CETP - Optimal operation and decentralized control of offshore DC grid with RES / electrolyzer and hybrid energy storage system

This project is focused on design, control and energy management of offshore MVDC grid for green hydrogenproduction. The MVDC grid contains RES (offshore wind turbine or floating PV), electrolyzer stacks and a hybridsupercapacitor/battery storage system. Modular power electronics converters are utilized to interface each unit to theDC bus. A new decentralized and multi agent control system will be developed to enable coordinated operation of theelectrolyzer stacks and energy storage units to achieve optimum H2 production cost while preventing electrolyzer celldegradation. An optimal energy management by considering wind/solar forecasting will be implemented. Prototypebusiness models for the new energy storage technology will be developed. Substantial cost reduction will be achievedthrough development of a hybrid battery/supercapacitor energy storage system with novel and application tailored lowcost supercapacitor technology. The proposal is focused on the second main area of the call (Operation, control andprotection) but also involves Verification, test and maintenance (main area 3). The optimal control and energymanagement of the hybrid energy storage system along with intelligent control of parallel and modular stacks booststhe flexibility and stability of the islanded MVDC grid and increases the lifetime of the electrolyzer due to reduction influctuations. In addition, the decentralization in both hardware (modular power electronics/modular stacks) andsoftware (distributed control/energy management) boosts the reliability and scalability of the MVDC grid.

The OptiDCG4H2 project is a pioneering initiative aimed at advancing offshore green hydrogen systems to align with the ambitious objectives outlined in the European Green Deal. Green hydrogen is a key player in the green energy transition. With the overarching goal of achieving a competitive and climate-neutral EU economy in 2025, OptiDCG4H2 focuses on developing an innovative and reliable hydrogen system that adds flexibility to renewable energy sources (RESs), such as offshore wind farms. One of the most important business cases for green hydrogen production is an energy island. Here, the integration of electrolyzers with offshore wind farms in these systems facilitates low-cost green hydrogen production. By converting to off-grid operation, substantial cost reduction is attained through the elimination of the electrical network between the offshore wind farm and the onshore grid. However, the intermittency of wind power gives rise to variations in the electrolyzer’s input power with oscillations of various periods (seconds, minutes, and hours). Those variations degrade the electrolyzer stack and reduce its lifetime, hence the overall system reliability will deteriorate. This issue is especially prominent in offshore applications, where maintenance is costly. Moreover, the stability of such an islanded system can be jeopardized if the rate of change of wind power exceeds the ramp rate of the electrolyzer. Additionally, the utilization factor of electrolyzer can be quite low, which increases the capital expenditure (CAPEX) per unit of hydrogen production. To cope with these fundamental problems, the OptiDCG4H2 project advances the islanded hydrogen system by including an energy storage system that works as an energy buffer between the wind turbine generators and the electrolyzers. The storage system smooths out power fluctuations on the electrolyzer, hence preventing fast degradation of electrolyzer cells.