Constraint-Based Graceful Degradation in Smart Grids

In a electrical distribution network, the challenges involved in the decentralized power generation and the resilience of the network to handle the failures, can be easily anticipated. With the use of information technology, a better control can be achieved over the distributed generation units and the fault handling in them. In this contribution, the use of a graceful degradation strategy is proposed as a means to improve the availability of the system during a fault situation. The Graceful degradation is presented as a constraint satisfaction problem. The trigger and the computation of the degradation process are formulated as the constraints. The concept of the utility of the resources is used to support a dynamic decision to trigger the degradation process. The computation of the graceful degradation strategy is formalized as an SMT problem and analyzed using the Z3 SMTsolver. The approach is illustrated with the help of a use case of applying the degradation strategy on a prosumer node during the power outage in the distribution network. It illustrates the dynamic calculation capability of the degradation scheme in the face of an unpredictable power from a renewable energy resource.