Power Flow Control in a Transmission Line Using D-facts Devices

Flexible AC transmission systems (FACTS) devices can control power flow in the transmission system to voltage source as it can inject an almost sinusoidal voltage of variable and controllable amplitude and phase angle, in series with a transmission line. Most of the injected voltage, which is in quadrature with the line current, provides the effect of inserting an inductive or capacitive reactance in series with the transmission line. This variable reactance influences the electric power flow in the transmission line. This paper illustrates the flexibility of control that is achievable with D-FACTS devices. D-FACTS converters are single-phase and floating with respect to the ground, there is no high-voltage isolation required between the phases. The impact of installing D-FACTS devices is examined by studying the sensitivities of power system quantities such as voltage magnitude, voltage angle, bus power injections, line power flows, and real power losses with respect to line impedance. Sensitivities enable us to quantify the amount of control D-FACTS devices offer to the system. Independently controllable lines are selected for power flow control and appropriate locations to install D-FACTS devices for line flow control are determined. Then, D-FACTS device settings are selected to achieve desired line flow objectives.