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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.
Under inductive (lagging) conditions, the capacitor banks are automatically switched in, thus providing a higher system voltage. By connecting the thyristor-controlled reactor, which is continuously variable, along with a capacitor bank step, the net result is continuously variable leading or lagging power.
Fixed, shunt capacitor and reactor banks filled this need by being deployed where needed. In particular, shunt capacitors switched by circuit breakers provided an effective means to managing varying reactive power requirements due to changing loads. [3] However, this was not without limitations.
Power factor correcting capacitors can be added externally to neutralize a constant amount of the variable reactive excitation current. After starting, an induction generator can use a capacitor bank to produce reactive excitation current, but the isolated power system's voltage and frequency are not self-regulating and destabilize readily.
A capacitive load bank or capacitor bank is similar to an inductive load bank in rating and purpose, except leading power factor loads are created, so reactive power is supplied from these loads to the system instead of vice versa. Hence for a mostly inductive load this can bring the power factor closer to unity improving the quality of supply.
Its principal advantage is the ease with which the amount of correction can be adjusted. Synchronous condensers are an alternative to capacitor banks and static VAR compensators for power-factor correction in power grids. [3] One advantage is that the amount of reactive power from a synchronous condenser can be continuously adjusted.
One type of series compensation is the Thyristor-Controlled Series Capacitor (TCSC), which combines the TCR from an SVC in parallel with a traditional fixed series capacitor. As using power electronics to switch capacitors sub-cycle is not feasible due to concerns of stored charge, a TCR is used to create a variable inductance to offset the ...