Research On Global Optimal Control Strategy Of Parallel Hybrid-power Gas Engine Heat Pump System Based On Dynamic Programming Algorithm

Hybrid-power gas engine heat pump system(HPGHP),which is combined by hybrid technology and traditional gas heat pump system,has an advantage of optimizing bad engine operating state of deviating from the economic operation area,comparing to conventional gas heat pump system.Hence to improve the primary energy utilization rate of the HPGHP system.The key to improve the rate is to optimizing the control strategy of hybrid-power drive system,which includes operating mode switching and energy matching of gas engine and motor in the drive system.In order to further improve the system efficiency,dynamic programming algorithm is introduced into the study of parallel HPGHP system,which was built by the Refrigeration and Cryogenic Engineering Laboratory of Southeast University,aiming at proposing a global optimal control strategy.The specific research contents are as follows:(1)The structure of the parallel HPGHP system is briefly explained and the mathematical modeling of the main equipment is constructed.Through the research and analysis of the main equipment,the universal characteristic curve of the gas engine,the power distribution curve of the motor,the efficiency distribution map of the battery and the performance curve of the compressor are obtained,and the efficient operation interval and boundary conditions of the gas engine,the motor and the battery are determined.(2)Based on the mathematical model of the system,the dynamic programming algorithm is introduced to analyze and solve the global optimal control strategy of HPGHP system with multi-stage transmission ratio and HPGHP system with continuously variable transmission.The results show that under the global optimal control strategy,the thermal efficiency of the gas engine is maintained at a high level throughout the cycle,which is better than that of previous studies.The battery SOC remains unchanged at the beginning and end of the cycle.The gas engine output torque remains relatively stable and basically operates in its economic operation area,maintaining high thermal efficiency.The average thermal efficiency of the gas engine under the MO1 strategy is 0.266,and the gas consumption in the cycle is 2.96 kg.The average thermal efficiency of the gas engine under the VO1 strategy is 0.272,and the gas consumption in the cycle is 2.86 kg.(3)The simulation results are compared with the existing research results to demonstrate the advantages of the global optimal control strategy in optimizing the operating conditions of the gas engine and reducing the gas consumption of the system.The results show that compared with the logic threshold and the instantaneous optimization control strategy,the multi-stage transmission ratio and the continuously variable transmission HPGHP system using the global optimal control strategy have significantly improved the average thermal efficiency of the gas engine,and the gas consumption has been reduced to varying degrees.Through the comparison of the multi-stage transmission ratio and the simulation results of the continuously variable HPGHP system,it is found that the continuously variable transmission can effectively improve the thermal efficiency of the gas engine and the system energy utilization.