Pure Integration-Based Stator Flux Acquisition of AC Drives at Low Stator Frequency

This paper develops an accurate acquisition method of pure integration-based flux estimation down to sub-hertz stator frequency for AC drives. A resonant type observer-based approach is taken as one possible solution of eliminating the dc offset originated in the acquisition process and the negative sequence component of unbalanced gains of current measurement channels. All the processes in correcting these problems do not rely on motor parameters and interfere with inverter nonlinearity effects. At the same time, the positive sequence component estimation is performed by creating an error signal between a motor model reference and an estimated q-axis rotor flux established by a permanent magnet (PM) in the synchronous coordinate. The acquisition accuracy of the stator flux is significantly improved through the pure integration scheme for restraining the error of the flux magnitude and phase angle. The proposed technique further contains a residual error compensator to completely eliminate miscellaneous disturbances in the estimated flux. The developed algorithm has been implemented on an 1.1-kW permanent magnet synchronous motor (PMSM) drive to confirm the effectiveness of the proposed scheme.