Predictive variable-structure system control of unity power factor rectifiers

This study presents the design of a current control loop and the selection of switching logic for pulse-width modulation (PWM) of three-phase switching converters. This approach is based on a deliberate introduction of the predictive sliding mode motion within a control system. It shows that the selection of the PWM pattern is a direct result of sliding mode existence within the current control closed-loop system. The design specifications are robustness to load electrical parameters, fast dynamic response, reduced switching frequency and simple hardware implementation. To meet previous specifications, a sliding mode controller has been developed, designed as a finite state machine, and implemented within a field programmable gate array device. The switching strategy implemented within the state transition diagram provides for a minimum number of switch state changes by the three-phase converter that is confirmed through simulation and experimental results.