Direct Field-Oriented Control of Induction Motor With Discrete Full-Order Flux Observer

The full-order flux observer has only been preliminarily applied in high-performance direct field orientation control (DFOC) of induction motors (IMs). However, in high-power and high-speed motor drives, the control system operates under a low switching-to-fundamental frequency ratio (SFR), so the full-order flux observer based on conventional discretization methods no longer meets the requirements due to significant discretization errors. To solve this problem, this article proposes an eigenvalue-based discrete full-order flux observer, and feedback gains are designed in the z-domain to ensure stability and dynamic performance. Additionally, the parameter robustness analysis is conducted on the proposed DFOC system to ensure high parameter robustness in the medium- and high-speed ranges. Rigorous simulations and experiments are performed to verify that the proposed discrete full-order flux observer exhibits a high level of discretization accuracy and the proposed DFOC system achieves excellent stability and dynamic performance under a low SFR.