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) is a direct torque control method that provides the fastest possible torque control, low ripple, easily integrated dynamic loss minimization control, and one control law that uses the inherent volt-second source properties of power electronics to enable operation over all operating conditions, including voltage limits. DB-DTFC is a model-based discrete time controller that relies on precise machine parameter, flux, and torque estimation to provide fast dynamic torque control. In this paper, a new method for high-frequency injection (HFI)-based self- and mutual incremental inductance estimation is proposed and evaluated in both simulations and experiments. In this new method, the estimated incremental inductances including cross-coupling inductance due to cross saturation are curve fitted offline and then used to calculate the apparent inductances. With the apparent inductances, the stator resistance and permanent-magnet flux linkage are estimated using recursive least squares method online. 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 interior permanent-magnet synchronous machine drive test bench with a torque transducer mounted.