Cooperative ESS management strategy for stable islanded operations in a bipolar-type LVDC system

In this paper, a new energy storage system (ESS) management strategy for a bipolar-type low voltage direct current (LVDC) distribution system is being proposed. The dc distribution system is considered as an alternative to the increase of dc loads and dc output type distribution energy resources (DERs) such as photovoltaic (PV) systems and ESSs. The dc distribution system has several advantages such as conversion losses reduction, easy connection scheme for dc based DER, simple energy management strategies (no reactive power issues). In a bipolar-type, if it has each grid-interfaced converter, both sides (upper, lower-side) can be operated individually or collectively. A cooperative ESS strategy using interchange and transfer algorithm in both sides for effective and stable operation is proposed in this paper. Detailed energy management strategies of the main controller and local controllers are described. Simulation analysis using PSCAD/EMTDC is being performed to verify the performances of the proposed control strategy. In recent, the authors are trying to implement this strategy in real hardware pilot plant.