Hybrid Energy Storage System With Active Filter Function for Shipboard MVDC System Applications Based on Isolated Modular Multilevel DC/DC Converter

This paper proposes an isolated modular multilevel dc/dc converter (iM2DC)-based hybrid energy storage system (ESS) for shipboard MVDC grid application. The cell capacitors of the iM2DC are applied to implement the dc active power filter capability, which improves the MVDC bus power quality without auxiliary devices or sacrificing the battery lifetime. In addition, the proposed ESS achieves superior fault response with fault current limiting function, which benefits the fault localization and fast recovery. The operation principle of the proposed system is introduced first and the converter equivalent averaged model is derived. Then the multifunctional control method is presented, including the virtualimpedance-based ripple distribution strategy. Both offline simulation and controller hardware-in-the-loop test results are provided to validate the control strategy as well as the ESS performance.