A novel sliding mode control of a high-voltage transformerless hybrid shunt active power filter

In this paper a novel sliding mode control approach is presented for a medium-high voltage hybrid shunt active power filter, the harmonics suppression effect of which is restricted by the switching frequency of power semiconductor devices, and EMI caused by which is also related with the switching frequency nearly. The proposed control approach combines state variables tracking with PWM, in which source currents and the neutral point voltage of APF DC bus are decoupled and tracked simultaneously. With similar tracking accuracy, the switching frequency can be optimized and limited in a certain lower frequency band via the neutral point voltage control. An ultra-low stray inductive planar bus bar is also designed for APF main circuit to minimize EMI. The simulation and experiment results demonstrate that the proposed control strategy allows HAPF to eliminate harmonic currents caused by source voltage distorting and nonlinear loads effectively.