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Sep 19,2020

Common types of photovoltaic grid-connected inverters

The inverter structures used in photovoltaic power stations mainly include centralized photovoltaic inverter systems, string photovoltaic inverter systems, distributed photovoltaic inverter systems, and micro-inverters. For these types of inverters, what are their characteristics before?

photovoltaic grid-connected inverters

The centralized inverter is a device that connects many photovoltaic strings to the DC input end of the inverter after confluence and completes the centralized conversion of direct current to alternating current. A centralized photovoltaic inverter system is a power conversion device commonly used in large photovoltaic power stations, and it is also one of the most mature technical solutions.

The centralized photovoltaic inverter system uses a maximum power point tracking (MPPT) input, centralized MPPT optimization, and centralized inverter output. The installation of the centralized inverter is relatively simple and convenient. The inverter system adopts a single-stage control method, which is relatively simple in control. At the same time, the technology is relatively mature and the cost of the unit system is low.

The string photovoltaic inverter system was originally designed for small photovoltaic power generation systems such as rooftop photovoltaics. It can be directly connected to the low-voltage power grid without isolation transformers or step-up transformers. It is especially suitable for low-voltage grid-connected distributed photovoltaic power generation.

The string inverter is based on the concept of modularity. Each photovoltaic string in the photovoltaic array is connected to the DC input of the designated inverter, and each completes the equipment that converts direct current to alternating current. String inverters usually use a two-level three-level three-phase full-bridge topology, select small and medium power IGBTs and SVPWM modulation algorithms, and use DSP to control IGBT to emit three-level square waves, and the output meets the standard after filtering through LCL or LC filters Sine wave.

Multi-channel MPPT string photovoltaic inverters can better solve the problem of "mismatch" loss of photovoltaic strings in large photovoltaic power stations.