RT23 | Smart-Integrated-Grid: PHIL island grid comprising electric and hydrogen systems

Modern energy systems require tremendous changes in our energy infrastructure in order to cope with the consequences of decarbonization. Two big challenges arise from, firstly, the volatile nature of renewable energy sources such as wind and solar leading to an energy injection profile of intermittent character and, secondly, the decommissioning of rotating generators. These two circumstances combined could create a perfect storm that is apt to destabilize the energy system for the following reason. As long as electrical energy grids based on alternating current (AC) existed, it has been imperative to stabilize the AC frequency to a predefined value, e. g. 50 Hz in Europe. Fluctuations were always a factor and were caused e. g. by load shedding and shifting. Rotating generators owing to the inherent mass inertia of their components countered this phenomenon by performing a buffer function to smooth out frequency fluctuations. Sacrificing this equilibrating property obviously exposes the grid to dangers emanating from such fluctuations. In addition to the abolition of this mass inertia-based compensation mechanism, the shift in energy input towards inherently volatile energy sources will exacerbate this problem dramatically. More succinctly, we face two problems: more fluctuations and less capability to counter them. A promising solution to this conundrum is the coupling of energy sectors in order recreate a buffer capability, albeit of a different nature. The idea is to couple the electrical energy grid to a hydrogen energy grid and use hydrogen as the buffer component. This approach is based on a seamless coupling of power-to-gas (via an electrolyzer) and gas-to-power (via a fuel cell) technologies. However, the implementation of sector coupling is not a straightforward affair and requires a holistic approach encompassing the scientific domains of power electronics, electrochemistry, and electrical energy systems. Additionally, intelligent control and communication is necessary for the operation of different technical components needed for the intersection of energy systems. This is especially the case for non-stiff energy systems where disturbances have a great impact on system behaviour. Thus, coordination, communication, and load distribution need to be fast and reliable. For that purpose, a low voltage AC island grid consisting of an AC-load, battery string, and emulated photovoltaic (PV) and fuel cell strings has been set up and is being investigated. The direct current (DC) sources, viz. battery and PV are connected at the intersection point via DC/DC and DC/AC power electronics. On an overarching hierarchy level, an OPAL real-time simulator has been implemented that serves three purposes: 1. Centralized control: Generates reference values and initializes sequences, 2. Monitoring device: Acquisition and display of measurement data in real-time, 3. Real-time simulations: Generates input/output parameters for emulated devices. All three points can summarily be demonstrated through an OPAL-initialized automated start up sequence involving all components, the implementation of sequences including transient events, and safe shutdown protocols, again involving all components. Acknowledgement: This research is part of the project CoupleIT!, funded by dtec.bw – Digitalization and Technology Research Center of the Bundeswehr which we gratefully acknowledge. dtec.bw is funded by the European Union – NextGenerationEU.