POWER FACTOR IMPROVEMENT OF SINGLE PHASE AC VOLTAGECONTROLLER EMPLOYING

EXTINCTION ANGLE CONTROL TECHNIQUE

Group number :-5Group member

1:-Diwakar singh (0806313017)

2:-Dharmesh singh(0806321029)

3:-Poonam yadav(2906321006)

4:-Alice singh(0806321006)

PROJECT GUIDE Mr. Nitin Dixit

ABSTRACT

The general study of power converters is to improve the overall efficiency of the power system by some advanced methods of control techniques. Forced commutation of the power semiconductor switches leads to improved power factor in dc converters.

Many solutions exist to alter the power factor of dynamic ac loadsthrough an ac controller. In this project ,we use “extinction angle control technique” for improving power factor of ac voltage controller .the performance evaluation of the extinction-angle control technique has been illustrated as applied to a single-phase voltageconverter by examples of static load and the widely usedsingle-phase induction motor to verify the feasibility of theproposed technique.

NEED FOR POWER FACTOR IMPORVEMENT

Consider a canal boat being pulled by a horse. If the horse could walk on water then the angle (Phi) Ø would be zero and COSINE Ø=1. Meaning all the horse power is being used to pull the load. However the relative position of the horse influences the power. As the horse gets closer to the barge, angle Ø1 increases and power is wasted, but, as the horse is positioned further away, then angle Ø2 gets closer to zero and less power is waste

USE OF AC VOLTAGE CONTROLLER

AC voltage converters are widely used as one of the power electronics systems to control an output ac voltage; where a variable ac voltage is obtained from a fixed ac voltage, for power ranges from few watts (as in light dimmers) up to fraction of megawatts (as in starting systems of large induction motors).

EXISTING TECHNIQUES FOR REGULATING POWER FACTOR OF AC VOLTAGE CONTROLLER

Phase-angle control (PAC) linecommutated voltage controllers integral-cycle control of thyristors

ADVANTAGE

1):-Simplisity 2):- Ability of controlling large amount of power economically.

DISADVANTAGE:-

1)-RETARDATION OF THE FIRING ANGLE CAUSES LAGGING POWER FACTOR AT THE INPUT SIDE ESPECIALLY AT LARGE FIRING ANGLES2)-A DISCONTINUITY OF POWER FLOW APPEARS AT BOTH INPUT AND OUTPUT SIDES3)-HIGH LOW ORDER HARMONIC CONTENT IN BOTH OF LOAD AND SUPPLY SIDES

NEED FOR EXTINCTION ANGLE CONTROL TECHNIQUE

1):-Trying to solve this problem with simple ac voltage converters is an almost impossible task.

2):-On the other hand,adding a complex controller costing several times the price of the motor, is in itself an objectionable solution.

INTRODUCTION TO EAC TECHNIQUE 1):- The extinction-angle control (EAC) is similar to that of phase-angle control where there is only one pulse Per half cycle.

2):-In the phase-angle control the conduction is started at the required delay angle (@ ) and continues until the current reaches zero value naturally, while in the EAC control the conduction is started at zero crossing of the supply voltageand forced commutated at a certain angle before the next zero crossing (beta).

3):-freewheeling path is provided for the load current to discharge the stored energy of the load inductance.

4):-The output voltage is controlled by varying the extinction angle (beta). The fundamental component of input current leads the input voltage, and the displacement factor (and power factor) is leading.

5):-In some applications,this feature may be desirable to simulate a capacitive loadand to compensate for line voltage drops.

DETAIL STUDY OF EAC TECHNIQUE

This study is concerned with the investigation of acvoltage controllers with EAC technique applied to a staticload and the widely used squirrel cage single-phase induction motor. The operation of this controller as a variable voltage source employing EAC is evaluated and compared with conventional PAC from supply power factorimprovement point of view. The simulation results areverified experimentally.

CIRCUIT DIAGRAM and waveform

SPECIAL IMPORTANCE

It is worth to mention that the input power factor is improved gradually from its lagging value and becomes leading after the extinction angle exceeds the load angle and as the extinction angle increases, the input power factor gets more improved and this feature gives more importance for EAC technique.

CONCLUSION

1):-The EAC technique provides a considerable improvement in the input power factor. This improvement is mainly due to the improvement in the displacement factor.

2):-The ac voltage controller with the EAC technique has been applied to a static load and a dynamic load which is a squirrel cage single-phase induction motor loaded by a fan. A full control range of the ac output power and a wide control range of the motor speed can be achieved.

3):-Thus, this technique is suitable for speed control of single-phase induction motor as it is required a simple and less costly technique.

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