Enhanced three phase ac stationary frame PI current regulators

Current regulation is an essential element of modern power electronic AC conversion systems. However it is well known that simple stationary frame PI current regulators cannot achieve zero steady state error for AC systems because of the instability that inevitably occurs as the PI gains are increased in an attempt to reduce this error. Recent work has shown for single phase systems that the gains are in fact limited by the second order effects of sampling and transport delays, rather than any fundamental theoretical constraints. This paper extends this understanding to three phase systems, presents a deterministic strategy to maximize the PI gains for practical AC current regulation systems, and proposes some additional strategies to further enhance the performance of a basic PI regulator. The conclusions presented are confirmed by detailed simulation investigations and matching experimental results.