A Robust Semantic Overlay Network for Microgrid Control Applications

Control systems for electrical microgrids rely ever more on heterogeneous off-the-shelf technology for hardware, software and networking among the intelligent electronic devices that are associated with dispersed energy resources. For distributed microgrid applications in a dynamic environment, overlay networks provide an opportunity for a flexible and robust logical communication infrastructure among these intelligent electronic devices. Agora is a semantic overlay network that allows to efficiently route queries -related to microgrid controlin the overlay network, based on an XML description of the static and dynamic characteristics of the intelligent electronic devices. It is robust against changes in the microgrid and ICT infrastructure, and provides graceful degradation in case of unrecovered failures. 1 Motivating a Flexible, Dependable Information Infrastructure More and more small-scale dispersed energy resources (DERs) (e.g. wind turbines, photovoltaic panels, coupled heat-power units) are being deployed in the electrical distribution grid. This puts extra stress on the power grid in an era where electricity is one of the most important commodities for economical, industrial and everyday activities. Main factors causing this shift from centralised electricity production to a decentralised power generation with DERs are the availability of small-scale units, which offer an increased flexibility in the liberalized energy market, and the growing trend towards sustainable development which favours energy efficient and low CO2emitting plants [1, 2]. Regarding power system reliability, integrating DER units can bring benefits, as well as deteriorated grid performance. Therefore new control strategies are being proposed to maintain the desired degree of dependability for the electricity supply [3-5]. As such, many of these distributed control algorithms rely on distributed computer and communication systems, running on several computing nodes with an off-the-shelf ICT infrastructure for communication. Many DERs and loads become intelligent electronic devices (IEDs) that are interconnected over this information infrastructure, as indicated in Fig. 1. This trend can also be found in many other critical infrastructures (gas, water, transport, telecommunication, etc.). Over this information infrastructure, new services can be delivered by exploiting both the power and ICT infrastructure simultaneously. For instance, external information such as the instantaneous electricity price from real-time market places, can be 102 G. Deconinck et al.