Series Connection of Supercapacitor Modules for Energy Storage

STATCOMs have been considered as a technology to stabilise the grid voltage dynamically. However, its capability of instantaneous active power circulation is limited by a small amount of stored energy in a conventional capacitor. Supercapacitors are a promising energy storage technology to enhance the performance of a STATCOM by giving it the ability to exchange bursts of power. In transmission and distribution (T & D) applications, supercapacitors have to be connected in series in order to withstand high voltage stress. This paper describes the tests that were carried out to evaluate how supercapacitor modules can be connected in series, and to get insight into the characteristics of series-connected modules. Dominant parameters were identified and a suitable model of a high voltage/power supercapacitor was developed. This model can aid the design of topologies and control strategies to enhance the dynamic performance of STATCOMs.