High frequency injection-based stator flux linkage and torque estimation for DB-DTFC implementation on IPMSMs considering cross-saturation effects

Deadbeat-direct torque and flux control (DB-DTFC) has demonstrated several technical advantages over classical hysteresis DTC and PI regulator based direct torque control (DTC) methods. These include fast torque control, low ripple, easily integrated dynamic loss minimization control, and one control law that uses the inherent Volt-sec. source properties of power electronics to enable operation over all operating conditions including voltage limits. DB-DTFC uses the fundamental machine model to form the inverse solution for Volt-sec selection at each switching period. Therefore, DB-DTFC is a model-based discrete time controller that relies on accurate machine parameter estimation to provide accurate dynamic torque control. In this paper, a new method for high frequency injection-based real-time self- and mutual inductance estimation is proposed and evaluated in both simulations and experiments. In this new method, the estimated inductances including cross-coupling inductance due to cross-saturation are then used to estimate the stator resistance and permanent magnet flux linkage. The stator flux linkage observer using the identified machine parameters, yields improved stator flux linkage estimates that enable precise torque calculation. Experimental evaluation of the HFI-based flux estimates on torque estimation and control accuracy is performed at an IPMSM drive test bench with torque transducer mounted.