Towards a new technological solution for Community Energy Storage

Abstract

Energy storage in low voltage grid is receiving increased attention due to renewables integration and consumption growth, challenges faced nowadays by grid operators. In this work, a study of main implementation issues for community energy storage (CES) is presented along with a comparison between possible solutions for the bidirectional isolated power conversion system (PCS) to interface a battery pack with the electric power grid. The aim of this research is to increase the power density of the power converter and keeping simultaneously the same reliability of traditional solutions. These goals are pursued to be achieved through the reduction of the conversion stages and utilization of new optimization methodologies to reduce the volume of the passive components. The proposed topology for the PCS is based on a matrix converter (MC) that performs a direct AC to AC conversion between the grid and a high-frequency transformer (HFT). With this solution it is possible to eliminate the traditional DC-link capacitor and obtain a single-stage power conversion with bidirectional power flow capability. This proposed solution is evaluated and compared with a conventional two-stage topology through extensive simulation. Two prototypes systems were designed for a 10kW PCS to connect the three-phase 230/400Vrms, 50Hz mains to a battery pack with voltage range of 320V to 490V. Simulation results are presented to assess the power quality provided by the front-end and the battery side converters, as well as performance evaluation and efficiency analysis.