Power Engineering

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Browsing Power Engineering by Author "Anthony Alemayehu"

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    Digital Control for Switched Mode Converters Input Power Factor Correction
    (Addis Ababa University, 2011-07) Anthony Alemayehu; Mengesha Mamo (PhD)
    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.