Design and analysis of a feedforward control scheme for a three-phase voltage source pulse width modulation rectifier using sensorless load current signal

A load current observer based feedforward control scheme for three-phase voltage source pulse width modulation (PWM) active rectifiers is presented. The observer is designed to identify the load current disturbance, which is then forwarded to an inner current controller. Details of the design of the inner current controller and outer dc voltage regulator are also presented. To cope with the delay time of the digital control loop, Smith-predictor is employed in the current control loop to stop overshoots and oscillations during transient current regulation. Simulation model has been set up using commercially available VisSim software and then implemented in a digitally controlled prototype of a three-phase PWM active rectifier. The simulation and experimental results show that without using an actual load current sensor, the proposed observer based feedforward control scheme provides almost the same performance as the traditional feedforward control based on actual load current measurement.