The use of a Static Synchronous Series Compensator (SSSC) for power flow control in the 220 kV Spanish transmission network

The project described in this paper consists of the development of a FACTS device for the control and direction of flows of a power line through the use of a Static Synchronous Series Compensator (SSSC). The article describes the need satisfied with this development and the implementation of this type of device in future energy systems. With the installation of this device, the risk of overload situations in a 220 kV line that has a high variability in its flow in certain situations of demand and generation will be minimized. The SSSC operates by injecting a voltage controlled in amplitude and phase, in series with the transmission power line. This voltage, which is 90° out of phase with the line current, will have the effect of either decreasing or increasing the power flow when it is leading or lagging that current respectively. The initial parameters of the most likely scenario under which the device will be working, and the functionality intended are described. Taking these parameters into account, a preliminary design of the device and its components has been developed. To validate this design several simulations have been carried out in which, using various simplified models of the transmission network, the behaviour of the device has been studied in normal operation and during temporary situations caused by disturbances of the network. The results of these simulations are summarized in the article. In parallel, as an important aspect for the device's final definition, the selection of the site where to implement it has been studied. In addition to the initial characteristics and the requirements defined for the previous design other technical restrictions for physical implementation have to be studied, such as surface area needs, connection to the existent equipment installed in the substation, other constraints from the functional point of view and possible impact to system security.