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High-Accuracy Position Sensorless ZCP Detection In PMBLDC Motor Drive For LEV Applications

This paper presents a new high precision position sensorless control of permanent magnet brushless DC (PMBLDC) motor suitable for a wide speed range in low-cost light EV (LEV)applications. Speed independent flux linkage function is used to estimate rotor positions that address a key challenge operating at low speed. Back EMF of the motor at low speed is small and is not accessible in practical scenarios. Here, the line voltage of the motor is sensed for sensorless algorithm, which is developed using basic mathematical model of PMBLDCM. The usage of low pass filter (LPF) creates magnitude attenuation and phase lag in the system. This lag in commutation signals causes serious current and torque ripple at lower speed. A compensation method with feedback loop is used to minimize delay and commutation errors. Speed estimation using virtual Hall signals has an inherent delay due to discrete position information. Therefore, an improved speed calculation method is presented with minimum delay. The proposed method is also suitable for regenerative braking. Results and analysis validate the reliability and stability of this method.