Classification of FACTS

· The FACTS controllers can be listed as: according to the power electronic devices used in the regulation.

1. Variable Impedance Type

• Static Var Compensator (SVC :( A shunt-connected static var generator or absorber whose output is adjusted to swap capacitive or inductive current in order to retain or control specific parameters (typically bus voltage) of the electrical power system.

•      Thyristor Controlled Series Capacitor (TCSC): TCSC is a series connected device.
•      It is a variable impedance type device.
•      It can affect active power flow.
•      The switching frequency is small relative to other FACTS apps.
•      Insertion of a capacitive reactance in combination with the line's endogenous
•      inductive reactance reduces the overall effective impedance of the line and so both angular and voltage stability gets enhanced.

2. voltage source converter (VSC)

•      Static Synchronous Compensator (STATCOM): STATCOM is a ‘Voltage Source Converter 'based device. STATCOM is designed to support energy networks that have a low power factor and inadequate voltage control. The voltage supply is generated from a DC capacitor and hence a STATCOM has very little active power capability. If the terminal voltage of the VSC is greater than the AC voltage at the point of contact, the STATCOM produces reactive power. When the amplitude of the voltage source is smaller than the AC voltage, it consumes reactive power.
•      Static Synchronous Series Compensator (SSSC) : A static synchronous generator operated as a series compensator without an external electrical source whose output voltage is in quadrature and controllable independently of the line current in order to increase or decrease the total reactive voltage drop across the line and thereby control the transmitted electrical power. The SSSC may include transiently rated energy storage or energy-absorbing devices to enhance the power system's dynamic behavior through additional temporary real power compensation, to momentarily increase or decrease the total real (resistive) voltage drop across the line
•      Unified Power Flow Controller (UPFC)
It is STATCOM and SSSC combined.
This is a system that is type VSC.
Voltage, impedance, and angle of phase regulation.
Impacts the distribution of active as well as reactive power in transmission cable.
The shunt converter (STATCOM) is primarily used to support the series converter's (SSSC) active power demand through a-DC connection.
STATCOM is also able to generate or absorb reactive power and thus provide independent reactive shunt compensation for the line.
SSSC provides the UPFC's key feature by injecting, from a voltage source, a voltage with controllable magnitude and phase angle in series with line.

· Facts Controllers may also be classified as follows according to the controller 's connection:

Connected Shunt Controllers
Connected Series Controllers
Hybrid/Combined Controllers

· otherwise FACTS Controller

.    Thyristor Controlled Phase Shifting Transformer (TCPST)
.    Interline Power Flow Controller (IPFC)
.    Thyristor Controlled Braking Resistor (TCBR)
.    Thyristor Controlled Voltage Limiter (TCVL)
.    Thyristor Controlled Voltage Regulator (TCVR)
.    Interphase Power Controller (IPC)
.    Distributed Power Flow Controller (DPFC)
  NGH-SSR damping