Resonant-impedance type hybrid active electric filter and control method thereof

The disclosed filter includes active power filter (APF) and passive filter (PF). Output of APF is connected to primary side of isolating transformer. Being connected to series resonance circuit in parallel, the isolating transformer is connected to PF in series, and then connected to electric network. Steady state error of APF is lowered through iterative control algorithm of improper integral. Result output from the control algorithm is as equivalent control in slipform variable structure control, realizing combination of two methods so as to form triplet variable control structure. Comparing with slipform variable structure control or iterative control of improper integral adopted in solely, the invention possesses features of quicker responsibility and smaller steady state error.