Novel Rotor Flux Amplitude Estimation Method for PMSM with Flux dq-Cross Coupling

An important issue in permanent-magnet synchronous motors (PMSMs) for electric vehicle (EV) traction is estimating the temperature of the rotor permanent-magnet in real-time. This paper proposes a novel rotor flux amplitude estimation method to enable real-time rotor magnet temperature estimation of the PMSMs with flux dq-cross coupling. The proposed method has the following features: (a) A novel minimum-order D-flux state observer, included in the D-filter, is used for the real-time rotor flux-amplitude estimation in the PMSMs with flux dq-cross coupling. (b) The three inductances of d-axis, q-axis, and cross-coupling required for the D-filter are identified simultaneously using an adaptive parameter identifier. (c) The adverse effect caused by the current detection offset on the flux-amplitude estimate and the indentified inductances is overcome by utilizing the characteristics unique to each system. (d) The instability caused by the coupling of two real-time systems is addressed by adopting a special system structure that prevents such instability. (e) Using the novel method, the real value of the rotor flux-amplitude can be estimated in 0.9s after the zero initial-state start for the PMSMs with flux dq-cross coupling.