Advanced Hardware-in-the-Loop Testbed for Development of Grid Connected Medium Voltage Modular Multilevel Converter

Advancement in power electronic converters (PEC) are driven by the need for controllable, flexible, and compatible grid connected devices. In the medium voltage (MV) realm, modular multilevel converters (MMC) have become a favorite in the power systems industry for their suite of benefits. MMCs have been shown to operate as excellent high voltage conversion equipments and active front ends (AFE) in ac application. Furthermore, back-to-back (B2B) MMC configurations have been explored for use as IEEE 1547-2018 compliant direct-connected grid inverter. This paper demonstrates application of an advanced hardware-in-the-loop (HIL) testbed to test a MV PEC. The proposed HIL testbed unifies controller hardware-in-the-loop (CHIL) and power hardware-in-the-loop (PHIL) capabilities and enables MV MW-scaled development process for grid application. A third generation 10 kV silicon-carbide (SiC) metal-oxide-semiconductor field-effect transistor (MOSFET)-based MMC with a middle switching cell was developed using the process laid out in the paper, and experimental results from the HIL testbed operating at 250 kVA, 7 kV<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dc</inf>, 3.64 kV line-to-line rms 60 Hz are exhibited. Additionally, the developed MMC demonstrates robust response to IEEE 1547-2018 scenarios. From the results, the development methodology and the MMC are validated, providing excellent testing capability for future grid-connected devices.