Hybrid ac / dc microgrid based on reconfigurable modular multilevel converter

Abstract

The application relates to a hybrid AC / DC microgrid based on a reconfigurable modular multilevel converter and an operation method and a storage medium thereof. The microgrid comprises a modular multilevel converter (MMC), the MMC comprises a plurality of phase legs, each phase leg comprises an upper arm and a lower arm, each arm is connected with a plurality of sub-modules in series, each sub-module comprises a semiconductor switching device, a capacitor energy storage unit and a controllable bypass switch structure; the MMC is connected with an AC bus and a DC bus respectively to realize bidirectional power conversion. The system comprises a plurality of feeder branches which are connected with the bus through power switching devices. Distributed edge controllers are arranged at the sub-modules or feeder interfaces to collect voltage and current parameters and output isolation or bypass signals in an abnormal condition; meanwhile, hierarchical reconfiguration controllers are arranged to perform structure reconfiguration and power path redistribution. The application realizes fault rapid isolation and reconfiguration cooperation through hierarchical control, maintains the voltage stability of the key load bus, and realizes the effect of improving the system reliability and power supply continuity.

Description

Technical Field

[0001] This application relates to the field of power electronics and microgrid control, and in particular to a hybrid AC / DC microgrid based on a reconfigurable modular multi-stage converter. Background Technology

[0002] Hybrid AC / DC microgrids in existing technologies are increasingly being used in the integration of distributed energy resources (DERs), energy storage systems (ESSs), and critical loads. Modular multilevel converters (MMCs) are widely adopted as AC / DC interface converters due to their modular structure, scalability, and ability to synthesize high-quality voltages.

[0003] In typical embodiments, the system disclosed herein may be implemented in accordance with IEEE standards such as microgrids, distributed energy interconnection, DC microgrids, and power system protection, including but not limited to IEEE 2030.7, IEEE 1547, IEEE 2030.10, and IEEE 519. While these standards provide general interoperability and performance specifications, they do not specify the internal hierarchical reconfiguration mechanism, distributed fault handling, or MMC submodule-level control technologies disclosed herein.

[0004] However, MMC-based hybrid AC / DC microgrids are inherently more complex than traditional AC systems because they involve: AC and DC dynamic domain synchronization bidirectional power flow path Converter with both source and sink functions Frequent topology changes caused by feeder switching and the connection or disconnection of distributed energy / storage systems (DER / ESS).

[0005] The existing technology has the following technical problems: (1) Heterogeneous fault dynamics cannot be processed through centralized control. Different failure events require fundamentally different response times: Fault events Required response time Required control position Submodule short circuit µs–ms Submodule / arm level Arm voltage imbalance millisecond Converter level Feeder fault ms–100 ms microgrid level Outlying islands / reconnection 10s–100s ms microgrid level Centralized controllers cannot meet these heterogeneous timing constraints, leading to fault propagation and loss of critical loads.

[0006] (2) Ignore the physical location of the fault The fault occurred at a specific physical location: MMC internal submodule failure Switchgear feeder fault Load prioritization decision-making at the microgrid level.

[0007] Centralized protection devices cannot directly access the local electrical status and cannot safely perform time-critical operations.

[0008] (3) Low internal redundancy utilization of MMC Each arm of an MMC contains dozens of submodules, thermal storage elements, and complex voltage synthesis mechanisms. Without local control, this redundancy cannot be used safely or effectively.

[0009] (4) Dynamic microgrid topologies are not supported. Microgrids are non-static systems where feeders, DERs, and AC / DC power paths change dynamically. Existing MMC microgrids lack coordinated structure and power flow reconfiguration mechanisms. Summary of the Invention

[0010] In order to improve the above-mentioned technical problems existing in the prior art, this application provides a hybrid AC / DC microcurrent based on a reconfigurable modular multi-stage converter.

[0011] This application provides a hybrid AC / DC microgrid based on a reconfigurable modular multi-stage converter, employing the following technical solution: In a first aspect, a hybrid AC / DC microgrid based on a reconfigurable modular multi-stage converter includes: a modular multi-stage converter (MMC), wherein the MMC includes multiple phase legs, each phase leg includes an upper arm and a lower arm, each arm is connected in series with multiple sub-modules, and each sub-module includes a semiconductor switching device, a capacitor energy storage unit and a controllable bypass switch structure; The system includes at least one AC bus and at least one DC bus, with the MMC electrically connected to both the AC bus and the DC bus respectively, for bidirectional power conversion. It includes multiple feeder branches, which are connected to the AC bus or DC bus via corresponding power switching devices; It includes distributed edge controllers respectively set at sub-modules or feeder interfaces. The distributed edge controllers are connected to voltage and current sensors to collect local electrical parameters and directly output isolation or bypass control signals when an abnormality is detected. Includes a hierarchical reconfiguration controller, which is communicatively connected to the distributed edge controller and is used to perform MMC internal reconfiguration and feeder power path redistribution based on received status information; The microgrid adopts a hierarchical control architecture of submodule / arm level, converter level and microgrid level. Faults are preferentially isolated at the physical level where they occur and structural reconfiguration is completed at the upper control level to maintain the stability of the critical load bus voltage.

[0012] By adopting the above technical solutions, comprehensive technical functions such as rapid fault isolation, adaptive topology reconfiguration, and dynamic power path optimization are achieved. By configuring a controllable bypass switch structure at the sub-module level of the modular multi-stage converter, and combining it with the local fast detection and direct drive mechanism of the distributed edge controller, faults can be isolated locally at the physical level where they occur, achieving millisecond-level or even faster local isolation. This prevents faults from propagating to the bus and other healthy units, thereby significantly reducing the risk of system cascading failure. By setting up a hierarchical reconfiguration controller, after completing the bottom-level isolation, modulation redistribution is performed on the remaining healthy sub-modules, and power path reconfiguration is performed on the feeder branches, achieving continuous adjustment of voltage amplitude and power flow direction. This ensures that the AC and DC bus voltages remain within the allowable deviation range, guaranteeing continuous power supply to critical loads. The hierarchical control architecture decouples and coordinates control functions at the submodule, converter, and microgrid levels, improving control response speed and enhancing system stability and scalability under different disturbance levels. It supports flexible access to distributed energy sources and energy storage units, and can dynamically optimize configuration based on load changes and operating status during operation, improving the renewable energy absorption capacity and system operating efficiency. Through the collaborative mechanism of "local rapid isolation + upper-level coordinated reconfiguration," it achieves the goal of high reliability, high continuity, and high adaptability of the hybrid AC / DC microgrid under complex operating conditions.

[0013] Optionally, the control cycle of the submodule / arm level control layer is less than 1 millisecond, used to perform current modulation, capacitor voltage balancing and submodule fault detection, and to complete submodule bypass after a fault is detected.

[0014] By adopting the above technical solution, the control cycle of the submodule / arm level control layer is set to less than 1 millisecond, which can realize high-speed closed-loop regulation of submodule current and capacitor voltage, improve voltage balancing accuracy and current control response speed; at the same time, it can quickly complete fault detection and submodule bypass isolation when an anomaly occurs, reduce fault propagation time, reduce the impact on bus voltage and system stability, and improve the overall operational reliability and dynamic stability of the microgrid.

[0015] Optionally, the control cycle of the converter-level control layer is 1 millisecond to 10 milliseconds, used to generate AC bus voltage and frequency references, and to reallocate modulation strategies when the number of sub-modules changes.

[0016] By adopting the above technical solution, the control cycle of the converter-level control layer is set to 1 to 10 milliseconds, which can achieve stable generation and regulation of AC bus voltage and frequency while ensuring dynamic response capability. When the number of sub-modules changes, the modulation strategy can be reconstructed and the voltage command can be redistributed in a timely manner to ensure continuous and smooth output waveform, reduce harmonic distortion and voltage fluctuation, and improve the system's operational stability and power supply quality under structural change conditions.

[0017] Optionally, the control cycle of the microgrid-level control layer is 10 milliseconds to 100 milliseconds, used to perform feeder switch control and power rerouting decisions.

[0018] By adopting the above technical solutions, the system coordinates and controls the operation status of each node at the system level, and rationally executes feeder switch actions and power rerouting decisions. While ensuring the stability of the decisions, it avoids oscillations caused by frequent switching, realizes rapid reconfiguration of power supply paths and load balancing after a fault, and improves the overall reliability and economy of the microgrid.

[0019] Optionally, the distributed edge controller includes a finite state machine module for performing immediate bypass, delayed confirmation, and fault reporting operations based on the anomaly level.

[0020] By adopting the above technical solution and setting a finite state machine module in the distributed edge controller, a hierarchical response strategy can be implemented according to the anomaly level. Immediate bypass is performed for serious faults to achieve rapid isolation, and delayed confirmation is performed for suspicious anomalies to avoid false alarms. The fault information is reported to the upper control layer, achieving a balance between speed and selectivity, and improving the accuracy of protection and the reliability of system operation.

[0021] Optionally, the hierarchical reconfiguration controller sorts events based on time identifier information from multiple distributed edge controllers and generates corresponding MMC modulation redistribution instructions or feeder switching instructions.

[0022] By adopting the above technical solution, event sorting and correlation analysis can be performed on the time stamp information uploaded by multiple distributed edge controllers to accurately determine the order and scope of failures, avoiding control conflicts and misjudgments. On this basis, corresponding MMC modulation redistribution instructions or feeder switching instructions are generated to achieve orderly reconfiguration and power rerouting, thereby improving the system's coordinated control capability and operational stability under multi-point abnormal conditions.

[0023] Optionally, after each submodule is bypassed, the remaining submodules maintain the continuous amplitude of the AC bus or DC bus voltage by adjusting the modulation duty cycle.

[0024] By adopting the above technical solution, after a submodule is bypassed, the modulation duty cycle is dynamically adjusted by the remaining normal submodules, which can compensate the output voltage in real time, maintain the continuous and stable amplitude of the AC bus or DC bus voltage, avoid voltage sudden changes or waveform distortion caused by changes in the number of factor modules, thereby ensuring the power supply quality of the load and improving the continuity and stability of the system under local fault conditions.

[0025] Optionally, the system supports the access of distributed energy or energy storage systems through an interface unit, which includes a power conversion stage and a local control module. The local control module performs bus voltage detection and synchronization matching before access.

[0026] By adopting the above technical solutions, the interface unit performs bus voltage detection and synchronization matching before connection, which can ensure that distributed energy or energy storage systems are connected to the grid under the condition of consistent voltage amplitude, frequency and phase, avoiding inrush current and voltage fluctuations; at the same time, it can realize flexible access and smooth switching, improve the renewable energy absorption capacity and system operation safety.

[0027] Secondly, a hybrid AC / DC microgrid operation method based on a reconfigurable modular multi-stage converter includes: Collect electrical parameters at the submodule or feeder interface; When an anomaly is detected, the local distributed edge controller directly performs isolation or bypass operations. Upload abnormal status information to the hierarchical reconfiguration controller; The layered reconfiguration controller performs internal modulation redistribution and feeder power rerouting within the MMC; During the reconfiguration process, the voltage of the critical load bus should be maintained within the allowable deviation range.

[0028] By adopting the above technical solution, electrical parameters are collected in real time at submodules or feeder interfaces, enabling the system to continuously monitor key operating states such as voltage and current, improving the timeliness and accuracy of anomaly identification. When an anomaly is detected, the local distributed edge controller directly performs isolation or bypass operations to achieve rapid local fault isolation, shorten the fault duration, and suppress the spread of fault current. Subsequently, the abnormal status information is uploaded to the hierarchical reconfiguration controller, which analyzes and makes decisions based on the overall global operating status, executing internal modulation redistribution of the modular multi-stage converter and feeder power rerouting, completing system reconfiguration from both structural and power flow levels. During the reconfiguration process, the modulation strategy and power distribution are dynamically adjusted to maintain the voltage of key load buses within the allowable deviation range, avoiding voltage collapse or overshoot. Overall, a closed-loop control process of "rapid isolation - information reporting - coordinated reconfiguration - stable maintenance" is realized, improving the system's anti-disturbance capability, operational continuity, and power supply reliability.

[0029] Thirdly, a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method of claim 9.

[0030] By adopting the above technical solution, a computer program for implementing the operation method is stored in a computer-readable storage medium, enabling the processor to complete anomaly detection, rapid isolation, information reporting, and reconfiguration control according to predetermined steps. This achieves software-based and modular deployment of control functions, improves the system's flexibility, upgradeability, and maintenance convenience, while ensuring the consistency and reliability of the control logic.

[0031] In summary, this application includes at least one of the following beneficial technical effects: 1. By setting a controllable bypass switch structure at the modular multi-level converter sub-module level, and combining it with the local fast detection and direct drive mechanism of the distributed edge controller, millisecond-level local isolation of faults is achieved, fault propagation is suppressed, and the risk of system cascading failure is reduced. 2. By modulating and redistributing the remaining healthy sub-modules through the hierarchical reconfiguration controller and performing power rerouting on the feeder branches, topology adaptive reconfiguration and dynamic power path optimization are achieved, ensuring continuous and stable AC bus and DC bus voltages. 3. By constructing a hierarchical control architecture at the submodule / arm level, converter level, and microgrid level, the control functions are decoupled and coordinated, improving the control response speed and global decision stability, and enhancing the system's robustness and scalability under multiple disturbance conditions; 4. Through the modulation compensation mechanism after the submodule is bypassed, the output voltage amplitude is maintained continuously, voltage sudden changes and harmonic distortion are reduced, and the power supply quality and operation continuity are improved. 5. By supporting the synchronous detection and matching access of distributed energy and energy storage systems, flexible grid connection and smooth switching can be achieved, thereby improving the renewable energy absorption capacity and system operating efficiency; 6. By storing the operating method as a computer program and executing it with a processor, the control logic is software-based and modularly deployed, enhancing system upgradeability and maintenance convenience, and improving the overall engineering application value. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the overall architecture of a hybrid AC / DC microgrid according to an embodiment of this application.

[0033] Figure 2 This is a schematic diagram of the internal structure of the MMC and the reconstruction of its sub-modules in an embodiment of this application.

[0034] Figure 3 This is a topology diagram of the plug-and-play interface circuit according to an embodiment of this application.

[0035] Figure 4 This is a schematic diagram of the hierarchical control and unified decision-making framework of an embodiment of this application.

[0036] Figure 5This is a schematic diagram illustrating an event-driven hierarchical reconfiguration method for hybrid AC / DC microgrids based on MMC, according to an embodiment of this application.

[0037] Figure 6 This is a schematic diagram of the fault detection and reconstruction sequence (timeline) of an embodiment of this application.

[0038] Figure 7 This is a schematic diagram of the grid connection and off-grid mode switching in an embodiment of this application. Detailed Implementation

[0039] The following is in conjunction with the appendix Figure 1-7 This application will be described in further detail.

[0040] This application discloses a hybrid AC / DC microgrid based on a reconfigurable modular multi-stage converter. (Refer to...) Figures 1-7 It includes: a modular multi-stage converter (MMC), which includes multiple phase legs, each phase leg including an upper arm and a lower arm, each arm having multiple sub-modules connected in series, and each sub-module including a semiconductor switching device, a capacitor energy storage unit and a controllable bypass switch structure; At least one AC bus and at least one DC bus, with the MMC electrically connected to the AC bus and the DC bus respectively, for the purpose of realizing bidirectional power conversion; It includes multiple feeder branches, which are connected to the AC bus or DC bus via corresponding power switch devices; This includes distributed edge controllers, which are respectively set at the sub-modules or feeder interfaces. The distributed edge controllers are connected to voltage and current sensors to collect local electrical parameters and directly output isolation or bypass control signals when an abnormality is detected. It includes a hierarchical reconfiguration controller that communicates with the distributed edge controller to perform MMC internal reconfiguration and feeder power path reallocation based on received status information; The microgrid adopts a hierarchical control architecture of submodule / arm level, converter level and microgrid level. Faults are preferentially isolated at the physical level where they occur and structural reconfiguration is completed at the upper control level to maintain the stability of the critical load bus voltage.

[0041] A hybrid AC / DC microgrid operation method based on a reconfigurable modular multi-stage converter includes: acquiring electrical parameters at the sub-module or feeder interface; directly performing isolation or bypass operations by a local distributed edge controller when an anomaly is detected; uploading the anomaly status information to a hierarchical reconfiguration controller; performing internal modulation redistribution and feeder power rerouting by the hierarchical reconfiguration controller; and maintaining the critical load bus voltage within the allowable deviation range during the reconfiguration process.

[0042] A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method described above.

[0043] This application provides a hybrid AC / DC microgrid system based on MMC and its operation method, which needs to achieve the following technical functions: It is necessary to perform hierarchical operations of multiple control algorithms between distributed hardware layers; Isolate the source of the fault and handle it at an appropriate response speed; Coordinate the reconfiguration of the internal MMC (Modular Reconfigurable Controller) and the power routing at the feeder level; Under abnormal operating conditions, the voltage of the specified critical load bus will be maintained within a defined deviation range; Seamless plug-and-play integration of distributed energy resources (DER) and energy storage systems (ESS) can be achieved without shutting down the microgrid.

[0044] The technical solution of this application explicitly relies on the forced coordination of submodule-level, converter-level, and microgrid-level control algorithms executed by physically distributed controllers, rather than centralized or monolithic control.

[0045] Existing AC or DC microgrids typically employ a centralized control structure. When any power unit or feeder in the system fails, the fault information must be uploaded to the central controller before control decisions can be made. This results in: slow fault isolation response speed; easy fault propagation along the bus; long system reconfiguration time; and difficulty in ensuring the continuity of power supply to critical loads. Especially in hybrid AC / DC microgrids using modular multi-stage converters (MMC), due to the large number of sub-modules and complex topology, traditional centralized control methods cannot simultaneously meet the requirements of fast protection and global optimization control.

[0046] This application proposes a reconfigurable MMC hybrid AC / DC microgrid structure based on the coordinated operation of distributed edge control and hierarchical reconfiguration control. The core idea of ​​the technical solution is that faults are preferentially isolated at the occurrence level, and the system completes structural reconfiguration at the upper level. This forms a control mechanism that combines rapid local response with upper-level coordination and optimization.

[0047] The overall structure of the technical solution in this application is as follows: the provided hybrid AC / DC microgrid system mainly includes: a modular multi-stage converter (MMC); an AC bus; a DC bus; multiple feeder branches; a distributed edge controller; a hierarchical reconfiguration controller; a distributed energy and energy storage access interface; and a status detection and protection unit. Among them, the modular multi-stage converter (MMC) serves as the core energy exchange node of the system, realizing bidirectional power conversion between the AC bus and the DC bus.

[0048] I. The modular multi-stage converter structure includes: (a) Pair leg structure The MMC includes multiple phase legs, each phase leg including: an upper bridge arm; a lower bridge arm; each bridge arm is composed of multiple sub-modules connected in series; the number of sub-modules is determined according to the DC bus voltage level, and in a typical embodiment, each arm is provided with 6 to 30 sub-modules; (II) Sub-module composition Each submodule includes: semiconductor switching devices; capacitor energy storage unit; controllable bypass switch; and buffer protection circuit. Semiconductor devices that can be used include: IGBTs; silicon carbide MOSFETs; gallium nitride devices; The submodule capacitor is used to achieve voltage synthesis and energy balance; the controllable bypass structure is used to remove the submodule from the operating circuit when an abnormality occurs. (III) Arm-level current limiting structure Each bridge arm is equipped with an inductor to: suppress circulating current; limit fault current; and improve system stability.

[0049] II. The AC and DC bus structures shall include at least: 1. AC busbar The AC bus voltage level can be: 400V low voltage level; or 11kV medium voltage level, used to connect AC loads and external power grid; 2. DC bus The preferred DC bus voltage range is 750V to 5kV. The DC bus is used to connect to: energy storage systems. Photovoltaic systems, DC loads, and electrical equipment.

[0050] III. The feeder branch structure includes: multiple feeder branches connected to the AC or DC bus via power switching devices; each feeder includes: a switch execution unit; a feeder controller and a status detection device, the feeder controller being able to generate time-stamped operating status information; This structure enables: feeder isolation; power path switching; and network topology reconfiguration.

[0051] IV. Distributed Edge Controller: Control functions are pushed down to the physical device layer. The distributed edge controller is set up in: MMC submodule, MMC arm interface; feeder interface and power access end; (I) Functional Components The edge controller includes: a data acquisition module, a state estimation module, an anomaly detection module, a finite state machine (FSM), and a local execution driver module; (ii) Local detection mechanism The edge controller collects voltage, current, and power change rates in real time and performs state estimation using an extended Kalman filter algorithm.

[0052] (III) Rapid Protective Actions When overcurrent, voltage slump, submodule malfunction, direct execution by the edge controller, submodule bypass, and feeder isolation are detected, there is no need to wait for central control commands, and the response time can reach microseconds to milliseconds.

[0053] V. Time stamping and event coordination mechanism: Each edge controller adds a timestamp when performing control actions; The hierarchical reconfiguration of the controller is based on: time sequence, event correlation, and determination of fault propagation paths. Microgrid systems can use IEEE-1588 time synchronization technology to improve accuracy, but do not rely on strict synchronization.

[0054] VI. Hierarchical Control System This application adopts a three-tier control architecture: (a) Submodule / arm-level control layer: Control cycle: less than 1ms; Main functions: current prediction control, capacitor voltage balancing, submodule fault detection and bypass execution; this layer achieves the fastest control response. (ii) Converter-level control layer: Control cycle: 1-10ms; Functions include: AC voltage generation, frequency support, multiphase coordinated control, and modulation redistribution. Virtual synchronous machine control and adaptive droop control are employed; (III) Microgrid-level control layer: Control cycle: 10-100ms; Execution: Power path planning, feeder reconfiguration, and operating mode switching, using MPC or MILP optimization algorithms.

[0055] VII. Fault Detection and Dynamic Reconfiguration Process The system fault handling process is as follows: Step 1: Edge controller detects anomalies; Step 2: Immediately perform local bypass or isolation; Step 3: Upload abnormal information; Step 4: Converter-level modulation reallocation; Step 5: Perform power rerouting at the microgrid level; Step 6: The microgrid system returns to stable operation; Steps 1 through 6 form a closed-loop self-healing control mechanism.

[0056] The plug-and-play energy interface allows distributed energy sources to connect via an interface unit, which includes: Power conversion stage, control module, filter unit, controllable switch; before connection, the following are performed: bus voltage detection, phase synchronization, and dynamic admittance matching to avoid inrush current.

[0057] 9. Switching between operating modes The microgrid system supports grid-connected operation, islanded operation, rectifier mode, and inverter mode. Mode switching is automatically completed by hierarchical control without manual intervention.

[0058] 10. Virtual Inertial Cooperative Control During microgrid system reconfiguration: virtual inertia parameters and droop coefficients are dynamically adjusted, thereby: Suppress frequency fluctuations and improve transient stability.

[0059] XI. System Working Process When an anomaly occurs: the faulty submodule is bypassed, the remaining modules are remodulated, power is transmitted through the healthy path, and the voltage of critical loads remains stable, ensuring uninterrupted power supply to the microgrid system.

[0060] Compared with existing technologies, this application has at least the following technical effects: achieving millisecond-level local fault isolation, fully utilizing the internal redundancy of MMC without downtime, maintaining the voltage stability of critical loads, seamless and interference-free DER / ESS integration, supporting topology adaptive reconfiguration, enhancing the access capability of new energy sources, improving power supply continuity, reducing the risk of system cascading failures, and improving the operational stability of microgrids.

[0061] 12. Applicable Scenarios This microgrid system is applicable to at least the following: industrial park microgrids, data center power supply systems, port shore power systems, campus energy systems, and new energy integrated energy stations.

[0062] The key technical points of this application are: the mandatory hierarchical execution of the distributed control algorithm tightly coupled with the MMC hardware, the binding of the edge controller structure and algorithm, MMC reconfiguration, and microgrid-level optimization.

[0063] The technical solution in this application can only be replaced with other algorithms when maintaining hierarchical distribution and time separation.

[0064] The implementation principle of a hybrid AC / DC microgrid based on a reconfigurable modular multi-stage converter in this application embodiment is as follows: The implementation principle of a hybrid AC / DC microgrid based on a reconfigurable modular multi-stage converter in this application embodiment is as follows: During system operation, each distributed energy unit, energy storage unit, and load unit is connected to the AC bus or DC bus, and a unified energy coupling channel is established through the reconfigurable modular multi-stage converter, enabling bidirectional energy flow between the AC and DC sides. The reconfigurable modular multi-stage converter is composed of multiple cascaded power sub-modules, each of which has independent switching and operation control capabilities. The main controller performs topology reconfiguration and capacity allocation for each sub-module based on the real-time operating status of the microgrid. When the AC side load demand increases, the control system increases the number of sub-modules in operation to improve the AC side output voltage level and power capacity, achieving dynamic capacity expansion. When the DC side power fluctuates or the output of new energy sources is unstable, the sub-module connection method is reorganized to allow some modules to participate in DC voltage regulation control first, thereby maintaining the DC bus voltage stability. During energy dispatch, the system constructs a hierarchical control mechanism based on the bus voltage deviation and power balance relationship. The upper-level energy management unit is responsible for power allocation decisions, the middle-level coordination control unit completes AC / DC power decoupling control, and the lower-level module control unit realizes voltage balancing and current control of each power submodule, enabling the multi-stage converter to maintain stable operation under different operating modes. When the microgrid is in grid-connected operation mode, the reconfigurable modular multi-stage converter performs power tracking control to achieve active and reactive power exchange with the external grid. When the system switches to islanded operation mode, the converter automatically switches to voltage source control mode, maintaining bus voltage and frequency stability through module redundancy reconfiguration, thereby ensuring continuous power supply to critical loads. Each power submodule has bypass and hot-swappable characteristics. When some modules fail, the control system can quickly take the faulty modules out of operation and reconfigure the remaining modules to form a new operating topology, achieving uninterrupted system operation and improving the overall reliability and fault tolerance of the microgrid. It realizes flexible scheduling of energy flow, dynamic reconfigurability of topology, and stable operation under multiple energy access conditions in hybrid AC / DC microgrids, significantly improving the system's scalability, operating efficiency, and power supply reliability.

[0065] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A hybrid AC / DC microgrid based on a reconfigurable modular multi-stage converter, characterized in that, include: A modular multi-stage converter (MMC) includes multiple phase legs, each phase leg including an upper arm and a lower arm, and multiple sub-modules connected in series in each arm. Each sub-module includes a semiconductor switching device, a capacitor energy storage unit, and a controllable bypass switch structure. The system includes at least one AC bus and at least one DC bus, with the MMC electrically connected to both the AC bus and the DC bus respectively, for bidirectional power conversion. It includes multiple feeder branches, which are connected to the AC bus or DC bus via corresponding power switching devices; It includes distributed edge controllers respectively set at sub-modules or feeder interfaces. The distributed edge controllers are connected to voltage and current sensors to collect local electrical parameters and directly output isolation or bypass control signals when an abnormality is detected. Includes a hierarchical reconfiguration controller, which is communicatively connected to the distributed edge controller and is used to perform MMC internal reconfiguration and feeder power path redistribution based on received status information; The microgrid adopts a hierarchical control architecture of submodule / arm level, converter level and microgrid level. Faults are preferentially isolated at the physical level where they occur and structural reconfiguration is completed at the upper control level to maintain the stability of the critical load bus voltage.

2. The microgrid according to claim 1, characterized in that, The control cycle of the submodule / arm-level control layer is less than 1 millisecond. It is used to perform current modulation, capacitor voltage balancing and submodule fault detection, and to bypass the submodule after a fault is detected.

3. The microgrid according to claim 1, characterized in that, The control cycle of the converter-level control layer is 1 to 10 milliseconds, used to generate AC bus voltage and frequency references, and to reallocate modulation strategies when the number of sub-modules changes.

4. The microgrid according to claim 1, characterized in that, The control cycle of the microgrid-level control layer is 10 milliseconds to 100 milliseconds, and it is used to perform feeder switch control and power rerouting decisions.

5. The microgrid according to claim 1, characterized in that, The distributed edge controller includes a finite state machine module, which is used to perform immediate bypass, delayed confirmation, and fault reporting operations according to the anomaly level.

6. The microgrid according to claim 1, characterized in that, The hierarchical reconfiguration controller sorts events based on time identifier information from multiple distributed edge controllers and generates corresponding MMC modulation redistribution instructions or feeder switching instructions.

7. The microgrid according to claim 1, characterized in that, After each submodule is bypassed, the remaining submodules maintain the continuous amplitude of the AC bus or DC bus voltage by adjusting the modulation duty cycle.

8. The microgrid according to claim 1, characterized in that, The system supports the access of distributed energy or energy storage systems through an interface unit. The interface unit includes a power conversion stage and a local control module. The local control module performs bus voltage detection and synchronization matching before access.

9. A method for operating a hybrid AC / DC microgrid based on a reconfigurable modular multi-stage converter, characterized in that, include: Collect electrical parameters at the submodule or feeder interface; When an anomaly is detected, the local distributed edge controller directly performs isolation or bypass operations. Upload abnormal status information to the hierarchical reconfiguration controller; The layered reconfiguration controller performs internal modulation redistribution and feeder power rerouting within the MMC; During the reconfiguration process, the voltage of the critical load bus should be maintained within the allowable deviation range.

10. A computer-readable storage medium having a computer program stored thereon, the program being executed by a processor to implement the steps of the method of claim 9.

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