Optimization Methods for Hybrid Electric Vehicle Propulsion System

Sammanfattning: Design of hybrid vehicles is a hot topic because of the strict restriction on the emissions of the vehicle. The optimal design of hybrid vehicles becomes necessary to reduce the cost or emissions of the vehicle. The propulsion system of a hybrid electric vehicle is inherently more complex than that of a conventional vehicle as an electric power supply branch is added. The design involves topology design, component design and control design, where all phases are interrelated. The idea to handle all the three design phases together is called system level design. Due to its complexity, it is not possible time wise to evaluate all possible design options. Optimization algorithms are therefore needed to speed up the process. The variable types that appear in each design phase are different and multiple algorithms are needed. In this thesis, different algorithms are studied for their robustness for both continuous variables and discrete variables, as well as benchmarked for the Volvo internal optimization platform afterwards. Standard test cases are used to validate the algorithms and several features are added to an algorithm to make it more generic and efficient. Based on theoretical and experimental studies, recommendations for the selection of algorithms are proposed based on different types of variables.Based on the optimization platform, several different optimization coordination architectures for system level design are introduced and simultaneous and nested coordination architectures are tested by one specific industrial case in the second part of the thesis. Both methods appeared to be promising according to the result of the test case and they managed to reduce the convergence time dramatically. The vehicle model used was not precise enough to prove which method is the superior one but a more precise model can be introduced in the future to facilitate such a conclusion.