Control of a microgrid-connected hybrid energy storage system

A promising solution to face the problems related to the integration of the Distributed Generation (DG) with a high renewable energy penetration level is to redesign the distribution grid using the concept of MicroGrids (MGs). Due to its constitutive components, production capacities, controllable loads and storage systems, a MG can contribute to the market either as load or production and its status can change according with the renewable energy resources availability and the needs of the main grid. The use of storage system in a MG plays an essential role in order to ensure energy balance and also allowing maintaining high power quality. In order to satisfy these two constraints, this paper proposes the association of a Vanadium Redox Battery (VRB) and SuperCapacitor (SC) bank in a Hybrid Energy Storage System (HESS). A Three-level Neutral Point Clamped (3LNPC) Inverter is used as a unique interface between the HESS and the MG. The paper focuses on the modelling and validation of the HESS, the power division limits using the 3LNPC inverter and its operation integrated in the MG. The validity of the proposed solution has been confirmed using both simulation and experimental tests.