POWER QUALITY ENHANCEMENT TECHNIQUES
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 seminar class Active In SP Posts: 5,361 Joined: Feb 2011 24-02-2011, 12:09 PM PRESENTED BY: Ezhil Bharathi .S.A Infanta Nancy .S   paper.doc (Size: 427.5 KB / Downloads: 104) POWER QUALITY ENHANCEMENT TECHNIQUES ABSTRACT: This paper presents operation and performance of a boost converter used for a power factor correction. The mode of operation of boost converter in continuous and discontinuous mode is explained which helps the input current to follow the input voltage, thus making the power factor unity. The correction converter reduces harmonic pollution and disturbance on the supply mains. This method is suitable for medium and high power applications. INTRODUCTION: In the last years there have been increasing demands for high power factor and reduced harmonic distortion in the current drawn from the utility, specially when the forthcoming harmonic standards, such as IEC-555-2, must be satisfied. Therefore, in these applications, AC-DC converters featuring almost unity power factor have been required. A variety of circuit topologies are available for powerfactor correction, and among the usually employed in singlephase power supplies are the boost derived topologies. POWER FACTOR: Power factor is defined as the ratio of the real power to apparent power. It can vary between zero and one ,and can either inductive or capacitive. The whole purpose of making the power factor equal to one is to make the circuit look purely resistive. REASON FOR POWER FACTOR CORRECTION: The reason of the power factor circuit is to minimize the input current distortion and make the current in phase with the voltage.When the power factor is not equal to one,current waveform does not follow the voltage waveform.This results not only in power losses,but may also cause harmonics that travel down the neutral line and disrupt other devices connected to the line. This correction also reduces heating in cable transformers,frees up system capacity,saves money , reduces power bills,improves voltage drop and reduces I 2 R losses. POWER FACTOR CORRECTION CONVERTERS: Power factor correction converters are required to present themselves as linear resistances to the supply. Power factor correction converters brings the power factor closer to 1 by suppling reactive power of opposite sign,adding capacitor or inductors which act to cancel the inductive or capacitive effects of the load. One such converter is boost converter. Lets see in detail the working of boost converter as a power factor correction converter. BOOST CONVERTOR: Boost converter is one of the most popular choice for using as the power factor correction(P.F.C) converter. The boost converter is used because it is easy to implement and works well. There are two modes of pfc operation. • Discontinous mode • Continous mode DISCONTINOUS MODE: Discontinuous mode can be used for SMPS that have power levels of 300W or less. In comparison with continuous mode devices, discontinuous ones use larger cores and have higher I 2R and skin effect losses due to the larger inductor current swings. With the increased swing a larger input ﬁlter is also required. On the positive side, since discontinuous mode devices switch the boost MOSFET on when the inductor current is at zero, there is no reverse recovery current (IRR) speciﬁcation required on the boost diode. This means that less expensive diodes can be used.