无位置传感器无刷直流电机闭环三段式启动策略

Closed-loop 3-step start-up strategy for brushless DC motor without position sensor

针对无位置传感器无刷直流电机(brushless DC motor,BLDCM)启动问题,提出了一种转子初始位置精准预定位与加速过程中优化定位相结合的闭环三段式启动策略。在电机绕组中施加短时间脉冲电压矢量,通过检测直流母线电流可以将转子位置锁定在60°电度角范围内,在此基础上通过向指定绕组通电与检测电流比较阈值完成转子精准预定位。预定位后进入优化定位与加速阶段,此时电流比较阈值作为换相条件,保证转子在加速过程中准确换相,当转速达到一定值时系统切换到反电势运行状态(back electro-motive-force,EMF)。实验结果表明,提出的三段式闭环启动方法无需传感器、成本低、可靠性高,能保证系统在整个启动过程中均处于闭环工作状态,不会出现失步或启动失败现象。

Aiming at the starting problem of sensorless permanent magnet brushless DC motor （ BLDCM ）, a novel closed-loop 3-step start-up strategy is proposed,which integrates the precise pre-location of initial rotor-position and the location optimization in accelerating process. When short-width-time pulse voltage vectors are injected into 3- phase stator windings, the initial rotor-position is locked in a 60° electrical angle range through detecting the current in the DC link of the inverter. Based on above, the precise pre-location is achieved by detecting the current threshold when constant voltage is applied to the assigned stator windings. After pre-location,location optimization and acceleration process proceeds. In this process, the current threshold is used to ensure the correct commutation, such that the system can be switched to backelectro-motive-force（EMF） mode when the rotor is accelerated from standstill to certain speed. Experimental results show that the proposed closed-loop 3-step start-up method is simple to implement without any sensors, cost-effective and highly reliable; it can avoid loss of synchronization or starting failure, and ensure the system work in closed-loop state during the whole start-up process.