Phase Current Reconstruction Of Brushless DC Motor With Single Current Sensor

Brushless DC motor is widely used in the field of vehicle traction and electric propulsion,because it has many advantages,such as large output torque,high power density,good speed performance.Low-voltage high-current is a significant feature of this type of controller,MOSFET is its typical power electronic device.However,MOSFET silicon diode has a large conduction voltage drop.In order to meet the high efficiency requirements,low-voltage high-current controller should adopt synchronous rectification control.At the same time,brushless DC motors are required for three-phase current closed-loop control to precisely control torque both in motor mode and in brake mode.Traditional phase current detection methods usually use multiple current sensors,resulting in low controller integration,large size,high cost.This paper mainly studies the phase current reconstruction method of brushless DC motor current closed-loop synchronous rectification control system under single current sensor condition.The details are as follows.Firstly,the commutation characteristics of the brushless DC motor synchronous rectification control are analyzed in motor mode,the relationship between the bus current and the phase current is deduced in the three-phase conduction interval and two-phase conduction interval.Realizing the phase current reconstruction in motor mode.Secondly,the commutation characteristics of the brushless DC motor synchronous rectification control are analyzed in brake mode,the relationship between the bus current and the phase current is deduced in the three-phase conduction interval and two-phase conduction interval.Realizing the phase current reconstruction in brake mode.Thirdly,the simulation of single current sensor brushless DC motor system is carried out.The relationship between the bus current and the phase current under open loop control is verified both in motor mode and in brake mode.And the current closed-loop control is realized based on the phase current reconstruction method.Finally,the experiment of single current sensor brushless DC motor system is completed.And the relationship between the bus current and the phase current under open loop control is verified.And the phase current reconstruction closed loop control is realized.