Compensation of Demagnetization Characteristics to Improve the Turn-to-Turn Short-Circuit Insulation Resistance Estimation in PMSG Using Moving Horizon Estimation Method

The severity of turn-to-turn short circuit (TTSC) faults reported in the literature considers the fault progression as number of short circuit turns. However, the deterioration of the winding insulation linked to the insulation/contact resistance is neglected. This article proposes a novel framework to improve the estimation of insulation resistance, and a TTSC fault indicator to capture the degradation of winding insulation. A model-based approach, based on moving horizon estimation with control reference, and current and voltage residuals are used. In addition to the TTSC fault effect on magnetic flux linkage, the demagnetization fault effect overlap resulting in reduced estimation accuracy. Therefore, a novel framework is proposed to compensate the effect, which includes real-time update of the magnet's knee point, and a fault indicator that reflects the initialization of the irreversible demagnetization state. A finite element method-based simulation and an experimental test-rig are used to validate the proposed approach. The proposed estimation method can accurately estimate the TTSC fault parameters for different load conditions under constant frequency generator operation, and can identify a low severity TTSC fault of 5% for any low severity of insulation resistance.