Sensorless Control of Induction Motor Based on Rotors Slot Harmonics and Digital Adaptive Filters

The paper presents the design of an induction motor speed estimator based on rotor slot harmonics (RSH), with a focus on analysis of its integration within the current and speed control loops. In the literature, RSH-based methods are dominantly used for speed estimation for monitoring purposes, without further discussion of their use in control loops. The proposed estimator consists of a PLL and digital adaptive filters, and the design is based on the requirements of the speed control loop. The estimator has negligible steady-state error and a low delay. An analytical model of the estimator and a linear stability analysis is provided. The estimation and control algorithms are implemented on a single processor with no additional software or hardware requirements or modifications. Experimental results demonstrate sensorless vector closed-loop operation of a three-phase 2.2 kW induction motor, with speed closed-loop bandwidth of up to 15 Hz and high disturbance rejection capability. Operation is presented over a wide speed range, from nominal speeds to very low speeds. The presented method can be applied to any IM capable of generating RSHs. The performance can be guaranteed if the RSH is represented with a minimum of 5 ADC quantization levels.