Three-phase voltage-source convertor with controlled DC current for the minimisation of filter capacitance

The authors present a novel control strategy for the output DC current in a three-phase AC/DC convertor using diodes, combined with a boost-type DC chopper. This contributes to the suppression of the output voltage ripples so that the size of the filter capacitor can be minimised. The steady-state characteristics and transient response of the system, with a digital proportional-integral (PI) controller, which has a variable proportional gain to allow stable steady-state operation, are investigated