A frequency converter is an electrical system that converts
the frequency of an AC input signal to another frequency. This
frequency converters are subdevided into two category. In the
first category, the AC input is converted to DC with a rectifier
and after converted to AC with an inverter. A good example for
this method is DC link inverter fed from voltage/current source
inverter. In these configurations we have loss in both recti fire
stage and inverter stage. In addition the DC linl( capacitor is
bullky and has a short lifetime [9]. In the second category, the
frequency convrted to another only in one stage, directly. This
type of conveter is consists of an array of static switches that
directly connect the input to the output. A good example for
this type is the cycloconverter that usually used for high power
applications [6].