An alternative PI controller design approach for PWM-regulated ac/dc three-phase converters

A new design for cascaded PI controllers used in PWM-regulated ac/dc converters is proposed. The design makes possible the selection of the PI controllers' gains in a manner that is more independent from the system parameters. To this end, a system and controller analysis is conducted that results in the determination of an effective time constant for the closed-loop system. It is proven that this variable time constant results from the response of an arbitrarily selected lead or lag transfer function. This enables to select an arbitrary integrator gain that leads in an initial time constant which is corrected by the selection of suitable proportional gain values. For a given integrator gain, small enough proportional gain values lead to slower responses while large enough proportional gain values lead to faster responses. The evaluation of the proposed design approach is easily obtained by simulation results.