Three-phase four-wire shunt active filter under unbalanced loads with backstepping and PI controllers

Abstract

This paper proposes backstepping technique for the direct-current bus voltage control in three-phase four-wire shunt active filter. The identification of reference currents is made by synchronous referential frame theory with self-tuning filter. The three-phase four-wire shunt active filter is implemented with DSPACE 1104 system to compensate harmonics generated by unbalanced system of non-linear loads. Four-leg topology is used for the inverter of shunt active filter and the switching patterns of the inverter are generated by analogue hysteresis card. The experimental results verify the good performance of the proposed shunt active filter in term of harmonic currents reduction and improvement of power quality. A comparison between backstepping controller and the conventional proportional-integral controller is illustrated, in steady state, the two controllers fixe direct-current bus voltage at its reference value, however, a clear advantage of the backstepping control in dynamic state can be observed.