Active power filter for harmonic distortion compensation of induction motors with soft starting

A parallel active power filter for harmonic distortion compensation, its signal processing unit, control principle and power stage are described. Power stage of the proposed active filter is realised using three serial inductance, three-phase IGBT based current controlled voltage inverter with two symmetrical capacitors on dc bus. Three independent hysteresis controllers on the base of current references are used to generate switching signals for inverter transistors. The current references are obtained by taking the difference of load current and its fundamental harmonic. For fundamental harmonic determination with no time delay a combination of digital predictive filter and low pass filter is used. The experimental results illustrate the active power filter performance in system with induction motor drives with soft starting.