Research Of Braking Control Strategy Of Torque Compensation System Applied In Diesel Engine

Due to the limited instantaneous power output, diesel engine will suffer a speedfall under highly impact load, which causes abnormal halts or other severe problemsunexpectedly and restricts the application range badly. Therefore, a set of torquecompensation system is employed into diesel engine to stable the speed, thusachieving instantaneous torque compensation. In this paper, some correlationtechniques applied in the braking process of the torque compensator are detailedanalyzed.To begin with, after referring to current literatures, the mathematic models ofthe permanent magnet synchronous motor (PMSM) and super-capacitor are built up.What’s more, the operation principle of power conversion circuit of super-capacitoris studied in theory. Therefore, a simulation of triple bi-directional DC/DC convertoris built with Matlab/Simulink, which verifies the results of the aforementionedanalysis and lays a theoretical foundation of the following braking control strategy.In addition, the braking process of the PMSM in the torque compensationsystem is analyzed, based on which, the whole process is divided into decelerationbrake period, constant-speed brake period and generation period. In terms of firsttwo, an vector control strategy based speed closed-loop control scheme is designed.Further, to deal with the last one, voltage closed-loop vector control strategy whichis based on constant voltage vector is proposed and the rules of calculation of thekey parameters are presented. What’s more, all the periods in the braking processare simulated and analyzed with the method once used in DC motor. Besides, thetransformation of both voltage and current vectors in the braking process isdemonstrated with the vector diagram in detail.Moreover, the super-capacitor based energy storage system (ESS) is researchedto figure out the power flow under the whole operation conditions. Based on theanalysis, a triple bi-directional DC-DC convertor based ESS is proposed. Plus, twodual-loop control methods with inductance current as inner loop and super-capacitoror DC voltage as outer loop are presented respectively. Also, an improved non-linearproportional factor based control scheme is put forward, which can solve theover-charge issue of super-capacitor caused by double deloading.System models are built with Matlab/simulink which testifies the rightness ofthe proposed control scheme. The experiments of torque compensation system underbraking condition are conducted. Therefore, the effectiveness and feasibility oftorque compensation system applied in diesel engine is verified.