2
Chapter 1
In this introductory chapter, an overview is given of the various changes and the possible steps to be taken in power systems. The specific research objectives, questions and approach of this thesis are given, as well as how this fits in national and international research programs. The chapter ends with an outline of the thesis.
1.1
Changes in electrical power generation
In the early days of electrical power systems the grid consisted of small island grids with a local balance of load and generation. Later, to improve reliability in an efficient way, interconnections were made between these island grids, creating a larger power system. Due to economies of scale the power rating of individual power plants increased. These two trends caused an evolution of power systems into the current situation, which is characterized by large central power generation plants feeding into networks which span entire continents. In these networks, electrical energy is delivered from the higher voltage levels to the lower voltage levels where the loads are connected. On the primary energy source side, an ever existing concern is the increasing scarcity of fossil energy sources such as oil and gas. Further there has always been the awareness that being dependent from other countries for energy supply, makes a nation politically dependent, an unwanted situation, especially when the political bonds with those countries are unstable. Diversification of primary energy sources has always been the primary means to mitigate this dependence. As a result of the availability of primary energy sources the electrical power generation mix consists mainly of coal, gas, nuclear power, hydro power and oil. A strong driver to reconsider this generation mix is the growing concern over anthropogenic climate change [2]. The most important maninfluenced gas to contribute to global warming is CO2 which is unbreakably connected to the use of fossil fuels. This concern has led to a global political intention to reduce the emission of greenhouse gases, written down in the Kyoto Protocol of 1997 [3], after which several international conferences were held on the implementation, the latest one was held in Copenhagen, Denmark [4]. One of the means to reach these targets is to use renewable energy sources, which emit no or less CO2 , or which have a short CO2 life cycle. These include biogas, biomass, geothermal electricity, large and small scale hydro, photovoltaic (PV) and wind power. Some examples of these generation technologies are shown in Figure 1.1. Wave and tidal energy are RES technologies that are still in an infant stage. The European Commission set an indicative objective for the contribution by RES to the European Unions gross inland energy