Self-Commissioning of Synchronous Reluctance Motor at Standstill With Inverter Nonlinearity and Resistance Error Compensation

The accuracy of the self-commissioning method for synchronous reluctance motor (SynRM) is reduced by various errors, mainly caused by inverter nonlinearity and resistance error. Generally, the fitting method is used in data post-processing for error suppression, but it still suffers from selecting exact fitting functions. This paper investigates the identification and compensation methods of these errors during testing for standstill self-commissioning. Firstly, the analytical formulations of the self-commissioning errors related to these errors are derived, in which the effects of zero-axis voltage and the thermal losses caused by signal injection are considered. The conditions for error elimination and the limitations of error suppression using data post-processing methods are pointed out. Subsequently, two error identification procedures are added to optimize the self-commissioning method. One estimates the voltage error caused by inverter nonlinearity using a step current injection method, in which the identification method is optimized to avoid accuracy degradation due to zero-axis voltage. The other one estimates the resistance error caused by bipolar voltage injection. With the error compensation during testing, the self-commissioning accuracy is improved without using fitting for error suppression in data post-processing. The effectiveness of the proposed self-commissioning method is validated on a 3-kW SynRM drive.