Control of Three-Level T-Type Inverter Based Grid Connected PV System

Multilevel inverters topology is an effective way to improve the capacity of full power converter in distributed generation system. However, the major concern for multilevel inverters is the fluctuation in the neutral-point (NP) voltage. This paper focuses on overall control including NP voltage balancing of a photovoltaic (PV) distributed generation system based on dual-stage conversion of three level DC-DC boost converter (3LBC) and three-level T-type inverter (3LT(2)I). The voltage-balancing control of two split DC capacitors of the 3LT(2)I has been transferred to the 3LBC, and thereby there is no need to change the conventional three-level space vector modulation (SVPWM) algorithm or to add additional components. Furthermore, it is simple and easy to implement and only one proportional-integral (PI) is needed to achieve good NP voltage balancing. Last, the capability of the overall system to control the current injected into the grid, reactive power compensation and keep DC-link NP voltage balance is investigated at different operating conditions.