Speed Estimation Scheme Based on the New-Type Quadrature PLL for Sensorless Control of Induction Motor Drives

Abstract

The speed-sensorless techniques based on the phase-locked loop (PLL) attract much popularity. However, most of the existing PLL schemes may be difficult to achieve accurate estimation during frequency ramps. So, the performance of the PLL schemes may be degraded during acceleration and deceleration eases, when being applied in motor drives. Moreover, the estimation performance of the PLL scheme is adversely affected by disturbance, e.g., DC offsets. Considering this, this paper proposes a new-type quadrature PLL-based speed estimation scheme. In this scheme, the new quadrature PLL is used to achieve accurate estimation. In addition, a flux observer that can eliminate the DC offsets is employed to provide flux estimation, as the inputs of the proposed estimation scheme. Meanwhile, an online stator resistance correction scheme is employed to improve the robustness against parameter variations. Finally, simulation results are given to verify the effectiveness of the proposed scheme.