Three-phase PWM AC/AC Cúk converter for voltage sag compensation

A three-phase PWM AC/AC Cúk converter aimed at voltage sag compensation is presented. Unlike other configurations, the converter has a modular structure, allowing individual phase compensation, and thus providing a balanced response to voltage sags. The design procedure is derived from the basic DC/DC converter analysis, and conveniently modified for AC/AC operation. The control stage is implemented using commercial analog PWM ICs along with digital logic for gating pulse distribution. The converter was tested in static and dynamic operating conditions. The tests performed show that the output voltage is kept within a ±3% range of the nominal voltage, and its THD level is below 5%, operating with an average efficiency of 89.44%. The response time to a 63% depth voltage sags is good, returning the output voltage to −10% of the nominal voltage in less than a half line cycle, in full compliance with the ITIC curve for information equipment. These performance characteristics make the converter a suitable choice for power conditioning sensitive loads.