Accurate Condition Monitoring of Semiconductor Devices in Cascaded H-Bridge Modular Multilevel Converters

This article presents an online condition monitoring (CM) scheme for semiconductors used in modular multilevel converters (MMCs) that comprise cascaded H-bridge submodules. The CM algorithm is based on detecting changes the on -state resistance of over time. proposed method shown to successfully perform a curve tracing MMCs while semiconductor junction remains at temperature readily measurable and undergoes minute during measurement process. value estimated from measured voltage drop arm current. Measuring known temperatures allows separating temperature-dependent variations age-dependent this parameter. Suitable methods reducing effect noise curve-traced data are proposed, recursive least square estimator extract optimum traced $v_{CE}-i_{C}$ curve. Simulation results show can accurately determine under various levels noise. Moreover, experimental low-power prototype applicable practice, provides similar curves what commercial tracer produce offline. verification has been conducted constant load conditions; however, be any variable as well.