Wind Power Integration: Network Issues

Abstract

Rise of energy prices and the growing concern about global warming have exerted big pressure on the use of fossil fuels to reduce emissions especially CO2. Instability in some of the major oil producing countries may affect the supplies and price of oil. On the other hand the growing need for energy consumption cannot be stopped or even limited as it is directly related to the rate of development and the standard of living. Renewable energy systems offer a solution to these conflicting issues by providing a clean energy that can supply a reasonable share of the total energy requirement without contributing to air pollution. With the 20% target of the total energy consumption to be supplied by renewable energies by 2020, and the high potential of wind energy in most European countries, wind energy systems are being installed and the penetration levels of wind energy into the electrical power systems are increasing at high rates. Concerns about integrating wind power at high penetration levels arise from the fact that the conventional network is well suited for large synchronous generators with firm capacity and fully controlled output; this network is faced with a large number of wind farms utilizing either Induction Generators (IGs) or Doubly Fed IGs (DFIGs) with small capacity spread over different voltage levels. IGs and DFIGs have no inherent voltage control capability; it is rather reactive power loads adding to the system reactive power burden and voltage control problems. Moreover, wind farms are usually installed at remote areas where strong connections to the network is are not available. The capability of the existing network to accommodate the power generated from wind becomes an important issue to investigate. The unusual power flow patterns due the injection of power at nodes at the load ends of the network require reviewing the protection system settings and may need new protection schemes based on new rules to suite the new situation. The focus of this chapter will be on the voltage stability problem and the network capability to accommodate power from the wind. As the chapter is aimed to be a teaching tool, analysis is presented in a graphical manner using a simple two bus system.