Extended SVM for Dual Inverter Fed Adjustable Field Permanent Magnet Synchronous Motor Using Zero-Sequence Current

The authors have investigated a dual-inverter system for driving an adjustable field permanent magnet synchronous motor (PMSM) with both open-end three-phase windings and two zero-sequence windings. The zero-sequence windings are connected between the positive or negative terminals of two independent DC-bus voltages, enabling precise control of DC zero-sequence current i<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">z</inf>. By utilizing the magnetomotive force (MMF) generated by i<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">z</inf> in the zero-sequence windings, the proposed motor achieves adjustable field control. A conventional dual-inverter with a common DC bus can apply a larger voltage to the motor than a single-inverter system. In contrast, the proposed dual-inverter can further increase the applied voltage while also reducing harmonic distortion. Furthermore, a novel three-dimensional space vector modulation (3D-SVM) method is introduced to accurately regulate i<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">z</inf> while maximizing voltage utilization. Circuit simulations demonstrate that the proposed 3D-SVM significantly reduces the total harmonic distortion (THD) of the output voltage to less than half compared to conventional subharmonic modulation.