TO MITIGATE THE EFFECT OF DIFFERENT FAULTS ON COMMUTATION OF LCC HVDC SYSTEM by Kamaljeet Kaur
To transfer large amount of direct current power having high amplitude voltage over long distance HVDC transmission system is used. HVDC is abbreviation of high voltage direct current. This system was introduced 60 year ago and now it is widely used all over the world. In power transmission field there are various types of High voltage direct current systems. Some examples are Voltage-Sourced-Converter (VSC), capacitor commutated converter (CCC) and line commutated converter (LCC) dependant HVDC techniques.VSC method used for multi-terminal Direct Current grid, but line commutated direct current method performs better as compare to VSC in broad distance large amount of power transmission due to its efficiency. Various difficulties faced in LCC HVDC system like while voltage is reduced from (10% to 15%) and commutate fails. The LCC HVDC system is having better performance in comparison to others so the analysis is done on this system to reduce the commutation distortion. The 500 kV, 5000 MVA at 60 Hz system is connected to 345 kV, 10000 MVA at 50 Hz system using DC line of 1000 MW, 500 kV and 2 kA line. The 12 pulse monopolar thyristor converter based HVDC system is used for this analysis. The DC fault is having less effect on commutation as compare to the AC single and three phase fault. During DC fault only the distortion is occurring which is minimized with the help of DC filter. During AC faults the commutation failure is occur that is minimized by using IGBT capacitor circuit. The comparison of results is done with the system having no fault and it is conclude that the AC faults are the main reason of commutation failure and that effect is mitigate with the help of IGBT capacitor circuit.