Hybrid shunt active power filter based on novel sliding mode control

A novel sliding mode control approach was presented for a medium-high voltage hybrid shunt active power filter (APF), since the harmonics suppression effect of the filter was restricted by the switching frequency of power semiconductor devices, and electromagnetic interference (EMI) caused by the filter was also related with the switching frequency nearly. The proposed control approach combines state variables tracking with pulse width modulation (PWM), in which source currents and the neutral point voltage of APF DC bus were decoupled and tracked simultaneously. With similar tracking accuracy, the switching frequency can be optimized and limited to a certain lower frequency band via the neutral point voltage control. The simulation and experiment results demonstrate that the proposed control strategy allows hybrid APF to eliminate harmonic currents caused by source voltage distorting and nonlinear loads effectively with low EMI.