5 points for attention when choosing solar inverter

1. It should have sufficient rated output capacity and load capacity. The selection of solar inverters must first consider having sufficient rated capacity to meet the electrical power requirements of the equipment under maximum load. For solar inverters with a single device as the load, the selection of the rated capacity is relatively simple. When the electrical equipment is a purely resistive load or the power factor is greater than 0.9, the rated capacity of the solar inverter is selected as the capacity of the electrical equipment 1.1 to 1.15 times. Some margin should be reserved and cannot be loaded at full load; when the electrical equipment is an inductive load (such as air conditioner, motor, motor, etc.), the starting impact power of the inductive load should be considered, calculated at the maximum value, and it should be understood at the time of purchase The actual load capacity of the inverter manufacturer; when the inverter is loaded with multiple devices, the selection of the inverter capacity should consider the possibility of several electrical equipment working at the same time, that is, the “load simultaneous coefficient”.

2. It should have high voltage stability. In off-grid photovoltaic power generation systems, batteries are used as energy storage devices. When the battery with a nominal voltage of 12V is in a floating charge state, the terminal voltage can reach 13.5V, and the short-term overcharge state can reach more than 15V. The terminal voltage can be reduced to 10V or lower when the battery is discharged under load. The fluctuation of the battery terminal voltage can reach about 30% of the nominal voltage. This requires that the solar inverter has a good voltage regulation performance in order to ensure that the photovoltaic power generation system is powered by a stable AC voltage.

3. High efficiency or higher efficiency under various loads. The high efficiency of the whole machine is a distinguishing feature of the inverter for photovoltaic power generation which is different from the universal inverter. The actual efficiency of the 5kW class universal inverter is only 70% to 80%. When it is used in a photovoltaic power generation system, it will bring about 20% to 30% of the total power loss. Therefore, special inverters for photovoltaic power generation systems should pay special attention to reduce their own power losses and improve the overall efficiency. Therefore, this is an important measure to improve the technical and economic indicators of the photovoltaic power generation system. In terms of overall efficiency, the requirements for photovoltaic power inverters are as follows: rated load efficiency of inverters below kW level is more than 88%, low load efficiency ≥85%; rated load efficiency of 10kW inverters is ≥85%%, low Load efficiency ≥80%.

4. It should have good overcurrent protection and short circuit protection. During the normal operation of the photovoltaic power generation system, overcurrent or short circuit of the power supply system due to load failure, personnel misoperation and external interference are completely possible. Solar inverters are most sensitive to overcurrent and short-circuit phenomena in external circuits, and are the weak link in photovoltaic power generation systems. Therefore, when choosing a solar inverter, it is required to have a good self-protection function against overcurrent and short circuit.

5. Easy maintenance. After several years of operation, a high-quality inverter will fail due to component failure, which should be normal. In addition to the inverter manufacturer’s need for a good after-sales service system, the inverter manufacturer is also required to have good maintainability in terms of inverter production process, structure and component selection. For example, damaged components have sufficient spare parts or are easy to buy, and the interchangeability of the components is good; in the process structure, the components are easy to disassemble and replace.