JOURNAL OF APPLIED SCIENCES RESEARCH

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1 Copyright 2015, American-Eurasian Network for Scientific Information publisher JOURNAL OF APPLIED SCIENCES RESEARCH ISSN: X EISSN: X JOURNAL home page: October; 11(19): pages Published Online 10 November Research Article Impacts of Integration of Wind Turbine Generators In Tamil Nadu Grid 1 Madan A Sendhil and 2 Balasubramanian S 1 Research Scholar, 2 Professor, Dept. of Mechanical Engg. Rathinam Technical Campus, Coimbatore, India, Postal Code Received: 23 September 2015; Accepted: 25 October AENSI PUBLISHER All rights reserved ABSTRACT Wind Energy Conservation Systems (WECS) exhibits variability in their output power as a result of change in their prime movers (wind speed). Uncertainty, a new factor has been introduced on the grid and posses a lot of challenges to the power system planner and the utility operators in terms of power system grid integrity of power system stability, power system security and power quality. This paper discusses the various challenges in power systems such as poor voltage profile, over loading of components, increase in loss, increased short circuit rating, harmonics, maloperation of relays etc. This paper enables the specifications for mitigation or integration technologies to be appreciated and quantified and also aims to reduce the losses and increasing the voltage profile by adding wind turbine generator to Tamil Nadu grid in appropriate location. The entire Tamil Nadu grid of 33 KV transmission line is modeled using the Electrical Transient Analysis and Programme (ETAP) software and a load flow and harmonic analysis study has been carried out and the results were discussed. Keywords: Wind Energy Conversion System, Total Harmonic Distortion, Transients, Harmonics, Load flow analysis INTRODUCTION Wind energy is considered to be the most important renewable energy resources because of its inherent characteristics such as technological maturity, good infrastructure and relative cost competitiveness. It is predicted that nearly 12% of the entire world will receive the electricity from wind power by the year Due to the fluctuation in the wind power, the grid integration of WECS [1], [5], [11] will affect the power system negatively. The output power from the WECS will vary due to the changes in the weather conditions. Due to this nature, a new factor referred to as uncertainty is introduced, that creates the negative impact on the grid integrity. As the nature changes the wind energy, there occurs a tremendous effect in the power system. Implication of certain technology is needed to enable smooth and proper integration of WECS to the grid. This paper discusses the various challenges, when the wind turbine [6] is directly integrated with the utility grid. Challenges: 2.1. Impact of Wind Power on System Security: Generally, the security of a power system is referred to the ability of the system to withstand the disturbances. The voltage and frequency control [16] are the most important parameters in regards to wind power generators. The power system stabilization plays a major role, when the insecurity occurs and the system should be capable of operating in the island mode, even when the supply from the grid is lost. The operators confidence level will always be low, when the systems capability is concerned. It is very difficult to meet the peak demands. Even though the electricity systems are unreliable, the level of uncertainty will be increased, which in turn increases the generation cost. The above challenges reflect on the power imbalance, reserve management, control and system stability [12], [14] Impact of Wind Power on Power Quality: As per the prediction of the electricity market, Power Quality [2] becomes a major issue of focus. Corresponding Author: Madan A Sendhil, Research Scholar, Professor, Dept. of Mechanical Engg. Rathinam Technical Campus, Coimbatore, India, Postal Code mas2rtc@gmail.com

2 175 Madan A Sendhil and Balasubramanian S, 2015 /Journal Of Applied Sciences Research 11(19), October, Pages: Flickers, Harmonic distortions, voltage imbalance, voltage sag and voltage swells are the major components of the power quality. Based on the sensitivity of the load installed, the level of tolerance varies. If the poor power quality exists, this might lead to losses and the malfunctioning of the grid equipments. Low power quality will have negative consequences on the economic and social life. Recently European survey revealed an estimated loss of approximately 150 billion Euros (b ) in a year, while the same was between billion Dollars (b$) per annum in the United States of America. The following are the standards set for the uniform power quality measurement. They are IEEE , IEC and EN IEEE It deals with the practices and requirements for harmonic control [3] in electrical power systems [7]. The standard requires the participation of both the utilities and the customers. IEC describes the adequate measurement methods for ensuring voltage [8] and current quantities. The EN50160 code is mostly adopted by European countries and it sets the standard level for different power quality [4] components which should not be exceeded. IEC issued a standard in 2001 (IEC ) for the measurement and assessment of the power quality in wind turbines Challenges of Wind Power on Power System Stability: Kundur stated that When a power system maintain a state of equilibrium during normal operating condition or returns to acceptable state of equilibrium after being subjected to a disturbance, then the system is said to be stable. When there is an occurrence of insufficient damping of system oscillations, these results in operating parameter changes in the power system. This is referred to as the Small Signal Stability. The major problem that is related to dynamics is the frequency stability, which ranges from 10 seconds to a minute and loss of generation is a typical cause of frequency instability. For the production of electricity, synchronous generators are the major resources used by the power systems in the earlier stages. The utility operators understood the behaviour of the system, due to their experiences thereof over the years. When the wind turbines are introduced with the induction generators [9], the generation cost of the electricity becomes cheap, robust and variable speed operations are also supported by this system. 3Load Flow Analysis Using Etap Software: 3.1 ETAP software: ETAP is a fully integrated electrical power system analysis tool for both AC and DC. Nowadays, Engineers are using ETAP in thousands of companies for the purpose of design, analysis, maintenance, and operation of electrical power systems. ETAP Real-Time offers more features and benefits than any other product of its kind. As this tool is fully integrated, through continuous monitoring, simulation [13], optimization process, manufacturing, and management systems, this tool can maximize the entire production process, minimizing the losses, and increases profits. 3.2 Load Flow Analysis: The ETAP Load Flow Analysis module calculates the bus voltages, branch power factors, currents, and power flows throughout the electrical system. ETAP allows for swing, voltage regulated, and unregulated power sources with multiple power grids [10] and generator connections. It is capable of performing analysis on both radial and loop systems. ETAP allows you to select from several different methods in order to achieve the best calculation efficiency. Scenarios For Analysis: At present, the contribution of wind energy in Tamil Nadu power generation is about 40%. So we had chosen for integrating wind turbine generators to Tamil Nadu grid. Nature of wind is seasonal, based on the wind speed and demand it is categorized into nine scenarios. They are Peak Wind Peak Load Peak Wind Average Load Peak Wind Low Load Average Wind Peak Load Average Wind Average Load Average Wind Low Load Low Wind Peak Load Low Wind Average Load Low Wind Low Load. The major impacts of integrating wind turbine generator are because of their poor voltage profile, increases in losses and loading. That can be overcome by choosing the right place for adding the wind turbine generators. Simulation And Results: The following data provides the depth of analysis for different scenarios carried out with the TNEB 33-kV subsystem. The voltage level and the transmission losses had been found out and tabulated for the aforesaid scenarios and it has been represented in the graphical form and it is found that the voltage profile [15] of the system gets increased by adding the WTG at appropriate places. The analysis has been tabulated below: 5.1 Graphical Representation of wind speed:

3 176 Madan A Sendhil and Balasubramanian S, 2015 /Journal Of Applied Sciences Research 11(19), October, Pages: Fig. 1.1: Voltage profile without generator when wind speed is at peak (say wind speed = 100%) Fig. 1.2: Voltage profile without generator when wind speed is at average (say wind speed = 70%) Fig. 1.3: Voltage profile without generator when wind speed is at low (say wind speed = 0%) Fig. 1.4: Voltage profile with generator when wind speed is at peak (say wind speed = 100%) Fig. 1.5: Voltage profile with generator when wind speed is at average (say wind speed = 70%)

4 177 Madan A Sendhil and Balasubramanian S, 2015 /Journal Of Applied Sciences Research 11(19), October, Pages: Fig. 1.6: Voltage profile without generator when wind speed is at low (say wind speed = 0%) 5.2 Graphical Representation for Losses in Transmission Line: Fig. 1.7: Losses in Transmission Line with generator when wind is average (wind speed = 70%) Fig. 1.8: Losses in Transmission Line with generator when wind is low (wind speed = 0%) Fig. 1.9: Total Harmonic Distortion at grid after the usage of filter. Conclusion: A detailed analysis on the impacts of integrating the wind turbine generators with the Tamilnadu grid has been presented in this paper. A 33 kv transmission system has been taken as an example for the analysis. The system has been modeled with the ETAP software. The voltage level at each bus and the losses occurred in the transmission lines has been simulated and tabulated. The impacts of integrating the wind turbine generators along with the specified grid has been analyzed by choosing different scenarios such as low wind, average wind and peak wind. The outcome of the scenarios has been represented in a graphical representation. Moreover, harmonic analysis has been carried out for the aforesaid system by injecting harmonics through

5 178 Madan A Sendhil and Balasubramanian S, 2015 /Journal Of Applied Sciences Research 11(19), October, Pages: Variable Frequency Drive. The Total Harmonic Distortion (THD) before adding the filter at the point of connecting the grid with the transmission system is found to be 11.99% and after adding filter, the total harmonic distortion is found to be 9.56%. From the above analysis, it has been predicted that the harmonics got reduced to about 20% at the point of intersection of grid and transmission system after adding the filter. References 1. Abbes, M., J. Belhadj, Supervisory control strategy for optimal integration of direct drive wind turbine to the grid in Electrical Engineering and Software Applications (ICEESA) International Conference on. (1-7): Abrantes, A., Overview of power quality aspects in wind generation in North American Power Symposium (NAPS) (1-6): Aho, J et al A Tutorial of wind turbine control for supporting grid frequency through active power control in American Control Conference (ACC), (27-29): Fanxin Kong et al., Quantity Versus Quality: Optimal Harvesting Wind Power for the Smart Grid in Proceedings of the IEEE, (102): Jingguo Ren et al., Wind power integration and operation in an AC/DC hybrid transmission system of Shandong province in Electric Utility Deregulation and Restructuring and Power Technologies (DRPT) th International Conference on Malinga, B, et al Modeling and control of a wind turbine as a distributed resource in System Theory Proceedings of the 35th Southeastern Symposium on, : Nishida, K. et al., Cost-effective highreliability power-conditioning system used for grid integration of variable-speed wind turbine in Future Energy Electronics Conference (IFEEC), pp: Ntshangase, M. et al., Stability analysis of electricity networks with DFIG-based wind power plants in Power and Energy Society General Meeting, pp: Shaltout, A et al., Power coordination of grid-connected wind turbine doubly fed induction generator augmented with battery storage in Smart Energy Grid Engineering (SEGE) 2013 IEEE International Conference on, pp: Shaolin, Li et al., Analysis and experiment research on transient behavior of flexible drive train for doubly-fed wind turbine under grid fault in Power System Technology (POWERCON) 2014 International Conference on, pp: Smolka Thomas et al., Grid integration of Wind Energy Converter Experiences of measurements and status Quo of certification procedures in Integration of Wide-Scale Renewable Resources Into the Power Delivery System CIGRE/IEEE PES Joint Symposium, pp: Ullah, N.R., Small scale integration of variable speed wind turbines into the local grid and its voltage stability aspects in Future Power Systems 2005 International Conference on, (8): Wang Yingying, et al., A new method of wind turbines modeling based on combined simulation in Power System Technology (POWERCON) 2014 International Conference on, pp: Yongning Chi et al., Stability Analysis of Wind Farm Integration into Transmission Network in Power System Technology (POWERCON) International Conference, pp: Yousef, A. et al., Wind turbine level energy storage for low voltage ride through (LVRT) support in Power Electronics and Machines for Wind and Water Applications (PEMWA) IEEE Symposium, pp: Yun, Li et al Research on DFIGs' participation in frequency regulation and penetration ratio of wind power integration in Power System Technology (POWERCON) International Conference, pp: