iosr-JEEE   Volume-7 ~ Issue-4

Abstract: The study addresses the architecture of a hybrid PLL circuit technique for synchronizing a PV system with single phase grid. For determination of synchronization, the PV system is based on a reference system .The reference system is controlled by a microcontroller and pulse width modulation technique is used within the microcontroller to trigger the inverter in order to achieve efficient synchronization. Optocoupler is used to detect the real-time zero crossing detection and the digital phase lock loop system is used to control the phase angle and frequency of the system. The architecture of system is designed in Proteus simulator. The proposed architecture has performed well in reducing the harmonics produced because of inverter switching. Also if there are any abrupt changes in frequency or phase angle, the system can effectively manage changes.

Keywords: PV Array, Grid synchronization, Microcontroller, Optocoupler, DPLL, PWM and Power Quality.

[1] M.A.S Masoum, H. Dehbonei and E.F. Fuchs, "Theoretical and Experimental Analyses of Photovoltaic System with Voltage- and Current-Based Maximum Power-Paint Tracking,'' IEEE Trans. Energy Conversion, Vol.

[2] Z. Yishu, et al., "The circuit topology for single-phase Grid connected system and the control technology on converters, International Conference on Sustainable Power Generation and Supply, SUPERGEN '09, 2009, pp. 1-5.

[3] F. Blaabjerg, R. Teodorescu, M. Liserre, A. V. Timbus Overview of control and grid synchronization for distributed power generation systems, IEEE Trans. On Ind. Electronics, vol.53, pp. 1398-1409, Oct.2006. [4] P. W. Sauer, M. A. Pai, Power Systems Dynamics and Stability, Pren-tice-Hall, 1998.

[5] J.svensson, "synchronization methods for grid connected voltage source converters", IEE proceedings Generations, Transmission and Distribution, vol. 148, N0 3s, pp.229-235 May 2001.

[6] R. Weidenbrug, F.P. Dawson, and R. Bonert, "New synchronization method for Thyristor power converters connected to weak AC system" , IEEE Trans. On Industrial Electronics, vol. 40, N0 5, pp.505-511, Oct 1993.
[7] TMS320F/C240 DSP Controllers Reference Guide: Peripheral Library and Specgc Devices, Texas Instruments Incorporated.1999.17, No. 4, pp 514-522, Dec. 2002.

Abstract: With the advent of digital computers the engineers felt the need of utilizing computer advantages in the industrial process through the centralized control system. This thought led to the introduction of direct digital control (DDC) phylisophy. In this paper the author has presented a brief review of the structure of DDC as well as its working with illustration. The two types of algorithm used for programming as PID controller are discussed. The author has also pointed out the merits of DDC over analog control.Besides a few practical application has also been described.

Keywords: digital control, structure, algorithm,application

[1]. C.D JohnsJon, "Process Control Instrumentation Technology", 8th Edition, PHI, 11.
[2]. D. Patronobis "Principles of Industrial Instrumentation", 3rd Edition, TMH, 2010.
[3]. S.K Singh "Process Control Concepts, Dynamics and Applications", PHI, 
[4]. S. Bhanot "Process Control Principles and Applications", OUP, .
[5]. Krishna Kant "Computer Based Industrial Control", 2nd Edition, PHI, 12.
[6]. O.N Pandey, "Instrumentation and Process Control", Kataria & Sons, .

Abstract: Electric Power systems are composed of a very large number of subsystems and components which are subject to failures. The consequences of a failure of a component or subsystem may range from no effect at all on the operation of the system to wide-scale power interruptions caused by system instability. The cost associated with component failure may depend on the severity of the failure and on the corrective action undertaken to remedy the situation. In most of the cases, there will be some cost associated with the use of manpower and equipment. To solve this problem, a mathematical optimization technique was adopted to determine the optimum preventive maintenance periods and the number of men required to perform the Preventive maintenance such that the total maintenance cost is minimized. Results from the search technique, demonstrated a minimized maintenance cost rate.

Key Words: Preventive Maintenance, Inspection, Replacement, Availability, Breakdown

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