Ultracapacitor/battery electronic interface development. Final report

A flexible, highly efficient laboratory proof-of-concept Ultracapacitor/Battery Interface power electronic circuit with associated controls was developed on a cost-shared contract funded by the US Department of Energy (DOE), the New York State Energy Research and Development Authority (NYSERDA), and the General Electric Company (GE). This power electronic interface translates the varying dc voltage on an ultracapacitor with bi-directional power flow to the dc bus of an inverter-supplied ac propulsion system in an electric vehicle application. In a related application, the electronic interface can also be utilized to interface a low-voltage battery to a dc bus of an inverter supplied ac propulsion system. Variations in voltage for these two intended applications occur (1) while extracting energy (discharge) or supplying energy (charge) to an ultracapacitor, and (2) while extracting energy (discharge) or supplying energy (charge) to a low-voltage battery. The control electronics of this interface is designed to be operated as a stand-alone unit acting in response to an external power command. However, the interface unit`s control is not configured to provide any of the vehicle system control functions associated with load leveling or power splitting between the propulsion battery and the ultracapacitor in an electric or hybrid vehicle application. A system study/preliminary design effort established the functional specification of the interface unit, including voltage, current, and power ratings, to meet the program objectives and technical goals for the development of a highly efficient ultracapacitor/battery electronic interface unit; and performed a system/application study of a hybrid-electric transit bus including an ultracapacitor and appropriate electronic interface. The maximum power capability of the ultracapacitor/battery electronic interface unit is 25 kW