Grid Integration of Heterogeneous Energy Sources/Loads using a Multi-port MMC with Independent Power Flow

Recent surge in the adoption and grid-integration of renewable distributed energy resources (DERs) at utility scale has spurred the interest in power-electronic architectures for interface at medium-voltage (MV) grid. The constant endeavor to achieve higher power densities has brought forth the need for multi-port converter topologies capable of integrating heterogeneous energy resources through a common interface scheme. In this paper, a novel high-frequency link transformer based multi-port power converter termed Distributed-Phase-MMC (DP-MMC) is proposed for the grid-integration of DERs at MV level. The topology has several advantages such as modularity at sub-module as well as sub-system level, decoupled/independent power flow through its input ports and reduced voltage stresses in the HF-transformer windings. A simplified equivalent circuit and a phasor-based analysis are proposed for the system, which provide qualitative and quantitative insights into the power transfer mechanism across different ports. In addition, a control scheme is proposed based on this analysis for the operation of the system while injecting the required active/reactive power to the grid. The proposed scheme achieves the critical objective of unifying dispatchable storage systems with intermittent renewable energy systems at MV-level. Detailed MATLAB-Simulink results validate the overall operation and control of the proposed multi-port DP-MMC architecture.