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Title: Megawatt Scale Demonstration of High Speed Fault Clearing and Power Restoration for MVDC Systems Utilizing Fast Disconnect Switch

Authors: Michael Sloderbeck, Dionne Soto, Harsha Ravindra, Michael Steurer and Antonios Challita

Abstract: The Center for Advanced Power Systems (CAPS) at Florida State University operates an advanced MW-scale Power Hardware-in-the-Loop (PHIL) test facility. The installation of a Medium Voltage DC (MVDC) supply, consisting of 4 modular multi-level converters (MMCs) with a total capacity of 5 MW at 24 kV, was presented at EMTS 2014 [1] and described in detail in [2]. The current-limiting capability of the MMCs has also been demonstrated in low- impedance faults [3]. A high speed mechanical MVDC isolation device was described in [4]. The device is designed for operation at 6 kV and 2 kA. Fitness testing of this no-load disconnect switch was performed at CAPS and the results are in submission.

The results presented here are subsequent to the above testing and relate specifically to the very demanding fault detection and clearing operation required in breakerless MVDC systems. A rapid sequence of events must occur:

1. After fault initialization, the MMCs will go into current limiting mode and an algorithm must determine the fault location.
2. All participating MMCs will reduce voltage to zero and stop their active cell charging (stop firing bridge cells).
3. Signal(s) will be sent to the appropriate isolation device(s) to open.
4. The MMCs will be re-enabled, and full voltage operation continues in the rest of system.

1. M. Sloderbeck, K. Schoder, J. Leonard, C. Edrington, M. Steurer, “Development of a 5 MW, 24 kV DC power hardware in the loop laboratory based on modular multilevel converter (MMC) technology,” ASNE EMTS 2014, Philadelphia, PA.
2. M. Steurer, et al., “Multifunctional megawatt scale medium voltage DC test bed based on modular multilevel converter (MMC) technology,” ESARS 2015, Aachen, Germany.
3. K. Sun, D. Soto, M. Steurer, M.O. Faruque, “Experimental verification of limiting fault currents in MVDC systems by using modular multilevel converters,” IEEE ESTS 2015, Alexandria, VA.
4. A. Challita, M. Uva, “High speed, medium voltage direct current isolation device,” ASNE EMTS 2014, Philadelphia, PA.