Abstract
M.Phil. (Electrical and Electronic Engineering)
There are two methods that can be used when power is converted from one frequency
to another. One way uses a DC link as an intermediate stage and the other uses no
intermediate stage. When no DC link exists, the conversion process is referred to as
AC-AC conversion, (Cha, Enjeti & Ratanapanachote, 2004:2237).
This method essentially chops the AC signal in a specific manner which yields an AC
signal with a different frequency directly. Depending on how the AC signal is chopped,
it would result in a varied number of wave shapes are constructed. The construction of
these various wave shapes results in devices that can accomplish different tasks.
One such device is called a unity displacement factor frequency converter (UDFFC).
This research attempts to develop a model, to simulate and design a unity displacement
factor frequency converter. The primary idea about this device is that the power factor
or displacement factor is unity regardless of the load.
There are three parts in the development of the UDFFC. The power circuit is an array
or matrix of switches that link the three phase supply to the three phase load. The
power circuit is interfaced to the control circuit which generates pulses that control the
matrix of switches. The control circuit utilizes embedded control software that
performs the control logic in a microcontroller.
The development of the UDFFC has a potential to solve real power engineering
problems, such as eliminating the DC link in a converter. This achieves the conversion
of AC directly to AC in the absence of a DC link. The other major advantage is the
variation of the output frequency to a desired value. The most important is that the
displacement factor can be controlled as well.