Study On The Control Of Integrated Starter-generator Of 48V Sytem For Internal Combustion Engine

Based on strict fuel consumption and emissions regulations and increasing vehicle power requirements,48 V system additional cost is relatively low and meets the requirements for fuel consumption and emissions,so 48 V system caused the concerns of OEMs and auto parts suppliers.48 V system adds DC/DC voltage converter,battery and ISG motor,based on original 12 V system.ISG motor can achieve rapid Stop-starter,brakeing energy recovery,torque assist,driving power generation.The paper is mainly for functional requirements of 48 V system ISG motor,taking ISG motor as the research object,DC motor as an external laod,completed the vector control of the ISG motor.The main work includes mathematical modeling of ISG motor,model simulation,motor controller development,PC debugging interface development,test bench design and processing,controller performance test,concrete works such as:First,referenced to domestic and foreign literature of permamnent magnet synchronous(PMSM)motor,the mathematical model of PMSM is deduced under three-phase stationary coordinate system(a,b,c),(?-?)orthogonal coordinate system,(d-q)rotating coordinate system.Analyzed the vector control algorithm of ISG motor,the torque control is converted to d-q axis stator current control.Studied control strategy of Maximum Torque Per Ampere(MTPA).In this paper,the strategy of Id =0 is used for ISG motor control.Based on mathematical model in(d-q)rotating coordinate system and strategy of MTPA,established controller,converter and motor simulation model in the Matlab/SIMULINK.The target speed is resolverd to target torque in speed controller,the torque/current controller output the target voltage into SVPWM algorithm to get duty cycle signal,it is to output drive signal into the inverter model through the PWM generator.Feed-forward decoupling algorithm is added to decouple coupling of flux in d-q axis voltage equation in current controller,the performance of PI controller is increased.Switch characteristics are ignored in the process of modeling inverter.The voltage and flux linkage eqution achieved electromagnetic process in the motor model,mechanical motion equation is to get motor speed.Applied different load torque at different times,the speed controller can stabilize speed at target speed 800r/min.Speed can also quickly return to target values in the moment of load torque change.Developed ISG motor controller,DC motor controller and test-bench to fix two motors.ISG motor controller includes main control part based on TMS320F23885,signal conditioning part,three-phase full bridge inverter circui.DC motor contoller share one controller with ISG motor,it's power part is H bridge inverter circuit.The test-bench is to fix two motors,the coupling is to connect two motor shaft.Developed PC debugging interface based on Lab VIEW,it can send control command and show eight variables on display window,clearly observe response process of the current and speed.Taking the target voltage vector in first sector as an example,deduced the process of voltage modulation using SVPWM.The algorithm of SVPWM based on TI's technical documentation.Analyzed the mechanism of inverter disturbance voltage,measured the waveform of inverter disturbance voltage,designed and verified compensation algorith.The phase current waveform become more significant sinusoidal.Tested motor speed and torque control based on test-bench,the response of speed and current is analyzed,speed and d-q axis can quickly follow the new target value.The operating points of rapid Stop-starter,brakeing energy recovery and driving power generation are tested.The speed of DC motor quickly increases driven by ISG motor in condition of rapid Stop-start.During the process of DC motor braking,the state of negative torque and positive speed appears,so ISG motor is in condition of brakeing energy recovery.The DC motor drivers the ISG motor to run in condition of driving power generation,and measured phase voltage waveform at 720r/min.Through model simulation and experimental verification,realized the vector control of ISG motor.Tested the performance of ISG motor controller by controling speed and torque.The functions of rapid Stop-start,brakeing energy recovery and driving power generation are tested by using a DC motor to simulate an external load.