Research On Flexible Startup Control Strategy For Electric Vehicle Heat Pump Fan Under Multiple Operating Conditions

The vehicle-mounted heat pump air-conditioning system for electric vehicles has high energy efficiency ratio,which can improve the vehicle’s endurance and driving comfort.It is one of the hot research issues of energy saving and efficiency improvement for new energy vehicles.In winter heating,the energy conversion efficiency of traditional air conditioning system PTC heating mode is low,and the heat pump heating mode can increase the mileage of electric vehicles by about 20%compared with PTC heating mode.As one of the important components of heat exchange in heat pump air-conditioning,heat pump fan usually adopts permanent magnet synchronous motor with low noise,small size and high performance,and combines with sensorless control technology to achieve high energy efficiency ratio operation,while saving the hardware cost and space position of the system.Under the startup condition of the heat pump fan,the initial startup state of the fan has positive rotation,inversion,static and other conditions.In order to reliably identify the complex startup condition of the fan and effectively startup and control the fan motor,this paper carried out the following research on the permanent magnet fan :(1)A multi-condition flexible startup control strategy based on the permanent magnet fan of heat pump is designed.In view of the difficulty in judging the startup state of the permanent magnet fan,the current suppression method combined with the back-EMF sensorless control strategy is adopted to realize the accurate identification of the motor speed and the working state of the motor.According to different operating conditions of the motor,the complete starting control strategies such as static startup,forward free-coasting startup and reverse deceleration startup are designed.(2)Aiming at the problem of current overload and tracking error when current loop cuts in the process of free-coasting startup control,a free-coasting startup strategy based on resonant tracking is proposed to realize the smooth transition of speed loop and improve the dynamic performance of motor.The torque-power angle self-balancing relationship between the I/F open-loop control and the sensorless algorithm is analyzed,and a flexible switching strategy is designed to achieve the switching effect of smooth current,smooth speed and smooth torque.(3)The simulation platform and experimental platform of permanent magnet fan are built,and the multi-condition starting experiment of fan based on resonant tracking algorithm is designed.The effectiveness of the starting control strategy and the reliability of the flexible switching strategy are verified.In the forward acceleration starting switching process,the proposed flexible switching strategy can reduce about95.04 % of the speed jitter caused by direct switching.In the process of rotating startup,the compensation algorithm based on resonant tracking can reduce the steady-state error current amplitude of stator by about 47.10%,and improve the angle estimation accuracy of the sensorless algorithm by about 8.48%.