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Flexible Power Converter Structure for Interfacing Battery and Ultracapacitor to Dc Link for High Performance Energy Storage

Energy storage is vital to balance uncertain electricity demand and fluctuating renewable sources. It is desired that the energy storage is able to provide both high power and high energy. However none of the energy storage in current market is able to match these requirements. Therefore it is necessary to combine different energy storages together to utilize their individual merits. To effectively connect various energy storages this work proposes a unique flexible power converter structure to interface battery and ultracapacitor. Dynamic allocation of current between battery and ultracapacitor is possible to exploit the respective energy density and power density characteristics. Battery charge balancing and replacement are also possible without disrupting the normal operation. Above functionalities are achieved by modular power converter structure to bring down the device voltage and current stresses. In this proposed system the modular design approach of parallel or series connection of bi-directional converters is applied. This approach achieves different voltage current and power rating for various energy storages. Modular design also brings down the device voltage and current stress within each converter. The system is also has the capability to provide different output voltages and enable other different voltage rated devices to be directly connected to the DC bus. Applications: Hybrid energy storage Electric vehicle Residential stand-alone Micro-grid Patent: Patent Pending Opportunity: ·Exclusive/ non-exclusive licensing ·Partnership in commercial development

Benefits:

1) Many batteries are not connected in series. So higher volumetric efficiency of batteries are achievable. 2) Battery charge balancing does not require any extra circuitry. 3) Batteries have lower power density so one converter is connected to one battery. But UC is having higher power density so it can supply higher instantaneous current. But as four converters are connected to the UC the individual converter rating need not be increased. 4) The DC bus can be configured for 200 400 or 800V. This flexibility is a very important feature of the proposed scheme.

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