Classification of photovoltaic Inverters

Photovoltaic inverters are generally divided into three categories: centralized inverter, series inverter and micro inverter.

Centralized inverter

The photovoltaic inverter mode of centralized inverter is to connect many parallel photovoltaic groups in series to the DC input of the same centralized inverter, track the maximum power peak, and then connect to the power grid after inverter.

The single capacity of centralized inverter is usually more than 500kW, with high single power, low cost and good grid regulation. However, it is required to have a good match between photovoltaic strings. Once cloudy, partial shading or single string failure occurs, it will affect the efficiency and electrical capacity of the whole photovoltaic system. The maximum power tracking voltage range of centralized inverter is narrow, the flexibility of component configuration is low, and the power generation time is short. It requires a special machine room with ventilation and heat dissipation, which is mainly suitable for centralized ground large-scale photovoltaic power stations with uniform light.

Series inverter

The series inverter is used to track the maximum power peak of several groups (generally 1-4 groups) of photovoltaic series separately, and then connected to the AC power grid after inverter. A series inverter can have multiple maximum power peak tracking modules. The single capacity of the series inverter is generally below 100kW. Its advantage is that there can be voltage and current mismatch between the strings of different maximum power peak tracking modules. When a component fails or is shaded, it will only affect the power generation of a few strings of the corresponding maximum power peak tracking module, which has no impact on the whole system. The inverter has wide maximum power tracking voltage range, flexible component configuration and long power generation time; It can be installed directly outdoors.

Compared with the centralized inverter, the price of series inverter is slightly higher. When a large number of series inverters are connected in parallel, they need to technically suppress the occurrence of resonance. They are mainly used in distributed power generation system and centralized photovoltaic power generation system.

Micro inverter

The micro inverter tracks the maximum power peak of each photovoltaic module separately, and then is connected to the AC power grid after inverter.

The unit capacity of micro inverter is generally less than 1kW. Its advantage is that it can carry out independent maximum power tracking control for each component, and improve the overall efficiency in case of partial shading or component performance differences. In addition, the micro inverter has only a DC voltage of tens of volts, all of which are connected in parallel, which reduces the potential safety hazards to the greatest extent. Its price is high and it is difficult to maintain after failure.