Improvement of back-EMF self-sensing for induction machines when using deadbeat-direct torque and flux control (DB-DTFC)

Back-EMF self-sensing is commonly used in induction machine (IM) drive systems for its maintenance cost and safety considerations. In recent years, deadbeat-direct torque and flux control (DB-DTFC) has been shown to be a highly effective method for induction machine control. It has advantages such as the fastest possible torque dynamics, dynamically loss manipulation capability independent of torque dynamics, and parameter insensitivity. This paper evaluates the synergy between back-EMF self-sensing technology and DB-DTFC for IM drive systems. In this paper, an observer-based closed-loop back-EMF tracking self-sensing control in an IM DB-DTFC drive system is presented. It includes a back-EMF state filter, back-EMF tracking observer, and cascaded motion observer. Back-EMF harmonic decoupling is explored to improve the low speed performance. The bandpass filter method (BPF) for back-EMF self-sensing is also presented. Finally, the closed loop system dynamic stiffness at very low speeds, with and without the BPF method, is experimentally evaluated.