Optimal Current Setpoints for Five-Phase Synchronous Drive

Abstract

Maximum torque per current (MTPA) and other optimal curves are well-known for three-phase machines. Since multiphase machines dispose by more degrees of freedom than their three-phase counterparts, the solution is much more complicated and a variety of regimes can be found. In this paper, optimal current setpoints for five-phase synchronous machines are analyzed. Besides the first harmonic, the optimization includes also the third harmonic, used for both torque enhancement and waveform shaping. It is shown that the MTPA curves, field weakening (FW) and maximum current (MC) regions have an inner structure with multiple regimes. This variety comes from the phase voltage and phase current limits that yield optimizing waveforms containing multiple peaks (peak shaving). A taxonomy of these regimes is provided, and their mutual relations are demonstrated on a case study machine. The optimal current setpoints in their waveforms are analyzed in selected operating points.