iosr-JEEE   Volume-9 ~ Issue-4 ~ July-August 2014

Abstract: This paper investigates various aspects of voltage-power relationships in power systems. Conditions for feasible generating points are analytically derived for a simple power system with a detailed generator model. The set of Hopf Bifurcation points for the sample system are visualized on the feasible operating surface. The effect of damping on the onset of bifurcations in the system is briefly investigated. The role of different ating bifurcations and subsidiary phenomena in a multi-machine system are also presented. The effect of nonlinear indices of voltage dependent load models on system bifurcations is dealt with as also the effect of AVR gains.
Keywords : Steady-state Stability, bifurcations, critical eigenvalues, P-V curves.

[1] J. Guckenheimer and P.Holmes, Nonlinear Oscillations, Dynamical Systems and Bifurcations of vector fields,' Applied mathematical
Sciences 42, Springer-Verlag, 1983.
[2] V. Ajjarapu and B.Lee, 'Bifurcation theory and its application to nonlinear dynamical phenomena in an electric power system,' IEEE
Transactions on Power Systems, vol 7, No.1, February 1992, pp 424-431.
[3] P.W.Sauer, B.C. Lesieutre and M.A.Pai, ' Dynamic vs Static aspects of voltage problems,' Bulk Power System Voltage Phenomena,
voltage stability and security, International Workshop, Deep Creek Lake, Maryland, Aug 4-7, 1991.
[4] C.Rajagopalan, B.Lesieutre, P.W.Sauer and M.A.Pai, 'Dynamic Aspects of Voltage/Power characteristics,' IEEE Transactions on
Power Systems, vol 7, No. 3, August 1992, pp 990-1000.
[5] M.A.Pai, P.W.Sauer, B.C. Lesieutre and A.Adapa, 'Structural Stability in Power Systems- Effect of Load Models,' IEEE
Transactions on Power Systems, Vol. 10, No. 2, May 1995, pp 609-615.

Abstract: Metamaterials exhibiting negative index of refraction has attracted a great amount of attention in recent years. These materials are artificial structures that exhibit characteristics not found in nature. Microstrip antennas covered by metamaterial are one of the interesting areas of study. In this paper fractal shape antenna is proposed and covered by two layers of modified split ring resonator. The results shows an enhancement in Reflection Coefficients, gain, directivity and far field shapes.
Keywords: Fractal Antenna, left handed materials, metamaterials, negative refractive index, split ring resonators

[1]. V. G. Veselago, Electrodynamics of substrates with simultaneously negative values of and , Sov. Phys. Usp., Vol. 10, No. 4, 509-514, Apr. 1968.
[2]. Wu, B-I, W. Wang, J. Pacheco, X. Chen, T. Grzegorczyk, and J.A. Kong, A study of using metamaterials as antenna substrate to enhance gain, Progress in Electromagnetic Research, PIERS 51, pp. 295-328, 2005.
[3]. B. Garg, R. Tiwari, A. Kumar and T. Chitransh, Design of factored 'X' shaped metamaterial structure for enhancement of patch antenna gain, International Conference on Communication Systems and Network Technologies 2011
[4]. D. Sarkar, K. Saurav, and K. Vaibhav Srivastava, Design of a Novel Dual-band Microstrip Patch Antenna for WLAN/WiMAX Applications Using Complementary Split Ring Resonators and Partially Defected Ground Structure, Progress In Electromagnetics Research Symposium proceedings, Taipei, March 25-28, 2013
[5]. A. Foroozesh and L. Shafai, Effects of artificial magnetic conductors in the design of low-profile high-gain planar antennas with high permittivity dielectric superstrate, IEEE Antenna Wireless Propagat.Lett., vol. 8, pp. 10 –13, 2009

Abstract: We demonstrate InGaN/GaN nanorod light emitting diode (LED) with significantly enhanced emission efficiency. Our nanorod LED has been fabricated by top down approach using self-assembled Ni nano-clusters as an etching mask during ICP etching. Nanorod LED has nowadays become very interesting to the researchers because of it's strain relaxation effect that induced in InGaN/GaN MQWs. Our nanorod LED structure showed 9 nm (54meV) blue shift in peak emission wavelength compared to conventional LED which confirms the strain relaxation in InGaN/GaN MQWs and 2.8 times PL intensity enhancement which reflects the enhancement of internal quantum efficiency (IQE). Furthermore, extraction efficiency has been calculated using FDTD simulation. Our simulation results showed extraction efficiency up to 80% for nanorod LED.

Keywords: Light emitting diode, Nano-cluster, Nanorod, Strain relaxation, Internal quantum efficiency, Light extraction efficiency, Finite Difference Time Domain (FDTD).

[1] F. Kopp, T. Lermer, C. Eichler, U. Strauss, Cyan superluminescent light-emitting diode based on. InGaN quantum wells, Appl. Phys. Express 5 (2012) 082105.
[2] E. F. Schubert, Light Emitting Diode (Cambridge University Press, Cambridge, England, 2003).
[3] N. Grandjean, M. Ilegems, Visible InGan/GaN quantum-dot materials and devices, Proceedings of the IEEE, 95, 9 (2007).
[4] K. P. O'Donnell, R. W. Martin, P. G. Middleton, Origin of Luminescence from InGaN Diodes, Phys. Rev. Lett. 82, 237 (1999).
[5] T. Wang, J. Bai, S. Sakai, J. K. Ho, Investigation of the emission mechanism in InGaN/GaN-based light emitting diodes, Appl. Phys. Lett. 78, 2617-2619 (2001).
[6] S. Chichibu, A. Uedono, T. Onuma, B. A. Haskell, A. Chakraborty, T. Koyama, P. T. Fini, S. Keller, S. P. DenBaars, J. S. Speck, U. K. Mishra, S. Nakamura, S. Yamaguchi, S. Kamiyama, H. Amano, I. Akasaki, J. Han, T. Sota, Nature Mater. 5, 810 (2006).

Abstract: full-order observer-based state feedback linear controller design approach for a single area load frequency problem is presented. The load frequency control model incorporates integral control for improved command tracking response and disturbance rejection. A full state feedback is implemented through full-order< state observer design. State feedback with integral controllers design is carried out through a pole-placement technique using symmetrical root locus method. Parametric model uncertainty has been considered and stability robustness study has been carried out assigning a bound on the deviations in parameters of single area load frequency model. The proposed design methodology achieves performance satisfying the specified stability margins. The methodology provides a control over peak values of the frequency and control signal deviations which may be utilized to meet hardware constraints. A numerical example illustrates the effectiveness of the developed methodology.
Keywords: Load frequency control, Control area, Integral control, Full order state observer, Augmented system, MATLAB simulation.

[1] Olle l. Elgerd, Electric Energy Systems Theory; An Introduction (2nd Edition, McGraw-Hill Inc. 1982).

[2] K. Ogata, Modern Control Engineering (4th edition, Prentice Hall Inc. 2002).

[3] Gene F. Franklin, David Powell and Abbas Emami-Naeini, Feedback Control of Dynamic Systems (4th Edition, Pearsons Education Inc. 2002).

[4] S.K. Goswami and K. Datta, On estimation errors in linear systems due to parametric variations, Journal of the institute of engineers (India), vol. 86, Dec. 2005, p(s) 192.

[5] D.P. Kothari and I.J. Nagrath, Modern Power system Analysis (3rd Edition, Tata McGraw-Hill Inc. 2003).

Abstract: Hyperthermia is the most recent therapy in investigating the biological effects and applications of microwaves for treatment of cancer and tumour. It refers to an artificial heating above 45°C in order to cure cancer. Various antennas like slot antenna, loop antenna, dipole antenna and patch antenna etc. are used as Hyperthermia applicators for damaging and killing cancerous cells from the body. In this paper, an annular patch antenna operating at 434 MHz has been use as applicator. A simple planar three layer phantom model has been used to examine the effect of applicator at varying distances from the body. The Specific Absorption Rate and return loss are computed and compared at different distance of antenna from body. Finite Element Method is used to generate the model and predict the absorbed energy.

Keywords: Applicators, Hyperthermia, Finite Element Method (FEM), Specific Absorption Rate ( SAR), Radiotherapy.

[1] Davi Correia, H. Petra Kok, Martijn de Greef, Arjan Bel, Niek van Wieringen, and Johannes Crezee ,Body Conformal Antennas for Superficial Hyperthermia: The Impact of Bending Contact Flexible Microstrip Applicators on Their Electromagnetic Behavior , IEEE transactions on Biomedical Engineering, 56(12), 2009, 2917-2926.
[2] P.Wust, Hyperthermia in combined treatment of cancer, The Lancet Oncology, 3(8), 2002,487-497.
[3] Riadh W. Y. Habash, Rajeev Bansal, Thermal Therapy, Part 2: Hyperthermia Techniques , Critical reviews in biomedical engineering,34(6),2006,491-542.
[4] Zastrow, E, Time-multiplexed beam forming for non invasive microwave hyperthermia treatment, IEEE Trans. Microwave Theory Tech, 58, (6),,2011,1574–1584.
[5] M. R. Horsman and J. Overgaard, Hyperthermia: A potent enhancer of radiotherapy, Clinical Oncology.,19( 6), Aug. 2007, 418–426.

Abstract: Using from the first principle to ascertain the status of a faulty Distribution Transformer is very important. In a situation where digitalized computer system is not available, performance test can be carried out on any distribution transformer along the street or roads. However, to get an insight of this field test on faulty distribution transformers especially in the developing countries – a Single-phase Voltage transformation ratio test, Step-up voltage ratio test, Insulation resistance test, Earthing (ground resistance test), Dielectric oil test, Load test, etc., should be carried out properly. Power failure or sudden power outage as a result of blown on the High Voltage Distribution fuses or consequent loss of a transformer cannot be overemphasized, therefore, indiscriminate connection of consumers' service mains(lines) should be checked and discourage by both the power provider and the end users (consumers). This technical article shall discuss a practical approach of faulty distribution transformer carried out with the following tests: Single-phase voltage transformation ratio test, Single phase Step-up voltage ratio (output) test, Insulation resistance test with XLPE cable and Earthing (ground Resistance) test.

Keywords: Distribution transformer, Rating, Voltage Levels (HV and LV), feeder pillar, Cables, Inspection tests, etc.

[1]. DistributionTransformer:http://en.wikipedia.org/w/index.php?title=Distribution_transformer&oldid=570740977Retrieved (January, 2013)
[2]. William H.B, An Analysis of Transformer Failures, Part 2: Causes, Prevention, and Maximum Service Life, online http://www.hsb.com/thelocomotive/ananalysisoftransformerspart2.aspxRetrieved (January, 2013)
[3]. http://grouper.ieee.org/.../transformers/.../Short%20circuit%20test%20code%2
[4]. Tesla Transformer ltd, (2013).Installation, Commissioning operation & Maintenance: instruction for distribution Transformer (small &medium capacity), 30-B, industrial area, govindpura Bhopal -462023, Madhya,
[5]. Phcn, Diobu District (2007). Protection, control and metering (PC&M) section, (Distribution Department) Port Harcourt, Nigeria

Abstract: DC motors are widely used in industrial and household applications as they provide benefits of high performance response, high efficiency, high torque and lower volume. This paper proposes the idea of implementing fuzzy logic controller to control the speed of separately excited DC motor. It provides an overview of performance with PID controller and fuzzy logic controller. Though PID controller improves both transients and steady state response characteristics with reduced rise time and steady state error, yet it has limitations of tuning its parameters and unsatisfactory control characteristics. Fuzzy logic can be described simply as computing words and can be designed without knowing the exact mathematical model of the process. Initially these controllers are designed and then tuned to analyze the performance of DC motor. Then the speed response of fuzzy logic is compared with the response achieved by PID controller. The experimental results prove that the control characteristic with fuzzy logic is better than that with the conventional PID controller. The modeling of separately excited DC motor and implementation of the two controllers is performed on software MATLAB/SIMULINK.

Keywords: DC motor, Fuzzy logic controller, membership functions, PID controller, tuned parameters.

[1]. Ramesh Chandra Chourasia and Mukesh Kumar, "Speed control of S.E.D.C Motor by using PI and Fuzzy Logic Controller", International Journal of Soft Computing and Engineering (IJSCE), Volume-3, Issue-2, page 135-139, May2013.
[2]. R Arulmozhiyal. and R. Kandiban, "Design of Fuzzy PID controller for Brushless DC Motor", International Conference on Computer Communication and Informatics (ICCCI-2012), Jan10-12, 2012.
[3]. M. Surya Kalavathi and C. Subba Rami Reddy, "Performance Evaluation of Classical and Fuzzy Logic Control Techniques for Brushless DC Motor Drive", IEEE, page 488-491, 2012.
[4]. E. Gowthaman and C. Dinesh Balaji, "Self Tuned PID Based Speed Control of PMDC Drive", IEEE, page 686-692, 2013.
[5]. J.N. Rai, Mayank Singhal and Mayank Nandwani, "Speed Control of DC Motor using Fuzzy Logic Technique", IOSR Journal of Electrical and Electronics Engineering (IOSR-JEEE), Volume 3, Issue 6, page 41-48, Nov.-Dec. 2012.
[6]. Heidar A. Malki and Denny Feigenspan, "DC Motor Control Using Fuzzy Proportional-Derivative Technique", IEEE, page 373-374, 1994.

Abstract: This paper represents the modelling and simulation of 2 MW Direct Drive PMSG Wind energy conversion system (WECS). The modelling of wind turbine and PMSG is carried out in simulink to determine its parameter. WECS consists different components namely Wind turbine, Generator, rectifier-inverter, controller system including transformer, grid etc. The PMSG and converter model are established in the d-q model.

Keywords: PMSG, WECS, Wind turbine, rectifier, inverter, MATLAB/SIMLINK, transformer, Grid.

[1]. S. Samanvorakij, P. Kumkratug ―Modeling and Simulation PMSG based on Wind Energy Conversion System in MATLAB/SIMULINK‖ Proc. of the Second Intl. Conf. on Advances in Electronics and Electrical Engineering — AEEE 2013
[2]. M.Ying, G.Li, M.zhou, and C.Zhao,"Modeling of the wind turbine with a permanent magnet synchronous generator for integration," IEEE,pp.1-6,2007.ISBN1-4244-1298-6
[3]. Suman Nath, Somnath Rana ―The Modeling and Simulation of Wind Energy Based Power System using MATLAB‖ International Journal of Power System Operation and Energy Management, ISSN (PRINT): 2231–4407, Volume-1, Issue-2, 2011
[4]. A. B. Cultura and Z. M. Salameh, ―Modeling and Simulation of a Wind Turbine-
Generator System‖
[5]. S. Saikuma, S. Saravanan, and R. V. Sandip, ― Modelling and Control of a Wind Turbine using Permanent Magnet Synchronous Generator‖, IJEST, Vol3, no., pp.2377-2384, 3 March 2011.

Abstract: The work developed in this article, has aims to control design law is based on Backstepping metho to ensure the servo-control of the permanent magnet synchronous motors (PMSM). The slow convergence of adaptation can result, in some cases; irreversible instabilization loop, especially in the presence of nonlinearity and/or couplings. Hence, the Backstepping method coupled with introduction of integral actions is an alternative choice. Moreover, the Backstepping theory is a recursive design methodology that makes use of the Lyapunov stability theory. Strong properties of overall and asymptotic stability can be achieved. The second part of this work is a direct application of the control proposed to associate an observer, is the Model Reference Adaptive System (MRAS) to observe the position and the rotor speed of the MRAS. Furthermore, the simulation under the Matlab/Simulink software allows highlighting the performance of the control strategy adopted.
Keywords: Backstepping control, Lyapunov theorem, Integral action, Permanent Magnet Synchronous Motor (PMSM), Model Reference Adaptive System (MRAS), observer.

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