FACTS-based reactive power compensation of wind energy conversion system
Voltage control and reactive power compensation in a distribution network with embedded wind energy conversion system (WECS) represent main concern of this paper. The WECS is of a fixed speed/constant frequency type that is equipped with an induction generator driven by an unregulated wind turbine. The problem is viewed from short term (10 seconds) and mid-term (10 minutes) time domain responses of the system to different wind speed changes. Being disturbed by a variable wind speed, the WECS injects variable active and reactive power into the distribution network exposing nearby consumers to excessive voltage changes. In the FACTS-based solution approach, the Unified Power Flow Controller (UPFC) is used at the point of the WECS network connection to help solve technical issues related to voltage support and series reactive power flow control.
Recently, alternative solutions treating distributed generation of electrical energy have appeared as a consequence of strong ecological concerns with regard to almost all major industrial branches. Moreover, initiatives of potential investors come along with liberalization of electrical energy market. It results with an --additional impact to a need for conducting a new kind of technical analysis. Grid integration aspects of renewable sources have become increasingly important as incentives come in large numbers. From distribution network viewpoint, connection of small power plants with dispersed generation of electricity calls for urgent attention. In case of increased power ratings, dispersed power plants could be integrated in a transmission network. Dispersed generation of electricity is often a subject of polarized discussions. At one side, experienced engineers motivated by wide knowledge of complex power system operation are concerned regarding fundamental realization of massive introduction of unregulated and uncontrollable Generators into a distribution network. At the other side, enthusiastic proponents of renewable sources believe that such generating units are a necessity in operation should domestic and international requirements for reduction of CO2 emission be fulfilled. Moreover, they are convinced that renewable decrease dependence on dominant energy fuels (gas, oil, coal…) in times of large international crisis. Increased penetration of renewable such as wind energy creates an uncontrollable component in electric power system. Based on weather forecasts it is possible to predict a mean wind speed in short-term time period, but not dynamic changes as well, smaller or larger, which take place around a base speed. Dynamic changes of wind speed make amount of power injected to a network highly variable. Depending on intensity and rate of changes, difficulties with frequency and voltage regulation could appear making a direct impact to quality level of delivered electrical energy. Conditions of economic justification set project requirements for wind power plant installations in areas with high wind utilization. Such areas are often located in rural zones with relatively Weak electrical networks. In order to establish a balance between polarized attitudes, it is necessary to provide answers concerning technical, economic, and security aspects related to grid integration of wind power plants. From that viewpoint, the objective of this paper is set as to create a countermeasure Without a countermeasure, it is possible that at some locations only a small number of wind turbines could be connected due to weak voltage conditions and increased losses in the nearby network. That would not only leave assessed wind potential unused, but also it could also prohibit installation of larger number of wind turbines jeopardizing the economics of the whole project. In an attempt to overcome negative dynamic impacts caused by wind speed changes, the voltage regulation...
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