An Analytical Approach to Direct Torque and Flux Control of Interior Permanent Magnet Synchronous Machine for Deep Field Weakening Without Using Pre-calculated Lookup Tables

This paper presents an analytic approach to direct torque and flux controller (DTFC) for Interior permanent magnet synchronous machine (IPMSM) which includes deep flux weakening. Unlike the conventional lookup tables (LUTs) based DTFC, this paper proposes a direct mathematical calculation approach for the stator flux reference as well as the torque limit in field weakening (FW) and maximum-torque-per-voltage (MTPV) regions. The proposed method will thus allow flexibility of using online estimated machine parameters directly for an optimized IPMSM drive. This study also explores the voltage and current limit trajectories on a torque-flux linkage plane to operate the machine in deep field weakening. It incorporates maximum-torque-per-ampere (MTPA), FW, and MTPV trajectories control under voltage and current constraints. Experimental results are shown to verify the effectiveness of the proposed algorithm.