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injection of reactive power into transmission lines causes losses that waste power, forcing an increase in power supplied by the prime mover. Use of specialized voltage control devices in the grid also improves the power system stability by reducing the fluctuations of the rotor angle of a synchronous generator (that are caused by generators ...
A unified power flow controller (UPFC) is an electrical device for providing fast-acting reactive power compensation on high-voltage electricity transmission networks. It uses a pair of three-phase controllable bridges to produce current that is injected into a transmission line using a series transformer. [ 1 ]
Heavily loaded lines consumed reactive power due to the line's inductance, and as transmission voltage increased throughout the 20th century, the higher voltage supplied capacitive reactive power. As operating a transmission line only at it surge impedance loading (SIL) was not feasible, [ 2 ] other means to manage the reactive power was needed.
Unlike the TCR, the TSC is only ever operated fully on or fully off. An attempt to operate a TSC in ‘’phase control’’ would result in the generation of very large amplitude resonant currents, leading to overheating of the capacitor bank and thyristor valve, and harmonic distortion in the AC system to which the SVC is connected.
The term power system control describes actions taken in response to unplanned disturbances (e.g., changes in demand or equipment failures) in order to provide reliable electric supply of acceptable quality. [3] The corresponding engineering branch is called Power System Operations and Control.
In other words, the DVR is a solid state DC to AC switching power converter that injects a set of three-phase AC output voltages in series and synchronicity with the distribution and transmission line voltages. The source of the injected voltage is the commutation process for reactive power demand and an energy source for the real power demand.
However, due to Kirchhoff's Laws, the voltage magnitude and thus the service voltage to customers will in fact vary along the length of a conductor such as a distribution feeder (see Electric power distribution). Depending on law and local practice, actual service voltage within a tolerance band such as ±5% or ±10% may be considered acceptable.
The current in the TCR is varied from maximum (determined by the connection voltage and the inductance of the reactor) to almost zero by varying the "Firing Delay Angle", α. α is defined as the delay angle from the point at which the voltage becomes positive to the point at which the thyristor valve is turned on and current starts to flow.