Sensorless Identification of the Initial Rotor Slot Position using One Active Inverter State Excitation in Induction Machines

Sensorless induction machine drives have been deeply investigated in the last three decades, showing good performance during online operation. Most of the literature is focused on methods to track the rotor position in the most accurate way. However, there has been no research on how to start up the complete sensorless drive in case there is no position sensor at any time. If a position sensor is not available at startup, the initial position of the rotor slot is unknown. Yet, this position is essential for sensorless drives that rely on saliency compensation based on LUTs that require the estimated rotor angle as input. Therefore, this paper proposes a sensorless identification strategy of the initial rotor slot position. Experimental results, carried out in a traction motor, are presented in this paper to prove the accuracy of the proposed strategy.

I. Introduction

Sensorless AC drives have been intensively investigated in the last three decades, showing several benefits in terms of cost and reliability as well as good performance during dynamic operation. A common classification of sensorless strategies divides those between model-based ( [1] –[4]) and signal-injection-based ( [5] –[16]). For traction applications, it is well known that the model-based methods suffer from system non-linearity and signal noise, and fail to provide a stable position at a certain low speed and downwards until zero speed. Therefore, signal injection strategies have been mostly researched in this field, which rely on the calculation of the actual position of the machine’s saliencies. Within this type, voltage step excitations appear to be a good solution to deal with zero and low frequency control, avoiding the common high frequency disadvantages such as current ripple or high frequency losses.