Dynamic adjustments of the D-Q axes reference voltage limits during flux weakening and MTPA control of an IPMSM drive for an EV application

Electric Vehicles (EV) or Hybrid electric vehicles (HEV) require an electric motor which has high power density, high efficiency and a wide constant power operating region with flux weakening (FW) capability. Three phase Interior Permanent Magnet Synchronous Motors (IPMSMs) meet these criteria and are hence used in most commercial electrified vehicles. This work presents analysis, control system design and simulation of the Maximum torque per ampere (MTPA) control strategy in the two-axes (d-q) rotor reference frame. The control is applied on a custom-designed three-phase EV traction IPMSM for an electric scooter direct-drive up to base speed and beyond the base speed with flux-weakening control taking care of the machine's voltage and current constraints. A novel way to dynamically change the limits of the d-axis and q-axis reference voltages yet remaining within the machine's voltage constraints is presented in this paper in order to exploit the large flux-weakening range effectively.