According to different applications, solar photovoltaic power generation systems are generally divided into five types: grid-connected power generation system, off-grid power generation system and off-grid energy storage system, grid-connected energy storage system and multi-energy hybrid microgrid system.
1: Grid-connected PV power generation system
Photovoltaic grid-connected system consists of photovoltaic module, photovoltaic grid-connected inverter, photovoltaic meter load, bidirectional meter, grid-connected cabinet and power grid. Photovoltaic module generates direct current from illumination and converts it into alternating current through inverter to supply load and send it into power grid. Grid-connected photovoltaic system mainly has two Internet access modes, one is "spontaneous self-use, surplus electricity to connect to the Internet" and the other is "full Internet access".
Generally, distributed photovoltaic power generation systems mainly adopt the mode of "spontaneous self-use, surplus electricity to connect to the Internet". The electricity generated by solar cells is preferentially given to the load. When the load is not used up, the surplus electricity is sent to the power grid. When the power supply to the load is insufficient, the power grid and photovoltaic system can supply power to the load at the same time.
2: Off-grid PV power generation system
Off-grid photovoltaic power generation system does not depend on the power grid and operates independently. Generally, it is applied to island communication base stations and street lamps in remote mountainous areas without electricity The system is generally composed of photovoltaic module, solar controller, inverter, battery load and so on. The off-grid power generation system converts solar energy into electric energy under the condition of illumination, and supplies power to the load and charges the battery through the solar energy control inverter integrated machine; When there is no illumination, the battery supplies power to the AC load through the inverter. It is very practical for areas without power grid or areas with frequent power outages.
3: Off-grid photovoltaic energy storage system
Off-grid photovoltaic power generation system is widely used in frequent power outages or photovoltaic spontaneous self-use can not use surplus electricity to connect the Internet, and the on-grid self-use electricity price is much more expensive than the on-grid electricity price, and the peak electricity price is much more expensive than the trough electricity price.
The system is composed of photovoltaic module, solar energy and off-grid integrated machine, battery load, etc. The photovoltaic array converts solar energy into electric energy under the condition of illumination, and supplies power to the load and charges the battery through the solar energy control inverter integrated machine; When there is no illumination, the battery supplies power to the solar controlled inverter integrated machine and then supplies power to the AC load.
Compared with the grid-connected power generation system, the system adds a charge-discharge controller and a battery. When the power grid is cut off, the photovoltaic system can continue to work, and the inverter can switch to the off-grid working mode to supply power to the load.
4: Grid-connected energy storage photovoltaic power generation system
Grid-connected energy storage photovoltaic power generation system can store redundant power generation and increase the proportion of spontaneous self-use. The system consists of photovoltaic module, solar controller, battery, grid-connected inverter, current detection device, load and so on. When the solar power is less than the load power, the system is powered by solar energy and the power grid together. When the solar power is greater than the load power, part of the solar energy supplies power to the load and part stores the inexhaustible electricity through the controller.
5: Micro-grid system
Microgrid is a new type of network structure, which is composed of distributed power, load, energy storage system and control device. Dispersed energy can be converted into electric energy locally and then supplied to local load nearby. Microgrid is an autonomous system that can realize self-control, protection and management. It can be connected with the external grid or run in isolation.
Microgrid is the effective combination of various types of distributed power sources to achieve multiple energy complementarity and improve energy utilization rate. It can fully promote the large-scale access of distributed generation and renewable energy, and realize the high reliable supply of various energy forms to the load. It is an effective way to realize the active distribution network and the transition from traditional power grid to smart grid.
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