Power Factor Improvement of Single Phase AC-DC System using Parallel Boost Converterud

摘要

Power factor in an AC electrical power system is described as the ratio of the actual power passing though the load to the virtual power flowing through the circuit or the cosine angle of the potential and charge of an AC circuit. A phase difference Ø exists between the potential and charge of an AC circuit and cosine which is called the circuit’s power factor. Suppose we get an inductive circuit we generally get the lagging by the voltage and that will be called a lagging power factor. And suppose we get the capacitive circuit then the current will be leading by the voltage and that will be referred as a leading power factor. The usage of power electronic system has reached to a new application stage that include residential, commercial, and aerospace and many others. Power electronic interfaces e.g. Switch Mode Power Supplies (SMPS) have proved to be superior over traditional linear power supplies. However their nonlinear behavior puts a question mark on their efficiency. The current drawn by the SMPS from the line is distorted resulting in a high Total Harmonic Distortion (THD) and low Power Factor (PF). Other adverse effects on the power system includes increased magnitudes of neutral current in three phase systems, overheating of transformers and induction motors etc. Therefore there is a continuous need of power factor improvement and reduction of line current harmonics. A large range of PFC circuits have been proposed with diverse operating modes to solve the situation. These PFC circuits adjust the waveforms of the current in the input side so that the maximum power can be tapped from the supplies. For every equipment the load should try to match a resistive one as closely as possible, only then the PF will be near to unity as there will be reduction of reactive power in the circuit. The current in this situation is free from all the lower as well as higher order harmonics thus copies the input voltage waveform. So this causes the current in the circuit to be at the lowest possible value to do the same work. As a result, the losses associated with circuit are reduced. Hence the consumption in power is reduced greatly. Boost converter accomplishes this active power-factor correction (ACMC) in discontinuous as well as in continuous modes. Simulation of a single phase bridge converter without using any converter is performed first. Then a current control circuit and a voltage control circuit were added to the boost converter which improved the input THD. This project aims to develop a circuit for power factor improvement using two Boost converters connected in parallel. It is based on the power sharing method to improve the current quality and to reduce the switching losses. In this method current in one circuit has to keep up with the one in parallel to it.