Modelling and implementation of a unified voltage controller : an alternative FACTS controller to improve power transfer
In the last years, the planning of optimised electric power systems, in addition to a more efficient operation of already installed systems, has resulted in an appealing development of controllers which make transmission systems more flexible. The acronym FACTS (Flexible AC Transmission Systems) has become a synonym of electronic-based controllers that perform a quick and safe control of system parameters. A large number of FACTS controllers have been proposed, most of them already in operation. The construction of a comprehensive controller, which would provide simultaneous control of several system parameters at a reduced cost and size, has been the challenge addressed to power engineering designers. This thesis presents the Unified Voltage Controller (UVC), which is an alternative to the control of power flow. The UVC is based on the control of local and remote voltage vectors of the transmission line ends. The concept of the parameters involved in power transfer is discussed. Equations of space vector control for the UVC are defined, and the pulse-width modulation to control the UVC converters is presented. A simplified three-phase system is simulated to show the efficacy of the UVC when operating as a conditioner of power systems. Several simulations have been developed to show the efficiency of the UVC. The control of the local and the remote voltage magnitude, besides the control of transmission angle have been illustrated through computational simulation.