Sensorless Control Design and Stability Analysis of High-Speed Dual Three-Phase Permanent Motor Drive for Future Aircraft Applications

Dual three-phase PMSM sensorless drive systems become attractive solutions for more electric aircraft applications due to their high-power density and potential fault tolerance capabilities. The model reference adaptive system (MRAS) is a commonly used sensorless control method. The high-speed operation of aircraft engines places higher demands on its discretisation design. In this paper, to improve the discretisation precision and stability of the control system, a second-order Taylor expansion based MRAS sensorless control design method in the discrete-time domain is proposed, which also includes the modelling and analysis of the entire current-loop control system. This method can directly derive the discrete nonlinear mathematical models of both the MRAS and current control parts, reducing the impact of discretisation step size. To further analyse the stability and parameter influence, relevant linearized discrete small-signal models are developed. On this basis, a full-order discrete state evolution equation of sensorless control system is presented. By analysing the eigenvalues of the state matrix, the stable regions of the system under different operation conditions are illustrated, providing guidance for parameter selection and validating that the proposed method has superior stability than the traditional first-order Taylor expansion-based method in the higher-speed range. The effectiveness of this approach is verified by experiments on a dual three-phase PMSM drive platform.