Direct Flux Control: a Viable Torque Control Approach for Three-Phase and Multi-Phase Motor Drives for Transportation Electrification

Electrification applied to leading mobility sectors like automotive, naval and aircraft is pushing the development of three-phase and multi-phase electric drives using high-power density synchronous motors exhibiting significant magnetic saturation. These motors require torque controllers that ensure linear torque regulation while complying with requirements of mobility applications like high dynamic performance, simplicity, reduced development efforts, etc. High-power and safety-critical applications, like naval propulsion and more electric aircraft, are focusing on modular multi-three-phase motor drives since these multi-phase topologies implement three-phase modularity vertically, i.e., involving the electric motor, the power electronics inverter, and the torque controller. However, the magnetic couplings between three-phase winding sets of multi-three-phase motors, combined with the need for digital controller modularity, make the development of modular and decoupled torque controllers challenging. According to this scenario, this paper presents a literature review of leading torque controllers for three-phase and multi-three-phase traction motors, including emerging solutions based on direct flux control (DFC) as a promising unified approach suitable for transport applications. In-depth attention is given to a particular DFC-based torque controller, the flux polar control (FPC), whose excellent experimental performance is shown on three-phase and multi-three-phase motor drive examples.