A Simpler Gopinath-Style Flux Observer without a Constant Speed Assumption for Low and High Sampling-to-Fundamental Frequency Ratios for Induction Machines

State-of-the-art stator and rotor flux observers implemented in the discrete domain for high-performance drives, such as those used in deadbeat-direct torque and flux control, have become increasingly complex in nature and have an underlying linearizing constant speed assumption. The proposed observer is expected to consume less computational resources, does not make linearizing assumptions about the motor, and has shown to run well at low sampling-to-fundamental frequency ratios. The observer also does not rely on lookup tables or compensation curves to correct for errors caused by approximations, allowing easier tuning than the state-of-the-art flux observer. In this paper, this observer is developed in the continuous and discrete domain and analyzed for rotor flux estimation accuracy performance.