Integrated photovoltaic, energy storage and charging energy system solution

Our integrated photovoltaic, energy storage, and charging energy system solution attempts to intelligently address the range anxiety of electric vehicles by combining ev charging piles, photovoltaics, and battery energy storage technologies. It promotes green travel for electric vehicles through photovoltaic new energy, while supporting energy storage alleviates grid pressure caused by heavy loads. It completes the battery industry chain through tiered utilization, ensuring the healthy development of the industry. The construction of this integrated energy system promotes the electrification and intelligent development of the industry, enabling the conversion of clean energy, such as solar energy, into electrical energy through photovoltaics and storing it in batteries. Electric vehicle charging piles then transfer this electrical energy from the batteries to the electric vehicles, solving the charging problem.

I. Topology of Photovoltaic-Storage-Charging Microgrid System

As shown in the diagram above, the main equipment of the integrated photovoltaic, energy storage, and charging microgrid system topology is described below:

1. Off-grid energy storage converter: The AC side of a 250kW converter is connected in parallel to a 380V AC bus, and the DC side is connected in parallel to four 50kW bidirectional DC/DC converters, enabling bidirectional energy flow, i.e., battery charging and discharging.

2. Bidirectional DC/DC converters: The high-voltage side of four 50kW DC/DC converters is connected to the DC terminal of the converter, and the low-voltage side is connected to the power battery pack. Each DC/DC converter is connected to one battery pack.

3. Power battery system: Sixteen 3.6V/100Ah cells (1P16S) constitute one battery module (57.6V/100Ah, nominal capacity 5.76KWh). Twelve battery modules are connected in series to form a battery cluster (691.2V/100Ah, nominal capacity 69.12KWh). The battery cluster is connected to the low-voltage terminal of the bidirectional DC/DC converter. The battery system comprises four battery clusters with a nominal capacity of 276.48 kWh.

4. MPPT Module: The high-voltage side of the MPPT module is connected in parallel to the 750V DC bus, while the low-voltage side is connected to the photovoltaic array. The photovoltaic array consists of six strings, each containing 18 275Wp modules connected in series, for a total of 108 photovoltaic modules and a total power output of 29.7 kWp.

5. Charging Stations: The system includes three 60kW dc ev charging stations (the number and power of charging stations can be adjusted based on traffic flow and daily energy demand). The AC side of the charging stations is connected to the AC bus and can be powered by photovoltaics, energy storage, and the grid.

6. EMS & MGCC: These systems perform functions such as charging and discharging control of the energy storage system and monitoring of battery SOC information according to instructions from the higher-level dispatch center.

II. Characteristics of Integrated Photovoltaic-Storage-Charging Energy Systems

1. The system adopts a three-layer control architecture: the top layer is the energy management system, the middle layer is the central control system, and the bottom layer is the equipment layer. The system integrates quantity conversion devices, related load monitoring and protection devices, making it an autonomous system capable of self-control, protection, and management.

2. The energy dispatch strategy of the energy storage system is flexibly adjusted/set based on the peak, valley, and flat-peak electricity prices of the power grid and the SOC (or terminal voltage) of the energy storage batteries. The system accepts dispatch from the energy management system (EMS) for intelligent charging and discharging control.

3. The system possesses comprehensive communication, monitoring, management, control, early warning, and protection functions, ensuring continuous and safe operation over long periods. The system’s operating status can be monitored via a host computer, and it has rich data analysis capabilities.

4. The battery management system (BMS) communicates with the energy management system (EMS), uploading battery pack information and, in cooperation with the EMS and PCS, achieving monitoring and protection functions for the battery pack.

The project uses a tower-type energy storage converter PCS, which integrates on-grid and off-grid switching devices and distribution cabinets. It has the function of seamless switching between on-grid and off-grid in zero seconds, supports two charging modes: on-grid constant current and constant power, and accepts real-time scheduling from the host computer.

III. Control and Management of Photovoltaic Storage and Charging System

The system control adopts a three-level architecture: EMS is the top scheduling layer, system controller is the intermediate coordination layer, and DC-DC and charging piles are the equipment layer.

The EMS and system controller are key components, working together to manage and schedule the photovoltaic-storage-charging system:

1. EMS Functions

1) Energy dispatch control strategies can be flexibly adjusted and the energy storage charging and discharging modes and power commands can be set according to the local grid’s peak-valley-flat period electricity prices.

2) The EMS performs real-time telemetry and remote signaling safety monitoring of the main equipment within the system, including but not limited to PCS, BMS, photovoltaic inverters, and charging piles, and manages alarm events reported by the equipment and historical data storage in a unified manner.

3) The EMS can upload system prediction data and calculation analysis results to the upper-level dispatch center or remote communication server via Ethernet or 4G communication, and receive dispatch instructions in real time, responding to AGC frequency regulation, peak shaving, and other dispatching to meet the needs of the power system.

4) The EMS achieves linkage control with the environmental monitoring and fire protection systems: ensuring that all equipment is shut down before a fire occurs, issuing alarms and audible and visual alarms, and uploading alarm events to the backend.

2. System Controller Functions:

1) The system coordinating controller receives scheduling strategies from the EMS: charge/discharge modes and power scheduling commands. Based on the SOC capacity of the energy storage battery, battery charge/discharge status, photovoltaic power generation, and charging pile usage, it flexibly adjusts bus management. By managing the charging and discharging of the DC-DC converter, it achieves charge/discharge control of the energy storage battery, maximizing the utilization of the energy storage system.

2) Combining the DC-DC charge/discharge mode and the electric car charging pile charging status, it needs to adjust the power limiting of the photovoltaic inverter and the PV module power generation. It also needs to adjust the PV module operating mode and manage the system bus.

3. Equipment Layer – DC-DC Functions:

1) Power actuator, realizing the mutual conversion between solar energy and electrochemical energy storage.

2) The DC-DC converter obtains the BMS status and, combined with the system controller’s scheduling commands, performs DC cluster control to ensure battery consistency.

3) It can achieve self-management, control, and protection according to predetermined goals.

—THE END—