Power balancing and dc fault ride through in DC grids with dc hubs and wind farms

Acknowledgment This project was funded by European Research Council under the Ideas program in FP7; grant no 259328, 2010.Peer reviewedPostprin

Dual Channel Control with DC Fault Ride Through for MMC-based, Isolated DC/DC Converter

This study is sponsored by the Engineering and Physical Sciences Research Council (EPSRC) grant no EP/K006428/1, 2013.D. Jovcic and H. Zhang are with the School of Engineering, University of Aberdeen, AB24 3UE, U.K. ([email protected], [email protected]).Peer reviewedPostprin

Analysis and hardware testing of cell capacitor discharge currents during DC faults in half-bridge modular multilevel converters

This paper focuses on the behaviour of the cell capacitor discharge currents during DC faults in half-bridge modular multilevel converters. Active switches, not designed for fault conditions, are tripped to minimize discharge currents effect on the semiconductor switches. Two levels of device protection are commonly in place; driver level protection monitoring collector-emitter voltage and overcurrent protection with feedback measurement and control. However, unavoidable tripping delay times, arising from factors such as sensor lags, controller sampling delays and hardware propagation delays, impact transient current shape and hence affect the selection of semiconductor device ratings as well as arm inductance. Analytical expressions are obtained for current slew rate, peak transient current and resultant I2t for the cell capacitor discharge current taking into account such delays. The study is backed by experimental testing on discharge of a 900V MMC capacitor

Modular multilevel converter based LCL DC/DC converter for high power DC transmission grids

This paper presents a modular multilevel converter (MMC) based DC/DC converter with LCL inner circuit for HVDC transmission and DC grids. Three main design challenges are addressed. The first challenge is the use of MMCs with higher operating frequency compared to common transformer-based DC/DC converters where MMC operating frequency is limited to a few hundred hertz due to core losses. The second issue is the DC fault response. With the LCL circuit, the steady state fault current is limited to a low magnitude which is tolerable by MMC semiconductors. Mechanical DC circuit breakers can therefore be used to interrupt fault current for permanent faults and extra sub-module bypass thyristors are not necessary to protect antiparallel diodes. Thirdly, a novel controller structure is introduced with multiple coordinate frames ensuring zero local reactive power at both bridges in the whole load range. The proposed controller structure is also expandable to a DC hub with multiple ports. Detailed simulations using PSCAD/EMTDC are performed to verify the aforementioned design solutions in normal and fault conditions

Full Bridge MMC Converter Optimal Design to HVDC Operational Requirements

This project is funded by RTE, Paris, FrancePeer reviewedPostprin

Series LC DC Circuit Breaker

This work was supported by the Europend Udiod’s Horizon 2020 research and innovation program under grant No. 691714. The author is thankful to Mr R. Osborne from University of Aberdeen for help with the experimental studiesPeer reviewedPublisher PD

LC DC Circuit Breaker based on Precharged Capacitor Commutation

Acknowledgment This project is funded by SFC COVID 19 grant. The author is thankful to Mr Richard Osborne, technician from University of Aberdeen for the experimental studies.Peer reviewedPostprin

Multibreak LC DC Circuit Breaker

ACKNOWLEDGMENT The author is thankful to Mr Richard Osborne, technician from University of Aberdeen for the experimental support. This work was supported by the European Union’s Horizon 2020 research and innovation program under grant No. 691714, and SFC COVID 19 grant

Fast Commutation of DC Current into a Capacitor Using Moving Contacts

The author is thankful to Mr R. Osborne from University of Aberdeen for help with the experimental studies.Peer reviewedPostprin

Control of HVDC systems operating with long DC cables

Postprin