Thesis defence replay:
“Condition and Health Monitoring of Modular Multilevel Converter for HVDC Grids”

There was a big crowd gathered in our conference room last Monday, the 12th of June, to attend Diego Velazco’s thesis defense. Entitled “Condition and Health Monitoring of Modular Multilevel Converter for HVDC Grids”, this thesis was supervised by Guy Clerc (UCBL) and co-supervised by Emmanuel Boutleux (ECL). Diego’s work is particularly interesting for converter manufacturers and users who want to optimise the maintenance of their equipment. Intrigued? Here’s a summary of the key points and a replay of the thesis.

Diego Velazco was able to determine the Modular Multilevel Converter’s (MMC) reliability for HVDC networks in relation to the MMC’s mission profile, and establish how many redundant sub-modules are required to reach the converter’s availability target. He also tested different maintenance methods which can be applied to the MMC. Lastly, he custom-built an IGBT ageing bench to perform power cycling tests which then enabled him to analyse the IGBT module’s degradation over time.

The jury emphasised the broad spectrum of Diego’s work, from the component to system level, which touched on everything from designing, modelling, performing simulations and developing an entire test bench which was fully operational at the end of his thesis. Bravo!

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Diego’s test bench is of particular interest to visitors when they come to look around our platforms at the Institute. And with good reason: it allows the junction temperature of an IGBT to be increased from 40°C to 125°C every two seconds. For a fortnight, the module undergoes what it will see in the field during its whole lifetime. This allows our experts to determine the number of thermal cycles the IGBT can endure until failure, measure its degradation over time and analyse its failure mechanisms.

Technical characteristics:
sinusoidal current with an amplitude of 230 Apeak and a DC voltage of 600 V.

This thesis opens the door to a number of possibilities: can we imagine a device that can give us a reliable report of an IGBT’s state of health ? Could we diagnose and predict equipment conditions to optimise power converter maintenance or even postpone it? This would mean fewer sub-modules and lower costs. These are questions that fascinate us at SuperGrid Institute!

Get in touch if you want to see how Diego’s work could help you develop your innovations!