Power Electronics Integral Cycle Control - Power Electronics

What is the use of Integral Cycle Control in Power Electronics?

Integral cycle controllers are converters which have the ability to perform direct switching without losses. This process will directly convert AC to AC without performing the halfway processes of AC to DC then DC to AC.

Basic integral control cycle is sinusoidal in nature and it can operate by uniting and removing higher frequency half cycles from AC input. Controllers are basically turned ON of OFF at the time of half cycles where the voltage input is at zero because only the full or half cycles will be used. Thus, integral cycle circuits gain switching at zero voltage without the help of a resonant circuit.

Below diagram displays a simple integral cycle controller which consists of a load and a power switch to perform the direct conversion. This diagram shows the conversion of source frequency from a factor of three to one.

integral_cycle_control.jpg

Power Factor Control

Power factor control also called as correction of power factor, decreases the amount of reactive power. Power electronic device used in this case is known as a power factor controller (PFC). From the power triangle (which comprises reactive, true and apparent power), reactive power will be at right angle (90°) to the true power and it will be utilized to strengthen the magnetic field. Though reactive power has no real value in electronic equipment, electricity bill will include the real and reactive power costs. This will make it compulsory to have power factor controllers in electronic devices.

Power factor (k) can be defined as the ratio of the real power (in kW) to the reactive power (in kVAr) and its value will be ranging from 0 to 1. If a device has a power factor of 0.8 and above, it is said to use the power capably. Including a PFC will make sure that the power factor will range from 0.95 to 0.99. Power factor controllers are widely used in industrial equipment for minimizing the reactive power which is produced by the fluorescent lighting and electric motors.

To make sure that the power factor is enhanced without causing harmonic distortion, conventional capacitors should not be used. Rather, filters (combination of capacitors and reactors) for harmonic suppression can be used. Below figure shows a harmonic filter.

harmonic_filter.jpg

Above harmonic filter type can be referred to as a single tuned filter. A quality factor Q of this filter can be defined as quality factor of its reactance (XL) at Q (tuning frequency) where Q is given by (nXL/R).

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