A Flexible Alternating Current Transmission System (FACTS) device is a specialized piece of power electronics equipment used in power systems to control and optimize the flow of alternating current (AC) power. FACTS devices are designed to enhance the controllability, stability, and efficiency of AC power transmission and distribution systems.
The primary purpose of FACTS devices is to manipulate various parameters of the AC transmission system, such as voltage, impedance, and phase angle, in order to control the flow of power and manage system conditions. By doing so, they can help maintain system stability, increase transmission capacity, and improve overall system performance.
There are several types of FACTS devices, each with its own way of controlling AC power flow:
Thyristor-Controlled Series Capacitor (TCSC): This device is placed in series with a transmission line and can be used to vary the line's reactance. By adjusting the reactance, the TCSC can control the line's impedance and, consequently, the power flow. It can also be used to dampen power oscillations.
Thyristor-Controlled Phase Shifter (TCPS): A TCPS is inserted in series with a transmission line and can adjust the phase angle between the sending and receiving ends of the line. This capability allows for real and reactive power control and can help balance power flows.
Static Var Compensator (SVC): An SVC is connected in parallel to the transmission system and can rapidly inject or absorb reactive power into the system. This helps regulate voltage levels and control power flow by influencing the system's impedance.
Static Synchronous Compensator (STATCOM): Similar to an SVC, a STATCOM also provides reactive power support to the system. It uses voltage-source converters to inject or absorb reactive power, contributing to voltage control and power flow management.
Unified Power Flow Controller (UPFC): The UPFC combines the functionalities of series and shunt FACTS devices. It can control both the impedance of a transmission line and the voltage at a specific bus, enabling precise control over power flow and voltage levels.
Interline Power Flow Controller (IPFC): This device can control power flow between multiple transmission lines, allowing optimization of power flows within the network.
The control mechanisms for FACTS devices involve sophisticated algorithms and control strategies that continuously monitor system conditions and make adjustments to achieve specific objectives. These control strategies can include voltage regulation, power factor correction, damping of power oscillations, congestion management, and more.
Overall, FACTS devices play a crucial role in modern power systems by enhancing operational flexibility, reducing transmission losses, and improving system stability through precise control of AC power flow and voltage.