Wide-Range Operation Optimization Strategy of Bidirectional Energy Storage Converter for 10 kV Medium Voltage DC Integrated Power System

The main technical features that distinguish the next generation of medium voltage dc integrated power systems (MVDC-IPS) from the current ones are the 10 kV voltage level and the bi-directional energy storage system. The bi-directional energy storage converter is faced with the problems of voltage mismatch due to the wide range of voltage variations of the energy storage device and the exhaustive use of energy from the low voltage storage device. First, an isolated modular multilevel bidirectional dc converter (iM2BDC) is designed, and a novel chopping phase shift square modulation (CPS-SQM) is proposed for the characteristics of the topology. Subsequently, the steady-state characteristics of CPS-SQM are analyzed, and an optimization strategy is designed with the root mean square (rms) and peak value of ac current as the optimization objectives. Based on this, a comparison of the modulation strategies shows that the CPS-SQM has a wider power regulation range and a superior performance of ac current. Finally, the correctness and practicability of the proposed CPS-SQM and optimization strategy are demonstrated using simulation and an experimental 10 kW prototype.