An integrated learning control method for PWM-VSI based hybrid filter to dampen harmonic resonance in industrial power system

The operation of voltage source inverter (VSI) based active filtering technique can be viewed as compensation for the equivalent harmonic voltage source according to Thevnin theorem. The paper proposes an integrated current control method for PWM-VSI based hybrid filter, which is a learning control method with incorporation of boost converter technique, to produce the control voltage of PWM inverter. During every learning period, the controller views the PWM-VSI as a boost converter to shape the line current with the achievement of almost unity power factor in the harmonic domain. The repetitive operation of learning control is used to minimize the steady error caused by uncertainties of dynamics of boost converter, the passive filters connected to power system and the detection of line harmonic current. A PWM-VSI based hybrid active filter system consisting of 11th and 13th tuned L-C passive filters with 12-pulse thyristor rectifier is examined. The simulation and experimental results show the viability and effectiveness of the proposed controller.