Optimized Feed-forward Control Scheme for Vienna Rectifier with Estimated Load-Current

To improve the dynamic performance against load disturbance, a load current feed-forward(LCFF) control scheme for Vienna Rectifier using no load-current sensor is presented in this paper. The basic feed-forward terms is derived by control block diagram and explained based on the input-output power balance. Then a closed loop observer is designed for estimating the load-current. Nevertheless, the disturbance in estimated current caused by deviation of capacitor parameter, sampling error and PWM voltage distortion will deteriorate the input current heavily. With a low bandwidth filter inserted to feed-forward path, the harmonics is attenuated at the cost of reducing the load-disturbance rejection ability of basic feed-forward control. Accordingly, an improved Estimated Load Current feed-forward control scheme is implemented, which can reject the input current harmonics caused by distorted observed load current without compromising the dynamic performance of feed-forward control scheme. At last, the experimental result based on a three-phase Vienna Rectifier prototype is presented to validate the performance of the proposed control scheme.