Development And Research Of High Speed Brushless DC Motor Drives And Their Key Technologies

Fuel cell vehicles(FCV)are token as an ideal technology solution of new energy vehicles and are in the early stage of industrialization.With the increase of the national support and the research activities,FCV will be popularized in the coming years.The centrifugal air compressor that belongs to the FCV air supply system is an ultra-high-speed rotating machine,which is usually driven by the high-speed brushless direct current(BLDC)motor.To assure the stability and efficiency of the fuel cell air compressor,this thesis developed a high-speed brushless DC motor controller and conduct an intensive study on the key problems encountered during development process.They are mainly as follows:1)The steady model of phase currents was established for a symmetrical three phases motors.With the current model,a simulation model which could determine the ideal commutation position of BLDC motor was built up,inclusive of the optimization method.Following the simulation model,the variations of ideal commutation positions along with the stator resistor,stator inductance,electrical time constant,rotating speed and load were analyzed.2)The relationship between DC-link current and commutation position deviation was deduced by analyzing the phase difference between the amature current and the back electric motive force(BEMF).Based on this relationship,a PI controller whose input was the DC-link current and output was the phase compensation angle was built up to realize the "commutation position optimization strategy based on DC-link current".3)A new fast fault-tolerant control method was proposed by changing the external interrupt triggered diagnosis to the timer interrupt triggered diagnosis.This new method reduced the load of the microprocessor computation,expanded the applicable scenarios of fault-tolerant control method and shortened the time of fault diagnosis and signal reconstruction.4)This thesis has put forward a new single sensor current detecting method through a new three-phase current reconstruction strategy.By using precise mathematical model,the accuracy of the current reconstruction was improved.Based on the detailed freewheeling current analysis of the switched off phase,the applicable scope of the three-phase current reconstruction strategy was expanded.5)A high-speed sensorless square-wave BLDC motor controller was developed specially for FCV air compressor.The new control strategies proposed in this thesis were used in the motor controller successfully to shorten its startup time and improve its efficiency and reliability.Also a unique semi-close-loop startup method used for air compressor BLDC motor was proposed.