M. Venkatesh Int. Journal of Engineering Research and Applications www.ijera.com ISSN : 2248-9622, Vol. 4, Issue 7( Version 5), July 2014, pp.163-167 www.ijera.com 163 | Page Mitigation of Voltage Fluctuations in Power System Using STATCOM M. Venkatesh & Ramakrishna Raghutu Assistant Professors, Dept. of Electrical & Electronics Engineering, GMRIT, RAJAM Abstract Wind energy being a renewable source of energy is enjoying a rapid growth globally. However, wind energy being an uncontrollable source of energy coupled with the fact that it uses distributed induction generators for power conversion poses a challenge in integrating a large scale wind-farm into a weak power system. An actual weak power system with two large Wind-Farms (WFs) coupled to it is introduced as part of this study. A model of this integrated system along with a STATCOM for steady state and dynamic impact study is developed in the MATLAB/Simulink environment. The power quality issues are highlighted and a centralized STATCOM is proposed to solve the issue of the voltage fluctuations in particular in addition to addressing the other issues. Based on the results obtained from the simulation, the system voltage control issues are analyzed and the location of STATCOM is assessed. Finally, a STATCOM control strategy for suppression of voltage fluctuations is presented. Index Terms— Static synchronous compensator (STATCOM), voltage fluctuation, voltage stability, wind farm (WF). I. INTRODUCTION RECENTLY, mainly due to the technology innovation and cost reduction, renewable wind energy is enjoying a rapid growth globally to become an important green electricity source to replace polluting and exhausting fossil fuel. The wind turbines with 2–3-MW capability have already been commercially available and a 5-MW wind turbine also will be available in a few years. The cost of wind energy has been reduced to 4.5 cents/kWh and is very competitive against conventional fuels, and will be further reduced to 3 cents/kWh for utility-scale wind energy onshore and 5 cents/kWh offshore by 2012.Wind being an uncontrollable resource and the nature of distributed wind generators into a power system poses challenges. Conventionally, Mechanical Switched Cap (MSC) banks and Transformer Tap Changers (TCs) are used for Stability and Power Quality issues. The issues such as power fluctuations, voltage fluctuations, and harmonics, cannot be solved satisfactorily by them because these devices are not fast enough. Therefore, a fast response Shunt VAR Compensator (STATCOM) is needed to address these issues more effectively. The static synchronous compensator (STATCOM) is considered for this application, because it provides many advantages, in particular the fast response time (1–2 cycles) and superior voltage support capability with its nature of voltage source. With the recent innovations in high- power semiconductor switch, converter topology, and digital control technology, faster STATCOM (quarter cycle) with low cost is emerging, to achieve a more cost-effective and reliable renewable wind energy. Firstly, an actual weak power system with two large WFs are introduced. Secondly, a model of the system, WF and STATCOM for steady state and dynamic impact study is developed in MATLAB/ Simulink model. The power quality issues are highlighted and a centralized STATCOM is proposed to solve them, particularly voltage fluctuations. Based on the results obtained from the simulation the system voltage control issues are analyzed and the location of STATCOM are assessed. Finally, a STATCOM control strategy for voltage fluctuation suppression is presented. II. SYSTEM DESCRIPTION Fig. 1 shows the diagram of the system investigated in this paper. The two WFs, WF1 and WF2, are connected to the existing 69-kV loop system at bus 3 and 5. The system is supplied by the two main substations, which are represented by three remote boundary equivalent sources at bus 1, 2, and 12. Among them, bus 1 is a strong bus with a short-circuit capacity of about 4000 MVA. The WF2 at bus 3 is a large WF with a total rating of 100 MVA. It is a type C WF [2] with variable-speed double fed induction generators (DFIGs) and partial back-to-back converters. The WF1 at bus 5 is located at the middle of the weak 69-kV sub transmission system, and the short- circuit capacity at the bus 5 is about 152 MVA RESEARCH ARTICLE OPEN ACCESS