In traditional hybrid energy storage system (HESS), separated bidirectional dc/dc converter is usually used to interface energy storage system with dc bus. Though it has an advantage in flexibility of control system design using separated power converters, it results in more switches, auxiliary components, and cost for the whole system development. Particularly, since the energy storage system (ESS) designed for high dynamic compensation (e.g., supercapacitor) is mainly used to provide high-dynamic compensation in transient state process, the utilization rate of the corresponding interface dc/dc converter is relatively low. On the other hand, the dc bus voltage compensation performance will be discounted due to the inherent time delay for the current reference signal production of HESS with outer loop voltage control. In this paper, to address these two issues, an integrated topology of the hybrid energy storage system is proposed, and an improved control method that has the ability to enhance the control performance of HESS to compensate the dc bus voltage is developed too. The experimental test results are provided to validate the correctness and effectiveness of the proposed methods.
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