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Power factor correction brings the power factor of an AC power circuit closer to 1 by supplying or absorbing reactive power, adding capacitors or inductors that act to cancel the inductive or capacitive effects of the load, respectively. In the case of offsetting the inductive effect of motor loads, capacitors can be locally connected.
A valley-fill circuit is a type of passive power-factor correction (PFC) circuit. For purposes of illustration, a basic full-wave diode-bridge rectifier is shown in the first stage, which converts the AC input voltage to a DC voltage.
Using active rectification to implement AC/DC conversion allows a design to undergo further improvements (with more complexity) to achieve an active power factor correction, which forces the current waveform of the AC source to follow the voltage waveform, eliminating reactive currents and allowing the total system to achieve greater efficiency.
Power Interface Module (PIM) - (consisting of the input rectifier, power factor correction and inverter stages) Intelligent Power Module (IPM) - (consisting of the power stages with their dedicated gate drive protection circuits. May also be integrated with the input rectifier and power factor correction stages.)
This is traditionally done using shunt capacitors and inductors (reactors), [13] much like Power Factor Correction. The most common shunt compensation device is the Static VAR Compensator (SVC). [14] SVCs use power electronics, generally Thyristors, to switch fixed capacitors and reactors.
Turning off the switch causes the voltage across the inductor to reverse and the current to flow through the freewheeling diodes Da+ and Da-, decreasing linearly. By controlling the switch on-time, the topology is able to control the current in phase with the mains voltage, presenting a resistive load behavior (Power-factor correction capability).
In electric power distribution, capacitors are used for power factor correction. Such capacitors often come as three capacitors connected as a three-phase Electrical load. Usually, the values of these capacitors are given not in farads but rather as a reactive power in volt-amperes reactive (VAr).
As most modern VSCs are made of power electronics that are capable of making small voltage changes very quickly, [15] a dynamic reactive power output is possible. This compares to a traditional, fixed capacitor or inductor, that is either off (0 MVar) or at its maximum (for example, 50 MVar).