Novel Filter for Stator Harmonic Currents Reduction in Six-Step Converter Fed Multiphase Induction Motor Drives

Multiphase induction motors have a lot of advantages over the conventional three-phase induction motors. But when a motor is supplied with nonsinusoidal voltage source inverter (VSI), it will be found that unwanted harmonic currents substantially exist in stator windings. Focusing on the drawback, a strategy for filtering these kinds of current based on electromagnetic principle is proposed. Actually, the filter is a specially designed inductance that is connected between the multiphase motor and VSI. In this paper, research is carried out on a six-phase induction motor, the most typical multiphase motor being studied at present. Accordingly, the fifth and the seventh harmonic currents in stator should be reduced as the substantial harmonics. Different from the filtering inductances presented earlier, the novel one is of symmetrically round shape. Thus, it is possible to design the construction to be extremely compact. Principle of filter is expounded and considerations are taken for filter design. A prototype of the proposed filter is tested on a multiphase induction motor supplied with a six-step VSI. The experimental results show the validity of the filter as expected.