Using FACTS devices to resolve congestions in transmission grids

Abstract

Increased electric power consumption causes transmission lines to be driven close to or even beyond their transfer capacities resulting in overloaded lines and congestions. Flexible AC Transmission Systems (FACTS) provide an opportunity to resolve congestions by controlling power flows and voltages. The focus in this paper lies on the Thyristor Controlled Series Compensator (TCSC) and the Static Var Compensator (SVC) as they are already in use.In general, SVCs and TCSCs are controlled locally without any coordination. The resulting mutual influences may lead to a suboptimal control performance which may endanger the security of the system. In simulations where SVCs and TCSCs are controlled by local PI controllers with anti-windup, the interactions among the devices are demonstrated with TCSCs in parallel lines as well as in nonparallel lines, SVCs at different buses and a combination of TCSC and SVC in the same grid. It is shown how the controllers interact with each other, in the worst case ending up in an unsolvable conflict.Finally, a supervisory control based on optimal power flow is developed coordinating the actions of the FACTS devices placed in the same grid such that conflicts among devices are prevented. The objective is to ensure secure transmission of electrical power and to avoid congestions resulting in overloaded and possibly disconnected lines. In a test grid, the improvements in active power losses, in line loadings and in voltage profile are demonstrated.

A Novel Coordination Strategy for Multi-Agent Control Using Overlapping Subnetworks with Application to Power Systems

“…where the values of u B,SVC,min,m and u B,SVC,max,m are determined by the size of the device [7]. The constraints of an SVC at bus m are assigned to the node m.…”

“…where the values of u X,TCSC,min,mn and u X,TCSC,max,mn are determined by the size of the TCSC and the characteristics of the line in which it is placed, since due to the physics the allowed compensation rate of the line u X,TCSC,mn /η X,mn is limited [7]. The constraints of the TCSC at the line between bus m and n are assigned to node m, if m < n, and to node n otherwise.…”

Optimal transmission switching: economic efficiency and market implications

“…Shao and Vittal (2006a) proposes the use of FACTS devices as a corrective mechanism to relieve overloading and voltage violations. Glanzmann and Andersson (2005) proposes the use of FACTS devices as a congestion management tool. In this paper, the focus will be on transmission switching, i.e., the opening and closing of circuit breakers in order to temporarily take transmission assets (lines or transformers) in and out of service.…”

Improvement the Performance of the Power System by using an TCSC Device

“…where the values of X TCSC,min and X TCSC,max are determined by the size of the TCSC device and the characteristics of the line in which it is placed, since due to the physics the allowed compensation rate of the line is limited [17]. This range is set to 40% inductive and 90% capacitive.…”