An improved DC-link voltage fast control scheme for a PWM rectifier-inverter system

This paper presents an improved DC-link voltage fast control strategy for a PWM rectifier-inverter system to reduce the fluctuation of DC-link voltage. In this paper, a conclusion is drawn based on the instantaneous energy balance analysis of the whole system that the energy stored in the DC-link capacitor will fluctuate during dynamic process in rectifier mode, even in ideal case. Then, when the output power changes, the DC-link voltage fluctuation with proposed control strategy is analyzed. Accordingly, an improved predictive DC-link voltage control scheme, based on energy balance and system stability, is proposed. Moreover, if the above scheme is adopted, the average output active power estimation in several cycles for an induction machine is very important to stabilize the DC-link voltage, especially in dynamic process. Thus, an average active power estimation method in dynamic process is introduced. The simulation and experimental results demonstrate both good dynamic and steady-state performance of converter with the proposed control scheme.