An optimized common mode voltage reduction PWM strategy for T-type three phase three level photovoltaic grid-tied inverter

A pulse-width modulation strategy for the three-level photovoltaic grid-tied inverter with common mode voltage reduction is proposed in this paper. In the proposed PWM strategy, both the zero vectors V₀ and the medium vector are always selected to comprise the reference vector, and the zero vectors is utilized as the starting vector. Therefore, the amplitude of the common mode voltage is only U_dc/6, and the pulsating frequency of the common mode voltage is equal to the switching frequency. As a result, compared with the existing PWM strategy, the leakage currents of the three phase three level grid-tied inverter is reduced. The simulation and experimental results verify the feasibility and effectiveness of the proposed modulation strategy.