Enhancement of VoltaQuality IN ISOLATED POWER SYSTEM

Enhancement of Voltage Quality in Isolated Power Systems: 

Enhancement of Voltage Quality in Isolated Power Systems BY P.JAYAKRISHNA(07C91A0215 HOLY MARY INSTITUTE OF TE CHNOLOGY AND SCIENCE,HYD

ABSTRACT: 

ABSTRACT The use of series compensators (SCs) in improving voltage quality of isolated power systems is considered. The roles of the compensators are to mitigate the effects of momentary voltage sags/swells, and to control the level of harmonic distortions in the networks. A control strategy for the SC is developed to regulate power flow. This is achieved through phase adjustment of load terminal voltage. It leads to an increase in the ridethrough capability of loads to the voltage sags/swells.

INTRODUCTION: 

INTRODUCTION ISOLATED power systems are commonly found in rural an remote areas of the world. These systems represent the alternative to grid connection, where interconnection to a large grid is not viable due to high cost and/or geographical obstacles . Furthermore, power systems such as those onboard of ships, in oil exploration areas and remote mining districts are characterized by limited generating capacity, supplying loads which can consist of significant amount of motor drives and power converters.

Descriptions of above SC diagram: 

Descriptions of above SC diagram shows a typical isolated power system supplying a converter load. The RL load may be used to represent an aggregate of dc motor drives, supplied via the converter. The converter is often a controlled six-pulse rectifier through which the motor torque is regulated by adjusting the firing angle of the rectifier. The motor-drive load is nonlinear and would involve commutation process within the converter.

Examples of non- linear loads: 

Examples of non- linear loads fluorescent lamp . electric welding machine . Diode rectifier. Motor drives. Power discharging devices.

Examples of Sensitive load : 

Examples of Sensitive load Digital Computers . Variable Frequency Motor Drives. Programmable Logic Controllers . Computer Numerical Control (CNC) Equipment . Automated Systems and Processes. Consumer Electronics. Digital Clocks .

PowerPoint Presentation: 

Harmonic power flow in the isolated system: hth harmonic component.

Description of harmonic power flow: 

Description of harmonic power flow The main converter load is the dominant harmonic source in the power system due to its much larger capacity, compared to the SC and sensitive load. The SC is assumed to be “ideal” in that whatever harmonics generated by the VSI are effectively dealt with by its LC filter. The SC is a harmonic “sink.” In this way, the harmonic power “Pdh” produced by the nonlinear main drive load is dissipated in the upstream source impedance and is absorbed by the sensitive load.

PowerPoint Presentation: 

Equivalent circuits of the sensitive load-SC branch for (a) fundamental component and (b) hth harmonic component.

PowerPoint Presentation: 

Equivalent circuit describing harmonic compensation in practice and (b) phasor diagram for the hth harmonic order.

PowerPoint Presentation: 

Simulation Circuit Without Series Compensator

PowerPoint Presentation: 

Simulation Circuit with Series Compensator

Conclusion: 

Conclusion A method to control the injection voltage of the SC so that it can mitigate the effects of the harmonics has been proposed. The SC is also designed to maintain the fundamental frequency component of the terminal voltage of protected sensitive load. In the process of harmonic voltage compensation, it is shown that power exchange exists between the SC and the external network. A new SC control strategy is then proposed which involves the phase adjustment of the fundamental frequency component of the sensitive load terminal voltage.

BIBILOGRAPHY : 

BIBILOGRAPHY [ 1] I. Jonasson and L. Soder, “Power quality on ships-a questionnaire evaluation concerning island power system,” in Proc. IEEE Power Eng Soc. Summer Meeting, Jul. 2001, vol. 15–19, pp. 216–221. [2] J. J. Graham, C. L. Halsall, and I. S. McKay, “Isolated power systems Problems of waveform distortion due to thyristor converter loading,” in Proc. 4th Int. Conf. Power Electronics and Variable-Speed Drives , Jul. 1990, vol. 17–19, pp. 327–330. [3] ITI (CBEMA ) Curve Application Note , [Online]. Available: http://www.itic.org., Inf. Technol. Ind. Council (ITI). [4] J. C. Das, “Passive filter—Potentialities and limitations,” IEEE Trans. Ind. Appl., vol. 40, no. 1, pp. 232–241, Jan. 2004. [5] H. Akagi, “New trends in active filter for power conditioning,” IEEE Trans. Ind. Appl . , vol. 32, no. 6, pp. 1312–1322, Nov. 1996.

PowerPoint Presentation: 

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