1. With countercurrent grid-connected photovoltaic power generation system
A countercurrent grid-connected photovoltaic power generation system is shown in Figure 1. When the power generated by the photovoltaic power generation system is sufficient, the surplus power can be fed into the public grid and sent to the grid (selling power); when the power provided by the photovoltaic power generation system is insufficient, the grid will supply power to the load (buying power). Since this system is in the opposite direction when it sends power to the grid and when it is powered by the grid, it is called a countercurrent grid-connected photovoltaic power generation system.
2. Grid-connected photovoltaic power generation system without countercurrent
The grid-connected photovoltaic power generation system without countercurrent is shown in Figure 2. The grid-connected photovoltaic power generation system without countercurrent does not supply power to the public grid even when power generation is abundant, but when the photovoltaic system is insufficient, the public grid will supply power to the load.
3. Grid-connected photovoltaic power generation system with energy storage device
The grid-connected photovoltaic power generation system with energy storage devices is shown in Figure 3, which is to configure energy storage devices in the above-mentioned two grid-connected photovoltaic power generation systems as required. Photovoltaic power generation systems with energy storage devices are more proactive, and can operate independently and supply power to the load normally when there is a power outage, power limitation, or failure in the power grid. Therefore, the grid-connected photovoltaic power generation system with energy storage device can be used as a power supply system for important places such as emergency communication power supply, medical equipment, gas stations, refuge indication and lighting, or emergency loads. At the same time, grid-connected photovoltaic power generation with energy storage systems is of great significance to reduce grid impacts, cut peaks and fill valleys, improve user photovoltaic power utilization, and establish smart micro-grids. Photovoltaic + energy storage will also become the only way to expand the application of photovoltaic power generation in the future.
4. Large-scale grid-connected photovoltaic power generation system
The large-scale grid-connected photovoltaic power generation system is composed of several grid-connected photovoltaic power generation units. Each photovoltaic power generation unit converts the direct current generated by the solar cell array into 380V alternating current through the photovoltaic grid-connected inverter, and then becomes 10kV alternating high voltage through the boost system, and then sends it to the 35kV substation system, and then merges it into 35kV. AC high-voltage power grid. The 35kV AC high-voltage power is transformed into 380~400V AC power after the step-down system as the backup power source of the power station.
5. Distributed smart grid photovoltaic power generation system
The distributed smart grid photovoltaic power generation system is shown in Figure 4. The power generation system uses the charge and discharge control technology and electric energy storage technology in the off-grid photovoltaic power generation system to overcome the shortcomings of the pure grid-connected photovoltaic power generation system that is affected by natural environmental conditions, such as unstable output voltage and serious impact on the grid, and can partially increase photovoltaic power. Spontaneous consumption and online sales of power generation users. In addition, the difference in energy storage and power consumption and time differences in the respective systems can enable users to be integrated into the grid at different time periods, further reducing the impact on the grid.
Each unit in the system is a grid-connected photovoltaic power generation system with an energy storage device, which can realize automatic switching of photovoltaic grid-connected power generation and off-grid power generation, ensuring the reliability of photovoltaic grid-connected power generation and power supply, and alleviating photovoltaic power generation. The start-stop operation of the grid-connected power generation system has an impact on the public grid, increasing the self-generated and self-consumption of users’ electricity.
Distributed smart grid photovoltaic power generation system is the trend and direction of grid-connected photovoltaic power generation applications in the future, and its main advantages are as follows.
① Reduce the impact on the grid, stabilize the grid voltage, and offset the power consumption during peak hours.
② Increase the user’s self-sufficient consumption or sales of electricity.
③ It can operate independently when the power grid fails to solve the normal power supply of the coverage area.
④ Ensure and increase the proportion and position of photovoltaic power generation in the entire energy system.