Current ripple simulation of the electric system of an electric bus
Sammanfattning: With effect of global warming and climate change the electrification of vehicles enables a more sustainable and environmentally friendly alternative to conventional vehicles as it reduces toxic emissions and overall energy consumption. Different extents of electrification is today used. Hybrid and electric vehicles are two examples. Tools to simplify the design of electric vehicles are of value to predict the traction voltage system behaviour. One of these behaviours are current and voltage ripple. By making predictions of the life time of components in the traction voltage system, improvement of the system's overall electrical performance and reduction of development costs. A component level decomposition of the traction voltage system of two different buses was performed. Component specific information for each bus was gathered at Volvo, at Volvo's suppliers and by measurements. Simplified full-system models of two existing buses were built with associated subsystem in the chosen simulation environment. Verification tests were performed on one bus, the electric hybrid. The simulated system's behaviour and its consistency with reality was evaluated. A complete library of equivalent circuits of the two existing buses was built. The measurements on the electric hybrid followed custom test cases. Component measurements were also performed on four common mode filters as data was insufficient. Results show that the model is not fully consistent with reality. There is uncertainty with the parametrization of components in the model. The model is sensitive to small modifications of parameter values. Especially filter capacitors and inductors. When given parameter values was replaced with values found in literature some results were more consistent with reality. Further investigation is thus needed to ensure the correctness of the model. Therefore another master thesis is planned to continue the work.
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