Digital Implementation of Stator and Rotor Flux-Linkage Observers and a Stator-Current Observer for Deadbeat Direct Torque Control of Induction Machines

Properly formed discrete-time recursive models of a stator and rotor flux-linkage observer are presented. A model delay in the flux-linkage observer, which hindered previous work, is identified. To remove this delay, a new stationary frame current observer is developed and experimentally verified. With this new observer system, the flux linkages are properly estimated for the next sample instant, thus removing the computational delay. The improved and the delayed flux observer are evaluated in a deadbeat direct torque control algorithm.