SynRM Sensorless Torque Estimation Using High-Frequency Signal Injection

Precise output torque control is often required in applications using synchronous reluctance machines. Direct measurement of torque has drawbacks due to both cost and reliability issues. To overcome these limitations, the development of torque estimation methods has received significant research attention. Most of the exiting torque estimation methods require knowledge of machine parameters, suffering, therefore, from parameter sensitivity. Load and saturation are recognized as the primary source of parameter variation. This article proposes the use of a high-frequency signal injection for the online estimation of the machine parameters required for torque estimation. The improvement in the torque estimation will be especially relevant in deep-saturation regions. The method operates without interfering with the normal operation of the machine.