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

• Published in: IEEE transactions on power electronics 2023-03, Vol.38 (3), p.1-15
• Main Authors: Asoodar, Mohsen, Nahalparvari, Mehrdad, Zhang, Yi, Danielsson, Christer, Nee, Hans-Peter, Blaabjerg, Frede
• Format: Article
• Language: English
• Subjects: Algorithms; Automatic voltage control; Cascaded H-bridge; Change detection; Condition monitoring; condition monitoring (CM); Electrical resistance measurement; FACTS; flexible ac transmission systems (FACTS); health estimation; Modular equipment; modular multilevel converter; modular multilevel converter (MMC); Monitoring; Noise measurement; online monitoring; reliability; Resistance; Semiconductor device measurement; Semiconductor devices; Semiconductor junctions; Semiconductors; Temperature; Temperature dependence; Temperature measurement; Voltage drop; Voltage measurement
• ISSN: 0885-8993; 1941-0107; 1941-0107
• DOI: 10.1109/TPEL.2022.3221285

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