A Solid Oxide Fuel Cell model to investigate load following and stability issues in distribution networks

The increase of DG penetration in the distribution networks makes more and more interesting the investigation of security issues which are typical of the large transmission grids (transient stability, voltage stability and small signal stability) as well as the study of the DG responses to load changes in the grid. This paper presents the model of a Solid Oxide Fuel Cell (SOFC) dedicated to perform dynamic simulations on MV distribution networks. In particular in the present paper transient stability and load following issues are tackled. The first part of the paper is aimed at describing the model of the SOFC which is then used in the test system. As also a gas turbine is inserted into the test system, a brief look at the gas turbine model is mandatory. The aforementioned models include both the slow dynamics (GT prime mover, electrochemical system time constants for SOFC) necessary to study the DG response to load variations and the fast dynamics (e.g the power converter control and protection systems for SOFCs) necessary to study the transient stability related issues. The results of the analysis (carried out on a test MV distribution network) are reported and some conclusions are drawn.