Study of advanced current control strategies for three-phase grid-connected pwm inverters for distributed generation

Three-phase PWM voltage-source inverters (VSI) are widely employed for distributed generation (DG) systems. Since the voltage at the point of common coupling should not be regulated by DGs, the current control strategy of grid-connected inverters plays a dominant role in providing high quality power to electric grids. The authors have proposed two advanced SVPWM-based current controllers to improve the performance of grid-connected VSIs for DG systems. Three current control strategies, namely hysteresis current control, SVPWM-based PI control and SVPWM-based predictive control, have been developed, implemented, and studied on a 30kW three-phase grid-connected PWM VSI. Effective compensation for the grid harmonics and for the system nonlinearity due to control delay and switching dead time are investigated. The results of computer simulations and experimental tests are provided to verify and compare the performances of these three current control strategies