A novel initial rotor position estimation method for wound-rotor synchronous starter/generator

This paper proposes a novel initial rotor position estimation method for wound-rotor synchronous starter/generator (WRSSG). According to the saliency of main generator (MG) of WRSSG, the information of rotor position is implied in performance of d-q axis inductances. This paper studied the principle of initial rotor position estimation by injecting modulated pulse voltage vectors. During the process of position estimation, the excitation current of MG contains several pulsating components, which reduce the accuracy of estimation result. In order to obtain more accurate initial rotor positon, a current waveform processing method by using Fourier series is proposed in this paper. Meanwhile, the most suitable order of Fourier series for fitting the current waveform is obtained from simulation. The experimental results show that the fitting order of Fourier series obtained in this paper can effectively eliminate the drawback of the excitation current's pulsating components, therefore the accuracy of rotor initial position estimation is improved obviously. This method can be incorporated in a DSP-based motor drive system. The proposed method does not need any additional hardware and much computation time.