Control and PWM modulation scheme for dead-time compensation of CVCF inverters

The switching dead-time necessary in PWM inverters results in output distortions, and deteriorates the utilization of dc-link voltage. To solve these problems, the authors have developed an accurate dead-time effect mathematical model, and proposed a compensation scheme for grid-connected inverters. In this paper, a new voltage control and PWM modulation scheme is presented for the dead-time compensation of CVCF inverters. It consists of a PID voltage controller and a sliding mode controller (SMC). The PID controller operates in the linear areas; the SMC controller detects the dead-time nonlinear operations and operates for the dead-time compensation. In this control scheme, the PWM modulation gate drive is divided into three operation modes according to the SMC controller output. The unnecessary gate drive signals are removed and the counter side switch can be controlled up to truly 100% PWM duty ratio with a smooth transition between different modulation modes. The influence of switching dead-time can be eliminated almost completely. The proposed control scheme is verified by simulation results. The improvement of harmonic distortion, the minimization of dc-link voltage and the reduction of inductor ripple current are all confirmed by the simulation results. The comparison results between the conventional and the proposed control scheme are presented in this paper.