A rotation angle estimation module is provided. The rotation angle estimation module includes: a fixed flux instruction estimation unit calculating a rotating flux (λsd, λsq) and a fixed flux instruction (λsα*, λsβ*) based on a rotation angle θ and the current (Isα, Isβ) of a fixed coordinate system; a fixed flux estimation unit calculating a fixed flux (λsα, λsβ) based on the voltage (Vsα, Vsβ) of the fixed coordinate system, and the current (Isα, Isβ) and fixed flux error (Δsα, Δsβ) of the fixed coordinate system; a fixed flux error estimation unit using the fixed flux instruction (λsα*, λsβ*) and the fixed flux (λsα, λsβ) to calculate the fixed flux error (Δsα, Δsβ) and feed the errors back to the fixed flux estimation unit; and a trigonometric function calculation unit calculating the rotation angle θ based on the rotating flux (λsd, λsq) and the fixed flux (λsα, λsβ).
