RC Filter Free Flux-based Sensorless BLDC Drive for Permanent Magnet Motor using Pulse Amplitude Modulation

This paper proposes a novel flux-based sensorless BLDC drive position estimation using terminal phase voltage sensors without additional RC filters. Conventional sensorless BLDC drive estimates the rotor position through the zero-crossing point (ZCP) detection of electromotive force (EMF) voltage. Due to the pulse width modulation (PWM) control and inverter diode commutation, RC filters are added to remove additional voltage harmonics for the EMF ZCP detection. However, RC filters result in voltage phase and gain distortion, leading to the drive degradation at both low and high speed. In this paper, RC filters are eliminated by the pulse amplitude modulation (PAM) BLDC drive. Besides, the diode commutation reflected voltage spike can be compensated based on the flux estimation with phase voltage integration. This filter free flux-based sensorless BLDC drive directly measures phase voltages for position estimation. Without the influence of RC filter, the proposed sensorless drive is suited for high dynamic performance at full speed region. A 320W permanent magnet (PM) motor is used for experimental verification of the proposed filter free flux-based sensorless BLDC drive.