Current Control for Single-Inverter-Fed Series-Connected Five-phase PMSMs

Abstract

Recently, the advantage of multiphase drive (>3) is demonstrated by a novel system composed of series-connected five-phase induction motors (IMs) and single inverter where their IM windings are connected in series. Due to the additional degree of freedom provided by five-phase AC motors, two IM speeds can be regulated independently. In this paper, high-efficiency series-connected five-phase permanent magnet synchronous motors (PMSMs) are used. In order to regulate two PMSM speeds independently, two decoupled speed loops are designed in the control structure and each generates the corresponding current command set. The sums of the two current command sets become the desired currents and the five current controllers are used to generate the final switching signals to obtain the desired currents. In the equivalent model of PMSM current loop, back-electromotive forces (back-EMFs) and parameter differences can be seen as disturbances. In order to reduce the effects of the equivalent disturbances and improve the current tracking performance, a robust feedforward current control (RFCC) is used. The simulation and experimental results are provided and they also demonstrate the proposed RFCC.