In some remote areas, because the power grid cannot be covered, people will build small off-grid PV power stations. However, most PV power generation equipment (including home roof PV power generation) needs to be connected to the huge national grid through grid-connected equipment.

　　The grid-connected PV power generation system generally consists of PV arrays, energy storage systems, grid-connected inverters, controllers and integrated relay protection devices.

　　Since PV power generation is greatly affected by external factors such as light and temperature, the energy storage system will ensure the stable and continuous output of the PV power generation system.

　　The inverter converts the electrical energy generated by the PV cell into a sinusoidal current and merges it into the power grid.

　　The function of the controller is to track the maximum power point, control the waveform and power of the current, and generally it is integrated in the inverter.

　　The relay protection system can ensure the safety of the PV system and the power grid.

　　In the system, the inverter plays a pivotal role. It is a key device for energy conversion and is also responsible for the important task of controlling the Maximum Power Point Tracking (MPPT) of PV cells. Its safety, reliability, inverter efficiency, manufacturing cost and other properties have a huge impact on the normal operation and profit of the power generation system.

　　PV grid-connected inverters have different characteristics from ordinary inverters, mainly as follows:

　　A: High efficiency

　　Too low efficiency will lead to an increase in the number of PV cell modules in the matrix and the area occupied by the matrix, thereby greatly increasing the investment cost. Generally, the efficiency requirements for inverters are >90% for inverters below 10kVA, and >95% for inverters above 10kVA.

　　B: High reliability

　　At present, PV power generation systems are mainly used in remote areas, and many power stations are unattended and maintained. This requires the inverter to have a reasonable circuit structure, strict component selection, and various protection functions.

　　C: Wide range of adaptation to the input voltage

　　Since the terminal voltage of the PV cell changes with the load and the intensity of sunlight, which requires that the inverter must ensure normal operation within a larger DC input voltage range and ensure the stability of the AC output voltage.

　　D: Output qualified sine wave current

　　In order to avoid power pollution to the public grid, the inverter is required to output a sine wave current with high power factor.

　　E: Small electromagnetic interference

　　The electromagnetic interference of the inverter should be small enough, it does not affect people's living environment, nor hinder the normal operation of other electrical appliances.

　　Lithium-ion battery (LIB) has become the main energy storage solution in modern social life. Among them, lithium iron phosphate batteries are a perfect replacement for lead-acid batteries, and they are the first choice for grid-connected peak shaving, off-grid energy storage, PV energy storage, UPS, data center and other industries.

　　Solar power generation system with lithium battery energy storage system is a very promising clean energy.