Optical storage charging direct flexible power supply system applied to service area

Abstract

The invention relates to the technical field of new energy and electric vehicle charging facilities, and particularly discloses an optical storage and charging direct-flexible power supply system applied to a service area, which comprises a photovoltaic power generation unit, an energy storage unit, a charging unit and a bidirectional AC / DC converter interacting with a power grid, and the energy management unit carries out unified coordination control. The core of the system is that the loss of multiple times of electric energy conversion is reduced by using a flexible direct current bus, and a multi-mode flexible control strategy including peak load shifting, photovoltaic priority, power support and off-grid emergency is executed through an energy management unit. Therefore, the comprehensive benefits of improving the overall energy efficiency of the system, reducing the operation cost, stabilizing power grid impact and guaranteeing off-grid continuous power supply are achieved. Meanwhile, the system adopts a container type integrated energy storage design and supports networking operation of a plurality of service area subsystems, so that high integration, intelligent operation and maintenance and regional energy mutual aid are realized; the technical problem that a traditional service area power supply system is low in efficiency and poor in reliability is solved.

Description

Photovoltaic-storage-charging DC-flexible power supply system applied in service areas Technical Field

[0001] This invention relates to the field of new energy and electric vehicle charging facility technology, specifically to a photovoltaic-storage-charging DC-flexible power supply system applied in service areas. Background Technology

[0002] With the rapid popularization of new energy vehicles, the charging demand in highway service areas has exploded. Traditional service area power supply systems use AC distribution architecture, which has obvious technical limitations. Photovoltaic power generation, battery energy storage, and electric vehicle charging are all essentially DC systems. Under the traditional architecture, they need to undergo multiple AC-DC conversions, resulting in a reduction in overall system efficiency.

[0003] Currently, Chinese patent application number CN202310856901.X discloses a method for establishing a photovoltaic-storage-DC-flexible system architecture, including: establishing a system model library; sequentially selecting the photovoltaic-storage-DC-flexible system architecture, grid connection model, grid connection model, photovoltaic power generation system access model, energy storage system access model, feeder access model, and station power access model from the system model library; grafting the selected grid connection model, photovoltaic power generation system access model, energy storage system access model, feeder access model, and station power access model onto the photovoltaic-storage-DC-flexible system architecture to obtain a combined model; integrating the combined model into the AC-side grid to obtain the photovoltaic-storage-DC-flexible system; and using model selection and model combination to realize the construction of the photovoltaic-storage-DC-flexible system, providing a feasibility reference sample for building such a system.

[0004] However, existing photovoltaic-storage-DC-flexible systems focus on the early design and modeling stages of system architecture. Once the system is built, it is inconvenient to cope with complex dynamic operating conditions in actual operation. For example, how to achieve multi-mode flexible control through intelligent scheduling to smooth power fluctuations, how to achieve seamless switching between grid and off-grid to ensure power supply continuity, and how to improve overall economic efficiency through the coordinated management of photovoltaic-storage-charging systems. Summary of the Invention

[0005] The purpose of this invention is to provide a photovoltaic-storage-charging DC-flexible power supply system for use in service areas, in order to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a photovoltaic-storage-charging DC-DC flexible power supply system applied to service areas, comprising: a photovoltaic power generation unit, arranged on the rooftops of buildings, carports, or vacant land in the service area, for converting solar energy into DC power; an energy storage unit, including battery clusters, a battery management system, and an energy storage converter, for storing and releasing electrical energy; a charging unit, including at least one DC charging pile, for providing fast charging services for electric vehicles; and a flexible DC bus, serving as the core hub for power collection and distribution within the system, with a voltage level of 380V to 1500V DC. The voltage and energy management unit, as the control core of the system, communicates with the photovoltaic power generation unit, energy storage unit, and charging unit. The photovoltaic power generation unit is connected to the flexible DC bus via a combiner box and the DC side of the first DC / DC converter or integrated photovoltaic-energy storage inverter. The energy storage unit is connected to the flexible DC bus via the DC side of the energy storage converter. The charging unit is connected to the flexible DC bus via a second DC / DC converter. The system is connected to the external AC grid via at least one AC / DC converter to achieve grid-connected or off-grid operation.

[0007] Preferably, the energy management unit is configured to execute the following multi-mode flexible control strategy: based on real-time electricity price, photovoltaic power generation, and charging load demand, control the energy storage unit to charge during off-peak hours and discharge during peak hours to achieve peak shaving and valley filling; when photovoltaic power generation momentarily exceeds charging load demand, control the excess power to charge the energy storage unit or feed it into the grid through the AC / DC converter; when charging load demand surges and exceeds the sum of photovoltaic power generation and the grid's rated power supply capacity, control the energy storage unit and photovoltaic power generation unit to discharge together to support the fast charging demand of the charging unit and avoid excessive impact on the grid.

[0008] Preferably, the system further includes: a microgrid switching cabinet electrically connected between the AC / DC converter and the external AC power grid, and the local AC load served by the flexible DC bus; wherein, the energy management unit is communicatively connected to the microgrid switching cabinet and is configured to, upon detecting an external AC power grid fault, control the microgrid switching cabinet to disconnect from the power grid within milliseconds and put the system into off-grid operation mode, whereby the photovoltaic power generation unit and / or the energy storage unit supply power to the critical AC loads in the service area through the flexible DC bus and corresponding inverter equipment.

[0009] Preferably, the energy storage unit adopts a containerized integrated design, which integrates: multiple battery clusters with lithium iron phosphate cells as the core; the energy storage converter; a temperature control system that uses a combination of air conditioning and air ducts to precisely supply air to the battery clusters and maintain a consistent system temperature; and a fire protection system that uses a total flooding heptafluoropropane automatic fire extinguishing device and integrates a multi-parameter fire detection system with temperature, smoke and gas sensors.

[0010] Preferably, the energy management unit further includes a cloud platform and a remote monitoring module, which can perform the following functions through wired or wireless networks: real-time monitoring of the operating status, electrical parameters and fault information of the photovoltaic power generation unit, energy storage unit, charging unit and each converter; data statistics and analysis of the overall power generation, power consumption and carbon emission reduction of the system; and receiving and executing remote dispatch instructions from the operation center to adjust the system's operating strategy.

[0011] Preferably, the DC charging pile in the charging unit has a rated power of not less than 60kW, and at least one DC charging pile has a rated power of 150kW or more to support the rapid charging needs of electric vehicles.

[0012] Preferably, the system is further connected to the flexible DC bus to: a bidirectional AC / DC converter for bidirectional energy flow between the AC grid and the flexible DC bus; and a DC distribution cabinet for distributing the electrical energy on the flexible DC bus to different DC charging piles and DC loads within the service area.

[0013] Preferably, the photovoltaic power generation unit uses monocrystalline silicon double-glass high-efficiency battery modules with a conversion efficiency of not less than 20%, and the installation tilt angle is calculated based on the service area dimensions to achieve the maximum annual power generation.

[0014] Preferably, the system is configured to cover the entire highway service area, and the photovoltaic power generation units are preferentially arranged on the roof of the service area's main building, the parking lot canopy, and the sunny slopes of the interchange area, forming a distributed photovoltaic power generation network covering the entire service area.

[0015] Preferably, multiple systems can communicate and network through their respective energy management units to form a regional highway service area photovoltaic-storage-charging microgrid cluster, realizing energy mutual assistance and coordinated optimized operation among multiple service areas.

[0016] Preferably, the control method of the system includes the following steps: Real-time data acquisition step: acquiring the actual power generation of the photovoltaic power generation unit, the current state of charge of the energy storage unit, the total power demand of the charging unit, and the real-time electricity price and status of the external AC power grid; Operation mode decision step: based on the real-time data, determining the operation mode that the system should enter; Multi-mode flexible control step: when in peak shaving and valley filling mode, if the current period is a low-price period, controlling the energy storage unit to charge from the grid; if the current period is a high-price period, controlling the energy storage unit to discharge to the flexible DC bus, prioritizing the supply to the charging unit; when in photovoltaic priority mode... In the power supply mode, the photovoltaic power generation is prioritized for the charging unit, and the remaining power is used to charge the energy storage unit. If there is still a surplus, it is controlled to be inverted into AC power and fed into the grid. In the power support mode, if the instantaneous value of the total power demand of the charging unit exceeds the sum of the photovoltaic power generation and the grid's preset power supply capacity, the energy storage unit and the photovoltaic power generation unit are controlled to jointly discharge to the flexible DC bus to support the charging demand. In the off-grid emergency mode, if a grid fault is detected, the microgrid switching cabinet is controlled to disconnect from the grid, and the energy storage unit and / or the photovoltaic power generation unit are controlled to establish a stable off-grid microgrid to supply power to the critical loads in the service area.

[0017] Compared with existing technologies, the beneficial effects of this invention are as follows: By constructing an AC / DC hybrid microgrid architecture with a flexible DC bus as the core, this invention enables efficient coupling and direct distribution of DC power generated by photovoltaics, DC power stored in energy storage batteries, and DC power required by electric vehicles on the DC side, significantly reducing the energy loss caused by multiple AC / DC conversions in traditional systems; combined with a multi-mode flexible control strategy based on real-time electricity prices and load forecasting, the energy storage system is intelligently dispatched to perform peak shaving and valley filling, and priority is given to consuming local photovoltaic power generation, thereby effectively reducing the cost of purchasing electricity from the grid in the service area and achieving a dual improvement in energy efficiency and operational economy.

[0018] This invention uses an energy management unit to coordinate the control of photovoltaic, energy storage, and charging loads, which can smooth the fluctuations in photovoltaic power generation and utilize the rapid response characteristics of the energy storage system to provide instantaneous power support when charging load surges, effectively avoiding the impact of large-scale DC fast charging on the local power distribution network of the service area. At the same time, the system has millisecond-level and seamless off-grid switching capabilities. When the external power grid fails, it can quickly disconnect from the main grid to form an independently operating microgrid, continuously supplying power to electric vehicle charging piles and critical loads in the service area, greatly improving energy self-sufficiency and emergency response capabilities in extreme situations.

[0019] This invention designs the energy storage unit as a containerized integrated module, which highly integrates battery systems, temperature control, fire protection, and monitoring equipment. This not only saves space but also facilitates transportation and rapid deployment, improving engineering implementation efficiency and safety. Furthermore, through the cloud platform and remote monitoring module of the energy management unit, real-time perception, intelligent analysis, and remote operation and maintenance of the entire system's operating status are achieved. In addition, the system has good scalability; subsystems in multiple service areas can form a regional microgrid group through communication networking, realizing cross-regional energy sharing and coordinated optimized operation, laying a solid foundation for building a green and resilient smart energy network for highways. Attached Figure Description

[0020] Figure 1 is a block diagram of the overall system structure of the present invention; Figure 2 is a schematic diagram of the photovoltaic module unit connected to the flexible DC bus of the present invention; Figure 3 is a schematic diagram of the integrated structure of the energy storage unit of the present invention; Figure 4 is a schematic diagram of the connection between the flexible DC bus and the charging unit of the present invention; Figure 5 is a control structure diagram of the microgrid switching cabinet and the energy management unit of the present invention; Figure 6 is an electrical connection diagram of the battery cluster, energy storage converter and microgrid switching cabinet of the present invention; Figure 7 is a schematic diagram of the battery management system of the present invention; Figure 8 is a flowchart of the temperature control system of the present invention.

[0021] In the diagram: Photovoltaic power generation unit-1, energy storage unit-2, charging unit-3, flexible DC bus-4, energy management unit-5, AC / DC converter-6, microgrid switching cabinet-7, combiner box-11, first DC / DC converter or integrated photovoltaic-storage inverter-12, battery cluster-21, battery management system-22, energy storage converter-23, temperature control system-24, fire protection system-25, DC charging pile-31, second DC / DC converter-32, cloud platform and remote monitoring module-51. Detailed Implementation

[0022] To further explain the technical solution of the present invention, a detailed description is provided below through specific embodiments.

[0023] Please refer to Figures 1-8. This invention provides a photovoltaic-storage-charging-DC-flexible power supply system for service areas, including a photovoltaic power generation unit 1, an energy storage unit 2, a charging unit 3, a flexible DC bus 4, and an energy management unit 5. The photovoltaic power generation unit 1 uses monocrystalline silicon double-glass high-efficiency solar cell modules with a conversion efficiency of not less than 20%. The installation tilt angle is calculated based on the service area's dimensions to achieve maximum annual power generation. The photovoltaic power generation unit 1 is arranged on building rooftops, carport roofs, or vacant land in the service area to convert solar energy into DC power. The energy storage unit 2 includes a battery cluster 21 and battery tubes. The system includes a power management system 22 and an energy storage converter 23 for storing and releasing electrical energy; a charging unit 3, including at least one DC charging pile 31 for providing fast charging services for electric vehicles, wherein the rated power of the DC charging pile 31 is not less than 60kW, and at least one DC charging pile 31 has a rated power of 150kW or more to support the rapid charging needs of electric vehicles; a flexible DC bus 4, serving as the core hub for the collection and distribution of electrical energy within the system, with a DC voltage level of 380V to 1500V; and a DC distribution cabinet for distributing the electrical energy on the flexible DC bus 4. The system connects to different DC charging piles 31 and DC loads within the service area; the energy management unit 5, as the control core of the system, is communicatively connected to the photovoltaic power generation unit 1, the energy storage unit 2, and the charging unit 3; the microgrid switching cabinet 7 is electrically connected between the AC / DC converter 6 and the external AC grid, as well as the local AC loads served by the flexible DC bus 4; wherein, the photovoltaic power generation unit 1 is connected to the flexible DC bus 4 via the combiner box 11 and the DC side of the first DC / DC converter or the photovoltaic-energy storage integrated inverter 12; the energy storage unit 2 is connected to the flexible DC bus 4 via the DC side of the energy storage converter 23. Line 4; Charging unit 3 is connected to flexible DC bus 4 through second DC / DC converter 32; The system is connected to the external AC grid through at least one AC / DC converter 6 to achieve grid-connected or off-grid operation; Energy management unit 5 is communicatively connected to microgrid switching cabinet 7 and is configured to control microgrid switching cabinet 7 to disconnect from the grid within milliseconds when an external AC grid fault is detected, and to put the system into off-grid operation mode, where photovoltaic power generation unit 1 and / or energy storage unit 2 supply power to the critical AC loads in the service area through flexible DC bus 4 and corresponding inverter equipment.

[0024] Among them, the energy management unit 5 is configured to execute the following multi-mode flexible control strategy: (1) According to the real-time electricity price, photovoltaic power generation and charging load demand, control the energy storage unit 2 to charge during the electricity price valley period and discharge during the electricity price peak period to achieve peak shaving and valley filling; (2) When the photovoltaic power generation instantaneously exceeds the charging load demand, control the excess power to charge the energy storage unit 2 or feed it into the grid through the AC / DC converter 6; (3) When the charging load demand surges and exceeds the sum of the photovoltaic power generation and the grid's rated power supply capacity, control the energy storage unit 2 and the photovoltaic power generation unit 1 to discharge together to jointly support the fast charging demand of the charging unit and avoid causing excessive impact on the grid.

[0025] Among them, the energy storage unit 2 adopts a container-type integrated design, which integrates multiple battery clusters 21 with lithium iron phosphate cells as the core; energy storage converter 23; temperature control system 24, which uses a combination of air conditioning and air duct to accurately supply air to the battery clusters 21 and maintain the system temperature consistency; and fire protection system 25, which adopts a total flooding heptafluoropropane automatic fire extinguishing device and integrates a multi-parameter fire detection system with temperature, smoke and gas sensors.

[0026] The energy management unit 5 further includes a cloud platform and a remote monitoring module 51, which can perform the following functions through wired or wireless networks: real-time monitoring of the operating status, electrical parameters and fault information of the photovoltaic power generation unit 1, energy storage unit 2, charging unit 3 and each converter; data statistics and analysis of the overall power generation, power consumption and carbon emission reduction of the system; and receiving and executing remote dispatch instructions from the operation center to adjust the system's operating strategy.

[0027] The system is configured to cover the entire highway service area. Photovoltaic power generation units 1 are preferentially arranged on the roof of the service area's main building, the parking lot canopy, and the sunny slopes of the interchange area, forming a distributed photovoltaic power generation network covering the entire service area. Furthermore, multiple systems can communicate and network through their respective energy management units 5 to form a regional highway service area photovoltaic-storage-charging microgrid group, realizing energy mutual assistance and coordinated optimized operation among multiple service areas.

[0028] The system control method includes the following steps: Real-time data acquisition step: acquiring the actual power generation of photovoltaic power generation unit 1, the current state of charge of energy storage unit 2, the total power demand of charging unit 3, and the real-time electricity price and status of the external AC grid; Operation mode decision step: determining the operation mode the system should enter based on real-time data; Multi-mode flexible control step: when in peak shaving and valley filling mode, if the current electricity price is in a valley period, controlling energy storage unit 2 to charge from the grid; if the current electricity price is in a peak period, controlling energy storage unit 2 to discharge to flexible DC bus 4, prioritizing supply to charging unit 3; when in photovoltaic priority mode, controlling... The photovoltaic power generation is prioritized for charging unit 3, and the remaining power is used to charge energy storage unit 2. If there is still surplus power, it is controlled to be inverted into AC power and fed into the grid. When in power support mode, if the instantaneous value of the total power demand of charging unit 3 exceeds the sum of photovoltaic power generation and the grid's preset power supply capacity, the energy storage unit 2 and photovoltaic power generation unit 1 are controlled to discharge together to the flexible DC bus 4 to jointly support the charging demand. When in off-grid emergency mode, if a grid fault is detected, the microgrid switching cabinet 7 is controlled to disconnect from the grid, and the energy storage unit 2 and / or photovoltaic power generation unit 1 are controlled to establish a stable off-grid microgrid to supply power to the critical loads in the service area.

[0029] Example 1: This example provides a typical power supply system for a highway service area, which combines photovoltaic, energy storage, charging, direct current, and flexible power supply.

[0030] 1. System Architecture and Connections: The physical core of the system is a flexible DC bus, which in this embodiment is set to 750V DC. This flexible DC bus serves as a common connection point and integrates the following units: Photovoltaic Power Generation Unit: A total of 500kWp of monocrystalline silicon double-glass high-efficiency modules (conversion efficiency ≥20%) are installed on the roof of the service area's main building and the parking lot canopy. The installation tilt angle is optimized according to the local latitude (e.g., Bengbu area) to achieve the maximum annual power generation. The photovoltaic array is connected to the 750V DC bus after its voltage is boosted by a first DC / DC converter (or photovoltaic controller). The DC / DC converter has maximum power point tracking (MPPT) functionality to maximize photovoltaic power generation efficiency.

[0031] Energy storage unit: Utilizing a standard 20-foot shipping container, it integrates a 500kWh rated energy storage system. This system consists of a battery cluster composed of multiple lithium iron phosphate cells, a battery management system, a 250kW energy storage converter, and supporting temperature control and fire suppression systems. The DC side of the energy storage converter is directly connected to the 750V DC bus.

[0032] Charging Unit: Equipped with four DC charging stations, two of which are 60kW and two are 150kW, to meet the rapid charging needs of different vehicles. Each charging station draws power from the DC bus through a second DC / DC converter, which converts the bus voltage to a voltage range suitable for charging electric vehicle batteries.

[0033] Grid Interaction Unit: The system is connected to the low-voltage side (AC 400V) of a 10kV / 0.4kV transformer via a 315kW bidirectional AC / DC converter. This converter is a key device for achieving grid-connected and off-grid operation, responsible for bidirectional energy flow between the AC grid and the DC bus.

[0034] Energy Management Unit: As the system brain, it interacts with photovoltaic controllers, energy storage BMS, energy storage converters, charging piles, and bidirectional AC / DC converters in real time through communication methods such as CAN bus and Ethernet.

[0035] Microgrid switching cabinet: Installed between the bidirectional AC / DC converter and the grid connection point, it receives instructions from the energy management unit to achieve rapid grid-connected and off-grid switching.

[0036] 2. Operating Mode and Flexible Control Strategy: The energy management unit dynamically schedules system operation according to preset strategies: Normal economic operation mode: During off-peak electricity price periods at night (e.g., 22:00-8:00 the next day), the energy storage unit is controlled to charge from the grid; during peak electricity price periods during the day (e.g., 9:00-12:00, 17:00-22:00), the energy storage unit is controlled to discharge to the DC bus, prioritizing the use of charging piles and profiting from the price difference.

[0037] Photovoltaic priority mode: During the day, photovoltaic power generation is used first. Photovoltaic electricity first meets the immediate needs of charging piles, and any surplus is used to charge energy storage units. If the energy storage is full and there is still a surplus, it is inverted into AC power through a bidirectional AC / DC converter and fed into the grid.

[0038] Power support mode: When multiple high-power charging piles start up at the same time, and the instantaneous power demand exceeds the supply capacity of the grid and photovoltaic, the energy management unit immediately instructs the energy storage unit to discharge together with the photovoltaic to jointly support the DC bus voltage, ensuring that the charging power is uninterrupted, while avoiding drawing huge peak power from the grid.

[0039] Off-grid emergency mode: When the energy management unit detects a disappearance or abnormality in the grid voltage through the bidirectional AC / DC converter, it immediately sends a trip command to the microgrid switching cabinet to disconnect from the grid. Subsequently, the system enters off-grid mode, where the energy storage converter establishes a stable 750V DC bus voltage and 50Hz AC voltage (through an internal or external inverter). Photovoltaics and energy storage work together to power charging piles and critical AC loads (such as emergency lighting, toll collection systems, convenience store freezers, etc.) in the service area.

[0040] 3. Key Equipment Implementation: Energy Storage Unit: Inside the container, three clusters of lithium iron phosphate batteries are arranged in separate sections on the battery rack. A temperature-controlled ventilation duct is installed at the top to ensure air circulation and uniform temperature around each battery cluster. The container is equipped with a fire suppression system, employing a heptafluoropropane total flooding design, and features temperature, smoke, and CO gas sensors to provide early warning of battery thermal runaway and perform multi-parameter composite judgments, ensuring safety.

[0041] Energy Management Unit: Its cloud platform can display real-time data such as system power generation, energy storage SOC, charging volume, and carbon emission reduction, and generate operation reports. Maintenance personnel can remotely view the system status via mobile APP or computer and receive fault alarm information, realizing unattended operation and intelligent maintenance.

[0042] Example 2: Based on Example 1, this example further expands the application scope of the system. The system of this invention in multiple service areas along the route (such as Service Area A, Service Area B, and Service Area C) is interconnected through their respective energy management units to form a regional highway service area photovoltaic-storage-charging microgrid cluster.

[0043] The higher-level energy management unit can perform cross-regional collaborative optimization based on the photovoltaic power generation status, energy storage status, and charging load forecasts of each service area. For example, when service area A has surplus photovoltaic power while service area B has high charging demand, service area A can be instructed to reduce surplus power fed into the grid, and service area B's energy storage system can be instructed to prepare for discharge. This achieves macro-level energy mutual assistance and balance between regions, further improving the economy and reliability of the entire road network energy system.

[0044] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A photovoltaic-storage-charging DC-flexible power supply system applied in service areas, characterized in that, include: A photovoltaic power generation unit (1) is arranged on the rooftops of buildings, carports, or vacant land in the service area to convert solar energy into DC power. An energy storage unit (2) includes a battery cluster (21), a battery management system (22), and an energy storage converter (23) for storing and releasing electrical energy. A charging unit (3) includes at least one DC charging pile (31) for providing fast charging services for electric vehicles. A flexible DC bus (4) serves as the core hub for collecting and distributing electrical energy within the system, with a DC voltage level of 380V to 1500V. An energy management unit (5) serves as the control core of the system and is communicatively connected to the photovoltaic power generation unit. The system comprises a power generation unit (1), an energy storage unit (2), and a charging unit (3); wherein the photovoltaic power generation unit (1) is connected to the flexible DC bus (4) via a combiner box (11) and the DC side of the first DC / DC converter or the photovoltaic-energy storage integrated inverter (12); the energy storage unit (2) is connected to the flexible DC bus (4) via the DC side of the energy storage converter (23); the charging unit (3) is connected to the flexible DC bus (4) via the second DC / DC converter (32); the system is connected to the external AC grid via at least one AC / DC converter (6) to achieve grid-connected or off-grid operation.

2. The photovoltaic-storage-charging DC-flexible power supply system applied to service areas according to claim 1, characterized in that, The energy management unit (5) is configured to execute the following multi-mode flexible control strategy: based on the real-time electricity price, photovoltaic power generation and charging load demand, the energy storage unit (2) is controlled to charge during the off-peak period and discharge during the peak period to achieve peak shaving and valley filling; when the photovoltaic power generation instantaneously exceeds the charging load demand, the excess power is controlled to charge the energy storage unit (2) or fed into the grid through the AC / DC converter (6); when the charging load demand surges and exceeds the sum of the photovoltaic power generation and the grid's rated power supply capacity, the energy storage unit (2) and the photovoltaic power generation unit (1) are controlled to discharge together to jointly support the fast charging demand of the charging unit (3) and avoid causing excessive impact on the grid.

3. The photovoltaic-storage-charging DC-flexible power supply system applied to service areas according to claim 1, characterized in that, The system also includes: a microgrid switching cabinet (7), electrically connected between the AC / DC converter (6) and the external AC grid, and the local AC load served by the flexible DC bus (4); wherein, the energy management unit (5) is communicatively connected to the microgrid switching cabinet (7) and is configured to control the microgrid switching cabinet (7) to disconnect from the grid within milliseconds when an external AC grid fault is detected, and to put the system into off-grid operation mode, so that the photovoltaic power generation unit (1) and / or the energy storage unit (2) supply power to the critical AC loads in the service area through the flexible DC bus (4) and the corresponding inverter equipment.

4. The photovoltaic-storage-charging DC-flexible power supply system applied to service areas according to claim 1, characterized in that: The energy storage unit (2) adopts a container-type integrated design and integrates: multiple battery clusters (21) with lithium iron phosphate cells as the core; the energy storage converter (23); the temperature control system (24), which uses a combination of air conditioning and air ducts to accurately supply air to the battery clusters (21) and maintain the system temperature consistency; and the fire protection system (25), which adopts a total flooding type heptafluoropropane automatic fire extinguishing device and integrates a multi-parameter fire detection system with temperature, smoke and gas sensors.

5. The photovoltaic-storage-charging DC-flexible power supply system applied to service areas according to claim 1, characterized in that, The energy management unit (5) further includes a cloud platform and a remote monitoring module (51), which can perform the following functions through wired or wireless networks: real-time monitoring of the operating status, electrical parameters and fault information of the photovoltaic power generation unit (1), energy storage unit (2), charging unit (3) and each converter; data statistics and analysis of the overall power generation, power consumption and carbon emission reduction of the system; receiving and executing remote dispatch instructions from the operation center and adjusting the system's operating strategy.

6. The photovoltaic-storage-charging DC-flexible power supply system applied to service areas according to claim 1, characterized in that: The DC charging pile (31) in the charging unit (3) has a rated power of not less than 60kW, and at least one DC charging pile (31) has a rated power of 150kW or more to support the rapid charging needs of electric vehicles.

7. The photovoltaic-storage-charging DC-flexible power supply system applied to service areas according to claim 1, characterized in that, The system is also connected to the flexible DC bus (4) with: a bidirectional AC / DC converter (6) for bidirectional energy flow between the AC grid and the flexible DC bus (4); and a DC distribution cabinet for distributing the electrical energy on the flexible DC bus to different DC charging piles and DC loads in the service area.

8. The photovoltaic-storage-charging DC-flexible power supply system applied to service areas according to claim 1, characterized in that: The photovoltaic power generation unit (1) uses a monocrystalline silicon double-glass high-efficiency battery module with a conversion efficiency of not less than 20%. The installation tilt angle is calculated based on the service area dimension to achieve the maximum annual power generation.

9. The photovoltaic-storage-charging DC-flexible power supply system applied to service areas according to claim 1, characterized in that: The system is configured to cover the entire highway service area, and the photovoltaic power generation units (1) are preferentially arranged on the roof of the service area building, the parking lot canopy, and the sunny slope of the interchange area to form a distributed photovoltaic power generation network covering the entire service area.

10. The photovoltaic-storage-charging DC-flexible power supply system applied to a service area according to any one of claims 1 to 9, characterized in that: Multiple systems can communicate and network through their respective energy management units (5) to form a regional highway service area photovoltaic-storage-charging microgrid group, realizing energy mutual assistance and coordinated optimized operation among multiple service areas.

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