Automatic power factor correction using microcontroller
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Date
2013-08
Journal Title
Journal ISSN
Volume Title
Publisher
University of Management and Technology
Abstract
Wasted energy capacity, also known as poor power factor, is often overlooked. It can result in poor reliability, safety problems and higher energy costs. The lower your power factor, the less economically your system operates. The actual amount of power being used, or dissipated, in a circuit is called true power. Reactive loads such as inductors and capacitors make up what is called reactive power. The linear combination of true power and reactive power is called apparent power. Power system loads consist of resistive, inductive, and capacitive loads. Examples of resistive loads are incandescent lighting and electric heaters. Examples of inductive loads are induction motors, transformers, and reactors. Examples of capacitive loads are capacitors, variable or fixed capacitor banks, motor starting capacitors, generators, and synchronous motors.
Power factor correction (PFC) is usually achieved by adding capacitive load to offset the inductive load present in the power system. The power factor of the power system is constantly changing due to variations in the size and number of the motors or inductive loads of any kind being used at one time. This makes it difficult to balance the inductive and capacitive loads continuously. There are many benefits of having power factor correction. As a customer the cost does not get passed on for having a low power factor. As a utility company, equipment has a much longer life span and maintenance costs remain low.
In recent years, the power quality of the AC system has become a great concern due to the rapidly increased number of inductive loads, electronic equipment, power electronics and high voltage power systems. In order to reduce line losses and improve the transmission efficiency, power factor correction research became a hot topic. Many control methods for the Power Factor Correction (PFC) were proposed. This project report describes the design and development of a single-phase (240V, 50Hz) capacitor bank power factor correction device using PIC (Peripheral Interface Controller) micro-controlling chip. Power factor correction using capacitor banks reduces reactive power consumption which will lead in minimization of losses and at the same time increases the electrical system’s efficiency. Power saving issues and reactive power management has brought us to the creation of single phase capacitor banks for domestic applications. The development of this project is to enhance and upgrade the operation of single phase capacitor banks by developing a micro-processor based control system. The control unit will be able to control capacitor bank operating steps based on the varying load current. This project applies the Peripheral Interface Controller ( PIC ) microcontroller to produce switching commands in order to control the capacitor bank steps. Intelligent control using this micro-processor control unit ensures even utilization of capacitor steps, minimizes number of switching operations and optimizes power factor correction. Transformer-type variable inductive load specially designed to meet the requirements of this project is used as load in this single phase capacitor bank developments. This transformer-type variable inductive load is varied over various ranges and different load values by using variable resistance dimmer to enable capacitor bank model to be controlled systematically. This project involves measuring the power factor value from the load using current transformer, potential transformer, and zero crossing detector, then using proper algorithm of switching on and switching off the capacitors in order to compensate excessive reactive power, thus withdraw PF near to unity (0.9 approximately) as a result acquires higher efficiency and better quality AC output.
Description
Project Advisor:Asif Hussain
Keywords
BS Thesis, Electrical Engineering, Microcontroller, Automatic Power