Grid-connected and Islanded Control of Energy Storage Converter

The development of distributed generation systems allows for the widespread application of microgrids in electric power systems. In most cases, renewable energy sources (RES) are used to provide power generation. Use of RES reduces environmental impact over conventional generation units but can lead to power outages in microgrids. In order to alleviate this and other drawbacks of RES, battery energy storage systems (BESS) can be used in coordination with RES. Amongst other functions, BESS can provide microgrids with power during outages. The main parts of BESS are the voltage source converter (VSC) and batteries. VSC allows for both grid-connected and islanded operation of the BESS. This paper presents simple control algorithms of battery storage converter during grid-connected and islanded mode of operation as well as algorithms for transition from one mode to another and vice versa. Experimental verification of presented algorithms is performed using prototype of 100 kVA storage converter and battery string with capacity of 70 kWh.