Solar inverter is a main device and important part of PV on grid power system. In order to ensure the normal operation of the solar PV grid tie system, the correct configuration and selection of solar inverters are particularly important. For the configuration of the solar inverter, in addition to considering the technical specifications of the entire photovoltaic power generation system and referring to the product manual, the following technical features should also be considered.
1. Rated Output Power of the Solar Inverter
The rated output power represents the ability of the solar inverter to supply power to the load. Solar inverters with high rated output power can carry more electrical loads. When selecting a solar inverter, the first consideration should be that the inverter should have sufficient rated power to meet the electrical power requirements of the equipment under the maximum load, as well as the expansion of the system and the access of some temporary loads. When the electrical equipment is living on pure resistive load, or its power factor is greater than 0.9, the selected rated output power of solar inverter should be 10%~15% higher than the total power of the electrical equipment.
2. Output Voltage Adjustability of the Solar Inverter
Adjustment performance of the output voltage represents the ability of the solar inverter to stabilize its output voltage. Generally, solar inverter products show the percentage of fluctuation deviation of the output voltage of the solar inverter when the DC input voltage changes within the allowable fluctuation range. Usually, this percentage is called the voltage regulation rate. High-performance solar inverters should also provide the percentage deviation of the output voltage of the solar inverter when the load changes from 0 to 100%. This percentage is usually called the load regulation rate. The voltage regulation rate of a solar inverter with good performance should be less than or equal to ±3%, and the load regulation rate should be less than or equal to ±6%.
3. Overall Efficiency of the Solar Inverter
The overall efficiency represents the power loss of the solar inverter itself. Larger capacity solar inverters should also provide efficiency values under full load and low load operation. In general, the efficiency of inverters below the kW class should be 80%~85%. The efficiency of a 10kW grid tie solar inverter should be 85%~90%. The efficiency of more power must be above 90%~95%. Efficiency of the solar inverter has an important impact on the solar on grid power system to increase the effective power generation and reduce the cost of power generation. Therefore, when choosing a solar inverter, it is necessary to compare as much as possible, and then choose a product with a higher overall efficiency.
4. Start-Up Performance of the Solar Inverter
Solar inverter should be guaranteed to start reliably under rated load. The high-performance solar inverter can be started at full load multiple times without damaging the power switching devices and other circuits. For their own safety, small inverters sometimes adopt soft start or current limiting start measures or circuits.
When buying a solar inverter, the first consideration is the scale of the PV on grid power station. You need to determine whether it is used in the home or in the business. In some places, solar panels cannot be installed due to the structural conditions of the houses, but they are still very advantageous for factories and enterprises. Small family PV on grid power plants are mainly installed for villas.
The second consideration is efficiency. Efficiency is directly linked to power generation.
Finally, reliability should be considered. Photovoltaic grid tie power system is a system that converts the direct current generated by solar cells into alternating current with the same frequency and phase as the grid voltage, and realizes both power supply to the load and power generation to the grid. The PV on grid power system is mainly composed of photovoltaic arrays, solar grid tie inverters, controllers and relay protection devices. The PV array is the main component of the solar on grid power system, which directly converts the received solar energy into electrical energy. At present, photovoltaic arrays used in engineering are generally composed of a certain number of crystalline silicon solar cell modules in series and parallel according to the voltage requirements of the system.