As energy demand continues to rise, cost-effective delivery of electric power becomes a daunting task. Many jurisdictions responded by introducing legislation to privatize the power generation industry, so that large networks of systems with multiple different owners could share the load. As remote power systems add more interconnections, new challenges are emerging related to overall power system stability, particularly in relation to distributed generation as with renewable power sources in the home.
Traditionally, engineers integrated power systems under the assumption that power consumption increases gradually such that operators can simply add generation capacity to meet demand and one can consider the system relatively unchanging with time. Similarly, operators could compensate for changes in the overall power profile by adding inductors or capacitors to substations depending on the typical load. For example, a substation supplying power to an industrial mill would consume reactive volt-amperes (VARs) so the local utility would add a capacitor to compensate for the inductive load, in order to preserve voltage regulation. However, once the mill is no longer operating (for example, at night), the resulting reduction of load causes a rise in the supply voltage, which can be well above the desired voltage.
Flexible AC Transmission Systems (FACTS) are different because, as the name implies, they are flexible: designed to be dynamically adjusting to the power demand and other conditions of power quality. A basic installation might consist of an operator- or microprocessor-controlled bank of capacitors can consume reactive power when necessary. The state of the art is to provide continuous switching using power electronic devices, which have a much faster response time than a human operator or even a microprocessor-based control system. Novel devices even filter harmonic oscillations, which can significantly reduce power flow and cause stability issues.
Optimum usage of current transmission line assets is the most cost effective option available and FACTS devices allow utilities to provide greater power delivery with better system stability and power quality. It is often prohibitively expensive to build new power lines, so these devices provide a stopgap measure capable of delivering increased capacity while also reducing transmission losses.
This article was taken from a report which I co-authored. It was submitted to ECE3333: Power Systems I, taught by Professor Rajiv Varma at the University of Western Ontario in Spring 2009.