Practical Investigations on SCR Based HVDC Power Transmission Systems

Abstract

HVDC power transmission based converter uses both 6 pulse and 12 pulse schemes system. It is constructed mainly using the semiconductor devices for transfer of bulk amount of electric power, so that transmission cost reduces and efficiency increases. The AC power at the input of the HVDC transmission system is converted into high voltage dc for transmission. At the receiving end, this HVDC is converted back to high voltage AC using inverter technology. The conversion of AC input into dc output is done by SCR and IGBT.A high current and high power thyristor is employed in phase controlled rectifier circuit for converting AC input power into dc output power. This is used to provide variable voltage output DC and variable DC load current. The average output load voltage is controlled by varying the thyristor triggering angle. The IGBT based inverter is used with a set of LC filters to reduce output harmonics for load endurance protection and for elimination of various harmonics related problems. Here the degree of freedom is 2 because one phase voltage is reference and other two relative voltages are free to control. So the IGBT based 3 phase invetrter converts the HVDC into HVAC at the output. The output voltage is controlled by varying thyristor triggering angle. In the SCR based converter both 6 pulse and 12 pulse schemes are employed.