PLC based Structure for Management and Control of Distributed Energy Production Units

Abstract

Renewable Energy consists of energy generated from natural and unlimited sources, which include, among others, wind, solar, biomass and hydroelectricity. These energy sources, unlike the fossil fuels, do not contribute to the greenhouse gas emissions, namely the carbon dioxide emissions, and do not suffer from depletion as well. The global environmental alertness to protect Earth from the devastation of global warming has widespread, and consequently, governments’ incentive policies have driven to a massive investment in renewable energy, namely wind power. These incentives not only avoid a direct competition between clean energy and the one obtained from the conventional technologies, but also minor the damages on environment and mitigate human activity impacts on ecosystems. The continuous growth of the world demand has conducted to an increase of the total electricity power installed capacity, including renewable energy. The European electricity grid is one of the largest power systems in the world. Due to economies of scale it has always been advantageous to increase its size. Most of the European countries are synchronously connected to his grid. This means that the frequency in all of these interconnected countries is identical (in steady-state). The vast majority of the electricity in this grid is produced with large synchronous generators. Due to environmental, economical and geopolitical reasons there will be a shift in the production of energy. More and more distributed generation will be integrated in the system, some of which have significantly different characteristics when compared to the existing large synchronous generators (Doherty et al., 2005). There should always be a balance between the supply and the demand of electricity. Any deviation results in a change of the frequency of 50Hz. A set of ancillary services is in use to control the frequency, and therefore the power balance of the grid. In order to confront the variable or even stochastic behavior of the Renewable Energy Sources (RES), usually not meeting the electricity grid’s demand, the adaptation of an appropriate Energy Storage System (ESS) is thought to be essential. On the other hand, storage techniques are faced with controversies mainly referring to the high initial cost rates, the additional transformation losses and the noteworthy environmental impacts, largely depending on the correlation between the type of technology used and the selected site (Denholm & Kulcinski, 2004).