Digital Control for Switched Mode Converters Input Power Factor Correction
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Date
2011-07
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Addis Ababa University
Abstract
Input power factor of static power converters is generally low due to angular displacement
between input voltage and current plus due to current distortion. On the other hand, static power
converters usage is increasing continuously with the increase in use of power supply units to
commercial, industrial and residential complex automation and communication systems. This
increase in application of power converters has increased the reactive power demand from the
utility grid resulting in inefficiency and overloading of the transmission and distribution network.
In this thesis, a digitally controlled switched mode PFC (power factor correction) converter has
been designed, modeled and simulated. The three major control modes which are used for
switched mode converter control are the voltage mode control, current mode control and the PFC
mode control. These three control modes have been simulated using the MATLAB Simulink for
100%, 75%, 50%, 25% and 10% power loading. For the 100% load (full load) it has been found
that the PFC mode controller achieves a near unity input power factor with power factor of
0.99975. At full load, the voltage mode and current mode controller have a lower power factor of
0.943 and 0.945 respectively. For the other loadings, the PFC mode controller has a near unity
power factor which is greater than 0.99, whereas the voltage mode and current mode controller
have a lower power factor. The PFC mode controller performs well even if there is variation in
input voltage and load. In addition, the lowest total harmonic distortion (THD) and reactive
power, and the highest power factor (PF) are obtained using the PFC mode control. From the
results obtained, it can be concluded that the PFC mode controller is the best control scheme to
be used for such control applications.
Digital control for power factor correction is an important field of study since it can be used to
reduce the harmonics in the line current, increase the efficiency of power systems, and reduce
customers’ utility bills. The results of this study are useful for many applications such as an
uninterrupted power supply (UPS), telecom power supply, motor drive inverter, personal
computers, battery charging, DC motor drive, welding machine and other power supplies for
electronic equipment.
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Keywords
Power factor, PFC converter, Boost converter, Digital control