Integration Technologies for a Medium Voltage Modular Multi-Level Converter with Hot Swap Capability

Recent development in modular converter topologies have raised the discussion about exploiting the inherent redundancy of such converters in order to maximize their availability. One such solution involves the replacement of power electronic building blocks (PEBBs) during operation, a procedure also referred to as 'hot swap'. Hot swap is considered as state-of-the-art in today's IT systems and low voltage power supplies. At medium voltage however, hot swap is getting more demanding, mainly because of the higher voltages and because of the often series connected PEBBs. In this paper we therefore present dedicated integration technologies addressing the required pluggability and insulation of PEBBs, and therefore enabling hot swap at medium voltage. The technologies developed cover auxiliary power supply, cooling, communication and insulation, and are demonstrated under real conditions in a full scale medium voltage concept converter. Hot swap was successfully demonstrated at a DC-link voltage of 3.4 kV, an output current of 460 A(rms) and an output power of 0.55 MW.