First, it's necessary to determine whether to use a grid-connected or off-grid photovoltaic inverter. In addition to considering the overall technical specifications of the photovoltaic power generation system and referring to the manufacturer's product catalog, the following technical specifications should generally be given special attention.
1. Rated output power
Rated output power indicates the ability of a photovoltaic (PV) inverter to supply power to a load. A PV inverter with higher rated output power can handle a larger electrical load. When selecting a PV inverter, sufficient rated power should be considered to meet the power requirements of the equipment under maximum load, as well as system expansion and the connection of temporary loads. When the electrical equipment is a purely resistive load or has a power factor greater than 0.9, the rated output power of the PV inverter is generally selected to be 10%-15% higher than the total power of the electrical equipment.
2. Output voltage adjustment performance
Output voltage regulation performance indicates the voltage stabilization capability of a photovoltaic (PV) inverter's output voltage. Most PV inverter products specify the percentage deviation of the output voltage when the DC input voltage fluctuates within its allowable range; this is commonly referred to as the voltage regulation rate. High-performance PV inverters should also specify the percentage deviation of the output voltage when the load changes from zero to 100%; this is commonly referred to as the load regulation rate. A high-performance PV inverter should have a voltage regulation rate of less than or equal to ±3%, and a load regulation rate of less than or equal to ±6%.
3. Overall machine efficiency
Overall efficiency indicates the magnitude of power loss within a photovoltaic inverter. For larger capacity inverters, efficiency values under full load and low load conditions must also be provided. Generally, inverters below 1kW should have an efficiency of 85% or higher; 10kW inverters should have an efficiency of 90% or higher; and inverters with even higher power outputs must have an efficiency of 95% or higher. Inverter efficiency significantly impacts the effective power generation and cost reduction of photovoltaic power generation systems. Therefore, when selecting photovoltaic inverters, it is essential to compare different models and choose products with higher overall efficiency.
4. Startup performance
Photovoltaic inverters should be guaranteed to start reliably under rated load. High-performance photovoltaic inverters can perform multiple consecutive full-load starts without damaging power switching devices and other circuits. For their own safety, small inverters sometimes employ soft-start or current-limiting start measures or circuits.
The above points serve as the main basis for the design and selection of photovoltaic inverters, and are also important indicators for evaluating the technical performance of photovoltaic inverters.
