High voltage energy storage system design for a parallel-through-the-road plug-in hybrid electric vehicle

Bryan Whitney D Belt, Purdue University

Abstract

A parallel-through-the-road (PTTR) plug-in hybrid electric vehicle (PHEV) pairs an engine powering the front wheels of a vehicle with an electric motor powering the rear wheels. This arrangement gives the flexibility of being able to operate the vehicle in an all-electric mode, an all biodiesel mode, or a combination of both to create maximum power. For this work, a 1.7 L CIDI engine running on biodiesel will be the engine being used and a 103 kW Magna motor will power the rear wheels. In order to power the motor, a high voltage (HV) energy storage system (ESS) needs to be designed and integrated into the vehicle. The goal for the mechanical design of the ESS is to create a structure that will enclose all of the batteries and battery control modules to protect them from environmental factors such as dirt and water as well as to prevent them from becoming dislodged in the event of a collision. The enclosure will also serve as a means to protect the consumer from the dangers of HV. The mechanical design also entailed designing a cooling system that will keep the batteries operating in an acceptable temperature range while they are charging and discharging. The electrical design focused on designing a HV system that could adequately supply enough current flow to each component to meet the peak loading condition yet be able to disconnect should a fault occur to prevent component damage. The system was also designed with safety in mind. Controllers will constantly be monitoring both the HV and LV systems to make sure that each is isolated from the other. Should a controller detect a problem, it will disconnect the HV system. The electrical system will have a high voltage interlock loop (HVIL). The HVIL will be a continuous LV circuit that passes through every HV connector and various switches, so that, if a connector is unplugged or a switch is flipped, the circuit will open. A controller will be monitoring the HVIL for LV. Should it not detect LV, the controller will disconnect the HV system. Several simulations and calculations were conducted as to whether six or seven batteries should be used. Seven batteries will allow the vehicle to accelerate quicker and have lower fuel consumption and emissions produced. However, there are several integration and cooling challenges that arise when trying to integrate seven batteries onto the vehicle. In the end, these challenges outweighed the benefits of seven batteries, and the six battery system was chosen. On top of all of the design and simulation results discussed above, there were also many lessons learned in regards to managing the design team involved in this project. The best way found to keep all members on task was to split the project into smaller sections, create a timeline with specific tasks and corresponding completion dates, and assign a person to be responsible for each task. This helped to gauge whether the project was behind schedule but also gave each member a responsibility and ownership to the project. It was also established that the best way to transmit data was to have a secure, networked drive that allowed members to access it from any computer at any time. This gave members the flexibility to work whenever and wherever was most convenient for them and allowed them to easily share data amongst members without having to attach large files to emails.

Degree

M.S.M.E.

Advisors

Shaver, Purdue University.

Subject Area

Alternative Energy|Automotive engineering|Energy

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