Rotor position estimation for dual-three-phase permanent magnet synchronous machine based on third harmonic back-EMF

In this paper, an improved rotor position estimation strategy based on third harmonic back-EMF for a dual-three-phase permanent magnet synchronous machine (PMSM) is proposed. Due to the phase shift of π/6 between the two sets of windings in dual-three-phase PMSM, the triplen harmonic flux-linkages derived from the measured triplen harmonic back-EMFs are with constant amplitude and orthogonal under third harmonic reference frame. By applying EKF based rotor position estimator the rotor position can be estimated even though there may contain too much high order harmonic components. Furthermore, to improve the robustness and frequency response, the speed-dependent triplen harmonic back-EMF can be directly applied for rotor position estimation by estimator with speed-variable parameters without any filter. The proposed strategies have been implemented on a dSPACE platform with a prototype of dual-three-phase PMSM. The experimental results prove that both of the proposed rotor position estimation strategies have accurate rotor position estimation under steady-state, whilst the strategy based on third harmonic back-EMF can achieve outstanding dynamic performance of rotor estimation due to the removal of all filters.