Converter Switching Based Generic Loss Evaluation in Semiconductor and Clamp Circuit of IGCT Based MMC Converter Cells for HVDC Applications

摘要

IGCTs are increasingly becoming the device of choice for high power applications such as HVDC and FACTS with low losses and high reliability. Voltage Source Converters (VSC) with IGCT semiconductors are the choice in high demanding applications with high power and current ratings primarily due to low overall losses and high power handling capability. IGCT circuit typically require a di/dt limiting snubber for the protection of freewheeling diodes from huge current derivatives and so an over voltage limiting mechanism for the protection of IGCTs. This paper presents the performance evaluation of IGCT and its Clamp Circuit in terms of losses, focusing on MMC converter cells for use in high power applications such as HVDC, FACTS. The proposed method is based on look up tables generated for clamp circuit energy dissipation for the different converter switching states and is synchronized with the actual switching transitions. Additionally, the temperature dependency of the reverse recovery current for the freewheeling diode losses also considered. Hence, it yields an accurate, yet computationally efficient method of loss calculation. The results for IGCT based MMC converters are also compared with IGBT based MMC converter to clearly highlight the advantages of one over the other.