BEGIN:VCALENDAR VERSION:2.0 PRODID:IEEE vTools.Events//EN CALSCALE:GREGORIAN BEGIN:VTIMEZONE TZID:America/Denver BEGIN:DAYLIGHT DTSTART:20250309T030000 TZOFFSETFROM:-0700 TZOFFSETTO:-0600 RRULE:FREQ=YEARLY;BYDAY=2SU;BYMONTH=3 TZNAME:MDT END:DAYLIGHT BEGIN:STANDARD DTSTART:20251102T010000 TZOFFSETFROM:-0600 TZOFFSETTO:-0700 RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=11 TZNAME:MST END:STANDARD END:VTIMEZONE BEGIN:VEVENT DTSTAMP:20250919T061544Z UID:137AA1B3-9C21-4F5C-AFC1-7CDBCB270745 DTSTART;TZID=America/Denver:20250918T170000 DTEND;TZID=America/Denver:20250918T200000 DESCRIPTION:Registration is required\, and walk-ins are not permitted. Limi ted seats are available.\n\nEvent Description\n\nHigh Voltage Direct Curre nt (HVDC) transmission is evolving rapidly with new technologies like Volt age Source Converters (VSC) and Modular Multilevel Converters (MMC). These advancements are paving the way for the creation of complex\, multi-termi nal HVDC transmission grids.\n\nThis seminar will explore the key componen ts\, topologies\, control strategies\, modeling approaches\, and protectio n challenges associated with the development of HVDC grids. With real-worl d examples\, including China’s Zhangbei four-terminal project and emergi ng hybrid LCC-VSC systems\, the talk will cover the state of the art and t he road ahead for high-performance\, secure HVDC power systems.\n\nTopics include:\n\n-\nHybrid LCC-VSC HVDC systems\n\n-\nFast DC circuit breakers\ n\n-\nDC/DC converters for multiport HVDC hubs\n\n-\nHVDC grid protection coordination and fault handling\n\n-\nReal-world VSC HVDC projects and mul titerminal deployment\n\n-\nSimulation and control frameworks for dynamic HVDC networks\n\n--------------------------------------------------------- ------\n\nTarget Audience\n\n-\nPower system engineers and researchers\n\n -\nUtility and transmission professionals\n\n-\nGraduate and undergraduate students\n\n-\nProfessionals interested in HVDC\, energy transition\, and system integration\n\n--------------------------------------------------- ------------\n\nAdditional Notes\n\n-\nCertificate of Participation availa ble for $10 (optional)\, please fill out the evaluation form after the eve nt to receive one for PDH.\n\n-------------------------------------------- -------------------\n\nParking info\n\nWindsor Carpark (WCP)\n\nLocation:\ n[University of Alberta\, Edmonton](https://www.google.com/maps/search/?ap i=1&query=53.52890700\,%20-113.52957100)\n\nHours & Notes:\n\nOpen 24 hour s a day\, view [rates for Windsor Carpark](https://www.ualberta.ca/en/park ing-services/locations-and-rates/index.html?search0=Windsor%20Car%20Park)\ nEvening Flat Rate: $6.00 (4:30 p.m. - 6 a.m.)\n\n------------------------ ---------------------------------------\n\nRoom info\n\nFred Pheasy Engine ering Commons (8-292)\nDonadeo Innovation Centre For Engineering (ICE)\n\n [Top 5: Places to study on campus - The Gateway]\n\nCo-sponsored by: Resil ient And Clean Energy Systems (RCES) - https://sites.engineering.ualberta. ca/rcesi/\n\nSpeaker(s): Professor Dragan Jovcic\, \n\nAgenda: \nDate: Thu rsday\, September 18\, 2025\n\nTime:\n\n-\n4:30 PM: Doors open for attende es\n\n-\n5:00 PM – 5:45 PM: Main talk by Prof. Dragan Jovcic (Part 1)\n\ n-\n5:45 PM – 6:30 PM: Social mixer with catering provided by Upper Crus t\, featuring a variety of assorted sandwiches\, potato salad\, fresh vege tables\, fruit\, coffee\, tea\, and sweets.\n\n-\n6:30 PM – 7:45 PM: Mai n talk by Prof. Dragan Jovcic (Part 2) and open discussion\n\n- 7:45 PM – 8:00 PM: Door prizes (USB C fast chargers\, water bottles)\n\nLocation :\n\n[Fred Pheasy Engineering Commons (8-292)](https://www.ualberta.ca/en/ maps.html?l=53.528307\,-113.52955&z=17&campus=north_campus&b=ice)\n[Donade o Innovation Centre For Engineering (ICE)](https://www.ualberta.ca/en/maps .html?l=53.528307\,-113.52955&z=17&campus=north_campus&b=ice)\nUniversity of Alberta\, Edmonton\, AB\n\nCapacity: Limited to 60 attendees\n\nAbstrac t:\n\nHigh Voltage DC Transmission has seen rapid technology advances in t he last 20 years driven by the implementation of VSC (Voltage Source Conve rters) at GW powers and in particular introduction of MMC (Modular Multile vel Converters). The development of interconnected DC transmission grids r equires significant further advance from the existing point-to-point HVDC links. It is widely believed that complex DC power grids can be built with comparable performance\, reliability\, flexibility and losses as traditio nal AC grids. The primary motivation for DC grid development is the need f or power flow and trading between many DC terminals\, as an example in the proposed (350 GW) North Sea DC grid\, or EU-wide overlay DC grid. AC tran smission is not feasible with long subsea cables\, and it is inferior to D C systems in many other conditions. This presentation addresses the option s and challenges with DC grid development\, referring also to state-of-art technology status.\n\nZhangbei 4-terminal DC system (China\, 2020) repres ents the first implemented GW-scale meshed DC transmission grid\, which em ploys bipolar ring topology with overhead lines and 16 DC Circuit Breakers . However\, multiple studies illustrate advantages of some radial\, hub-ba sed or segmented topologies\, because of component costs\, and challenges with interoperability\, ownership\, DC markets\, operation\, security and reliability.\n\nMMC concepts\, including half-bridge and full-bridge modul es\, will underpin DC grid converters and further advances like hybrid LCC /MMC converters have been implemented recently. DC/DC converters at hundre ds of MW are not yet commercially available but there is lot of research w orld-wide\, and some lower-power prototypes have been demonstrated. DC/DC converters may take multiple functions including: DC voltage stepping (tra nsformer role)\, DC fault interruption (DC CB role) and power flow control . Multiport DC hubs can be viewed as electronic DC substations\, capable o f interconnecting multiple DC lines.\n\nVery fast DC CB circuit breakers ( 2 ms) have become commercially available recently\, but the cost is consid erably higher than AC CBs. Slightly slower mechanical DC CBs (5-8 ms) are also available from multiple vendors\, while new technical solutions are e merging worldwide for achieving faster operation with lower size/weight/co sts.\n\nDC grid modelling will face the new challenge of numerous converte rs dynamically coupled through low-impedance DC cables/lines. A compromise between simulation speed and accuracy is required\, leading to some avera ge-value modelling\, commonly in rotating DQ frame\, but capturing very fa st dynamics and variable structure to represent fault conditions.\n\nThe p rinciples of control of DC grids have been developed. DC systems have no s ystem-wide common frequency to indicate power unbalance\, and voltage resp onds to local and global loading rather than reactive power flow. DC grid dynamics are 2 orders of magnitude faster than traditional AC systems and most components will be controllable implying numerous\, fast control loop interactions. Because of lack of inertia\, and minimal overload capabilit y for semiconductors\, DC grid primary and secondary control should be fee dback-based (man-made)\, fast\, and distributed. International standardisa tion efforts have begun.\n\nThe protection of DC grids is a significant te chnical challenge\, both in terms of components and protection logic. The selectivity has been demonstrated within 0.5 ms timeframe using commercial and open-source DC relays. Nevertheless\, grid operators have expressed c oncerns with self-protection on various components\, back-up grid-wide pro tection\, interoperability\, and in general if we can achieve power transf er security levels comparable with AC grids and acceptable to stakeholders .\n\nBldg: Donadeo Innovation Centre For Engineering (ICE)\, Fred Pheasy E ngineering Commons (8-292)\, 9211 116 St NW\, Edmonton\, Alberta\, Canada\ , T6G 1H9 LOCATION:Bldg: Donadeo Innovation Centre For Engineering (ICE)\, Fred Pheas y Engineering Commons (8-292)\, 9211 116 St NW\, Edmonton\, Alberta\, Cana da\, T6G 1H9 ORGANIZER:zizhao.wang@ieee.org SEQUENCE:136 SUMMARY:DC Transmission Grids: Topology\, Components\, Modelling\, Control\ , and Protection Challenges (Registration is required\, and walk-ins are n ot permitted. Limited seats are available.) URL;VALUE=URI:https://events.vtools.ieee.org/m/497110 X-ALT-DESC:Description: <br /><h3 class="p1" style="text-align: center\;">< span style="font-family: 'arial black'\, sans-serif\; color: rgb(0\, 0\, 0 )\;"><strong><span style="color: rgb(230\, 126\, 35)\;">Registration is re quired\, and walk-ins are not permitted. Limited seats are available.</spa n></strong></span></h3>\n<h4><span style="font-family: arial\, helvetica\, sans-serif\; color: rgb(0\, 0\, 0)\; font-size: 14pt\;"><strong><span sty le="font-family: 'arial black'\, sans-serif\; color: rgb(0\, 0\, 0)\;"><em ><img style="display: block\; margin-left: auto\; margin-right: auto\;" sr c="https://events.vtools.ieee.org/vtools_ui/media/display/c13a9db7-ac6d-4e 32-8a9e-807bdddbb999" width="417" height="417"></em></span></strong></span ></h4>\n<h4><span style="font-family: arial\, helvetica\, sans-serif\; col or: rgb(0\, 0\, 0)\; font-size: 14pt\;"><strong>Event Description</strong> </span></h4>\n<p class="p3"><span style="font-family: arial\, helvetica\, sans-serif\; color: rgb(0\, 0\, 0)\; font-size: 12pt\;">High Voltage Direc t Current (HVDC) transmission is evolving rapidly with new technologies li ke Voltage Source Converters (VSC) and Modular Multilevel Converters (MMC) . These advancements are paving the way for the creation of complex\, mult i-terminal HVDC transmission grids.</span></p>\n<p class="p3"><span style= "font-family: arial\, helvetica\, sans-serif\; color: rgb(0\, 0\, 0)\; fon t-size: 12pt\;">This seminar will explore the key components\, topologies\ , control strategies\, modeling approaches\, and protection challenges ass ociated with the development of HVDC grids. With real-world examples\, inc luding China&rsquo\;s Zhangbei four-terminal project and emerging hybrid L CC-VSC systems\, the talk will cover the state of the art and the road ahe ad for high-performance\, secure HVDC power systems.</span></p>\n<p class= "p2">&nbsp\;</p>\n<p class="p3"><span style="font-family: arial\, helvetic a\, sans-serif\; color: rgb(0\, 0\, 0)\; font-size: 12pt\;">Topics include :</span></p>\n<ul>\n<li style="font-family: arial\, helvetica\, sans-serif \; color: rgb(0\, 0\, 0)\; font-size: 12pt\;">\n<p class="p1"><span style= "font-family: arial\, helvetica\, sans-serif\; color: rgb(0\, 0\, 0)\; fon t-size: 12pt\;">Hybrid LCC-VSC HVDC systems</span></p>\n</li>\n<li style=" font-family: arial\, helvetica\, sans-serif\; color: rgb(0\, 0\, 0)\; font -size: 12pt\;">\n<p class="p1"><span style="font-family: arial\, helvetica \, sans-serif\; color: rgb(0\, 0\, 0)\; font-size: 12pt\;">Fast DC circuit breakers</span></p>\n</li>\n<li style="font-family: arial\, helvetica\, s ans-serif\; color: rgb(0\, 0\, 0)\; font-size: 12pt\;">\n<p class="p1"><sp an style="font-family: arial\, helvetica\, sans-serif\; color: rgb(0\, 0\, 0)\; font-size: 12pt\;">DC/DC converters for multiport HVDC hubs</span></ p>\n</li>\n<li style="font-family: arial\, helvetica\, sans-serif\; color: rgb(0\, 0\, 0)\; font-size: 12pt\;">\n<p class="p1"><span style="font-fam ily: arial\, helvetica\, sans-serif\; color: rgb(0\, 0\, 0)\; font-size: 1 2pt\;">HVDC grid protection coordination and fault handling</span></p>\n</ li>\n<li style="font-family: arial\, helvetica\, sans-serif\; color: rgb(0 \, 0\, 0)\; font-size: 12pt\;">\n<p class="p1"><span style="font-family: a rial\, helvetica\, sans-serif\; color: rgb(0\, 0\, 0)\; font-size: 12pt\;" >Real-world VSC HVDC projects and multiterminal deployment</span></p>\n</l i>\n<li style="font-family: arial\, helvetica\, sans-serif\; color: rgb(0\ , 0\, 0)\; font-size: 12pt\;">\n<p class="p1"><span style="font-family: ar ial\, helvetica\, sans-serif\; color: rgb(0\, 0\, 0)\; font-size: 12pt\;"> Simulation and control frameworks for dynamic HVDC networks</span></p>\n</ li>\n</ul>\n<hr>\n<h4><span style="font-family: arial\, helvetica\, sans-s erif\; color: rgb(0\, 0\, 0)\; font-size: 14pt\;"><strong>Target Audience< /strong></span></h4>\n<ul>\n<li style="font-family: arial\, helvetica\, sa ns-serif\; color: rgb(0\, 0\, 0)\; font-size: 12pt\;">\n<p class="p1"><spa n style="font-family: arial\, helvetica\, sans-serif\; color: rgb(0\, 0\, 0)\; font-size: 12pt\;">Power system engineers and researchers</span></p>\ n</li>\n<li style="font-family: arial\, helvetica\, sans-serif\; color: rg b(0\, 0\, 0)\; font-size: 12pt\;">\n<p class="p1"><span style="font-family : arial\, helvetica\, sans-serif\; color: rgb(0\, 0\, 0)\; font-size: 12pt \;">Utility and transmission professionals</span></p>\n</li>\n<li style="f ont-family: arial\, helvetica\, sans-serif\; color: rgb(0\, 0\, 0)\; font- size: 12pt\;">\n<p class="p1"><span style="font-family: arial\, helvetica\ , sans-serif\; color: rgb(0\, 0\, 0)\; font-size: 12pt\;">Graduate and und ergraduate students</span></p>\n</li>\n<li style="font-family: arial\, hel vetica\, sans-serif\; color: rgb(0\, 0\, 0)\; font-size: 12pt\;">\n<p clas s="p1"><span style="font-family: arial\, helvetica\, sans-serif\; color: r gb(0\, 0\, 0)\; font-size: 12pt\;">Professionals interested in HVDC\, ener gy transition\, and system integration</span></p>\n</li>\n</ul>\n<hr>\n<h4 ><span style="font-family: arial\, helvetica\, sans-serif\; color: rgb(0\, 0\, 0)\; font-size: 14pt\;"><strong>Additional Notes</strong></span></h4> \n<ul>\n<li style="font-family: arial\, helvetica\, sans-serif\; color: rg b(0\, 0\, 0)\; font-size: 12pt\;">\n<p class="p1"><span style="font-family : arial\, helvetica\, sans-serif\; color: rgb(0\, 0\, 0)\; font-size: 12pt \;">Certificate of Participation available for $10 (optional)\, please fil l out the evaluation form after the event to receive one for PDH.&nbsp\;</ span></p>\n</li>\n</ul>\n<hr>\n<h4><span style="font-family: arial\, helve tica\, sans-serif\; color: rgb(0\, 0\, 0)\; font-size: 14pt\;"><strong>Par king info</strong></span></h4>\n<div class="row">\n<div class="col-md-12"> \n<div class="page-title">\n<h5 style="text-align: left\;"><span style="fo nt-size: 12pt\;"><strong><span style="color: rgb(224\, 62\, 45)\; font-fam ily: arial\, helvetica\, sans-serif\;">Windsor Carpark (WCP)</span></stron g></span></h5>\n</div>\n</div>\n</div>\n<div class="row">\n<div class="col -sm-12">\n<table class="table table-borderless w-auto">\n<tbody>\n<tr>\n<t h style="line-height: 1\;" scope="row">\n<h5><span style="font-family: ari al\, helvetica\, sans-serif\; color: rgb(0\, 0\, 0)\; font-size: 12pt\;">L ocation:</span></h5>\n</th>\n<td style="line-height: 1\;"><span style="fon t-family: arial\, helvetica\, sans-serif\; color: rgb(230\, 126\, 35)\; fo nt-size: 12pt\;"><a style="color: rgb(230\, 126\, 35)\;" href="https://www .google.com/maps/search/?api=1&amp\;query=53.52890700\,%20-113.52957100" t arget="_blank" rel="noopener">University of Alberta\, Edmonton</a></span>< /td>\n</tr>\n<tr>\n<th style="line-height: 1\;" scope="row">\n<h5><span st yle="font-family: arial\, helvetica\, sans-serif\; color: rgb(0\, 0\, 0)\; font-size: 12pt\;">Hours &amp\; Notes:</span></h5>\n</th>\n<td style="lin e-height: 1\;">\n<p><span style="font-family: arial\, helvetica\, sans-ser if\; color: rgb(0\, 0\, 0)\; font-size: 12pt\;">Open 24 hours a day\, view <span style="color: rgb(230\, 126\, 35)\;"><a style="color: rgb(230\, 126 \, 35)\;" href="https://www.ualberta.ca/en/parking-services/locations-and- rates/index.html?search0=Windsor%20Car%20Park" target="_blank" rel="noopen er">rates for Windsor Carpark</a><br></span></span><span style="font-famil y: arial\, helvetica\, sans-serif\; color: rgb(224\, 62\, 45)\; font-size: 12pt\;">Evening&nbsp\;Flat Rate: $6.00 (4:30 p.m. - 6 a.m.)</span></p>\n< /td>\n</tr>\n</tbody>\n</table>\n</div>\n</div>\n<hr>\n<h4><span style="fo nt-family: arial\, helvetica\, sans-serif\; color: rgb(0\, 0\, 0)\; font-s ize: 14pt\;"><strong>Room info</strong></span></h4>\n<p style="text-align: center\;"><span style="color: rgb(224\, 62\, 45)\;"><strong><span style=" color: rgb(224\, 62\, 45)\;">Fred Pheasy Engineering Commons (8-292)</span ><br><span style="color: rgb(224\, 62\, 45)\;">Donadeo Innovation Centre F or Engineering (ICE)</span><br></strong></span></p>\n<p><span style="color : rgb(224\, 62\, 45)\;"><strong><img style="display: block\; margin-left: auto\; margin-right: auto\;" src="https://events.vtools.ieee.org/vtools_ui /media/display/8ec33b93-8d1e-4a87-a3a0-cdc9e0ac4a29" alt="Top 5: Places to study on campus - The Gateway" width="534" height="356"></strong></span>< /p><br /><br />Agenda: <br /><p class="p1"><span style="font-family: arial \, helvetica\, sans-serif\; color: rgb(0\, 0\, 0)\; font-size: 12pt\;"><sp an class="s1"><strong>Date:</strong></span> Thursday\, September 18\, 2025 </span></p>\n<p class="p2"><span style="font-family: arial\, helvetica\, s ans-serif\; color: rgb(0\, 0\, 0)\; font-size: 12pt\;"><strong>Time:</stro ng></span></p>\n<ul>\n<li style="font-family: arial\, helvetica\, sans-ser if\; color: rgb(0\, 0\, 0)\; font-size: 12pt\;">\n<p class="p1"><span styl e="font-family: arial\, helvetica\, sans-serif\; color: rgb(0\, 0\, 0)\; f ont-size: 12pt\;"><span class="s1"><strong>4:30 PM:</strong></span> Doors open for attendees</span></p>\n</li>\n<li style="font-family: arial\, helv etica\, sans-serif\; color: rgb(0\, 0\, 0)\; font-size: 12pt\;">\n<p class ="p1"><span style="font-family: arial\, helvetica\, sans-serif\; color: rg b(0\, 0\, 0)\; font-size: 12pt\;"><span class="s1"><strong>5:00 PM &ndash\ ; 5:45 PM:</strong></span> Main talk by Prof. Dragan Jovcic (Part 1)</span ></p>\n</li>\n<li style="font-family: arial\, helvetica\, sans-serif\; col or: rgb(0\, 0\, 0)\; font-size: 12pt\;">\n<p class="p1"><span style="font- family: arial\, helvetica\, sans-serif\; color: rgb(0\, 0\, 0)\; font-size : 12pt\;"><span class="s1"><strong>5:45 PM &ndash\; 6:30 PM:</strong></spa n>&nbsp\;Social mixer with catering provided by Upper Crust\, featuring a variety of assorted sandwiches\, potato salad\, fresh vegetables\, fruit\, coffee\, tea\, and sweets.</span></p>\n</li>\n<li style="font-family: ari al\, helvetica\, sans-serif\; color: rgb(0\, 0\, 0)\; font-size: 12pt\;">\ n<p class="p1"><span style="font-family: arial\, helvetica\, sans-serif\; color: rgb(0\, 0\, 0)\; font-size: 12pt\;"><span class="s1"><strong>6:30 P M &ndash\; 7:45 PM:</strong></span> Main talk by Prof. Dragan Jovcic (Part 2) and open discussion</span></p>\n</li>\n<li><span style="font-family: a rial\, helvetica\, sans-serif\; color: rgb(0\, 0\, 0)\; font-size: 12pt\;" ><span class="s1"><strong>7:45 PM &ndash\; 8:00 PM:</strong></span> Door p rizes (USB C fast chargers\, water bottles)</span></li>\n</ul>\n<p class=" p1"><span style="font-family: arial\, helvetica\, sans-serif\; color: rgb( 0\, 0\, 0)\; font-size: 12pt\;"><span class="s1"><strong>Location:</strong ></span> </span></p>\n<p class="p1" style="padding-left: 40px\;"><span sty le="color: rgb(230\, 126\, 35)\;"><a style="color: rgb(230\, 126\, 35)\;" href="https://www.ualberta.ca/en/maps.html?l=53.528307\,-113.52955&amp\;z= 17&amp\;campus=north_campus&amp\;b=ice" target="_blank" rel="noopener">Fre d Pheasy Engineering Commons (8-292)</a></span><br><span style="color: rgb (230\, 126\, 35)\;"><a style="color: rgb(230\, 126\, 35)\;" href="https:// www.ualberta.ca/en/maps.html?l=53.528307\,-113.52955&amp\;z=17&amp\;campus =north_campus&amp\;b=ice" target="_blank" rel="noopener">Donadeo Innovatio n Centre For Engineering (ICE)</a></span><br><span style="font-family: ari al\, helvetica\, sans-serif\; color: rgb(0\, 0\, 0)\; font-size: 12pt\;">U niversity of Alberta\, Edmonton\, AB</span></p>\n<p class="p1"><span style ="font-family: arial\, helvetica\, sans-serif\; color: rgb(0\, 0\, 0)\; fo nt-size: 12pt\;"><span class="s1"><strong>Capacity:</strong></span> Limite d to 60 attendees</span></p>\n<p class="p1">&nbsp\;</p>\n<h3><strong><span style="font-family: arial\, helvetica\, sans-serif\; color: rgb(0\, 0\, 0 )\; font-size: 18pt\;">Abstract:</span></strong></h3>\n<p><span lang="EN-G B" style="font-size: 12pt\; font-family: arial\, helvetica\, sans-serif\; color: rgb(0\, 0\, 0)\;">High Voltage DC Transmission has seen rapid techn ology advances in the last 20 years driven by the implementation of VSC (V oltage Source Converters) at GW powers and in particular introduction of M MC (Modular Multilevel Converters). The development of interconnected DC t ransmission grids requires significant further advance from the existing p oint-to-point HVDC links. It is widely believed that complex DC power grid s can be built with comparable performance\, reliability\, flexibility and losses as traditional AC grids. The primary motivation for DC grid develo pment is the need for power flow and trading between many DC terminals\, a s an example in the proposed (350 GW) North Sea DC grid\, or EU-wide overl ay DC grid. AC transmission is not feasible with long subsea cables\, and it is inferior to DC systems in many other conditions. This presentation a ddresses the options and challenges with DC grid development\, referring a lso to state-of-art technology status. </span></p>\n<p><span lang="EN-GB" style="font-size: 12pt\; font-family: arial\, helvetica\, sans-serif\; col or: rgb(0\, 0\, 0)\;">Zhangbei 4-terminal DC system (China\, 2020) represe nts the first implemented GW-scale meshed DC transmission grid\, which emp loys bipolar ring topology with overhead lines and 16 DC Circuit Breakers. However\, multiple studies illustrate advantages of some radial\, hub-bas ed or segmented topologies\, because of component costs\, and challenges w ith interoperability\, ownership\, DC markets\, operation\, security and r eliability. <span style="mso-spacerun: yes\;">&nbsp\;&nbsp\;&nbsp\;</span> </span></p>\n<p><span lang="EN-GB" style="font-size: 12pt\; font-family: a rial\, helvetica\, sans-serif\; color: rgb(0\, 0\, 0)\;">MMC concepts\, in cluding half-bridge and full-bridge modules\, will underpin DC grid conver ters and further advances like hybrid LCC/MMC converters have been impleme nted recently. DC/DC converters at hundreds of MW are not yet commercially available but there is lot of research world-wide\, and some lower-power prototypes have been demonstrated. DC/DC converters may take multiple func tions including: DC voltage stepping (transformer role)\, DC fault interru ption (DC CB role) and power flow control. Multiport DC hubs can be viewed as electronic DC substations\, capable of interconnecting multiple DC lin es. </span></p>\n<p><span lang="EN-GB" style="font-size: 12pt\; font-famil y: arial\, helvetica\, sans-serif\; color: rgb(0\, 0\, 0)\;">Very fast DC CB circuit breakers (2 ms) have become commercially available recently\, b ut the cost is considerably higher than AC CBs. Slightly slower mechanical DC CBs (5-8 ms) are also available from multiple vendors\, while new tech nical solutions are emerging worldwide for achieving faster operation with lower size/weight/costs.<span style="mso-spacerun: yes\;">&nbsp\; </span> </span></p>\n<p><span lang="EN-GB" style="font-size: 12pt\; font-family: a rial\, helvetica\, sans-serif\; color: rgb(0\, 0\, 0)\;">DC grid modelling will face the new challenge of numerous converters dynamically coupled th rough low-impedance DC cables/lines. A compromise between simulation speed and accuracy is required\, leading to some average-value modelling\, comm only in rotating DQ frame\, but capturing very fast dynamics and variable structure to represent fault conditions. </span></p>\n<p class="MsoNormal" ><span lang="EN-GB" style="font-size: 12pt\; font-family: arial\, helvetic a\, sans-serif\; color: rgb(0\, 0\, 0)\;">The principles of control of DC grids have been developed. DC systems have no system-wide common frequency to indicate power unbalance\, and voltage responds to local and global lo ading rather than reactive power flow. DC grid dynamics are 2 orders of ma gnitude faster than traditional AC systems and most components will be con trollable implying numerous\, fast control loop interactions. Because of l ack of inertia\, and minimal overload capability for semiconductors\, DC g rid primary and secondary control should be feedback-based (man-made)\, fa st\, and distributed. International standardisation efforts have begun. </ span></p>\n<p class="MsoNormal"><span lang="EN-GB" style="font-size: 12pt\ ; font-family: arial\, helvetica\, sans-serif\; color: rgb(0\, 0\, 0)\;">T he protection of DC grids is a significant technical challenge\, both in t erms of components and protection logic. The selectivity has been demonstr ated within 0.5 ms timeframe using commercial and open-source DC relays. N evertheless\, grid operators have expressed concerns with self-protection on various components\, back-up grid-wide protection\, interoperability\, and in general if we can achieve power transfer security levels comparable with AC grids and acceptable to stakeholders.<span style="mso-spacerun: y es\;">&nbsp\;</span></span></p> END:VEVENT END:VCALENDAR