DC link voltage balancing technique for cascaded H-bridge multilevel converter with selective harmonic current mitigation-PWM

摘要

In low frequency modulation techniques, grid-tied cascaded h-bridge (CHB) converter need to meet power quality standards. In addition, the effects of grid voltage harmonics must be considered in modulation technique. Furthermore, the DC link voltages of grid-tied converter need to be regulated. In this paper, a selective harmonic current mitigation-PWM (SHCM-PWM) technique is used to meet the current harmonic limits of power quality standard, when the effects of grid voltage harmonics are considered in the equation set of optimization process. Additionally, a voltage balancing technique based on average power, which flows through each cell, is obtained to regulate the DC link voltages of CHB converter without using DC voltage sensors. By using the proposed voltage balancing technique, the CHB converter also does not need complex DC link voltage controller. As a result, the cost and complexity of grid-tied converter is significantly reduced. To validate the proposed voltage balancing technique with SHCM-PWM modulation technique, simulations and experiments conduct on 7-level grid-tied CHB converter.