3 types of distributed PV inverters and their pros&cons

　　Distributed inverters are usually used in small and medium-sized industrial and commercial and home PV power generation systems. It includes three types: string type, distributed type, and micro type. Among them, string type inverters are the mainstream type.

　　The working process of the string inverter is to first convert the direct current generated by the PV module into alternating current, then converge, adjust the voltage, and finally merge into the power grid.

　　The string inverter adopts a modular design, the single capacity is small, usually 100KW and below, and it has multiple MPPTs. The number of PV modules connected to each MPPT is small, usually 1-4 groups, which can realize the function of automatically finding the best working point in a decentralized state. Since there are fewer PV modules connected, when a single component fails, only the corresponding module will be affected. This ensures that the overall power generation efficiency is not affected by a single component, and solves the "short-board effect of centralized PV power generation" "problem.

　　The string inverter has a wide operating voltage range, usually 200V-1000V, and has good adjustability. The wide operating voltage range can ensure that the system can maintain its working status when the light is insufficient or the weather is not conducive to power generation, thereby increasing power generation time and power generation.

　　Parallel connection of multiple string inverters will not only increase the wire loss, but also increase the total harmonics, serious resonance problems, and increase the difficulty of suppression, which may easily cause electrical equipment failures and burns.

　　Distributed inverters have the advantages of centralized inverters and string inverters, with excellent independent performance, high power generation, and overall system stability. Compared with the string inverter, the distributed inverter adopts the centralized convergent inverter after decentralized optimization, which greatly reduces the equipment cost of the system. Although its complex control logic and electronic design test the engineer's ability very much, it is undeniable that this is a very promising type of inverter.

　　The single capacity of a micro-inverter is generally about 1kW. It can be combined with each PV module to perform Maximum Power Peak Tracking (MPPT) control on a single PV module, thereby greatly improving the overall power generation efficiency and power generation.

　　It has the advantages of small size, light weight, high efficiency, no need for additional land, and easy installation. It is mainly suitable for family-style small and medium-sized power station projects. It is not suitable for application in large-scale PV power plants.

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