A New Method Of BLDCM Commutation Error Compensation Based On Line Voltage Difference

In recent years,BLDCM has been widely used in medical,aviation,home appliances,military and other fields because of its high efficiency,high reliability and low cost.In this paper,the new method of BLDCM commutation error compensation without position sensor is the main research content.Three key technical problems are discussed,which are rotor position detection method,motor starting strategy,the cause of commutation error and compensation method.Firstly,the phase change control scheme without position sensor based on line voltage difference is studied.The mathematical model of BLDCM in natural coordinate system is established.The three-phase six state control principle and speed regulation principle of BLDCM are analyzed and summarized.This paper analyzes the control principle of the zero crossing detection method of back EMF based on line voltage difference,simplifies the calculation formula of the zero crossing detection method of back EMF reasonably,and puts forward a new commutation control strategy of motor.However,the detection of the zero crossing point of electromotive force of the motor needs the help of virtual neutral point,which can be obtained indirectly through the detection terminal voltage,which increases the waste of the hardware circuit.Therefore,this paper proposes a method of rotor position detection of BLDCM without position sensor based on line voltage difference method,which can effectively reduce the hardware waste caused by constructing virtual neutral point,and can be widely used in rotor position detection of BLDCM without position sensor.Secondly,the starting method of sensorless BLDCM Based on short-time pulse detection is studied.The relationship between the equivalent inductance of the stator winding and the initial position of the rotor after the introduction of the short-time detection pulse is analyzed.The principle of the initial position of the rotor and the closed-loop acceleration starting of BLDCM without position sensor are studied,and the corresponding control method is given.Considering that the detection accuracy of the rotor in the critical area may be limited,the priority is set for the detection current.Then,based on the zero crossing detection method of back EMF,the mechanism of commutation error of BLDCM without position sensor is analyzed.The commutation error of motor is analyzed from two aspects of filter circuit and PWM inverter circuit.Because the line voltage difference method is affected by the filter circuit when obtaining the line voltage signal,the commutation error is caused.On this basis,a new method of BLDCM commutation error compensation based on line voltage difference is proposed.This method is easier to realize than the traditional BLDCM commutation position error compensation method.It does not need to build the virtual neutral point of the motor to avoid the waste of hardware circuit.Finally,a three-phase sensorless BLDCM starting control system model is built in Matlab/Simulink,and the starting performance of the short-time detection pulse starting method and the traditional "Three-stage" starting method is simulated and compared.A new double closed-loop control system with commutation signal delay compensation is built.The simulation results show that the phase current fluctuation,line current fluctuation and electromagnetic torque are obviously suppressed.At the same time,it can be found that the average output torque of the motor is improved by using the new method of BLDCM commutation error compensation based on line voltage difference.