A Simplified DC Capacitor Active Voltage-Balance Algorithm with Common-Mode Voltage Reduction using Active-Zero SVPWM for Three-Level Photovoltaic Grid-Tie Inverter Application

This paper presents: 1) a modulation method that combine active-zero PWM and conventional Space-Vector PWM (SVPWM) for three-level inverter, 2) a simplified DC capacitor active voltage-balance algorithm with common-mode voltage reduction using proposed modulation method. The presented modulation method and voltage-balance algorithm simplified calculation of both DC capacitor voltage balance and PWM generation, and take AC load current into consideration, which is suitable for wider range of load condition. In addition, both proposed methods can be programmed as add-on function of conventional SVPWM, which allow online enable/disable during operation of inverter for more flexible system control. The performance of proposed methods are demonstrated in both computer simulation and prototype test. A patent has been granted for the proposed methods and has been adopted in an industrial wide-bandgap semiconductor based PV prototype.