An Online Monitoring Method to Extract the Accurate Junction Temperature of High Power Press-Pack Thyristor via Gate Cathode Voltage

To extract the accurate junction temperature (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">temp</sub>) of a single high power press pack thyristor, a novel online monitoring method is proposed in this article. By collecting gate cathode voltage in real time, the system obtains more accurate junction temperature of thyristor. The feasibility of gate cathode voltage (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GK</sub>) as a junction temperature parameter is deduced by numerical model theory. A simulation model is constructed in TCAD to verify the conclusion that there is a negative temperature coefficient between the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GK</sub> and the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">temp</sub>. Based on this, preliminary tests from a developed online measurement system are presented. The gate drive circuit and junction temperature measurement circuit have been integrated in the design. The entire online monitoring system enables real time and accurate online measurement of the gate cathode voltage with the error of less than 2.3%. Moreover, comparing with thermocouple and thermal model methods, the junction temperature error value do not exceed 5 °C. This provides strong technical support for accurate junction temperature online monitoring.