INVESTIGATION ON HARMONIC PROBLEMS FOR N-1 CONTINGENCY IN INDUSTRIAL DISTRIBUTION AND MITIGATION USING FUZZY CONTROLLED HYBRID FILTER

Abstract

The electric distribution structure of modern industries is rapidly changing and becomes complex and complex as a result of an increase in demand and market competition. Effective nonlinear electronic devices were introduced recently to increase productivity and efficiency. However, installing devices such as; Programmable Logic Controllers (PLCs), Adjustable-Speed Drives (ASD), energy efficient motors and other power electronic devices are creating a power quality related problem namely harmonic distortion. Harmonic means the multiple of fundamental frequencies resulting in excessive current flow on lines due to power electronic devices, short circuits, and other contingency effect. This has a great threat to industrial consumers, results in equipment damages, poor power factor, and excessive neutral currents. Considering the economic consequence of harmonic problems due to damaging of electric equipment and an increase of electric bill due to poor power factor in Industries, this research project presents the modeling of an industrial distribution named Red Sea Bottlers Share Company in Eritrea using Matlab Simulink for an investigation of harmonic distortion level. To carry out the investigation, firstly the industrial network and loads were modeled. Specifically, the substation, transformer, transmission lines, variable frequency drive motors, induction motors, switch mode power supply were modeled using Matlab Simulink for harmonic study. After that, the modeled system was simulated to carry out the spectral analysis. Then harmonic distortion level at both Point of Common Coupling (PCC) and In Plant Coupling (IPC) were computed for normal operating conditions as well as for N-1 contingency cases. The result was compared with the IEEE 519-2 and IEC 61000-2-4 for class 2 standards and found don’t comply with the standards. A fuzzy logic controlled hybrid filter was designed to reduce the harmonic distortion level up to the threshold that satisfies the above-stated standards. To verify the whether the harmonic distortion level is within the stipulated limits the overall modeled industrial plant was simulated after the introduction of the designed hybrid filter. The harmonic distortion level was measured at both Point of Common Coupling (PCC) and In Plant Coupling (IPC) for the normal operating condition as well as N-1 contingency conditions. Then the result was compared IEEE 519-2 and IEC 61000-2-4 for class 2 standards. It was found out that the designed filter can able maintain the harmonic distortion level within the recommended limits as per the IEEE 519-2 and IEC 61000-2- 4 for class 2 standards regardless of the operating conditions of the industrial plant.