Evolution of the fast-acting power semiconductor-based Flexible Alternating Current Transmission System (FACTS) technology has enabled to enhance power system controllability over a wide spectrum, under varying system operating conditions, increase transmission loading capability and provide power quality to meet end-use requirements. With the advent of solid-state Voltage Source Inverter (VSI), the operational flexibility of FACTS controllers has increased manifold. Many state-of-the-art fast acting (sub-cycle) FACTS controllers, e.g., Thyristor Controlled Series Capacitor (TCSC), Static VAR Compensator (SVC), Static Synchronous Compensator (STATCOM), Unified Power Flow Controller (UPFC), Convertible Static Compensator (CSC), etc., are commercially being used to meet the various power system problems under different network operating scenarios. This paper presents a comprehensive review on the evaluation of FACTS technology, topologies, configurations, control techniques, comparative advantages, specific applications and a brief account of FACTS controllers that are commercially used by various utilities. A classified list of more than 340 research publications on the subject is appended for quick reference.
Power flow (both active and reactive) on transmission line is mainly governed by voltage,
line reactance and phase angle between the two ends. Traditional passive shunt and series
reactive power compensation devices are in use to improve the steady state conditions
enhancing reliability of the electrical system. Traditional control devices like circuit breakers,
transformer taps, etc., are slow acting devices (low response time) and unable to meet dynamic
system requirements. Added to that is the problem of reactive power balancing by passive
compensating devices (capacitors and inductors) in the network during transient system
conditions. Many practical constraints are experienced in system operation and control, like
non-utilization of transmission line capacity to the extent of thermal limit, Right-of-Way
(ROW) constraint, insulation constraint, poor steady-state, dynamic and voltage stability
margins, problems of Sub-synchronous Resonance (SSR), Power Oscillation Damping (POD),etc. Electric distribution/supply systems encounter power quality problems like voltage dip,
voltage swell, poor voltage regulation, high THD, low load power factor, load unbalance, etc.
These problems further aggravate due to stupendous growth of non-linear loads like TVs,
PCs, air conditioners, washing machines, xerox machines and many other electrical/electronic
appliances. |
