Optimized Anti-Windup Coordinating Strategy for Torque-maximized High-Speed Flux-weakening Operation of Constrained Induction Motor Drives

Due to the contradiction between torque-maximized requirements and limited voltage and current constraints, voltage closed-loop flux-weakening strategy is developed to circumvent the saturation problem for maximum torque control of induction motor when the accelerating speed enters high-speed region. At the same time, since voltage inconsistency caused by the saturation is employed to construct flux-weakening controller (FC), anti-windup (AW) item in current regulator needs to be cut off to avoid the conflict. However, the replacement discards part of AW’s utility and results in the distortion of command voltage, thus compromising system’s dynamic performance and making the tuning process of PI-based FC much trickier. To address this issue, an equivalent saturation model is presented. An optimized AW coordinating strategy is proposed, combining a novel structure, so-called virtual voltage buffer, with FC. Through an equivalent proof, it can be transformed into over-modulation block for a convenient implementation. Through its compensation in the transient period, d-axis current can be quickly and smoothly manipulated in a more concise tuning process. As a result, the overall system possesses a fast acceleration capability with maximum torque and a wide speed range, while retaining a desirable system response. Simulation and experimental results verify the effectiveness of proposed method.