Design and Assessment of a Battery-Supercapacitor Hybrid Energy Storage System for Remote Area Wind Power Systems

Recent advances in innovative energy storage devices such as supercapacitors have made battery-supercapacitor hybrid energy storage systems technically attractive. However the field of hybrid energy storage system control is relatively new, involving the major challenge of developing control techniques optimised for improved battery-life or other performance metrics. This thesis presents the design and analysis of an actively controlled hybrid energy storage system. Detailed information is given regarding the system implementation and dynamic controls developed as a part of the research. Novel use of the sliding-mode or hysteretic current-controlled DC/DC converter is shown to provide a versatile and robust power electronic building block for the power-control hardware implementation. Current state of the art in the field has converged around a frequency-domain approach to the overall power sharing strategy within hybrid energy storage systems employing batteries and high-power, low-energy density storage such as supercapacitors, with benefits in terms of reduced battery current maxima and an (un-quantified) increase in battery life having been reported. This research extends previous studies by considering the frequency-domain approach in further detail and providing quantitative simulation results confirming how an estimated increase in battery cycle-life of ~18% can be achieved. A systematic simulation framework used for the development and assessment of novel hybrid energy storage system control strategies is described and demonstrated in the context of a remote wind power application. The hardware design of all systems considered is described in detail and demonstrated by experiment.