Carrier Based Hybrid Modulation Scheme for Dual Inverter Fed Induction Motor Drive with Reduced Switching Loss

A carrier based hybrid pulse width modulation (PWM) strategy for dual inverter with reduced switching loss is proposed in this paper. The proposed hybrid modulation scheme clamps each phase 60° continuously to the DC bus mid-point at all load power factors and results in reduced switching loss for lower modulation range. The hybrid scheme is obtained after comparing different combinations of level shifted and decoupled PWM methods based on average switching energy loss, current harmonic distortion, common mode and differential mode voltage switchings. All PWM methods are analysed on a dual inverter fed induction motor (IM) drive operated with open loop v/f control. From the analysis, it is observed that the proposed carrier based hybrid PWM scheme results in upto 20% reduction in switching loss as compared to the conventional bus clamping PWM methods for low speed operations. The hybrid PWM also has improved performance in terms of common mode and differential mode voltage switchings. The performance of PWM methods are experimentally validated on an open end winding IM drive. The PWM methods are generated using triangle carrier comparison with synchronous sampling.