Generalized High-Frequency Injection Framework for Sensorless Control of Synchronous Reluctance Machines

The high-frequency injection (HFI) method is commonly used for sensorless control of synchronous reluctance motors (SynRMs) at low speeds. Injecting a high-frequency (HF) signal in a predefined direction, referred to as the d-axis, and further demodulating the excited signal in the q-axis are a popular sequence for SynRM position tracking. Injection in the q-axis is not usually considered due to its potential to increase torque ripple. This article proposes a generalized HF pulsating voltage injection approach for sensorless control of SynRM. This approach allows for the arbitrary selection of injection strategy and covers the injection and demodulation procedures in d- and q-axes in detail. Special attention is given to determining the amplitude of the injection voltage, which can extend the usage range of HFI and support sensorless control at high speeds. The effectiveness of the proposed structures is experimentally verified using 15 kW SynRM. During system validation, extra care is taken to investigate the overall system efficiency and vibration levels, including torque ripple issues. This solution contributes to the advancement of sensorless control for SynRM drives.