A sequence-dependent plug-in island direct-current micro-grid distributed control method and system

Abstract

The application relates to a sequence-dependent plug-in island direct-current micro-grid distributed control method and system, first, local electrical parameters and interconnection line parameters of each DGU are acquired, an island direct-current micro-grid state space model is established, and a distributed controller model is constructed based on local state variables of the DGU; second, aiming at the access or cut-off request of the target DGU, the cut-off request is equivalently converted into the access request in the sequence-dependent plug-in scene, a to-be-judged insertion sequence or a candidate insertion sub-sequence is generated; finally, a linear matrix inequality constraint is constructed according to a Lyapunov asymptotic stability condition, controller parameters meeting the stability requirement are solved, and pre-stability judgment and parameter optimization of the plug-in operation are realized. The application can effectively guarantee the asymptotic stability of the island direct-current micro-grid in the dynamic plug-in scene, and improve the plug-and-play capability of the system.

Description

Technical Field

[0001] This invention relates to the field of microgrid operation and control technology, and in particular to a distributed control method and system for islanded DC microgrids oriented towards sequence-dependent plug-in / plug-out. Background Technology

[0002] With the rapid development of new energy power generation technology and power electronic interface technology, the penetration rate of distributed energy sources, represented by photovoltaic, wind power, and energy storage systems, in power distribution systems is continuously increasing. Microgrids, as an autonomous power supply system capable of coordinating the operation of distributed energy sources, energy storage devices, loads, and control and protection devices, have significant application value in improving renewable energy absorption capacity, enhancing power supply reliability, and increasing power supply flexibility. Islanded DC microgrids have advantages such as simple structure, high conversion efficiency, and ease of distributed power source integration, making them a current research hotspot in academia and industry. In particular, islanded DC microgrids, because they do not rely on the upstream AC grid and can operate independently in remote areas, islands, electric transportation scenarios, and critical load power supply situations, their safe and stable operation highly depends on a high-performance control system.

[0003] Currently, the control methods for DC microgrids mainly include centralized control, decentralized control, and distributed control. Centralized control typically relies on a central control unit to collect global information and uniformly calculate control commands. While it can achieve good global coordination, it suffers from problems such as strong communication dependence, high risk of single-point failures, and poor system scalability. Decentralized control, on the other hand, relies solely on local measurement information from each generator unit for control, eliminating the need for a central controller. It is characterized by its simple structure and ease of implementation. However, typical droop control methods often struggle to balance voltage regulation accuracy and dynamic response performance under load disturbances, parameter uncertainties, and dynamic plugging and unplugging of subsystems, easily leading to problems such as steady-state deviation, power distribution errors, and slow voltage recovery.

[0004] In recent years, distributed control has gradually become an important research direction in DC microgrid control due to its ability to balance local autonomy and network coordination. This type of approach typically designs local controllers for each Distributed Generation Unit (DGU), allowing each controller to primarily rely on local state information and, when necessary, incorporate limited neighbor information. This enhances the flexibility and scalability of the control architecture while ensuring system stability. Especially in DC microgrid applications where frequent DGU connection and disconnection occur, distributed control is considered a crucial technology for achieving "plug-and-play" operation. Related research shows that while many existing scalable control methods support subsystem connection and disconnection, frequent connection and disconnection often require redesigning controllers for adjacent subsystems or adjusting the network structure, significantly increasing computational complexity and engineering implementation complexity.

[0005] However, in actual operation, plug-and-play control of islanded DC microgrids still faces a key problem: system stability is not only related to the DGUs to be plugged in or removed, but also to the connection and disconnection order of existing DGUs and the parameters of interconnecting lines. For the same set of DGUs and the same network topology, different insertion and removal orders may correspond to different stability results; a generator unit may be allowed to connect under one insertion order, while under another, it may lead to system instability or failure to meet controller design conditions. In islanded DC microgrids, for the same DGU composition and topology constraints, different insertion and removal orders and connecting wire parameters may lead to different system stability results, thus making the connection or disconnection request of the target DGU not always allowed. The above phenomenon constitutes the sequence-dependent insertion and removal problem. In existing plug-and-play control strategies, the controller parameters of generator units are generally designed during initialization. However, when other generator units are dynamically connected or existing units are disconnected, the stability of the entire microgrid is related to the insertion and removal order, so these operation requests cannot always be allowed.

[0006] In existing methods, "access determination" and "removal determination" are typically handled separately. For generator unit access, it's necessary to determine whether the new unit and its coupling with the existing network will disrupt system stability; for generator unit removal, it's necessary to re-analyze whether the remaining network remains stable under the new topology. Because the system models, topology change methods, and judgment processes for these two types of operations differ, two or more sets of judgment logic need to be established in practical engineering. This not only increases the difficulty of software implementation but also hinders the formation of a unified automated judgment mechanism. Especially when the microgrid scale increases and the topology changes frequently, handling different insertion and removal scenarios one by one will significantly increase the burden of online computing and control decisions.

[0007] A search revealed Chinese invention patent application publication number CN116131339A, which discloses a robust two-stage control method for an islanded microgrid based on a communication network and a randomly switching topology. This method includes the following sequential steps: (1) Constructing an asynchronous distributed two-level controller for an islanded microgrid system based on the hierarchical control principle; (2) Introduce an event-triggered mechanism for network communication, consider the impact of false data injection attacks in information transmission, and build a networked asynchronous distributed secondary controller for the islanded microgrid system; (3) Based on a networked asynchronous distributed two-level controller, define frequency error and power level error, design sliding mode control, and establish a global frequency error system and a global power level error system; (4) Use the Lyapunov stability method to derive the stability conditions of the global frequency error system and the global power level error system; (5) Testing and verification of the networked distributed secondary controller. The existing patent application does not address the stability issue of microgrids in sequence-dependent plug-in / plug-out scenarios.

[0008] Therefore, how to propose a method for islanded DC microgrids with order dependencies that can uniformly handle DGU access and disconnection requests, automatically decompose and transform the insertion and removal sequence, quickly determine whether the operation is allowed, and further solve the controller parameters when the operation is feasible has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a distributed control and plug-in / plug-out determination method for islanded DC microgrids oriented towards sequence-dependent plug-in / plug-out. The sequence-dependent plug-in / plug-out described in this invention refers to a plug-in / plug-out scenario in which the stability results of the interconnected system may differ due to the different access or removal order of the target DGU and the different changes in the connecting wire parameters under the same system composition and topology constraints.

[0010] The objective of this invention can be achieved through the following technical solutions: According to one aspect of the present invention, a distributed control method for a sequence-dependent plug-in / plug-out islanded DC microgrid is provided, comprising: Obtain the local electrical parameters and interconnection line parameters of each DGU in the isolated DC microgrid, and establish the state-space model of the microgrid under the current topology; construct the distributed controller model based on the local state variables of each DGU. For access requests or removal requests of the target DGU, in the order-dependent plug-in / plug-out scenario, the removal request is transformed into an equivalent access request relative to the topology without the target DGU, and the plug-in / plug-out path is decomposed into a sequence to be determined or a candidate insertion subsequence. Based on the plug-and-play stability condition for maintaining asymptotic stability in the Lyapunov sense, and based on the microgrid state-space model and distributed controller model, the insertion sequence or candidate insertion subsequence to be determined is transformed into linear matrix inequality constraints. Solve the linear matrix inequality. If a feasible solution exists, allow the access or removal operation corresponding to the target DGU and output the controller parameters that meet the stability requirements; otherwise, the operation is not allowed.

[0011] As a preferred technical solution, the process of transforming the cut-off request into an equivalent access request relative to the topology lacking the target DGU is as follows: taking the microgrid topology after the target DGU is cut off as the new reference topology, the target DGU is mapped from its pre-cut-off state to a state to be accessed relative to the new reference topology, thereby transforming the original cut-off determination problem into a state to be accessed determination problem.

[0012] As a preferred technical solution, the sequence decomposition of the plug-in / plug-out path corresponding to the equivalent access request includes: analyzing the plug-in / plug-out path related to the target DGU based on the current microgrid topology and historical plug-in / plug-out sequences; for the equivalent access request, the plug-in / plug-out path is decomposed into at least one candidate insertion sub-sequence, and the feasibility of each candidate insertion sub-sequence is judged in order, wherein each sub-sequence corresponds to one or more consecutive plug-in / plug-out operations.

[0013] As a preferred technical solution, the plug-and-play stability condition for determining feasibility is as follows: for an interconnected system under given topological constraints and a given plug-and-play operation sequence, if the controller of the target DGU can stabilize its local subsystem, and after the target DGU is connected or equivalently connected, the updated interconnected system can maintain asymptotic stability under Lyapunov, then the target DGU is determined to satisfy the plug-and-play stability condition.

[0014] As a preferred technical solution, the local state variables of each DGU include the output voltage and filter inductor current at the common coupling point of the i-th DGU.

[0015] As a preferred technical solution, the distributed controller model is as follows: , Among them, V ti V represents the control output voltage of the i-th DGU converter; i I represents the output voltage at the i-th DGU common coupling point; ti V represents the filter inductor current of the i-th DGU; ref,i V represents the reference voltage of the i-th DGU; ref,i -V i K represents the output voltage deviation of the i-th DGU; i,1 K i,2 and K i,3 These represent the output voltage feedback coefficient, filter inductor current feedback coefficient, and voltage deviation integral term coefficient of the i-th DGU, respectively, which are the controller parameters to be solved.

[0016] As a preferred technical solution, the state-space model of the islanded DC microgrid includes: The dynamic equations for voltage and inductor current for the i-th DGU; Dynamic equations for line currents in interconnected lines between DGUs; And a global state-space expression for coupling the states of each DGU based on line current.

[0017] According to another aspect of the present invention, a sequence-dependent plug-in / plug-out islanded DC microgrid distributed control system is provided, the system comprising: The model management module is used to obtain the local electrical parameters and interconnection line parameters of each DGU in the isolated DC microgrid, establish the microgrid state space model under the current topology, and construct the distributed controller model based on the local state variables of each DGU. The sequence processing module is used to transform the cut-off request into an equivalent access request relative to the topology without the target DGU in the order-dependent insertion and removal scenario, and to perform sequence decomposition on the insertion and removal path to generate the insertion sequence to be determined or the candidate insertion subsequence. The stability determination module is based on the plug-and-play stability condition for maintaining asymptotic stability in the Lyapunov sense. Based on the microgrid state-space model and distributed controller model, it transforms the insertion sequence or candidate insertion subsequence to be determined into linear matrix inequality constraints. The system also includes a controller parameter solving module, which solves linear matrix inequalities. If a feasible solution exists, the system allows the access or removal operation of the target DGU and outputs controller parameters that meet stability requirements; otherwise, the operation is not allowed.

[0018] As a preferred technical solution, in the sequence processing module, converting the cut-off request into an equivalent access request relative to the topology lacking the target DGU specifically involves: taking the microgrid topology after cutting off the target DGU as the new reference topology, mapping the target DGU from its pre-cut-off state to a state to be accessed relative to the new reference topology, thereby transforming the original cut-off determination problem into a state to be accessed determination problem.

[0019] As a preferred technical solution, in the stability determination module, the plug-and-play stability condition for feasibility determination is as follows: for an interconnected system under given topological constraints and a given plug-and-play operation sequence, if the controller of the target DGU can stabilize its local subsystem, and after the target DGU is connected or equivalently connected, the updated interconnected system can maintain asymptotic stability in the Lyapunov sense, then the target DGU is determined to satisfy the plug-and-play stability condition.

[0020] Compared with the prior art, the present invention has the following beneficial effects: 1) This invention addresses the sequence-dependent insertion / removal scenario by converting the cut-off request into an access request and generating an insertion sequence or candidate subsequence to be determined. Then, based on the Lyapunov asymptotic stability condition, the insertion / removal sequence is converted into a linear matrix inequality constraint and solved. This enables pre-operational stability prediction and online optimization of controller parameters, solving the problem of unpredictable stability of microgrids under dynamic topology and ensuring that the system remains asymptotically stable throughout the insertion / removal process. It forms a unified automated insertion / removal determination mechanism, significantly improving the plug-and-play capability and operational reliability of islanded DC microgrids.

[0021] 2) This invention transforms the original cut-off determination problem into an access determination problem, unifies the stability determination logic in the plug-in / plug-out scenario, and simplifies the stability analysis process under dynamic topology; it decomposes the complete DGU plug-in / plug-out sequence into at least one candidate insertion subsequence or insertion sequence to be determined, and performs feasibility judgment on each subsequence step by step, realizing refined stability verification of plug-in / plug-out operation, and further improving the reliability and controllability of the plug-in / plug-out process.

[0022] 3) This invention defines the specific connotation of the plug-and-play stability condition, clarifying that the target DGU must first stabilize its local subsystem, and after access, it must ensure that the updated interconnection system is asymptotically stable in the Lyapunov sense. This provides a clear and rigorous theoretical basis for determining the feasibility of plug-and-play operations and ensures the global stability of the system under dynamic topology changes. Attached Figure Description

[0023] Figure 1 This is a flowchart illustrating the distributed control method for islanded DC microgrids in this invention. Figure 2 This is a schematic diagram of the structure of the DGU in the islanded DC microgrid of this invention; Figure 3 This is a schematic diagram of the islanded DC microgrid topology consisting of four distributed generation units in this invention; Figure 4 This is a schematic diagram of the sequence initialization result of the input target DGU insertion / removal sequence in this invention; Figure 5 This is a schematic diagram of the logical decomposition result of the complete DGU plug-in sequence in this invention; Figure 6 This is a schematic diagram of the controller parameters obtained by solving each DGU in this invention; Figure 7 This is a schematic diagram of the insertion sequence or insertion subsequence to be determined after topological update in this invention; Figure 8 This is a schematic diagram of the sub-sequences and processing procedures monitored in real time by the system in this invention; Figure 9 This is a schematic diagram of the distributed control system for an islanded DC microgrid in this invention. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0025] This embodiment relates to a distributed control method for an islanded DC microgrid oriented towards sequence-dependent plug-in / plug-out, including the following steps: Step 1: Obtain the local electrical parameters and interconnection line parameters (line parameters of the connecting wires between DGUs) of each distributed generation unit in the isolated DC microgrid, and establish the state space model of the microgrid under the current topology; construct the corresponding distributed controller model based on the local state variables of each DGU, and set the reference voltage and controller parameters to be determined for each DGU. Step 2: For the access request or removal request of the target DGU, construct the insertion / removal operation sequence corresponding to the current microgrid topology in the sequence-dependent insertion / removal scenario; when the operation corresponding to the target DGU is a removal request, transform the removal request into an equivalent access request relative to the topology without the target DGU, and perform sequence decomposition on the insertion / removal path corresponding to the equivalent access request to generate candidate insertion subsequences; when the operation corresponding to the target DGU is an access request, directly construct the insertion sequence to be determined corresponding to the access request.

[0026] Sequence-dependent plug-in / plug-out scenarios refer to plug-in / plug-out scenarios in which, under the same system composition and topology constraints, the order in which the target DGU is connected or disconnected, as well as changes in interconnection line parameters, may lead to differences in the stability of the interconnection system.

[0027] Step 3: Based on the stability condition that the updated interconnected system remains asymptotically stable in the Lyapunov sense, determine the feasibility of the insertion sequence or candidate insertion subsequence to be determined. Step 4: For each insertion sequence or candidate insertion subsequence to be judged, construct the corresponding linear matrix inequality constraints using the established microgrid electrical parameters and distributed controller model.

[0028] Based on solving the linear matrix inequality and its corresponding controller parameters, when a feasible solution exists for the linear matrix inequality, the access request or removal request corresponding to the target DGU is allowed to be executed, and the corresponding controller parameters are output; when no feasible solution exists for the linear matrix inequality, the access request or removal request corresponding to the target DGU is not allowed to be executed.

[0029] In step one, the local electrical parameters include the filter resistor, filter inductor, filter capacitor, load parameters, and bus voltage reference value of the DGU, and the interconnection line parameters include the resistance and inductance parameters of the connecting wires between any adjacent DGUs.

[0030] In step two, the process of transforming the cut-off request into an equivalent access request under a topology lacking the target DGU includes: using the microgrid topology after the target DGU is cut off as the new reference topology, mapping the target DGU from its pre-cut-off state to a state to be accessed relative to the new reference topology, thereby transforming the original cut-off decision problem into a state to be accessed decision problem.

[0031] In step two, the insertion and removal paths corresponding to the equivalent access request are decomposed into sequences, including: analyzing the insertion and removal paths related to the target DGU based on the current microgrid topology and historical insertion and removal sequences; generating candidate insertion sub-sequences for the equivalent access request, and performing feasibility judgments on each candidate insertion sub-sequence in order.

[0032] In step three, the plug-and-play stability condition on which the feasibility determination is based is as follows: for an interconnected system constructed under given topological constraints and a given plug-and-play operation sequence, if the target DGU can stabilize its local subsystem under the action of its corresponding controller, and the target DGU can maintain the asymptotic stability of the updated interconnected system in the Lyapunov sense after performing access or equivalent access according to the plug-and-play operation sequence, then the target DGU is determined to satisfy the plug-and-play stability condition under the topological constraints and the plug-and-play operation sequence.

[0033] In step four, the controller parameters are solved based on linear matrix inequalities, including: substituting the local electrical parameters and interconnection line parameters of the target DGU into the preset controller constraints to construct linear matrix inequality constraints; and obtaining the local state feedback gain or controller parameters containing proportional-integral elements by solving the linear matrix inequalities.

[0034] This embodiment also relates to a sequence-dependent plug-and-play distributed control method for islanded DC microgrids, which is used to solve the problems of existing plug-and-play control strategies in dynamic topology changes, such as difficulty in judging control feasibility, separation of plug-out and plug-in logic, and difficulty in quickly solving controller parameters due to the influence of plug-and-play sequence and conductor parameters.

[0035] This invention establishes an islanded DC microgrid model and a distributed controller model, defines sequence-dependent insertion and removal stability conditions, and constructs a insertion and removal sequence logic conversion mechanism to transform the disconnection operation of the power generation unit into an equivalent access operation, thereby unifying the two types of judgment logic for access and disconnection, and thus realizing automated analysis of whether the target DGU can join or leave the current microgrid.

[0036] Sequence-dependent plug-in / plug-out refers to a plug-in / plug-out scenario where, under the same system composition and topology constraints, changes in the order of DGU connection or disconnection, as well as interconnection parameters, can lead to differences in system stability. Addressing the issue in existing plug-and-play control strategies where system stability is affected by the plug-in / plug-out sequence during dynamic DGU connection or disconnection, and where plug-in / plug-out requests are not always permitted, this invention first establishes an islanded DC microgrid model including DGU local parameters and interconnection parameters, and constructs a distributed controller model. In the sequence-dependent plug-in / plug-out scenario, for each target DGU connection or disconnection request, a plug-in / plug-out operation sequence corresponding to the current microgrid topology is constructed, and the disconnection request is transformed into an equivalent connection request relative to a topology lacking the target DGU. The transformed insertion sub-sequence is logically decomposed and subjected to step-by-step feasibility analysis, and the corresponding controller parameters are solved using linear matrix inequalities when determining whether execution is permitted. Finally, the determination result of whether the target DGU is permitted to be connected or disconnected is output.

[0037] like Figure 1 The method includes: S1. Determine the number of distributed generation units (DGUs) in the islanded DC microgrid and the electrical parameters of the microgrid. The structure diagram of the DGU is as follows: Figure 2 As shown. A microgrid state-space model under the current topology is established by quantitatively acquiring the local parameters of each DGU and the line parameters of the connecting wires between DGUs. Local parameters include the internal resistance, inductance, capacitance, load parameters, and bus reference voltage of each DGU, while interconnection line parameters include the resistance and inductance of the connecting wires between adjacent DGUs. The microgrid state-space model is established, and its expression is: (1) (2) (3) , , , , , , Among them, V i I represents the voltage at the i-th DGU common coupling point. ti V represents the filter inductor current of the i-th DGU. ti Ī represents the control output voltage of the i-th DGU converter. Li I represents the load current of the i-th DGU. ij R represents the branch current of the connection line between the i-th DGU and the j-th DGU.Li R represents the load equivalent resistance of the i-th DGU. ti L ti C ti R represents the filter resistor, filter inductor, and filter capacitor of the i-th DGU, respectively. ij and L ij Let N represent the resistance and inductance of the connecting wire between the i-th DGU and the j-th DGU, respectively. i Let represent the set of nodes adjacent to the i-th DGU. x i Let V be the state vector of the i-th DGU. i and I ti Composition; u i To control the input vector, corresponding to V ti ;z i The output vector corresponds to V. i ;d i The perturbation vector corresponds to Ī Li A ii B is the local state matrix. i Let M be the input matrix. i Let A be the perturbation matrix. ij This is the coupling matrix between adjacent DGUs. x j Let be the state vector of the j-th adjacent DGU.

[0038] The distributed controller includes a local information controller and an error PI controller. The local information controller uses the local state variables of each DGU to achieve feedback control, while the error PI controller is used to compensate for the deviation between the output voltage and the reference voltage to improve the steady-state voltage regulation accuracy. This is based on the local state variables (Vi, I) of each DGU. ti V ref,i Construct a distributed controller model, specifically as follows: (4) Among them, V ti V represents the control output voltage of the i-th distributed generation unit converter. i I represents the output voltage at the common coupling point of the i-th distributed generation unit. ti V represents the filter inductor current of the i-th distributed generation unit. ref,i V represents the reference voltage of the i-th distributed generation unit. ref,i -V i K represents the output voltage deviation of the i-th distributed generation unit. i,1 K i,2 and K i,3These represent the first, second, and third controller parameters of the local controller of the i-th distributed generation unit, respectively, and represent the output voltage feedback coefficient, the filter inductor current feedback coefficient, and the voltage deviation integral term coefficient (the integral gain of the error PI controller). These three controller parameters are combined to form the control gain matrix K of the i-th distributed generation unit. i .

[0039] S2, in the order-dependent plug-in / plug-out scenario, constructs the plug-in / plug-out operation sequence corresponding to the current islanded DC microgrid topology. Assume four distributed generation units constitute an islanded DC microgrid, with the following topology: Figure 3 As shown.

[0040] Sequence Initialization: Input the target DGU insertion / removal sequence. The initialization order of the microgrid is: +1+2+3-2+4, where the numbers represent the sequence number of each DGU, "+" indicates an insertion operation, and "-" indicates a removal operation. After initialization, as shown... Figure 4 As shown, the current number of DGUs is 3, and the current DGU sequence is 1->3->4.

[0041] The sequence is logically decomposed and transformed: Based on the initialization order described above, the complete DGU insertion / removal sequence is first logically decomposed into several insertion sequences to be determined or candidate insertion sub-sequences according to the initialization operations. When the operation corresponding to the target DGU is a cut-off request, the cut-off request is transformed into an equivalent access request relative to the topology lacking the target DGU, and the insertion / removal path corresponding to the equivalent access request is processed to generate candidate insertion sub-sequences; when the operation corresponding to the target DGU is an access request, the insertion sequence to be determined corresponding to the access request is directly constructed. For example... Figure 5 As shown, the subsequences of +1+2+3-2+4 are 1->2->3 and 1->3->4, used to verify the stability of the insertion and removal process step by step. To ensure that the entire microgrid remains stable during the initialization insertion and removal operation, the controller parameters of each relevant DGU must have feasible solutions when performing insertion analysis for each generated subsequence; otherwise, the system may become unstable during the initialization operation.

[0042] S3. For each insertion sequence or candidate insertion subsequence to be judged, construct corresponding linear matrix inequality constraints using the established microgrid electrical parameters and distributed controller model. Solve the linear matrix inequalities to obtain feasible solutions for the control parameters of each DGU that satisfy stability verification. If a feasible solution exists for the linear matrix inequality, determine that the access request or disconnection request corresponding to the target DGU is allowed to be executed, and further solve for the controller parameters K of each DGU. iIf the linear matrix inequality has no feasible solution, the plug-in / plug-out operation is deemed not to be allowed. The controller parameters must satisfy the linear matrix inequality: , , , Among them, P i It is an arbitrary 3×3 symmetric positive definite matrix (Lyapunov function matrix); ii The local state matrix of the i-th generation unit after dimension expansion is determined by the electrical parameters of the microgrid state-space model; B̂ i The expanded-dimensional input matrix is ​​determined by the electrical parameters of the microgrid state-space model; K i The control gain matrix for the i-th power generation unit is derived from the distributed controller model.

[0043] like Figure 6 As shown, when the controller parameters obtained by each DGU solution all exist (P) i K i If a feasible solution is found, it means that the corresponding insertion / removal operation is allowed to be executed; if there is no solution under a certain insertion sequence or insertion subsequence to be determined, it means that the operation is not allowed to be executed.

[0044] After initialization, if topology adjustments to the current microgrid are still required, an update operation sequence can be input to analyze the target DGU's access or disconnection requests. After the update operation is completed, the system also generates a corresponding insertion sequence or sub-sequence to be determined. For example... Figure 7 The image shows the generated subsequence corresponding to the update operation. For example... Figure 8 As shown, the microgrid initialization process and the sub-sequences generated by subsequent update operations can all be viewed and processed uniformly on the system monitoring page. The system also records the specific content and corresponding time information of each operation through real-time event logs, thereby realizing the visual management of the entire process of plugging and unplugging operations of the islanded DC microgrid.

[0045] This method unifies the two types of decisions, namely access and removal, into a single insertion logic, reducing the complexity of control decisions in sequence-dependent scenarios. It can realize the automated analysis of DGU insertion and removal requests and the generation of controller parameters, thereby improving the stability, flexibility and scalability of islanded DC microgrids under dynamic topology changes.

[0046] This embodiment also relates to a distributed control system for an islanded DC microgrid oriented towards sequence-dependent plug-in / plug-out, such as Figure 9 The system includes a model management module, a sequence processing module, a stability determination module, and a controller parameter solving module, wherein: The model management module is used to acquire and maintain the local electrical parameters and interconnection line parameters of each DGU, and to establish the microgrid state space model and distributed controller model under the current topology.

[0047] The sequence processing module is used to construct the insertion / removal operation sequence corresponding to the target DGU access request or removal request, and to complete the equivalent access transformation in the case of removal request, generating the insertion sequence to be judged or the candidate insertion subsequence.

[0048] The stability determination module is used to perform a feasibility analysis on the insertion sequence or candidate insertion subsequence to be determined based on the preset plug-and-play stabilization conditions. When the corresponding linear matrix inequality has a feasible solution, the insertion / removal request of the target DGU is allowed to be executed, and the corresponding controller parameters are output; when the corresponding linear matrix inequality does not have a feasible solution, the insertion / removal operation is not allowed to be executed.

[0049] The controller parameter solving module constructs and solves linear matrix inequalities for each insertion sequence or candidate insertion subsequence to be judged, using the established microgrid electrical parameters and distributed controller model, thereby outputting the judgment result of whether the target DGU insertion / removal request is allowed to be executed and the corresponding controller parameters.

[0050] This system is used to read microgrid topology information, acquire local parameters of the DGU (Distributed Generator Unit) and line parameters, and output the determination result of whether the target DGU is allowed to be connected or disconnected, the corresponding controller parameters, and the corresponding insertion sequence or candidate insertion sub-sequence. This system can be connected to an external circuit simulation platform. The electronic device of this invention includes a central processing unit (CPU), which can perform various appropriate actions and processes according to computer program instructions stored in read-only memory (ROM) or loaded from a storage unit into random access memory (RAM). The RAM may also store various programs and data required for device operation. The CPU, ROM, and RAM are interconnected via a bus. Input / output (I / O) interfaces are also connected to the bus.

[0051] Multiple components in the device are connected to the I / O interface, including: input units such as keyboards and mice; output units such as various types of displays and speakers; storage units such as disks and optical discs; and communication units such as network interface cards (NICs), modems, and wireless transceivers. The communication unit allows the device to exchange information / data with other devices through computer networks such as the Internet and / or various telecommunications networks.

[0052] The processing unit performs the various methods and processes described above. For example, in some embodiments, the methods may be implemented as computer software programs tangibly contained in a machine-readable medium, such as a storage unit. In some embodiments, part or all of the computer program may be loaded and / or installed on the device via ROM and / or a communication unit. When the computer program is loaded into RAM and executed by the CPU, one or more steps of the methods described above may be performed. Alternatively, in other embodiments, the CPU may be configured to execute the methods by any other suitable means (e.g., by means of firmware).

[0053] The functions described above in this document can be performed, at least in part, by one or more hardware logic components. For example, exemplary types of hardware logic components that can be used, without limitation, include: Field Programmable Gate Arrays (FPGAs), Application-Specific Integrated Circuits (ASICs), Application Standard Products (ASSPs), System-on-Chip (SoCs), Complex Programmable Logic Devices (CPLDs), and so on.

[0054] The program code used to implement the methods of the present invention can be written in any combination of one or more programming languages. This program code can be provided to a processor or controller of a general-purpose computer, special-purpose computer, or other programmable data processing device, such that when executed by the processor or controller, the program code causes the functions / operations specified in the flowcharts and / or block diagrams to be implemented. The program code can be executed entirely on the machine, partially on the machine, as a standalone software package partially on the machine and partially on a remote machine, or entirely on a remote machine or server.

[0055] In the context of this invention, a machine-readable medium can be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, apparatus, or device. A machine-readable medium can be a machine-readable signal medium or a machine-readable storage medium. Machine-readable media can include, but are not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination of the foregoing. More specific examples of machine-readable storage media include electrical connections based on one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, portable compact disk read-only memory, optical storage devices, magnetic storage devices, or any suitable combination of the foregoing.

[0056] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A distributed control method for an islanded DC microgrid with sequence-dependent plug-in / plug-out, characterized in that, include: Obtain the local electrical parameters and interconnection line parameters of each DGU in the isolated DC microgrid, and establish the state-space model of the microgrid under the current topology; Construct a distributed controller model based on the local state variables of each DGU; For access requests or removal requests of the target DGU, in the order-dependent plug-in / plug-out scenario, the removal request is transformed into an equivalent access request relative to the topology without the target DGU, and the plug-in / plug-out path is decomposed into a sequence to be determined or a candidate insertion subsequence. Based on the plug-and-play stability condition for maintaining asymptotic stability in the Lyapunov sense, and based on the microgrid state-space model and distributed controller model, the insertion sequence or candidate insertion subsequence to be determined is transformed into linear matrix inequality constraints. Solve the linear matrix inequality. If a feasible solution exists, allow the access or removal operation corresponding to the target DGU and output the controller parameters that meet the stability requirements; otherwise, the operation is not allowed.

2. The distributed control method for a sequence-dependent plug-in isolated DC microgrid according to claim 1, characterized in that, Transforming a cut-off request into an equivalent access request relative to a topology lacking the target DGU involves: using the microgrid topology after the target DGU is cut off as the new baseline topology, mapping the target DGU from its pre-cut-off state to a state awaiting access relative to the new baseline topology, thereby transforming the original cut-off determination problem into a awaiting access determination problem.

3. The distributed control method for a sequence-dependent plug-in / plug-out islanded DC microgrid according to claim 1, characterized in that, Sequence decomposition of the plug-in / plug-out path corresponding to the equivalent access request includes: analyzing the plug-in / plug-out path related to the target DGU based on the current microgrid topology and historical plug-in / plug-out sequences; for the equivalent access request, the plug-in / plug-out path is decomposed into at least one candidate insertion subsequence, and feasibility judgment is performed on each candidate insertion subsequence in sequence, wherein each subsequence corresponds to one or more consecutive plug-in / plug-out operations.

4. The distributed control method for a sequence-dependent plug-in / plug-out islanded DC microgrid according to claim 3, characterized in that, The plug-and-play stability condition used to determine feasibility is as follows: for an interconnected system under given topological constraints and a given plug-and-play operation sequence, if the controller of the target DGU can stabilize its local subsystem, and after the target DGU is connected or equivalently connected, the updated interconnected system can maintain asymptotic stability in the Lyapunov sense, then the target DGU is determined to satisfy the plug-and-play stability condition.

5. The distributed control method for a sequence-dependent plug-in isolated DC microgrid according to claim 1, characterized in that, The local state variables of each DGU include the output voltage and filter inductor current at the common coupling point of the i-th DGU.

6. The distributed control method for a sequence-dependent plug-in isolated DC microgrid according to claim 1, characterized in that, The distributed controller model is as follows: ， Among them, V ti V represents the control output voltage of the i-th DGU converter; i I represents the output voltage at the i-th DGU common coupling point; ti V represents the filter inductor current of the i-th DGU; ref,i V represents the reference voltage of the i-th DGU; ref,i -V i K represents the output voltage deviation of the i-th DGU; i,1 K i,2 and K i,3 These represent the output voltage feedback coefficient, filter inductor current feedback coefficient, and voltage deviation integral term coefficient of the i-th DGU, respectively, which are the controller parameters to be solved.

7. The distributed control method for a sequence-dependent plug-in isolated DC microgrid according to claim 1, characterized in that, The state-space model of the isolated DC microgrid includes: The dynamic equations for voltage and inductor current for the i-th DGU; Dynamic equations for line currents in interconnected lines between DGUs; And a global state-space expression for coupling the states of each DGU based on line current.

8. A sequence-dependent plug-in distributed control system for an islanded DC microgrid, characterized in that, This system is used to execute the sequence-dependent plug-in distributed control method for islanded DC microgrids as described in any one of claims 1 to 7, and the system includes: The model management module is used to obtain the local electrical parameters and interconnection line parameters of each DGU in the isolated DC microgrid, establish the microgrid state space model under the current topology, and construct the distributed controller model based on the local state variables of each DGU. The sequence processing module is used to transform the cut-off request into an equivalent access request relative to the topology without the target DGU in the order-dependent insertion and removal scenario, and to perform sequence decomposition on the insertion and removal path to generate the insertion sequence to be determined or the candidate insertion subsequence. The stability determination module, based on Lyapunov's asymptotic plug-and-play stability condition, and based on the microgrid state-space model and distributed controller model, transforms the insertion sequence or candidate insertion subsequence to be determined into linear matrix inequality constraints. The system also includes a controller parameter solving module, which solves linear matrix inequalities. If a feasible solution exists, the system allows the access or removal operation of the target DGU and outputs controller parameters that meet stability requirements; otherwise, the operation is not allowed.

9. A sequence-dependent pluggable islanded DC microgrid distributed control system according to claim 8, characterized in that, In the sequence processing module, the process of converting the cut-off request into an equivalent access request relative to the topology lacking the target DGU is as follows: taking the microgrid topology after the target DGU is cut off as the new reference topology, the target DGU is mapped from its pre-cut-off state to a state to be accessed relative to the new reference topology, thereby transforming the original cut-off determination problem into a state to be accessed determination problem.

10. A sequence-dependent plug-in distributed control system for an islanded DC microgrid according to claim 8, characterized in that, In the stability determination module, the plug-and-play stability condition for feasibility determination is as follows: for an interconnected system under given topological constraints and a given plug-and-play operation sequence, if the controller of the target DGU can stabilize its local subsystem, and after the target DGU is connected or equivalently connected, the updated interconnected system can maintain asymptotic stability in the Lyapunov sense, then the target DGU is determined to satisfy the plug-and-play stability condition.

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