Dead-Time Compensation Method Based on Current Ripple Estimation

This paper discusses the voltage error caused by the dead time in voltage-source PWM converters. The theoretical analysis in this paper derives the nonlinear voltage error paying attention to the parasitic output capacitance in each switching device. The analytical result reveals that the turn-off current or the switching current ripple strongly affects the voltage error. In addition, it is clarified that the conventional compensation methods based on linear and three-level approximation are suitable under small and large current ripple conditions, respectively. A simple calculation method of current ripples in three-phase PWM converters is also developed to estimate the turn-off currents. Turn-off transition compensation method which is a new compensation method based on the analysis is developed and compared with three different conventional methods in experiments using a 200-V, 5-kW three-phase grid-connection converter. The proposed method exhibits a good compensation performance having a lower voltage THD than the conventional methods in all over the operating range.