Single-cycle gas turbines operating at low-efficiency ranges due to redundancy concerns in offshore oil and gas platforms are responsible for considerable amounts of nitrogen oxides and greenhouse gas emissions in some countries. The abundant resource of offshore wind energy constitutes an extraordinary opportunity for reducing such emissions. However, new challenges are introduced when gas-powered generation is partially replaced by wind power. This paper investigates the possibilities provided by a centralized hybrid energy storage system (ESS) for addressing these challenges. It reviews frequency control concepts for isolated grids and discusses the analogous problem of power balancing within the ESS itself. A set of structures for control of the grid frequency and the ESS DC voltage are described and evaluated. All illustrated by results obtained within the frameworks of the Innovative Hybrid Energy System for Stable Power and Heat Supply in Offshore O&G Installation Project and the LowEmission Research Centre.