Integrated quasi-steady-state energy flow algorithms and flow distribution factors for future integrated energy systems (QUESTIES)

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The increasing share of volatile renewable energy sources in power generation, the phase out of fossil fuel power plants and a lack of transmission lines create great challenges in the power system. This leads more often to a missing flexibility resulting in an endangered system stability. Here, a great potential is ascribed to integrated energy systems (IES, i.e. electricity, gas and heat) to add flexibility to the power system. Yet, an integration leads to interdependencies in the operation of the single energy systems; a change in one system will affect the other systems. If the systems are operated independently and the impact of a change in one system on the other systems is not known the probability that threats to system security are shifted between networks and responsibility areas will increase. Thus, the influence of single assets on the entire IES needs to be analyzed precisely, resulting in the need for a suitable method to estimate the impact of assets on all energy flows in the IES. Yet, only in the electric power system methods (i.e. distribution factors) are used to determine the impact of a load change on the power flows, which are based on the power flow algorithm using the Newton method. In the two other systems such methods do not exist. Thus, no method, that determines the impact of assets on all flows, is currently available to meet the requirements of a future IES. Hence, the proposed project will develop a method that adapts the already existing approach of distribution factors, which is nowadays limited to the power system, to be used for an IES.To provide such a method the existing integrated power, gas and heat flow algorithms need to be enhanced to meet the requirements of future IES. Hence, the project deals with four aspects. First, the flow algorithm will include the transient behavior in the gas and heating network. Second, Power-to-X technologies (e.g. heat pump, electrolyzer) will be included. Third, the gas flow algorithm emphasizes a hydrogen infeed and the resulting varying heat value along the gas network. Fourth, based on this integrated flow algorithm, the project will develop a methodology to determine the distribution factors of an IES and its coupling technologies. Consequently, the proposed project will deliver an algorithm that provides a comprehensive and flexible solution for the analysis of a future IES. It will enhance the method of distribution factors to be used in the same use cases but for an IES. Thus, the methodology is able to deliver a global optimal result for the entire IES operation rather than a local optimal result for a single network. The importance of such an approach will increase in the future due to an intensified coupling of today’s independent energy systems. Because the developed method has many possible use cases, which serve a secure and reliable energy system, it can be seen as an essential and inevitable research for a future energy system.