Efficiency-optimal power partitioning for improved partial load efficiency of electric drives

•A review of techniques for energy efficiency enhancement of power converter interfaces.•Global power conversion efficiency improvement for a fault-tolerant drive architecture.•An original strategy to enhance partial load efficiency of electric drive is presented.•An experimental set-up based on hybrid microcontroller and FPGA platform has been built.•Detailed experimental results for large torque range are reported.

In this paper, the global power conversion efficiency is improved for a fault-tolerant drive architecture. The fault-tolerant architecture is obtained by combination of a 3-phase open-end winding machine and a 3H-bridge inverter. This combination offers more degrees of freedom for the control strategy than a classical 3-leg inverter. This paper demonstrates that the additional degree of freedom of this power system can be exploited for efficiency optimization purposes in normal operation mode. In the present work, the retained optimization criteria is the minimization of the drive losses which is a critical issue. In addition, to fulfill the torque demand, this leads to a constrained optimization problem which can be analytically solved using the Lagrange multipliers method. Besides, as each motor phase can be driven independently, the resolutions for three strategies, i.e. for three, two or one-phase simultaneous conduction of the inverter, provide three different optimal current waveforms. This is the key point of the proposed efficiency-optimal power partitioning for improved partial load efficiency of electric drives. Finally, on a test bench, the real-time tracking of the mentioned current waveforms is successfully tested and power measurements confirm the possibility of using the three different control strategies to realize an efficiency optimum phase-shedding strategy.