Protection and Control of a Dual MMC Medium Voltage Supply

Abstract:
The Modular Multilevel Converter (MMC) is a mature technology for high and medium voltage AC to DC power conversion. In the majority of applications, the MMC is interfacing well-defined voltage levels on either side. Contrary to that, this paper presents the use of the MMC as a bipolar DC power supply, operating both as a voltage or current source. Control methods ensuring correct operation while respecting operational voltage and current limits on the DC side are presented. Furthermore, results are validated on a single MMC, and extended to two MMC units connected in series/parallel on the DC side, using RT-HIL simulations.