Real-time operation surveillance of a static cycloconvertor based on waveform supervision

Conventional protection systems of large power converters offer high reliability in preventing destructive failures. Such systems include differential and absolute current protections, under and overvoltage protections and semiconductor fuses. Also, some systems use independent electronic monitoring to detect frequency deviations, earth currents and overtemperature of selected units. To improve performance a large number of feedback signals is required. This number is proportional to the number of power semiconductors used in the converter circuit. Therefore, the reliability of a complete and user-friendly diagnosis system is intrinsically low. To overcome this problem an expert system approach is proposed in this work for the surveillance of a cycloconverter. A true on-line operation surveillance of a cycloconvertor based an waveform supervision is discussed. Using this method, the diagnosis of the converter operation requires a reduced number of feedback signals. Some usual abnormal and faulty conditions are examined. Finally, selected experimental results obtained with a laboratory prototype are presented