POWER QUALITY IMPROVEMENT

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POWER QUALITY IMPROVEMENT USING RESONANT CIRCUIT By, M.V.S.PRAJITH B.NAGARJUNA REGENCY INST OF TECH YANAM

Abstract: 

Abstract Characteristics of HF modified series-parallel resonant converter operating in high power factor mode : high efficiency good regulation narrow variation in switching frequency high power factor Operates under lagging Pf for entire load range Index terms: high frequency resonant converter,high-voltage,fixed frequency control,power quality

Introduction: 

Introduction In earlier days, a number of APLC ‘s of the PWM type configurations are proposed .But these have got some problems A QRC has been proposed to overcome these problems Resonant converter is necessary in order to reduce the THD and to the input power factor Most of the schemes are series , parallel , series-parallel converters. But each has its own drawbacks A modified resonant converter is used as ac-dc converter but the drawback is that high component stresses of peak of ac input at the full load Hence high frequency MSPRC is proposed for improving PF

Proposed scheme: 

The closed loop control is used to meet the output ripple specifications. The closed loop gain should be chosen properly for achieving good transient response Proposed scheme

Operation of circuit : 

Operation of circuit This circuit consists of uncontrolled diode bridge rectifier followed by a small dc link capacitor connected to MSPRC The HF transformer non idealities like leakage inductance and winding capacitance are considered On considering these improvements ,the predicted performance of the proposed converter is improved in terms of efficiency and PF

Design of Tank Circuit: 

Design of Tank Circuit Tank circuit reduces the component stresses and this improves the efficiency and PF A useful analytical technique ,based on classical complex ac circuit analysis is suggested for designing the modified series-parallel resonant tank circuit

Idealized waveforms of MSPRC: 

Idealized waveforms of MSPRC Input line current of this converter is quasi square wave. This leads to the presence of THD more than 100% at load below 25% of full load. Therefore with the use of the active line current of ac to dc MSPRC, the line current waveform is purely sinusoidal in nature and power of the circuit is very high.

Important equations relating to tank circuit: 

Important equations relating to tank circuit Where n is turns ratio, LR is load resistance referred to the primary of HF transformer and v d is forward voltage drop of HF rectifier diodes Using equations (1) (2) (3) (4) & (5), the optimum component values are L 1 =15.78µH, L 2 =157.8µH, C 1 =0.044µF, C 2 =0.44µF, Cp=0.0044µF, C p '=n2Cp=58.2ÞF

Comparison of PF with & without active control : 

Comparison of PF with & without active control The above table shows the improvement in power factor with & without active control of input line current

Results : 

Results The input time current is sinusoidal in nature and converter has high power factor. The input line current waveform is slightly distorted at light loads this is because of the fact that the component values used were not exactly same as those obtained in designing .

References: 

References [1] R. L. Steigerwald, “A Comparison of half-bridge resonant converter topologies,” IEEE Trans. on Power Electronics, vol.3, no.2, pp.174-182, April 1988. [2] A. K. S. Bhat and M. M. Swamy, “Analysis and design of a parallel resonant converter including the effect of a high frequency trans-former, “IEEE Trans. on Industrial Electronics, vol.37, no.4, pp.297-306, Aug.1990. [3] A. K. S. Bhat, “Analysis and design of a series-parallel resonant converter, “IEEE Trans. on Power Electronics, vol.8, no.1, pp.1- 11, Jan.1993. [4] H. M. Suryawanshi and S. G. Tarnekar, “Modified LCLC-type series resonant converter with improved performance,” IEE Proc.-Electr. Power Appl., Vol.143, No.5, Sept.1996, pp.354-360.

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