Overmodulation Strategy for Deadbeat-Flux and Torque Control of IPMSM with Flux Trajectory Control in the Stationary Reference Frame

For traction drives, the operation in the overmodulation and six-step regions is crucial to increase the torque-speed range and the drive's efficiency. Deadbeat flux-control (DBFC) shows superior dynamic performance as compared to current-vector-controllers in these regions. In this paper, an overmodulation strategy for DBFC is presented. This technique, named minimum flux-phase error (MFPE), permits a smooth transition from the linear to the six-step regions. Consequently, abrupt changes of the modulation index are prevented which results in smoother transients and a closer operation to the maximum-torque-per-ampere (MTPA) line. DBFC can be combined with DB-DTFC (deadbeat direct torque and flux control) to ensure controllability throughout the entire torque-speed range. The complete control strategy is shown in this paper. Results from a 300kW IPMSM hardware-in-the-loop (HiL) testbench are shown to validate the strategy. Challenging caveats of the method are also discussed.