The use of small-scale generation based on disparate new and renewable technologies is becoming more prevalent due to the imperative to reduce greenhouse gas emissions that are thought to be the chief cause of climate change. As penetration of these distributed elements increases, displacing central generation, there is a growing need to understand the composite behaviour of groups of Distributed Generation (DG) devices, also known as Virtual Power Plants (VPPs). This paper presents an overview of the mathematical modelling of the VPP leading to the development of a user-friendly tool that can be used as a power system engineering teaching aid to demonstrate the characteristics of VPPs.