Optimal reactive power flow control for voltage profile improvement in AC-DC power systems

High Voltage Direct Current (HVDC) has been extensively used in modern transmission systems. An algorithm for optimum flow of reactive power in AC-DC systems with an objective of improving the voltage profile has been presented in this paper. The technique utilizes the reactive power sources in the system to improve the voltage profile as well as meeting the reactive power requirements at the AC-DC terminals to facilitate the smooth operation of DC links. The problem is formulated as an optimization problem, with an objective of loss minimization suitable for solution by linear programming technique. Control variables are transformer tap settings, generator voltages, switchable VAR compensator settings and the converter transformer tap settings. The method has been tested on an IEEE-14 bus system with two terminal DC link and the results are presented.