Photovoltaic inverters can be divided into single-phase and three-phase inverters based on the number of phases of the output AC voltage; grid-connected and off-grid inverters based on whether they are used in grid-connected or off-grid power generation systems; centralized and distributed photovoltaic inverters based on the type of photovoltaic power generation used; grid-connected and energy storage inverters based on whether energy is stored; and centralized, string, distributed, and micro inverters based on the technology used. The main classification method for photovoltaic inverter products is based on the technology used. According to the "China Photovoltaic Industry Development Roadmap" released by the China Photovoltaic Industry Association, the current photovoltaic inverter market is dominated by centralized and string inverters.
A centralized photovoltaic inverter is a power electronics device that aggregates the direct current (DC) generated by photovoltaic modules into a high-power DC power source before converting it into alternating current (AC). Therefore, these inverters are relatively powerful, typically exceeding 500 kW. In recent years, with the rapid advancement of power electronics technology, the power of large centralized photovoltaic inverters has increased significantly, from the initial 500 kW to 3.125 MW, while also achieving higher voltage ratings.
Large centralized photovoltaic inverters offer advantages such as high output power, simplified operation and maintenance, mature technology, high power quality, and low cost. They are typically suitable for large-scale ground-mounted photovoltaic power plants, agricultural photovoltaic power plants, and floating photovoltaic power plants. Furthermore, due to their high output power and high voltage rating, technological advancements have led to their integration with downstream transformers in recent years, creating integrated "inverter-boost" solutions and integrated photovoltaic-storage solutions combined with energy storage.
A string photovoltaic inverter is a power electronic device that directly converts the direct current (DC) generated by smaller photovoltaic modules into alternating current (AC). Therefore, the power of string photovoltaic inverters is relatively low, typically below 50kW. However, in recent years, with technological advancements and the need to reduce costs and increase efficiency, the power of string photovoltaic inverters has gradually increased, resulting in high-power string photovoltaic inverters exceeding 175kW.
Because of the low power output of a single string photovoltaic inverter, the number of inverters required for the same power generation capacity is increased. This allows for a better match between a single inverter and the optimal operating point of the photovoltaic modules, potentially increasing power generation under specific circumstances. String photovoltaic inverters are primarily used in smaller power plants, such as residential distributed generation and small- to medium-sized industrial and commercial rooftop power plants. In recent years, they have also been used in some large ground-mounted power plants.
Distributed inverter technology is a recently introduced solution that combines the advantages of large-scale centralized PV inverters with the distributed MPPT tracking of string-type PV inverters, achieving the low cost and high reliability of centralized inverters with the high energy yield of string-type inverters.
Because distributed PV inverters inherit the advantages of large-scale centralized PV inverters, their high power, high voltage rating, and integrated inverter-boosting technology have been gradually applied to distributed PV inverters in recent years. This improves power generation efficiency while significantly reducing costs, making them a key technology path for leading PV inverter manufacturers in my country.
Micro PV inverters typically operate for a single or several PV modules. Each micro inverter can track the maximum power point (MPP) of each module individually before being connected to the AC grid. The capacity of a single micro PV inverter is generally below 5kW. Micro PV inverters can independently track the MPP of each PV module, enabling precise adjustment and monitoring of each module's output power. Compared to centralized and string inverters, micro inverter PV systems can achieve higher power generation efficiency in situations involving partial shading or varying module performance. Furthermore, micro inverters operate in parallel and directly convert the DC power from each PV module into AC power before connecting it to the grid. During operation, the DC voltage is only tens of volts, minimizing safety risks.
Micro inverters are primarily used in distributed PV power generation systems. Their compact size and lightweight design eliminate the need for additional space, greatly enhancing installation convenience.
