Sensorless Control Method at Low-Speed Range using High-Frequency Voltage Injection for Synchronous Reluctance Motors considering to NonLinear Characteristic due to Magnetic Saturation

Synchronous Reluctance Motor (SynRM) has large magnetic saturation, and it experiences fluctuations in parameters such as flux and inductance because of magnetic saturation as the amount of current passing through it changes. Because of this, when saliency based sensorless control method is used for position estimation, the characteristic for position estimation becomes nonlinear. In this case, the accuracy of position estimation may decrease, or the controlled motor may lose synchronization. To solve this problem, the characteristics arising from the high-frequency square wave injection method is modeled including the cross-coupling effect and a method for combining two characteristics on dq-axes from the model equation is proposed in this paper. Then, by deriving characteristics from the result of electromagnetic field analysis using Finite Element Analysis (FEA) and theoretical equation, it is possible to verify their validity from the comparison results with the characteristics obtained from the actual machine. In the end, the proposed method is verified by experiments on a 2.2-kW SynRM drive platform.