Photovoltaic power generation systems can be divided into grid-connected photovoltaic power generation systems and stand-alone photovoltaic power generation systems depending on whether they are connected to the grid. Grid-connected photovoltaic power generation system mainly refers to photovoltaic systems that are connected to the grid and are subject to grid dispatching, such as various centralized or distributed photovoltaic power plants. The independent photovoltaic power generation system mainly refers to various photovoltaic power generation systems that are independent of the grid operation, such as solar street lamps and rural household photovoltaic power sources.
As an effective way to store electric energy, energy storage system can be divided into four types: mechanical energy storage, battery energy storage, electromagnetic energy storage and phase change energy storage. Among them, mechanical energy storage, such as pumped water storage, is widely used. As a new type of mechanical energy storage, flywheel energy storage is currently in the research and demonstration stage. Electromagnetic energy storage includes superconducting energy storage, supercapacitor energy storage, and high energy density capacitor energy storage. Thermal energy storage is the storage or release of energy through phase change of materials. Domestic related research is in the laboratory stage and has not been applied in practice. Battery energy storage technology is a technology that is mature in technology, widely used, and low in cost. The independent photovoltaic power generation products with lead-acid batteries as energy storage devices have been commercialized. In recent years, with the development of lithium battery technology and the reduction of cost, energy storage devices constructed with lithium batteries are currently the research hotspot.