An Improved Sensorless Control of BLDC Motor Using 1-Shunt Current Sensor for HVAC of EV

This paper presents a novel 3-phase current sensing and reconstruction method using a single-shunt. A single-shunt resistor is an attractive current sensing method because of its low cost and small size. However, it has non- detectable current sensing regions when each phase's Pulse Width Modulation(PWM) duty ratios are close. For continuous current sensing at every PWM period, the actual PWM durations of two effective voltage vectors must be longer than the necessary current detection time. Consequently, the limited PWM duration causes additional current distortion, leading to reduced control performance. In the proposed method, the current ratio between the detectable phase current and the non- detectable medium phase current of the 3-phase BLDC (brushless DC) motor is utilized to estimate the medium phase current. Then, the other phase current is calculated by multiplying the detected phase current by the estimated medium phase current. The proposed method does not restrict the PWM duty ratio to prevent a shorter duration than the required sensing time. Then, the sinusoidal phase current with reduced distortion can be implemented to enhance control performance. Furthermore, a complex mathematical model with parameter dependencies is not utilized. Only a basic derived current relation function based on the rotor position is used to calculate the undetectable phase current. The proposed method is tested and verified through simulation and experiments of sensorless control of fan blower BLDC motors for electric vehicles. In the simulation and experimental comparisons, the proposed method demonstrates enhanced current sensing capabilities along with improved sensorless control performance.