Energy management system of the hybrid ultracapacitor-battery electric drive vehicles

The search for new, alternative propulsion and energy sources in transport is one of the economic and technological priorities of the current decade. The modern development of hybrid drives and electric means of transport makes it possible to at least partially diversify conventional drive systems. The study discusses the use of a battery and ultracapacitor in electric vehicles. Simulation analyzes of energy flow were performed using the solutions of electric drive systems and various energy storage control algorithms. The research was carried out in relation to the use of braking energy, its conversion into electricity and its storage in a battery or ultracapacitor. The operating conditions of the battery and the ultracapacitor were assessed in terms of specific energy consumption while driving. The article proposed the use of a drive system connected in series, the last link of which was an ultracapacitor. Such a solution significantly reduced the use of the battery as well as its regular charging-discharging. At the same time, it required the use of a high-capacity ultracapacitor, which contributed to increasing its charging time. The analyzes were carried out using standardized research tests as well as tests in real traffic conditions. The research was carried out with the use of the AVL Cruise software for the analysis of energy flow in vehicles; a middle class passenger vehicle was selected for the tests, equipped with an electrochemical battery and - in the next stage of the research - an ultracapacitor. Three research models were used: I) typical electric drive system; II) a system with the use of ultracapacitors ran by a simple control algorithm; III) a system with the use of ultracapacitors with an advanced control algorithm (the algorithm took into account the change of driving conditions to the ultracapacitor charging conditions). The advantages of using ultracapacitors in the electric drive of a vehicle were demonstrated, especially for results obtained in real traffic conditions. Analyzing the simulation tests results allowed to determine the most advantageous options of utilizing these systems, in particular in the aspect of increased possibilities of algorithms controlling the flow of electricity in the drive system. © 2021 Warsaw University of Technology. All rights reserved.