BEGIN:VCALENDAR VERSION:2.0 PRODID:IEEE vTools.Events//EN CALSCALE:GREGORIAN BEGIN:VTIMEZONE TZID:Europe/Bucharest BEGIN:DAYLIGHT DTSTART:20200329T040000 TZOFFSETFROM:+0200 TZOFFSETTO:+0300 RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=3 TZNAME:EEST END:DAYLIGHT BEGIN:STANDARD DTSTART:20191027T030000 TZOFFSETFROM:+0300 TZOFFSETTO:+0200 RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10 TZNAME:EET END:STANDARD END:VTIMEZONE BEGIN:VEVENT DTSTAMP:20191127T100224Z UID:11A5E937-559A-42EB-A8DC-25B35F07D808 DTSTART;TZID=Europe/Bucharest:20191104T120000 DTEND;TZID=Europe/Bucharest:20191104T130000 DESCRIPTION:High Voltage DC Transmission has seen rapid technology advances in the last 20 years driven by the implementation of VSC (Voltage Source Converters) at GW powers and in particular introduction of MMC (Modular Mu ltilevel Converters). The development of interconnected DC transmission gr ids will require significant further advance from the existing point-to-po int HVDC links\, but it is widely believed that complex DC power grids can be built with comparable performance\, reliability\, flexibility and loss es as traditional AC grids. The primary motivation for DC grid development is the need to interconnect multiple DC lines located in close proximity\ , and to enable power trading between many DC terminals\, as an example in the proposed North Sea DC grid\, or EU-wide overlay DC grid. AC transmiss ion is not feasible with long subsea cables\, and it is inferior to DC sys tems in some other conditions. This presentation will address some key tec hnical challenges in DC Grid development\, and discuss the current technol ogy status.\n\nMMC concept\, including half-bridge and full-bridge modules \, will underpin building blocks in most DC grid converters and further im provements are expected in terms of efficiency and fault handling. DC/DC c onverters for transmission grids are not yet commercially available but th ere is lot of research world-wide and some prototypes have been demonstrat ed. DC/DC converters may take multiple functions including: DC voltage ste pping (transformer role)\, DC fault interruption (DC CB role) and power fl ow control. DC hubs can be viewed as electronic DC substations\, capable o f interconnecting multiple DC lines.\n\nVery fast DC CB circuit breakers ( 2ms) have become commercially available recently\, but the cost is still c onsiderably higher than AC CBs. Slightly slower mechanical DC CBs (8ms) ar e becoming commercially available at high voltages\, while new technical s olutions are emerging worldwide for achieving faster operation and lower s ize/weight/costs.\n\nDC grid modelling will face the challenge of numerous converters dynamically coupled through low-impedance DC cables/lines. A c ompromise between simulation speed and accuracy is required\, leading to a verage-value modelling\, commonly in rotating DQ frame and with variable s tructure to represent blocked state under fault conditions.\n\nThe control of DC grids will require new solutions\, since there is no system-wide co mmon frequency to indicate power unbalance. DC voltage responds to both: g lobal power balance and local power flow scenario. DC grid dynamics will b e 2 orders of magnitude faster than traditional AC systems and most compon ents will be controllable implying numerous\, fast control loop interactio ns. Because of lack of inertia\, and minimal overload capability for semic onductors\, DC grid primary and secondary control should be fast\, autonom ous and robust.\n\nThe protection of DC grids is a significant technical c hallenge\, both in terms of components and protection system development. A reasonably accurate and reliable DC grid protection can be developed usi ng local traveling wave measurements. Nevertheless\, there is a substantia l challenge to achieve security margins\, to manage self-protection on var ious components\, back-up grid-wide protection\, and in general to achieve reliability levels comparable with AC grids.\n\nThe topology with full br idge MMC converters and slow DC CB avoids any MMC blocking for DC faults a nd represents a possible low-risk solution.\n\nSpeaker(s): Dragan Jovcic\, \n\nTranselectrica\, 16-18 Hristo Botev\, Bucharest\, Municipiul Bucurest i\, Romania\, 030236 LOCATION:Transelectrica\, 16-18 Hristo Botev\, Bucharest\, Municipiul Bucur esti\, Romania\, 030236 ORGANIZER:eremia1@yahoo.com SEQUENCE:2 SUMMARY:Introduction to HVDC. LLC-HVDC\, VSC-HVDC and MMC HVDC URL;VALUE=URI:https://events.vtools.ieee.org/m/208063 X-ALT-DESC:Description: <br /><p>High Voltage DC Transmission has seen rapi d technology advances in the last 20 years driven by the implementation of VSC (Voltage Source Converters) at GW powers and in particular introducti on of MMC (Modular Multilevel Converters). The development of interconnect ed DC transmission grids will require significant further advance from the existing point-to-point HVDC links\, but it is widely believed that compl ex DC power grids can be built with comparable performance\, reliability\, flexibility and losses as traditional AC grids. The primary motivation fo r DC grid development is the need to interconnect multiple DC lines locate d in close proximity\, and to enable power trading between many DC termina ls\, as an example in the proposed North Sea DC grid\, or EU-wide overlay DC grid. AC transmission is not feasible with long subsea cables\, and it is inferior to DC systems in some other conditions. This presentation will address some key technical challenges in DC Grid development\, and discus s the current technology status.&nbsp\;&nbsp\;</p>\n<p>MMC concept\, inclu ding half-bridge and full-bridge modules\, will underpin building blocks i n most DC grid converters and further improvements are expected in terms o f efficiency and fault handling. DC/DC converters for transmission grids a re not yet commercially available but there is lot of research world-wide and some prototypes have been demonstrated. DC/DC converters may take mult iple functions including: DC voltage stepping (transformer role)\, DC faul t interruption (DC CB role) and power flow control. DC hubs can be viewed as electronic DC substations\, capable of interconnecting multiple DC line s.</p>\n<p>Very fast DC CB circuit breakers (2ms) have become commercially available recently\, but the cost is still considerably higher than AC CB s. Slightly slower mechanical DC CBs (8ms) are becoming commercially avail able at high voltages\, while new technical solutions are emerging worldwi de for achieving faster operation and lower size/weight/costs.&nbsp\;</p>\ n<p>DC grid modelling will face the challenge of numerous converters dynam ically coupled through low-impedance DC cables/lines. A compromise between simulation speed and accuracy is required\, leading to average-value mode lling\, commonly in rotating DQ frame and with variable structure to repre sent blocked state under fault conditions.</p>\n<p>The control of DC grids will require new solutions\, since there is no system-wide common frequen cy to indicate power unbalance. DC voltage responds to both: global power balance and local power flow scenario. DC grid dynamics will be 2 orders o f 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 capability for semiconductors\, DC grid primary and secondary control should be fast\, autonomous and robu st.&nbsp\;</p>\n<p>The protection of DC grids is a significant technical c hallenge\, both in terms of components and protection system development. A reasonably accurate and reliable DC grid protection can be developed usi ng local traveling wave measurements. Nevertheless\, there is a substantia l challenge to achieve security margins\, to manage self-protection on var ious components\, back-up grid-wide protection\, and in general to achieve reliability levels comparable with AC grids.</p>\n<p>The topology with fu ll bridge MMC converters and slow DC CB avoids any MMC blocking for DC fau lts and represents a possible low-risk solution.</p> END:VEVENT END:VCALENDAR