This document describes an automatic power factor correction system using a microcontroller. It measures the phase difference between the voltage and current waves using interrupts from a zero crossing detector. The microcontroller then calculates the power factor and switches capacitor banks as needed in steps to improve the power factor. This provides accurate and fast power factor correction to increase the efficiency of electrical systems.

1. Automatic Power Factor
Correction Using Microcontroller
NEEHAR

2. What is Power factor??
•Power Factor is the ratio of real power
and apparent power.
•It is a measure of how effectively the
current is being converted into useful
work output.
•Its an important parameter to decide the
efficiency of an electric circuit.

3. Power Triangle:

4. Advantages of improved
power factor:
•Reactive power decreases
•Efficiency of supply system and
apparatus increases
•The electrical consumption tariffs depend
on power factor.

5. Use of microcontroller in
power factor correction:

6. PRINCIPLE:
• Automatic Power Factor correction device is developed based on
microcontroller 89c51.
• The voltage and current sampled is converted into square wave
using a zero cross detector.
• The V and I sample signals are fed to the micro controller at INT0
and INT1 and the difference between the arrival of wave forms
indicate the phase angle difference.
• The difference is measured with high accuracy by using internal
timer.
• This time value is calibrated as phase angle and corresponding
power factor. The values are displayed in the 2x16 LCD modules
after converting suitably. The capacitor banks are switched as per
the calibration in steps.

7. Modules:
•Power supply
•Zero crossing detector
•Motherboard
•Algorithm
•Relay driver
•LCD Display

8. Control circuit:

9. Phase angle detection:
•Step-1:- Microcontroller started on interrupt mode.
•Step-2:- INT0 & INT1 are enabled.
•Step-3:- INT0 is given VOLTAGE (V), INT1 is given
CURRENT (I) from sampling circuit.
•Step-4:- Timer measures time interval between two
interrupts.
•Step-5:- Time interval calibrated as 0-5ms = 0-90
degree.
•Step-6:- Calibrated data is displayed on LCD.

10. Relay Circuit:

11. LCD display

12. Conclusion
•
It can be concluded that power factor correction
techniques can be applied to the industries, power
systems and also house holds to make them more
efficient.

More accurate and fast control.

Reduced size of control circuit.

13. Thank You