Deadbeat-direct torque and flux control on low switching frequency induction machine drives using the enhanced flux observer and torque model

Abstract

This paper presents a digital implementation of deadbeat-direct torque and flux control (DB-DTFC) for induction machines at low switching frequencies. For high switching frequencies, existing discrete time flux observers and Volt-sec.-based inverse torque models used for DB-DTFC achieve acceptable flux estimation accuracy and fast torque response. However, the flux estimate is less accurate when switching frequency is reduced and DB-DTFC performance degrades. This paper develops a more suitable flux observer and Volt-sec.-based inverse torque model that minimizes flux estimation error and improves torque control for DB-DTFC. Simulation and experimental results are provided to evaluate the performance of the proposed observer and torque model at very low switching frequencies. Consequently, digital implementation of low switching frequency DB-DTFC on high power induction machines is feasible.