ABSTRACT:

The Aluminum Smelter is basically a series connected electrolytic cells (Pots) supplied by direct current electrical equipment known as Rectiformers. The Rectiformer is a combination of rectifier coupled to a transformer and it is used in Aluminum smelters to supply the pot line with direct current. Aluminum Bahrain (ALBA) consumes more than 1.6GW DC power to feed their five pot lines. The conversion from alternating current to direct current unfortunately creates harmonics and causes a power quality issues especially when large amount of power being converted. ALBA and other aluminum smelter nowadays are relying on shunt passive harmonic filter for reactive power compensation and to reduce the harmful effect of harmonics on the AC power network.

In this thesis, ALBA power network with their large rectification systems has been simulated using MATLAB/Simulink to evaluate the harmonic distortions based on different practical operating scenarios. A new pot line Rectiformer scheme has been proposed in order to reduce the distortion at Rectiformer terminal. In addition, a better harmonic attenuation capability at point of common coupling (PCC) has been found by using parallel delta connected (PDC) tertiary winding between two adjacent Rectiformers. The proposed scheme is modeled and simulated using MATLAB/Simulink and its performance is compared with that of conventional schemes. Finally, a shunt active power filter (SAPF) for large scale Rectiformer is introduced. The SAPF is a good solution for harmonics as it is self-adaptive and does not involve any risk of resonant with the power network impedance. The topology and the control technique suits adequately the pot line load behavior.