Micro-grid system based on direct current bus and control method

Abstract

The invention discloses a micro-grid system based on a direct current bus and a control method, the micro-grid system comprises the direct current bus, an energy management unit and a plurality of power conversion modules, when the micro-grid system is in an independent adjusting mode, each power conversion module controls the direct current bus to operate according to bus operation parameters of the direct current bus; and when the micro-grid system is in a centralized regulation mode, the energy management unit issues a control instruction to coordinate the output power and / or the input power of each power conversion module. According to the technical scheme, a unified direct current bus framework is constructed, the photovoltaic energy unit, the energy storage energy unit, the commercial power energy unit, the direct current load and other loads are directly connected to the direct current bus, direct current direct supply and direct current direct charging are achieved, the energy link structure is simplified, the power conversion link is reduced, the overall energy efficiency of the system is improved, and the system cost is reduced. And the phenomena of multiple energy conversion and energy loss caused by dependence on an alternating current bus in the prior art are avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of charging, in particular to a micro-grid system based on a DC bus and a control method. BACKGROUND

[0002] The light storage charging and discharging system is a comprehensive energy solution integrating photovoltaic power generation, energy storage management and electric vehicle charging / discharging, and is widely used in intelligent power grids, distributed energy systems and new energy vehicle energy supply scenarios. The system generally includes a photovoltaic power module, an energy storage system, a power conversion unit and a charging and discharging interface, and aims to ensure user power demand while improving new energy utilization efficiency and reducing dependence on traditional power grids.

[0003] In related technologies, the photovoltaic power generation unit generally converts DC power into AC power through a photovoltaic inverter, and then the other functional modules (such as the energy storage system or charging pile) in the system convert the AC power into DC power again through AC / DC conversion to supply the energy storage unit or electric vehicle load. Therefore, the existing system generally adopts the energy link of "photovoltaic→AC→DC", which involves a multi-stage energy conversion process. Although this process has a certain universality, it also introduces significant energy loss, reducing the overall efficiency of the system, especially in high-power application scenarios, where conversion loss cannot be ignored.

[0004] In summary, the existing light storage charging and discharging system uses an AC bus as the central structure for energy allocation, which has maturity and compatibility, but still has obvious deficiencies in efficiency optimization, control strategy and system responsiveness, and there is an urgent need for a high-efficiency collaborative energy management solution based on a DC bus to simplify the energy flow path, reduce energy loss and improve system control accuracy and response capability. SUMMARY

[0005] The main purpose of the present application is to provide a micro-grid system based on a DC bus and a control method to at least solve the technical problems mentioned in the related art.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0007] In a first aspect of the present application, a micro-grid system based on a DC bus is provided, which includes a DC bus, an energy management unit and a plurality of power conversion modules.

[0008] The first end of each power conversion module in the plurality of power conversion modules is electrically connected to a photovoltaic energy unit, an energy storage energy unit, a mains energy unit and a DC load, respectively, and the second end of each power conversion module is electrically connected to the DC bus.

[0009] The energy management unit is in communication connection with each power conversion module and the DC bus;

[0010] When the micro-grid system is in the independent regulation mode, each power conversion module autonomously adjusts the corresponding output power and / or input power according to the bus operation parameter of the DC bus;

[0011] When the micro-grid system is in the centralized regulation mode, the energy management unit is configured to calculate a target power value according to the collected system operation parameter information, and send a control instruction corresponding to the target power value to coordinate the output power and / or input power of each power conversion module.

[0012] The second aspect of the present application also provides a control method of a DC bus-based micro-grid system, comprising:

[0013] When the micro-grid system is in the independent regulation mode, each power conversion module autonomously adjusts the corresponding output power and / or input power according to the bus operation parameter of the DC bus;

[0014] When the micro-grid system is in the centralized regulation mode, the energy management unit calculates a target power value of each power conversion module according to the collected system operation parameter, and sends a control instruction to coordinate the output power and / or input power of each power conversion module.

[0015] The DC bus-based micro-grid system and the control method of the present application simplify the energy link structure, reduce the power conversion link, improve the overall energy efficiency of the system, and avoid the multiple energy conversion and energy loss phenomenon caused by the dependence on the AC bus in the prior art. In addition, the system is provided with an energy management unit, which can realize flexible switching between the independent regulation mode and the centralized regulation mode, respectively support the power module to automatically adjust the power output according to the bus voltage, or be uniformly coordinated and controlled by the control module based on the system operation parameter, thereby improving the real-time performance and intelligence of power distribution. In addition, the DC architecture naturally has faster response speed and higher control accuracy, and is particularly suitable for complex application scenarios with multiple energy complementation and frequent load fluctuations, and has good expansibility and compatibility, effectively improving the stability, reliability and energy utilization efficiency of the micro-grid system. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the related art, the following will briefly introduce the drawings needed to be used in the embodiments or the related art description. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0017] Figure 1 An electrical principle block diagram of the micro-grid system based on the DC bus provided by the embodiment of the present application;

[0018] Figure 2 An electrical principle block diagram of the micro-grid system based on the DC bus provided by the embodiment of the present application;

[0019] Figure 3 A communication principle block diagram of the micro-grid system based on the DC bus provided by the embodiment of the present application;

[0020] Figure 4 A communication principle block diagram of the micro-grid system based on the DC bus provided by the embodiment of the present application. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0022] It should be noted that related terms such as "first", "second", etc. can be used to describe various components, but these terms do not limit the components. These terms are only used to distinguish one component from another component. For example, without departing from the scope of the present application, the first component can be referred to as the second component, and the second component can similarly be referred to as the first component. The term "and / or" refers to the combination of any one or more of the related terms and the described terms.

[0023] For the English abbreviations covered in some of the drawings, the corresponding Chinese explanations are given below:

[0024] CCU: charging pile controller;

[0025] DC SourceCU: utility power supply cabinet control unit;

[0026] AC SourceCU: bidirectional power supply cabinet control unit;

[0027] PVCU: photovoltaic power supply cabinet control unit

[0028] MPPT: photovoltaic module, essentially DC / DC module

[0029] ESPCU: energy storage power unit controller

[0030] EMS Conteoller: energy storage local coordination controller

[0031] SWH: network router

[0032] Please refer to Figures 1 to 4 The embodiment of the present application provides a micro-grid system 1 based on a DC bus, which comprises a DC bus 10, an energy management unit (not shown in the figure) and a plurality of power conversion modules (201, 202, 203, 204, 205, 206, 207). The components are described as follows:

[0033] In the embodiment, the DC bus 10 can be a public channel of DC power, which is used for unified collection and distribution of energy in the system and can realize bidirectional DC power transmission between different energy units (301, 302, 303, 304, 305, 307) and power equipment.

[0034] Specifically, the power conversion module refers to a power electronic device capable of realizing conversion, adjustment and control of electric energy between different voltage levels, different current characteristics or different power forms. In the embodiment, the plurality of power conversion modules include but are not limited to a photovoltaic DC / DC conversion module 201, a commercial AC / DC conversion module 202, a bidirectional power AC / DC conversion module 203, a bidirectional energy storage DC / DC conversion module 204, a DC charging DC / DC conversion module 205, a first unidirectional energy storage DC / DC conversion module 206 and a second unidirectional energy storage DC / DC conversion module 207.

[0035] The first end of each power conversion module is respectively used for electrical connection with the corresponding cabinet-type photovoltaic energy unit 301, the commercial power energy unit 302, the bidirectional power supply unit 303, the bidirectional energy storage unit 304, the direct-current load 305 (for example, a direct-current charging pile), the unidirectional energy storage unit 307, and the hydrogen energy unit. The second end of each power conversion module is respectively electrically connected with the direct-current bus 10, so that each energy unit can exchange electric energy with the direct-current bus 10 through the power conversion module. In this way, photovoltaic input is output to the direct-current bus 10 through the photovoltaic energy unit 301 and the photovoltaic DC / DC conversion module 201; commercial power input is output to the direct-current bus 10 through the commercial power energy unit 302 and the commercial AC / DC conversion module 202; the direct-current bus 10 is electrically connected with the bidirectional energy storage DC / DC conversion module 204 and the bidirectional energy storage module 304, so as to realize charging of the direct-current bus 10 to the bidirectional energy storage unit 304 or feedback of electric energy from the bidirectional energy storage unit 304 to the direct-current bus 10. Meanwhile, the direct-current bus 10 can supply power to the direct-current load 305 to charge the direct-current charging load (for example, an electric vehicle), or convert the electric energy on the direct-current bus 10 into alternating current through the bidirectional power supply unit 303 (bidirectional AC / DC conversion module) to supply power to an alternating current load.

[0036] The energy management unit can be a control module or a controller for monitoring, analyzing, decision-making and coordinated control of energy flow in the micro-grid system, and its functions include data acquisition, running state judgment, power distribution optimization and control instruction issuing. The energy management unit is in communication connection with the plurality of power conversion modules and the direct-current bus, and is used for acquiring system running parameter information and bus running parameters and issuing control instructions.

[0037] In the embodiment, the micro-grid system 1 supports but is not limited to the following two operating modes:

[0038] When the micro-grid system 1 is in the independent regulation mode (module autonomous control), each power conversion module is based on a pre-set independent closed-loop control unit in the internal, which is used for acquiring bus running parameters such as bus voltage and current of the direct-current bus 10, and autonomously adjusting output power and / or input power according to a pre-set control strategy (such as voltage-power droop control) without direct intervention of the energy management unit. For example, when it is detected that the bus voltage is lower than the lower limit value, the photovoltaic DC / DC module 201 can automatically increase the output power, and the energy storage DC / DC module 202 can automatically release the energy storage; when the bus voltage is higher than the upper limit value, the energy storage module can automatically absorb the excess electric energy or the photovoltaic module limits the output, so as to quickly and stably stabilize the bus voltage without communication dependence.

[0039] When the micro-grid system 1 is in the centralized regulation mode (energy management system EMS coordinated control), the energy management unit collects system operation parameters in real time, including bus voltage, output power of each power module, battery SOC, photovoltaic power generation power, grid power, etc., and calculates the target power value of each power conversion module based on a global optimization algorithm; the energy management unit then issues control instructions corresponding to the target power value to each power conversion module to coordinate its output power and / or input power. For example, when a sudden increase in load is detected, causing the bus voltage to drop, the energy management unit can instruct the energy storage module to increase the discharge power first, while reducing part of the charging pile power according to the demand; when a sudden drop in photovoltaic output is detected, the energy management unit can schedule energy storage compensation power in advance to compensate for the power gap and ensure system voltage stability.

[0040] It can be seen that the micro-grid system of the embodiment of the present application simplifies the energy link structure, reduces the power conversion link, improves the overall energy efficiency of the system, and avoids the multiple energy conversion and energy loss phenomenon caused by the dependence on the AC bus in the prior art. In addition, the system is provided with an energy management unit, which can realize flexible switching between independent regulation mode and centralized regulation mode, and support power module automatic regulation of power output according to bus voltage or unified coordinated control by the control module based on system operation parameters, thereby improving the real-time and intelligence of power distribution. In addition, through the formed efficient energy management system, real-time monitoring and management of various energy resources (such as solar energy, energy storage system and charging pile) in the micro-grid composed of the DC bus are realized, real-time monitoring of energy production and consumption is realized, energy distribution is optimized, charging demand is responded in time, DC bus power is adjusted, and bus power stability is ensured.

[0041] In the optional embodiment of the embodiment of the present application, when the micro-grid system is in the independent regulation mode, each power conversion module realizes autonomous power regulation based on the collected DC bus operation parameters and according to the preset voltage-current droop control strategy.

[0042] Specifically, each power conversion module (including but not limited to photovoltaic DC / DC module, energy storage DC / DC module, charging pile AC / DC module, etc.) accessing the DC bus is internally provided with an independent closed-loop control algorithm, which autonomously adjusts the output power and / or input power of the power conversion module according to the locally detected bus voltage signal without intervention of the upper energy management unit. For example, in this mode, the power conversion module operates based on a preset voltage-current droop control strategy, i.e., a voltage-power characteristic curve is set for each module, for example, when the bus voltage decreases by 1 V, the output current of the corresponding module increases by 0.5%. When the bus voltage decreases to 795 V (lower than the target value of 800 V) due to sudden load increase, the photovoltaic DC / DC module can automatically increase the output current to suppress the bus voltage drop; conversely, when the bus voltage is higher than 805 V, the energy storage DC / DC module can automatically absorb the excess energy for charging, thereby suppressing the continuous rise of the bus voltage.

[0043] In addition, the voltage-current droop control strategy (Droop Control) mainly refers to a distributed power control method, which aims to enable multiple power conversion modules (such as photovoltaic DC / DC, energy storage DC / DC, charging pile AC / DC, etc.) to achieve automatic power distribution and voltage stabilization without relying on communication. In droop control, each power module will preset a voltage-power (or voltage-current) characteristic curve, referred to as a "droop curve". When the bus voltage decreases (load increases), the module automatically increases the output power; when the bus voltage rises (load decreases), the module automatically reduces the output power.

[0044] In an optional embodiment, the formula used in the voltage-current droop control strategy is as follows:

[0045] V = V ref - KmI

[0046] In the above formula, V represents the current output voltage of the energy module, V ref represents the rated bus voltage (preset bus voltage threshold), K represents the droop coefficient (V / A), and I represents the output current of the energy module.

[0047] As can be seen, when the microgrid system is in the independent regulation mode, through the voltage-current droop control strategy built in each power conversion module, combined with the voltage limit protection, dynamic priority strategy and adaptive voltage adjustment rate, real-time detection and autonomous power regulation of the bus voltage are realized, so that millisecond-level fast response and stable control are completed without intervention of the upper energy management unit, effectively ensuring that the bus voltage is in the safe operation range and improving the reliability and stability of the overall operation of the system.

[0048] It should be noted that in the above independent regulation mode, the power conversion module can also be built-in with a voltage limit protection module for setting a safe operation window of the bus voltage, for example, 780V-820V. When the bus voltage is higher than 820V, the energy storage module and / or the adjustable load module (such as a direct current charging module) is forced to start power absorption to reduce the bus voltage; when the bus voltage is lower than 780V, the photovoltaic module and / or the grid power supply module automatically operates with limited power, thereby avoiding further reduction of the bus voltage to cause system collapse.

[0049] In an optional embodiment of the present application, when the micro-grid system is in the independent regulation mode, each power conversion module dynamically adjusts the voltage regulation rate according to the preset working parameters.

[0050] Specifically, when the micro-grid system is in the independent regulation mode, each power conversion module can dynamically adjust the voltage regulation rate based on the preset working parameters (including but not limited to environmental temperature, battery state of charge SOC, power module self-temperature rise condition, and load change trend, etc.) to reduce the risk of oscillation caused by excessive regulation while ensuring the stability of the bus voltage, and to take into account the efficiency and service life of the power module.

[0051] In addition, the power conversion module can be configured with a dynamic priority strategy to adjust the regulation priority of different types of loads or power modules in different operating states. For example, when the bus voltage is in a high voltage state, the direct current charging module is preferentially controlled to reduce power to release power balance space; when the bus voltage is in a low voltage state, part of the photovoltaic module or low-priority load is preferentially cut off to ensure the continuous power supply capability of the key load (such as a high-priority charging pile).

[0052] In some embodiments, the power conversion module can also include an adaptive voltage adjustment rate module for dynamically adjusting the voltage regulation sensitivity according to the real-time working condition to avoid overshoot or oscillation in the regulation process. For example, when the SOC of the energy storage system is higher than 95%, the power absorption capacity of the energy storage system is automatically enhanced; when the SOC is lower than 20%, the discharge power of the energy storage system is automatically reduced to preferentially ensure the stability of the bus voltage and the safe operation of the energy storage system.

[0053] The above-mentioned voltage limit protection, dynamic priority, and adaptive voltage adjustment rate can be combined to achieve millisecond-level fast response in the independent regulation mode, while avoiding system oscillation caused by excessive regulation, thereby significantly improving the bus voltage stability and operation safety of the micro-grid system.

[0054] In an optional implementation of the embodiments of the present application, when the micro-grid system is in the centralized regulation mode, the energy management unit is configured to calculate target power values of the power conversion modules based on system operation parameters using a global optimization algorithm, and dynamically allocate the target power values according to a priority strategy (such as charging demand priority, photovoltaic power consumption priority, or energy storage life priority, etc.). The energy management unit further transmits corresponding control instructions to each power conversion module through a high-speed communication network to coordinate the output power and / or input power of each power conversion module, so as to achieve stable DC bus voltage and optimal power distribution in the global range. The system operation parameters include voltage information of the DC bus, power information of each power conversion module, state of charge (SOC) of the battery, photovoltaic power generation output information, and load demand information.

[0055] Specifically, when the micro-grid system is in the centralized regulation mode, the energy management unit is an energy management system (EMS) that collects system operation parameters (including DC bus voltage, power information of each power conversion module, state of charge (SOC) of the battery, photovoltaic irradiance, and load demand, etc.) in real time through a high-speed communication network (CAN or Ethernet), calculates optimal target power based on the collected operation parameters using a global optimization algorithm and combining a dynamic weight allocation strategy according to a preset priority (for example, charging pile demand is prior to photovoltaic power consumption, and photovoltaic power consumption is prior to energy storage life protection), and transmits control coordination instructions corresponding to the target power to the corresponding power conversion modules for execution. When the bus voltage fluctuates, the energy storage module with faster response speed is preferentially regulated, and the photovoltaic power supply module with larger response inertia is not regulated, so as to achieve fast stabilization of the bus voltage and optimal coordinated distribution of system power.

[0056] It can be seen that when the system is in the centralized regulation mode, the energy management unit can make unified decisions and accurate scheduling based on global operation data, not only achieving stable control of the DC bus voltage in the global range, but also taking into account the response speed, operating efficiency, and life protection requirements between different energy units and loads through the priority strategy, thereby significantly improving the overall operating efficiency, reliability, and economy of the micro-grid system.

[0057] In an optional implementation of the embodiments of the present application, the energy management unit is further configured to use a dynamic priority allocation mechanism to preferentially schedule the energy storage module with faster response speed to perform charging and discharging regulation when detecting voltage fluctuation of the DC bus, so as to quickly suppress voltage deviation. In addition, the energy management unit is further configured to perform a predictive control strategy, predict the photovoltaic power generation output and load power change trend based on historical operation data, and adjust the charging and discharging plan of the energy storage module in advance when the prediction result indicates that power shortage or power surplus will occur, so as to achieve smooth regulation and optimal power distribution.

[0058] In addition, the energy management unit comprises at least an upper decision layer, an intermediate coordination layer and a bottom execution layer.

[0059] The upper decision layer is configured to calculate a power deficit based on a difference between a total load power of the system and a power of each distributed energy module, wherein the power deficit ΔP = total load power P_load - photovoltaic power P_pv - grid input power P_grid,

[0060] It should be noted that the total load power P_load of the system refers to the total power demand of all loads in the entire micro-grid system at present, the power deficit ΔP represents a difference between a current power supply capacity and a load demand, the photovoltaic power P_pv refers to an actual power output from a photovoltaic power module (such as a photovoltaic array + photovoltaic DC / DC converter) to a DC bus or system at a current time. This value is usually detected in real time by a photovoltaic power conversion module and fed back to the energy management unit (EMS), and the unit is kW or MW. In addition, the grid input power P_grid refers to an actual power provided by an external AC grid (mains) to the system through a power conversion module (such as an AC / DC converter). If the system can also feed back power to the grid, P_grid is positive when calculating the power deficit, which means power is taken from the grid, and negative when power is fed to the grid.

[0061] In actual implementation, if ΔP > 0, it means that the current photovoltaic + grid power supply is insufficient, and the energy storage needs to be discharged to compensate; if ΔP < 0, it means that the power supply is excessive, and the energy storage can be charged or the power generation can be reduced; if ΔP = 0: the supply and demand are balanced, and no additional adjustment is needed.

[0062] The intermediate coordination layer is configured to distribute target power instructions to controllable energy units such as energy storage modules and grid modules according to the power deficit ΔP calculated by the upper decision layer, in combination with a preset priority strategy, a cost factor and a response speed of each power conversion module; the priority strategy can include energy storage discharge priority, grid power purchase priority or comprehensive cost minimization.

[0063] The bottom execution layer is configured to receive the power instructions issued from the intermediate coordination layer, and perform voltage or current closed-loop control through the corresponding power conversion module to realize real-time and accurate adjustment of the power input or output of the photovoltaic power module, the energy storage module and the DC charging module.

[0064] In some embodiments, the energy management unit is further configured to execute a fault ride-through strategy: when a sudden surge or drop in bus voltage is detected (e.g. caused by a sudden start or stop of a charging pile), a charge-discharge switching instruction is issued to the energy storage module within a preset time (e.g. within 0.1 seconds), and non-critical loads are cut off, so as to ensure that the voltage of critical loads (e.g. high-priority charging piles) is stable within ±1% of the rated value.

[0065] For further reference Figure 3 and Figure 4 The energy management unit communicates with the photovoltaic energy unit 301, the bidirectional energy storage unit 304, the unidirectional energy storage unit 307, the bidirectional power supply unit 303, the DC load 305, and the utility energy unit 302 through CAN communication, for real-time collection of operating state parameters of each module and issuance of control instructions.

[0066] The utility energy unit, the photovoltaic energy unit, and the bidirectional energy storage unit further access a network switch (SWH) through a transmission control protocol (TCP) communication mode, so as to realize high-speed transmission and centralized management of data in a local area network. In addition, the bidirectional energy storage unit 304 and the DC load 305 further access a cloud platform through a 4G wireless communication router, so as to realize remote monitoring, operation data analysis, and strategy updating.

[0067] The following is a specific description of each energy unit involved in the embodiments of the present application:

[0068] The photovoltaic energy unit 301 is internally provided with a photovoltaic power cabinet control unit (PVCU) and a photovoltaic maximum power tracking module (MPPT, which is essentially a DC / DC module), for converting photovoltaic electric energy into DC electric energy and outputting to a DC bus;

[0069] The utility energy unit 302 is internally provided with a utility power cabinet control unit (DC SourceCU) and an AC / DC conversion module, for converting AC grid electric energy into DC electric energy and outputting to the DC bus;

[0070] The bidirectional power supply unit 303 is internally provided with a bidirectional power supply cabinet control unit (AC SourceCU) and a bidirectional AC / DC conversion module (BiAC / DC), for realizing bidirectional power flow between the DC bus and the AC grid;

[0071] The bidirectional energy storage unit 304 internally includes an energy storage power unit controller (ESPCU), a bidirectional DC / DC conversion module (DC / DC), and a battery management system (BMS), and communicates and coordinates with the system through an energy storage local coordination controller (EMS Controller);

[0072] The direct current load 305 can be a charging pile or a direct current charging device, which internally includes a charging pile controller (CCU) for outputting direct current power of the direct current bus;

[0073] The unidirectional energy storage unit 307 is used for realizing unidirectional storage and release of energy, and internally includes an energy storage power unit controller (ESPCU), a unidirectional DC / DC conversion module, a battery management system (BMS) and an energy storage local coordination controller (EMS Controller). The energy storage power unit controller is used for uniformly scheduling and controlling the unidirectional DC / DC conversion module and the battery management system, communicating with the energy storage local coordination controller (EMS Controller) through a CAN bus, receiving energy charging and discharging instructions and executing them, collecting running parameters such as current, voltage and temperature in real time, and processing power regulation, fault detection and protection logic. The unidirectional DC / DC conversion module adopts an isolation type topology and is provided with a high-frequency isolation transformer to realize electrical isolation between a primary side and a secondary side. In the charging process, the direct current bus power is converted and stored in the battery unit. In the discharging process, the direct current power of the battery unit is converted and released to the direct current bus. The unidirectional DC / DC conversion module has constant voltage / constant current control, power limitation and efficiency optimization functions. The battery management system (BMS) is directly connected with the battery unit, is used for monitoring battery voltage, current, SOC (state of charge), SOH (state of health) and temperature, realizing overcharge, overdischarge, overtemperature and other protection functions, and uploading monitoring information to the ESPCU in real time. The battery management system (BMS) can execute equalization management to improve consistency and service life of the battery pack.

[0074] That is, the unidirectional energy storage unit 307 accesses the direct current bus during system operation and works according to a scheduling strategy under the control of the EMS Controller: when it is detected that the bus power is surplus, the unidirectional DC / DC conversion module is controlled to perform a charging operation and store energy in the battery unit; when it is detected that the bus power is insufficient, the battery discharging unit 308 releases energy, which is converted by the DC / DC conversion module and then delivered to the bus to supply power to the direct current load or other electrical equipment. Through the above modular design, the unidirectional energy storage unit 307 can realize efficient and stable unidirectional energy flow, and ensure safety and reliability of overall system operation.

[0075] a battery discharge unit 308, which internally comprises a DC / DC conversion module for outputting direct current energy of the energy storage battery to the DC bus; specifically, during system operation, when the EMS Controller dispatches the unidirectional energy storage unit 307 to enter the discharge mode, the battery discharge unit 308 starts the DC / DC conversion module under the control of the ESPCU to convert the direct current energy of the energy storage battery unit and then incorporate it into the DC bus, thereby providing stable energy support for the DC load 305 or other power supply units. Through the above structure and working mode, the battery discharge unit 308 can realize efficient energy conversion and safe control of the discharge process of the energy storage battery unit.

[0076] a network router (SWH) for realizing TCP communication between modules;

[0077] a 4G communication module for connecting the system to the cloud platform to realize remote monitoring and data interaction.

[0078] In the embodiment, the communication mode between modules includes that the energy management system (EMS Controller) and the photovoltaic energy unit 301, the utility energy unit 302, the bidirectional power supply unit 303, the bidirectional energy storage unit 304, the DC load 305, etc. exchange data through TCP or CAN bus; the modules can also perform remote data transmission and receive control instructions from the cloud server through the network router (SWH) and the 4G module. That is, the embodiment realizes local high-speed control in real time through multi-communication channel design, and supports remote cloud optimization and management.

[0079] In the optional embodiment of the application, the power conversion modules can adopt an integrated structure, i.e., each power conversion module is integrated in the photovoltaic energy unit 301, the utility energy unit 302, the bidirectional power supply unit 303, the bidirectional energy storage unit 304, the DC load 305, etc., to reduce external connection cables of the system and improve overall structural compactness and electrical energy conversion efficiency; or the power conversion modules can adopt a discrete structure, i.e., each power conversion module is independent of each other and is electrically connected to the photovoltaic energy unit 301, the utility energy unit 302, the bidirectional power supply unit 303, the bidirectional energy storage unit 304, the DC load 305, etc., to facilitate modular maintenance and flexible expansion of system functions.

[0080] In the optional embodiment of the application, the energy storage unit is the bidirectional energy storage unit 304 or the unidirectional energy storage unit 307, and both have high-frequency isolation function.

[0081] Specifically, the unidirectional energy storage module 307 comprises a double-independent DC / DC topology structure, wherein a high-frequency isolation transformer is arranged in the double-independent DC / DC topology structure, and further comprises a high-efficiency LLC resonant DC / DC conversion module (a second unidirectional energy storage DC / DC conversion module 207) for charging the energy storage battery unit and a three-level Buck-Boost structure DC / DC conversion module (a first unidirectional energy storage DC / DC conversion module 206) for discharging the energy storage battery unit.

[0082] Specifically, the bidirectional energy storage module 307 comprises a bidirectional DC / DC topology structure (a bidirectional energy storage DC / DC conversion module 204), wherein a high-frequency isolation transformer is arranged in the bidirectional DC / DC topology structure, and the bidirectional energy storage DC / DC conversion module 204 is used to realize bidirectional energy flow of the energy storage battery unit through a single power conversion module and in combination with the battery discharge module 308.

[0083] The application further provides a control method of the DC bus-based micro-grid system, comprising:

[0084] When the micro-grid system is in the independent regulation mode, each power conversion module autonomously adjusts the corresponding output power and / or input power according to the bus operation parameter of the DC bus;

[0085] When the micro-grid system is in the centralized regulation mode, the energy management unit calculates the target power value of each power conversion module according to the collected system operation parameter, and issues a control instruction to coordinate the output power and / or input power of each power conversion module.

[0086] It should be noted that, in the embodiment of the control method, the structure, composition and functions of the DC bus-based micro-grid system have been described in detail in the foregoing system embodiment, and thus will not be described again here to avoid repetition.

[0087] The micro-grid system based on the DC bus and the control method according to the embodiments of the present application, by constructing a unified DC bus architecture, that is, the system directly connects the photovoltaic energy unit, the energy storage unit, the mains energy unit and the DC load to the DC bus through multiple power conversion modules, realizes DC direct supply and DC direct charging, simplifies the energy link structure, reduces the power conversion link, improves the overall energy efficiency of the system, and avoids the multiple energy conversion and energy loss phenomenon caused by the dependence on the AC bus in the prior art. In addition, the system is provided with an energy management unit, which can realize flexible switching between independent regulation mode and centralized regulation mode, respectively supports automatic power output adjustment of the power module according to the bus voltage, or unified coordinated control of the control module based on system operation parameters, thereby improving the real-time performance and intelligence of power distribution. In addition, the DC architecture naturally has faster response speed and higher control accuracy, and is particularly suitable for complex application scenarios with multiple energy complementation and frequent load fluctuations, and has good scalability and compatibility, effectively improving the stability, reliability and energy utilization efficiency of the micro-grid system.

[0088] The specific embodiments of the application are described in detail above, but only as examples, and the application is not limited to the specific embodiments described above. Any equivalent modification or substitution of the application made by those skilled in the art is also within the scope of the application, therefore, equivalent transformation, modification, improvement, etc. made without departing from the spirit and principle range of the application should be covered within the scope of the application.

Claims

1. A microgrid system based on a DC bus, characterized in that, The microgrid system based on a DC bus includes a DC bus, an energy management unit, and multiple power conversion modules. The first terminal of each of the multiple power conversion modules is respectively used to be electrically connected to the photovoltaic energy unit, the energy storage energy unit, the mains energy unit and the DC load, and the second terminal of each of the power conversion modules is respectively electrically connected to the DC bus. The energy management unit is communicatively connected to each of the power conversion modules and the DC bus; When the microgrid system is in independent regulation mode, each power conversion module autonomously adjusts its corresponding output power and / or input power according to the bus operating parameters of the DC bus. When the microgrid system is in centralized regulation mode, the energy management unit is used to calculate the target power value based on the collected system operating parameter information, and send control commands corresponding to the target power value to coordinate the output power and / or input power of each power conversion module.

2. The microgrid system based on a DC bus as described in claim 1, characterized in that, When the microgrid system is in independent regulation mode, each power conversion module performs autonomous regulation based on the bus operating parameters and using a preset voltage and current droop control strategy; the bus operating parameters include the bus voltage; Specifically, when the bus voltage in the bus operating parameters is lower than a preset bus voltage threshold, each of the power conversion modules increases power output or reduces power absorption; when the bus voltage is higher than the bus voltage threshold, each of the power conversion modules reduces power output or increases power absorption.

3. The microgrid system based on a DC bus as described in claim 2, characterized in that, When the microgrid system is in independent regulation mode, each power conversion module dynamically adjusts the voltage regulation rate according to preset operating parameters.

4. The microgrid system based on a DC bus as described in claim 1, characterized in that, When the microgrid system is in centralized regulation mode, the energy management unit is configured to dynamically allocate the target power value of each power conversion module based on the operating parameters using a global optimization algorithm, and to issue corresponding control commands to each power conversion module to coordinate and control its output power and / or input power; wherein, the system operating parameters include the DC bus voltage, the power information of the power conversion module, the state of charge of the battery, the photovoltaic output information, and the load demand information.

5. The microgrid system based on a DC bus as described in claim 4, characterized in that, The energy management unit is also used to control the energy storage module to perform charging and discharging regulation when the voltage fluctuates by employing a dynamic priority allocation mechanism. The energy management unit is also configured to execute a predictive control strategy, predict the changing trends of photovoltaic power generation and load power based on historical operating data, and pre-adjust the charging and discharging strategy of the energy storage module.

6. The microgrid system based on a DC bus as described in claim 5, characterized in that, The energy management unit includes an upper decision-making layer, an intermediate coordination layer, and a lower execution layer; The upper decision layer is used to calculate the power deficit based on the difference between the total system load power and the power of each distributed energy module; The intermediate coordination layer is used to distribute power commands to each power conversion module according to the power deficit based on a set priority, cost factor, or response speed. The underlying execution layer is used to receive the power command, perform voltage or current control through the power conversion module, and adjust the power input or output of the photovoltaic power module, energy storage module, and DC charging module in real time.

7. The microgrid system based on a DC bus as described in claim 1, characterized in that, The energy management unit communicates with the photovoltaic energy unit, energy storage energy unit, mains energy unit, hydrogen energy unit, and DC load via CAN communication. The mains power unit, photovoltaic power unit, and energy storage unit are all connected to the network switch via TCP communication. The energy storage unit and the DC load are connected to the cloud platform via a 4G router.

8. The microgrid system based on a DC bus as described in any one of claims 1 to 7, characterized in that, Each of the aforementioned power conversion modules is integrated into the photovoltaic energy unit, energy storage energy unit, mains power energy unit, hydrogen energy unit, and DC load, respectively; or, Each of the power conversion modules is independent of the others and is used to electrically connect to the photovoltaic energy unit, energy storage energy unit, mains energy unit, hydrogen energy unit and DC load, respectively.

9. The microgrid system based on a DC bus as described in any one of claims 1 to 7, characterized in that, The energy storage unit is a high-frequency isolated bidirectional energy storage module or a unidirectional energy storage module. The unidirectional energy storage module includes a dual independent DC / DC topology, which includes an LLC resonant DC / DC module for charging and a three-level Buck-Boost DC / DC module for discharging. The bidirectional energy storage module, with its bidirectional DC / DC topology, is used to achieve bidirectional energy flow for charging and discharging of the energy storage battery unit using a single module.

10. A control method for a microgrid system based on a DC bus as described in any one of claims 1 to 9, characterized in that, include: When the microgrid system is in independent regulation mode, each power conversion module autonomously adjusts its corresponding output power and / or input power according to the bus operating parameters of the DC bus. When the microgrid system is in centralized regulation mode, the energy management unit calculates the target power value of each power conversion module based on the collected system operating parameters, and issues control commands to coordinate the output power and / or input power of each power conversion module.

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