Improved Modular Multilevel Converter with Symmetrical Integrated Super Capacitor Energy Storage System for Electrical Energy Router Application

An improved modular multilevel converter with symmetrical integrated super capacitor energy storage system (IMMC-SSCESS) is proposed for interfacing energy interconnection and power buffering in electrical energy routers. Compared with traditional modular multilevel converter based distributed super capacitor energy storage system (MMC-DSCESS), the proposed IMMC-SSCESS increases the overall system rapidity and stability, reduces system control complexity and is suitable for energy storage system (ESS) management. Based on analysis of operation principles, the control algorithms are developed for both the sub-modules (SMs) capacitor voltage control and super capacitor state of charge (SOC) balancing control. Feasibility of proposed topology and control strategies are verified by simulation and experiment results.