Torque Ripple Reduction in PM Motors using Current Harmonics Controller

This paper presents novel modification of Field Oriented Control (FOC) in order to reduce torque ripple in 3-phase Permanent Magnet (PM) motors caused by non-sinusoidal BackEMF. A smooth torque operation is ensured by precise tracking of a modified q-axis current reference, which includes BackEMF shape. Alternating component added into q-axis current reference has 6 times higher frequency than fundamental stator electrical frequency. Therefore precise tracking of such current reference is usually not feasible with conventional PI controller due to its limited bandwidth. This paper introduces Current Harmonics Controller (CHC) added into current control loop in FOC structure in order to increase performance of the current loop if alternating current reference or alternating disturbances occurs as a 6th harmonic over one electrical revolution.