and only use the virtual synchronous machine to perform one control on the corresponding inverter to complete the active compensation of the unbalanced voltage of all distributed power sources.

[0015] Preferably, the rotor motion equations for each virtual synchronizer are constructed, wherein the first... The rotor motion equations of the virtual synchronous machine are constructed as follows:

[0016]

[0017] In the formula, For the first The virtual inertia of the virtual synchronizer. , For the first Taiwan Virtual Synchronizer The output angular frequency at time t, For the first Taiwan Virtual Synchronizer Output angular frequency at time The partial derivatives, For the first The reference active power of the virtual synchronous machine. For the first Taiwan Virtual Synchronizer Output active power at any time The rated angular frequency of the virtual synchronizer. The rated frequency of the virtual synchronizer. For the first Damping coefficient of the virtual synchronizer.

[0018] Preferably, the reference voltage control signal of each virtual synchronizer at the corresponding time is obtained, wherein the first... Taiwan Virtual Synchronizer Reference voltage control signal at time The formula is as follows:

[0019]

[0020] In the formula, For integrator, Input the scaling factor into the integrator. For reference three-phase voltage, For the first Taiwan Virtual Synchronizer Output three-phase voltage at any time The effective value, This is the voltage error scaling factor. This is the reactive power deviation proportional factor. For the first The reference reactive power of the virtual synchronous machine. For the first Taiwan Virtual Synchronizer Reactive power output at any given time .

[0021] Preferably, the three-phase voltage of the islanded microgrid at the current moment is decomposed into positive and negative sequences to obtain the voltage imbalance coefficient at the corresponding moment, as follows:

[0022] S211. Perform Clarke transformation on the three-phase voltage of the islanded microgrid to obtain the three-phase voltage. Axial components and three-phase voltage Axial components ;

[0023] S212, Employs a dual-channel generalized second-order integrator for three-phase voltage... Axial components and three-phase voltage Axial components Perform positive and negative sequence decomposition, that is, decompose the three-phase voltages Axial components and three-phase voltage Axial components Simultaneously, the voltage is fed into both the positive-sequence channel G1 and the negative-sequence channel G2 to obtain the positive-sequence voltage. Axial components Positive sequence voltage Axial components Negative sequence voltage Axial components and negative sequence voltage Axial components ;

[0024] S213. Obtain the voltage imbalance coefficient at the corresponding time based on the positive and negative sequence decomposition results, using the following formula:

[0025]

[0026] in,

[0027]

[0028] In the formula, This is the positive sequence voltage amplitude. This represents the negative sequence voltage amplitude.

[0029] Preferably, the three-phase voltage of the islanded microgrid is subjected to Clarke transformation, as shown in the following formula:

[0030]

[0031] In the formula, This refers to the three-phase voltage of an isolated microgrid.

[0032] Preferably, the positive sequence channel G1 and the negative sequence channel G2 satisfy the following formula:

[0033]

[0034] In the formula, As the reference frequency, For bandwidth adjustment parameters, For positive sequence voltages The derivative of the axial component, For positive sequence voltages The derivative of the axial component, For negative sequence voltages The derivative of the axial component, For negative sequence voltages The derivative of the axial component.

[0035] Preferably, the three-phase voltage of the islanded microgrid is the output voltage of the sensitive load bus.

[0036] Preferably, the distributed consensus algorithm satisfies the following formula:

[0037]

[0038] And it satisfies the dynamic model of the compensation command, as shown in the following formula:

[0039]

[0040] In the formula, for Time of the first The compensation amount of the distributed power source. for Time of the first The compensation amount of the distributed power source. For the first Taiwan distributed power supply Negative sequence compensation voltage command at time. for Time of the first Compensation amount of distributed power source The derivative of for The negative sequence voltage of the time-sensitive load bus, including the voltage at the moment-sensitive load bus. The negative sequence voltage obtained after decomposing the three-phase voltages of a time-isolated microgrid. Axial components and negative sequence voltages Axial components, To compensate for the gain coefficient and be greater than 0, For the first The set of neighboring nodes of the node where the distributed power source is located. For the first The leader coefficient of a distributed power source is determined, with the first distributed power source chosen as the leader and the other distributed power sources as followers. The leader's leader coefficient is 1, and the followers' leader coefficients are 0. For the preset threshold, for Voltage imbalance coefficient at time 10:00 .

[0041] Preferably, before calculating the negative-sequence compensation voltage command for each distributed power source at the corresponding time using a distributed consensus algorithm based on the undirected graph, a Lyapunov stability analysis is performed on the distributed consensus algorithm. A distributed consensus algorithm satisfying Lyapunov stability is then used to calculate the negative-sequence compensation voltage command for each distributed power source at the corresponding time. The specific details of the Lyapunov stability analysis are as follows:

[0042] S221. Construct Lyapunov functions The formula is as follows:

[0043]

[0044] In the formula, For the corresponding time number The compensation amount of the distributed power source. For the corresponding time number The compensation amount of the distributed power source;

[0045] S222, Let Furthermore, since the topology formed by all nodes is an undirected graph, it satisfies... For Lyapunov functions Taking the derivative and substituting it into the dynamic model of the compensation command, we finally simplify to:

[0046] ;

[0047] In the formula, For Lyapunov functions The derivative of For the first Taiwan's leader coefficient in distributed power generation. For the corresponding time number The compensation amount of the distributed power source. For the first The set of neighboring nodes of the node where the distributed power source is located;

[0048] S223. Obtain the Lyapunov function. derivative This satisfies the Lyapunov stability requirement, meaning that as the voltage imbalance coefficient at the corresponding moment during voltage compensation tends to a preset threshold, the error will be reduced. It equals 0 at this time. And when the compensation amount of distributed power sources is consistent, that is... hour, .

[0049] A microgrid unbalanced voltage compensation system based on distributed consensus, including The system consists of a distributed power source, a primary controller, a secondary controller, and a decision module. Each distributed power source is connected to an inverter.

[0050] The primary controller is used to construct an islanded microgrid model. The islanded microgrid model is used to control the inverter through a one-to-one corresponding virtual synchronous machine, that is, to construct the rotor motion equation of each virtual synchronous machine and obtain the reference voltage control signal of each virtual synchronous machine at the corresponding time.

[0051] A secondary controller is used to construct a distributed negative-sequence voltage compensator to perform the following operations:

[0052] The three-phase voltage of the islanded microgrid at the current moment is decomposed into positive and negative sequences to obtain the voltage imbalance coefficient at the corresponding moment.

[0053] A distributed power source is treated as a node to construct an undirected graph, and a distributed consensus algorithm is used to calculate the negative sequence compensation voltage command of each distributed power source at the corresponding time based on the undirected graph.

[0054] The reference voltage control signal of the virtual synchronous machine at the corresponding time and the negative sequence compensation voltage command of the distributed power source at the corresponding time are added together to form the final control signal of the corresponding distributed power source at the corresponding time.

[0055] The judgment module is used to determine whether the voltage imbalance coefficient at a corresponding moment exceeds a preset threshold. If so, it triggers the distributed negative sequence voltage compensator to perform secondary control on each inverter, that is, the final control signal of each distributed power source at the corresponding moment is input to the corresponding inverter to complete the active compensation of the unbalanced voltage of all distributed power sources. Otherwise, the distributed negative sequence voltage compensator is not triggered, and only the virtual synchronous machine is used to perform one control on the corresponding inverter to complete the active compensation of the unbalanced voltage of all distributed power sources.

[0056] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0057] This invention innovatively introduces distributed consistency negative-sequence compensation control into an islanded microgrid containing a virtual synchronizer. By superimposing this control with the output of the virtual synchronizer, it actively suppresses voltage imbalance. Simultaneously, by tracking a target value (preset threshold), it prevents severe voltage imbalance at the distributed power source terminals caused by over-compensation of sensitive load buses, thus improving adaptability to imbalance disturbances. Specifically:

[0058] The positive and negative sequence voltages are extracted by a dual-channel generalized second-order integrator. The negative sequence compensation voltage command is superimposed with the reference voltage control signal obtained from the primary control of the virtual synchronous machine via a distributed consensus algorithm and output to the inverter of the corresponding distributed power source to actively suppress unbalanced voltages. This improves the robustness and power quality of the system. The dual-channel generalized second-order integrator can quickly and accurately extract positive and negative sequence components, and has the advantages of fast response, high filtering accuracy, and simple implementation structure. The control strategy is designed based on the distributed consensus algorithm, which has good system scalability and node fault tolerance, and allows plug-and-play local nodes. It is especially suitable for complex operating scenarios such as islanded microgrids. Moreover, the consensus control command (the final control signal of the distributed power source) has the characteristics of clear direction, clear physical meaning, and controllable dynamic compensation, which facilitates integration with existing control logic and enhances the maintainability and deployment flexibility of the overall system. The final consistent bounded stability of the system under the condition of perturbation boundedness is proved by constructing a Lyapunov function. Simulation experiments also further verify the dynamic response characteristics and control performance of the invention. In summary, this invention can be widely applied to the secondary coordination control of grid-type microgrids or multi-virtual synchronous machine systems. While maintaining power quality, it has excellent dynamic response capability and control performance, namely, it has distributed cooperative control and unbalanced dynamic suppression capability. Attached Figure Description

[0059] Figure 1 This is a flowchart of the microgrid unbalanced voltage compensation method based on distributed consensus according to the present invention;

[0060] Figure 2 This is a communication topology diagram for unbalanced voltage compensation in an islanded microgrid according to the present invention.

[0061] Figure 3 This is a simulation waveform diagram of unbalanced voltage compensation at SLB in an embodiment of the present invention. Detailed Implementation

[0062] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0063] It should be noted that when a component is referred to as being "connected" to another component, it can be directly connected to the other component or there may be an intervening component. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the application.

[0064] Example 1:

[0065] like Figures 1-3 As shown, a microgrid unbalanced voltage compensation method based on distributed consensus is applied to, including... An islanded microgrid with distributed power sources, where each distributed power source is connected to an inverter, characterized by the following steps:

[0066] S1. Construct an islanded microgrid model. The islanded microgrid model is used to control the inverter through a one-to-one corresponding virtual synchronous machine, that is, to construct the rotor motion equation of each virtual synchronous machine and obtain the reference voltage control signal of each virtual synchronous machine at the corresponding time.

[0067] In one embodiment, the rotor motion equations of each virtual synchronizer are constructed, wherein the first... The rotor motion equations of the virtual synchronous machine are constructed as follows:

[0068]

[0069] In the formula, For the first The virtual inertia of the virtual synchronizer. , For the first Taiwan Virtual Synchronizer The output angular frequency at time t, For the first Taiwan Virtual Synchronizer Output angular frequency at time The partial derivatives, For the first The reference active power of the virtual synchronous machine. For the first Taiwan Virtual Synchronizer Output active power at any time The rated angular frequency of the virtual synchronizer. The rated frequency of the virtual synchronizer. For the first Damping coefficient of the virtual synchronizer.

[0070] In one embodiment, the reference voltage control signal of each virtual synchronizer at the corresponding time is obtained, wherein the first... Taiwan Virtual Synchronizer Reference voltage control signal at time The formula is as follows:

[0071]

[0072] In the formula, For integrator, Input the scaling factor into the integrator. For reference three-phase voltage, For the first Taiwan Virtual Synchronizer Output three-phase voltage at any time The effective value, This is the voltage error scaling factor. This is the reactive power deviation proportional factor. For the first The reference reactive power of the virtual synchronous machine. For the first Taiwan Virtual Synchronizer Reactive power output at any given time .

[0073] The islanded microgrid model is used to establish the mathematical foundation for the control scheme of the entire islanded microgrid. (This embodiment...) , No. Reference reactive power of the virtual synchronous machine Set to 0, referencing three-phase voltage. ,Pick V.

[0074] S2. Construct a distributed negative-sequence voltage compensator to perform the following operations:

[0075] S21. Perform positive and negative sequence decomposition on the three-phase voltage of the islanded microgrid at the current moment to obtain the voltage imbalance coefficient at the corresponding moment.

[0076] In one embodiment, the three-phase voltage of the islanded microgrid at the current moment is decomposed into positive and negative sequences to obtain the voltage imbalance coefficient at the corresponding moment, as follows:

[0077] S211. Perform Clarke transformation on the three-phase voltage of the islanded microgrid to obtain the three-phase voltage. Axial components and three-phase voltage Axial components ;

[0078] S212, Employs a dual-channel generalized second-order integrator for three-phase voltage... Axial components and three-phase voltage Axial components Perform positive and negative sequence decomposition, that is, decompose the three-phase voltages Axial components and three-phase voltage Axial components Simultaneously, the voltage is fed into both the positive-sequence channel G1 and the negative-sequence channel G2 to obtain the positive-sequence voltage. Axial components Positive sequence voltage Axial components Negative sequence voltage Axial components and negative sequence voltage Axial components ;

[0079] S213. Obtain the voltage imbalance coefficient at the corresponding time based on the positive and negative sequence decomposition results, using the following formula:

[0080]

[0081] in,

[0082]

[0083] In the formula, This is the positive sequence voltage amplitude. This represents the negative sequence voltage amplitude.

[0084] In one embodiment, the three-phase voltages of the islanded microgrid are subjected to Clarke transformation, as shown in the following formula:

[0085]

[0086] In the formula, This refers to the three-phase voltage of an isolated microgrid.

[0087] In one embodiment, the positive sequence channel G1 and the negative sequence channel G2 satisfy the following formula:

[0088]

[0089] In the formula, As the reference frequency, For bandwidth adjustment parameters, For positive sequence voltages The derivative of the axial component, For positive sequence voltages The derivative of the axial component, For negative sequence voltages The derivative of the axial component, For negative sequence voltages The derivative of the axial component.

[0090] In one embodiment, the three-phase voltage of the islanded microgrid is the output voltage of the sensitive load bus. While this embodiment uses the output voltage of the sensitive load bus for the islanded microgrid, the specific voltage can be adjusted according to actual needs.

[0091] To achieve high-precision detection and real-time response to imbalance, a dual-channel generalized second-order integrator is used to decompose the output voltage into positive and negative order. Compared with traditional phase-locked loop and windowed Fourier analysis, this method has a faster response speed and stronger steady-state filtering capability.

[0092] S22. Treat a distributed power source as a node and construct an undirected graph. Then, use a distributed consensus algorithm to calculate the negative-order compensation voltage command of each distributed power source at the corresponding time based on the undirected graph.

[0093] In one embodiment, the distributed consensus algorithm satisfies the following formula:

[0094]

[0095] And it satisfies the dynamic model of the compensation command, as shown in the following formula:

[0096]

[0097] In the formula, for Time of the first The compensation amount of the distributed power source. for Time of the first The compensation amount of the distributed power source. For the first Taiwan distributed power supply Negative sequence compensation voltage command at time. for Time of the first Compensation amount of distributed power source The derivative of for The negative sequence voltage of the time-sensitive load bus, including the voltage at the moment-sensitive load bus. The negative sequence voltage obtained after decomposing the three-phase voltages of a time-isolated microgrid. Axial components and negative sequence voltages Axial components, To compensate for the gain coefficient and be greater than 0, For the first The set of neighboring nodes of the node where the distributed power source is located. For the first The leader coefficient of a distributed power source is determined, with the first distributed power source chosen as the leader and the other distributed power sources as followers. The leader's leader coefficient is 1, and the followers' leader coefficients are 0. For the preset threshold, for Voltage imbalance coefficient at time 10:00 .

[0098] In this embodiment, a leader-follower model is used to reduce communication volume for the target value (preset threshold). Tracking only the first distributed power source ( As the leader, one can directly observe the voltage of the sensitive load bus (SLB), that is, only... The remaining distributed power sources act as followers. For ease of understanding, the corresponding virtual synchronous machines, inverters, distributed power sources, and nodes have the same index. In the construction of undirected graphs, the edges of the undirected graph indicate whether the nodes are connected. That is, if the nodes of two distributed power sources belong to the same connected network (i.e., energy can be transferred between them, including directly or indirectly), then they are connected by an undirected edge; otherwise, there is no edge connection. This is a technique well known to those skilled in the art and will not be elaborated here.

[0099] In one embodiment, before calculating the negative-sequence compensation voltage command for each distributed power source at the corresponding time using a distributed consensus algorithm based on the undirected graph, a Lyapunov stability analysis is performed on the distributed consensus algorithm. The distributed consensus algorithm that satisfies Lyapunov stability is then used to calculate the negative-sequence compensation voltage command for each distributed power source at the corresponding time. The Lyapunov stability analysis is as follows:

[0100] S221. Construct Lyapunov functions The formula is as follows:

[0101]

[0102] In the formula, For the corresponding time number The compensation amount of the distributed power source. For the corresponding time number The compensation amount of the distributed power source;

[0103] S222, Let Furthermore, since the topology formed by all nodes is an undirected graph, it satisfies... For Lyapunov functions Taking the derivative and substituting it into the dynamic model of the compensation command, we finally simplify to:

[0104] ;

[0105] In the formula, For Lyapunov functions The derivative of For the first Taiwan's leader coefficient in distributed power generation. For the corresponding time number The compensation amount of the distributed power source. For the first The set of neighboring nodes of the node where the distributed power source is located;

[0106] S223. Obtain the Lyapunov function. derivative This satisfies the Lyapunov stability requirement, meaning that as the voltage imbalance coefficient at the corresponding moment during voltage compensation tends to a preset threshold, the error will be reduced. It equals 0 at this time. And when the compensation amount of distributed power sources is consistent, that is... hour, .

[0107] Specifically, regarding the Lyapunov function The differentiation process is as follows:

[0108] 1) For Lyapunov functions Differentiate:

[0109]

[0110] In the formula, For Lyapunov functions The derivative of For the corresponding time number The derivative of the compensation amount of the distributed power source. For the corresponding time number The derivative of the compensation amount of the distributed power source;

[0111] set up Substituting the dynamic model of the compensation command into the above formula:

[0112]

[0113] Simplified to:

[0114]

[0115] In the formula, For the first Taiwan's leader coefficient in distributed power generation. For the corresponding time number The compensation amount of the distributed power source. For the first The set of neighboring nodes of the node where the distributed power source is located;

[0116] Since the topology formed by all nodes is an undirected graph, it satisfies... Ultimately, it can be simplified to:

[0117] .

[0118] Due to the Lyapunov function obtained after simplification derivative This satisfies the Lyapunov stability requirement, meaning that as the voltage imbalance coefficient at the corresponding moment during voltage compensation tends to a preset threshold, the error will be reduced. It equals 0 at this time. And when the compensation amount of distributed power sources is consistent, that is... hour, .

[0119] Among them, the Lyapunov function constructed by the Lyapunov stability analysis is used to measure the difference in compensation among all neighboring nodes of the corresponding distributed power source node. When the compensation amounts of all distributed power sources are consistent, the Lyapunov function takes its minimum value of 0. When the distributed consensus algorithm is in effect, the error... The trend is equal to 0, at which point It is 0, and Constant is not positive, at this time And only if the compensation amounts of the distributed power sources are consistent, i.e. When the time is 0, it satisfies Lyapunov stability.

[0120] S23. Add the reference voltage control signal of the virtual synchronous machine at the corresponding time and the negative sequence compensation voltage command of the distributed power source at the corresponding time to obtain the final control signal of the corresponding distributed power source at the corresponding time.

[0121] Among them, such as the first Taiwan Virtual Synchronizer Reference voltage control signal at time and the Taiwan distributed power supply Negative sequence compensation voltage command at time Adding them together gives the first The final control signal of the distributed power source :

[0122]

[0123] The first The final control signal of the distributed power source Enter the first The inverter of the distributed power source can realize the first Active suppression of unbalanced voltage in distributed power sources.

[0124] The purpose of constructing a distributed negative sequence voltage compensator is to ensure that the compensation amount of each distributed source (DG) is injected in a consistent manner.

[0125] S3. Determine whether the voltage imbalance coefficient at the corresponding moment exceeds the preset threshold. If so, trigger the distributed negative sequence voltage compensator to perform secondary control on each inverter. That is, input the final control signal of each distributed power source at the corresponding moment into the corresponding inverter to complete the active compensation of the unbalanced voltage of all distributed power sources. Otherwise, do not trigger the distributed negative sequence voltage compensator, and only use the virtual synchronous machine to perform one control on the corresponding inverter to complete the active compensation of the unbalanced voltage of all distributed power sources.

[0126] Specifically, in order to verify the actual control effect of the method, the following method was used: Figure 2 The communication topology for unbalanced voltage compensation in an islanded microgrid is verified and simulated. This embodiment of the islanded microgrid includes three distributed power sources, three primary controllers, and three secondary controllers. , The distributed power source, primary controller and secondary controller are one-to-one. The distributed power source is connected to the sensitive load bus (SLB). Each distributed power source is connected to an inverter. The primary controller performs primary control and the secondary controller performs secondary control. Figure 2 In the diagram, DGN represents the Nth distributed power source (inverter not shown), primary controller N and secondary controller N represent the corresponding distributed power source being controlled, and UCRN represents the Nth distributed power source. The negative sequence compensation voltage command of the distributed power source at the corresponding time is given. The same applies to others, so it will not be repeated. The dashed arrows between the secondary controllers indicate mutual communication, which is used to transmit the compensation amount of each distributed power source.

[0127] This embodiment demonstrates the full islanded operation of a microgrid consisting of three virtual synchronization mechanisms for primary control. At the start of the simulation, only primary control is active. =1s, a three-phase unbalanced load (unbalanced voltage acquisition) is connected at the sensitive load bus (SLB). Secondary control is activated at 2 seconds. At 3.5s, a plug-and-play test was performed, and the fourth distributed power supply was connected. Disconnect the fourth distributed power source after 5 seconds.

[0128] The simulation waveform for unbalanced voltage compensation at SLB is as follows: Figure 3 As shown. You can see that, =1s After a three-phase unbalanced load is connected at the SLB, the voltage imbalance coefficient increases significantly. At 2 seconds, the compensation signal (the final control signal of the distributed power source) is connected, and the voltage imbalance coefficient converges precisely to the preset threshold within one second. ; At 3.5s, a plug-and-play experiment was conducted, connecting the fourth distributed power source. After a brief oscillation, the isolated microgrid quickly recovered to the preset threshold. When the fourth distributed power source is disconnected at t=5s, the isolated microgrid also quickly recovers to the preset threshold within 1 second. .

[0129] In summary, this method achieves accurate compensation for unbalanced voltage at the SLB in an islanded microgrid environment. The leader-follower model used can effectively reduce the communication burden. Finally, plug-and-play testing verifies that the system has good dynamic response capability and control performance, realizes rapid detection of unbalanced disturbances, coordinated compensation and adjustment among multiple nodes, and maintains good output symmetry and system stability.

[0130] Example 2:

[0131] Based on Example 1, this example describes a distributed consensus-based microgrid unbalanced voltage compensation system, including... The system consists of a distributed power source, a primary controller, a secondary controller, and a decision module. Each distributed power source is connected to an inverter.

[0132] The primary controller is used to construct an islanded microgrid model. The islanded microgrid model is used to control the inverter through a one-to-one corresponding virtual synchronous machine, that is, to construct the rotor motion equation of each virtual synchronous machine and obtain the reference voltage control signal of each virtual synchronous machine at the corresponding time.

[0133] A secondary controller is used to construct a distributed negative-sequence voltage compensator to perform the following operations:

[0134] The three-phase voltage of the islanded microgrid at the current moment is decomposed into positive and negative sequences to obtain the voltage imbalance coefficient at the corresponding moment.

[0135] A distributed power source is treated as a node to construct an undirected graph, and a distributed consensus algorithm is used to calculate the negative sequence compensation voltage command of each distributed power source at the corresponding time based on the undirected graph.

[0136] The reference voltage control signal of the virtual synchronous machine at the corresponding time and the negative sequence compensation voltage command of the distributed power source at the corresponding time are added together to form the final control signal of the corresponding distributed power source at the corresponding time.

[0137] The judgment module is used to determine whether the voltage imbalance coefficient at a corresponding moment exceeds a preset threshold. If so, it triggers the distributed negative sequence voltage compensator to perform secondary control on each inverter, that is, the final control signal of each distributed power source at the corresponding moment is input to the corresponding inverter to complete the active compensation of the unbalanced voltage of all distributed power sources. Otherwise, the distributed negative sequence voltage compensator is not triggered, and only the virtual synchronous machine is used to perform one control on the corresponding inverter to complete the active compensation of the unbalanced voltage of all distributed power sources.

[0138] The isolated microgrid comprises several distributed generation (DGs), a primary controller, and a secondary controller. Each DG corresponds to N DGs, and the inverters of each DG are controlled via a virtual synchronous machine (VSM). The primary controller performs primary control, controlling the inverters through the VSM to actively compensate for the unbalanced voltage of all DGs. The secondary controller performs secondary control, adding the reference voltage control signal from the VSM at a given time and the negative-sequence compensation voltage command from the DG at the same time to form the final control signal for the DG at that time. This signal is then input to the corresponding inverter to actively compensate for the unbalanced voltage of all DGs. This system achieves accurate compensation for the unbalanced voltage at the SLB in an isolated microgrid environment, effectively reducing communication overhead, exhibiting good dynamic response and control performance, enabling rapid detection of unbalanced disturbances, coordinated compensation and adjustment among multiple nodes, and maintaining good output symmetry and system stability.

[0139] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0140] The embodiments described above are merely specific and detailed examples of the embodiments described in this application, and should not be construed as limiting the scope of the application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the appended claims.

Claims

1. A microgrid unbalanced voltage compensation method based on distributed consensus, applicable to including... An islanded microgrid of distributed power sources, wherein each of the distributed power sources is connected to an inverter in a one-to-one correspondence, characterized in that: Includes the following steps: S1. Construct an islanded microgrid model. The islanded microgrid model is used to control the inverter through a one-to-one corresponding virtual synchronous machine, that is, to construct the rotor motion equation of each virtual synchronous machine and obtain the reference voltage control signal of each virtual synchronous machine at the corresponding time. S2. Construct a distributed negative-sequence voltage compensator to perform the following operations: S21. Perform positive and negative sequence decomposition on the three-phase voltage of the islanded microgrid at the current moment to obtain the voltage imbalance coefficient at the corresponding moment. S22. Treat a distributed power source as a node to construct an undirected graph, and use the distributed consensus algorithm to calculate the negative sequence compensation voltage command of each distributed power source at the corresponding time according to the undirected graph. S23. Add the reference voltage control signal of the virtual synchronous machine at the corresponding time and the negative sequence compensation voltage command of the distributed power source at the corresponding time to obtain the final control signal of the corresponding distributed power source at the corresponding time. S3. Determine whether the voltage imbalance coefficient at the corresponding moment exceeds the preset threshold. If so, trigger the distributed negative sequence voltage compensator to perform secondary control on each inverter. That is, input the final control signal of each distributed power source at the corresponding moment into the corresponding inverter to complete the active compensation of the unbalanced voltage of all distributed power sources. Otherwise, do not trigger the distributed negative sequence voltage compensator, and only use the virtual synchronous machine to perform one control on the corresponding inverter to complete the active compensation of the unbalanced voltage of all distributed power sources.

2. The microgrid unbalanced voltage compensation method based on distributed consensus as described in claim 1, characterized in that: The rotor motion equations for each virtual synchronizer are constructed, wherein the first... The rotor motion equations of the virtual synchronous machine are constructed as follows: ； In the formula, For the first The virtual inertia of the virtual synchronizer. , For the first Taiwan Virtual Synchronizer The output angular frequency at time t, For the first Taiwan Virtual Synchronizer Output angular frequency at time The partial derivatives, For the first The reference active power of the virtual synchronous machine. For the first Taiwan Virtual Synchronizer Output active power at any time The rated angular frequency of the virtual synchronizer. The rated frequency of the virtual synchronizer. For the first Damping coefficient of the virtual synchronizer.

3. The microgrid unbalanced voltage compensation method based on distributed consensus as described in claim 1, characterized in that: The process involves acquiring the reference voltage control signal for each virtual synchronizer at the corresponding time, wherein the first... Taiwan Virtual Synchronizer Reference voltage control signal at time The formula is as follows: ； In the formula, For integrator, Input the scaling factor into the integrator. For reference three-phase voltage, For the first Taiwan Virtual Synchronizer Output three-phase voltage at any time The effective value, This is the voltage error scaling factor. This is the reactive power deviation proportional factor. For the first The reference reactive power of the virtual synchronous machine. For the first Taiwan Virtual Synchronizer Reactive power output at any given time .

4. The microgrid unbalanced voltage compensation method based on distributed consensus as described in claim 1, characterized in that: The process of performing positive and negative sequence decomposition on the three-phase voltage of the islanded microgrid at the current moment to obtain the voltage imbalance coefficient at the corresponding moment is as follows: S211. Perform Clarke transformation on the three-phase voltage of the islanded microgrid to obtain the three-phase voltage. Axial components and three-phase voltage Axial components ; S212, Employs a dual-channel generalized second-order integrator for three-phase voltage... Axial components and three-phase voltage Axial components Perform positive and negative sequence decomposition, that is, decompose the three-phase voltages Axial components and three-phase voltage Axial components Simultaneously, the voltage is fed into both the positive-sequence channel G1 and the negative-sequence channel G2 to obtain the positive-sequence voltage. Axial components Positive sequence voltage Axial components Negative sequence voltage Axial components and negative sequence voltage Axial components ; S213. Obtain the voltage imbalance coefficient at the corresponding time based on the positive and negative sequence decomposition results, using the following formula: ； in, ； In the formula, This is the positive sequence voltage amplitude. This represents the negative sequence voltage amplitude.

5. The microgrid unbalanced voltage compensation method based on distributed consensus as described in claim 4, characterized in that: The Clarke transformation formula for the three-phase voltage of the islanded microgrid is as follows: ； In the formula, This refers to the three-phase voltage of an isolated microgrid.

6. The microgrid unbalanced voltage compensation method based on distributed consensus as described in claim 4, characterized in that: The positive sequence channel G1 and the negative sequence channel G2 satisfy the following formula: ； In the formula, As the reference frequency, For bandwidth adjustment parameters, For positive sequence voltages The derivative of the axial component, For positive sequence voltages The derivative of the axial component, For negative sequence voltages The derivative of the axial component, For negative sequence voltages The derivative of the axial component.

7. The microgrid unbalanced voltage compensation method based on distributed consensus as described in claim 1, characterized in that: The three-phase voltage of the islanded microgrid is the output voltage of the sensitive load bus.

8. The microgrid unbalanced voltage compensation method based on distributed consensus as described in claim 7, characterized in that: The distributed consensus algorithm satisfies the following formula: ； And it satisfies the dynamic model of the compensation command, as shown in the following formula: ； In the formula, for Time of the first The compensation amount of the distributed power source. for Time of the first The compensation amount of the distributed power source. For the first Taiwan distributed power supply Negative sequence compensation voltage command at time. for Time of the first Compensation amount of distributed power source The derivative of for The negative sequence voltage of the time-sensitive load bus, including the voltage at the moment-sensitive load bus. The negative sequence voltage obtained after decomposing the three-phase voltages of a time-isolated microgrid. Axial components and negative sequence voltages Axial components, To compensate for the gain coefficient and be greater than 0, For the first The set of neighboring nodes of the node where the distributed power source is located. For the first The leader coefficient of a distributed power source is determined, with the first distributed power source chosen as the leader and the other distributed power sources as followers. The leader's leader coefficient is 1, and the followers' leader coefficients are 0. For the preset threshold, for Voltage imbalance coefficient at time 10:00 .

9. The microgrid unbalanced voltage compensation method based on distributed consensus as described in claim 8, characterized in that: Before calculating the negative-sequence compensation voltage command for each distributed power source at the corresponding time using a distributed consensus algorithm based on the undirected graph, a Lyapunov stability analysis is performed on the distributed consensus algorithm. A distributed consensus algorithm satisfying Lyapunov stability is then used to calculate the negative-sequence compensation voltage command for each distributed power source at the corresponding time. The specific details of the Lyapunov stability analysis are as follows: S221. Construct Lyapunov functions The formula is as follows: ； In the formula, For the corresponding time number The compensation amount of the distributed power source. For the corresponding time number The compensation amount of the distributed power source; S222, Let Furthermore, since the topology formed by all nodes is an undirected graph, it satisfies... For Lyapunov functions Taking the derivative and substituting it into the dynamic model of the compensation command, we finally simplify to: ； In the formula, For Lyapunov functions The derivative of For the first Taiwan's leader coefficient in distributed power generation. For the corresponding time number The compensation amount of the distributed power source. For the first The set of neighboring nodes of the node where the distributed power source is located; S223. Obtain the Lyapunov function. derivative This satisfies the Lyapunov stability requirement, meaning that as the voltage imbalance coefficient at the corresponding moment during voltage compensation tends to a preset threshold, the error will be reduced. It equals 0 at this time. And when the compensation amount of distributed power sources is consistent, that is... hour, .

10. A microgrid unbalanced voltage compensation system based on distributed consensus, characterized in that: include The system comprises a distributed power source, a primary controller, a secondary controller, and a judgment module. Each of the distributed power sources is connected to an inverter in a corresponding manner. The primary controller is used to construct an islanded microgrid model. The islanded microgrid model is used to perform primary control on the inverter through one-to-one corresponding virtual synchronous machines, that is, to construct the rotor motion equation of each virtual synchronous machine and obtain the reference voltage control signal of each virtual synchronous machine at the corresponding time. The secondary controller is used to construct a distributed negative-sequence voltage compensator to perform the following operations: The three-phase voltage of the islanded microgrid at the current moment is decomposed into positive and negative sequences to obtain the voltage imbalance coefficient at the corresponding moment. A distributed power source is treated as a node to construct an undirected graph, and a distributed consensus algorithm is used to calculate the negative sequence compensation voltage command of each distributed power source at the corresponding time based on the undirected graph. The reference voltage control signal of the virtual synchronous machine at the corresponding time and the negative sequence compensation voltage command of the distributed power source at the corresponding time are added together to form the final control signal of the corresponding distributed power source at the corresponding time. The judgment module is used to determine whether the voltage imbalance coefficient at the corresponding moment exceeds a preset threshold. If so, the distributed negative sequence voltage compensator is triggered to perform secondary control on each inverter, that is, the final control signal of each distributed power source at the corresponding moment is input to the corresponding inverter to complete the active compensation of the unbalanced voltage of all distributed power sources. Otherwise, the distributed negative sequence voltage compensator is not triggered, and only the virtual synchronous machine is used to perform one control on the corresponding inverter to complete the active compensation of the unbalanced voltage of all distributed power sources.

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