Photovoltaic off-grid inverter solar power generation system

Photovoltaic off-grid power generation system is mainly composed of six parts: solar module, bracket, solar controller, off-grid inverter, battery and distribution box. After the solar module is connected to the solar controller, the user's load is first satisfied, and then the remaining electrical energy is stored in the battery for night and rainy days. When the battery is dead, most inverters can also support a commercial power input (or a diesel generator) as a supplemental energy source to power the load.

The design of photovoltaic off-grid system is different from that of grid-connected power generation system. It needs to consider the user's load size, daily power consumption, local climate conditions and other factors. It is relatively complicated to choose different design schemes according to the actual needs of customers. In order to ensure the reliable operation of the off-grid system, it is necessary to do a preliminary customer demand survey. The design of photovoltaic off-grid system mainly includes inverter selection, module capacity design and battery capacity design.

First, inverter selection: according to the size and type of user load to determine the inverter power

The choice of inverter power is generally not less than the total power of the load, but considering the service life of the inverter and subsequent expansion, it is recommended to reserve a certain margin for the inverter power, generally 1.2 to 1.5 times the load power. In addition, if the load contains a motor induction load similar to that of a refrigerator, air conditioner, water pump, range hood, etc. (the starting power of the motor is 3 to 5 times the rated power). The starting power of the load should be considered, that is, the starting power of the load should be less than the maximum impact power of the inverter. The following is the calculation formula of inverter power selection for design reference.

Second, component capacity determination: according to the user's daily electricity consumption and light intensity to determine the component capacity

Part of the electricity generated by the PV modules during the day is supplied to the load, while the rest is used to charge the battery. At night or in the case of insufficient solar radiation, the electrical energy stored in the battery will be released to the load for use. It can be seen that the electricity consumed by the load comes from the electricity generated by the PV module during the day without commercial power/or diesel engines as supplementary energy. Taking into account the different light intensity in different seasons in different regions, in order to ensure the reliable operation of the system, the capacity design of photovoltaic panels should also meet the needs of the worst light season. The following is the capacity calculation formula for photovoltaic panels:

Third, determine the battery capacity: Determine the battery capacity according to the night power consumption or backup time

The battery of the photovoltaic off-grid system is mainly used for energy storage to ensure that the load can still work normally when the solar radiation is insufficient. For photovoltaic off-grid systems with significant loads, the design of battery capacity needs to take into account the local maximum rainy day. Ordinary photovoltaic off-grid systems do not require high-load power supplies. Considering the cost of the system, the use of the load can be adjusted according to the actual light intensity rather than rainy days.