An overlay network for Europe The DC Grid Option

Transcription

1 An overlay network for Europe The DC Grid Option Workshop, September 4, 2013 ABB Corporate Research Center Im Segelhof, 5405 Baden-Dättwil SUPERGRID INTERACTION BETWEEN AC AND DC POWER SYSTEMS

2 The DC Grid Option Why don t we operate DC grids today? Why will we have DC grids in future? 2

3 50Hertz Transmission a fully unbundled TSO 60 % 40 % Energinet.dk Eurogrid GmbH TenneT Amprion TenneT PL L F Transnet BW CZ CH A 3

4 Ilmenau University of Technology IEPC University Founded in 1894 Focus Engineering 6 Faculties approx Students Institute of Electric Power and Control Technologies (IEPC) Dept. of Power Systems Dept. of Switching Devices and Switchgears Dept. of Power Electronics Dept. of Electrical Machines Dept. of Electrical Process Engineering Dept. of Industrial Electronics Dept. of Lighting and Overvoltage Protection

5 1950: What was first? Converter Valve design: Oil cooled, Air cooled, water cooled, indoor or outdoor valves Air or oil insulated valves, standing or suspending valves Mercury-arc or thyristor valves Many different technical approaches and attempts from various suppliers GE, BBC + ASEA = ABB, Alsthom + GEC = Alstom Grid, Ansaldo German Consortium = Siemens + BBC + AEG = Siemens 5

6 The winner is Finally the broadly accepted technology is: - Indoor - water cooled - Air insulated - Suspending - thyristor equipped Common for all these installations is: - Line commutated - need of short circuit power (2 x) - reactive power consumption - high harmonics - land consuming and unidirectional current flow only (obstructive in operation) By courtesty of Siemens Quelle: SIEMENS; 600 m x m 6

7 Change of converter function: im-/export + I - I Thyristor valves unidirectional +500 kv +490 kv -490 kv -500 kv kv kv - I * R = I = > 0 R P è -490 kv - (- 500 kv) + I * R = I = > 0 R ç P Power reversal only by polarity reversal! i.e. change of converter function: im-/export 7

8 Development of semiconductor technolgy Entwicklung von Si-Fläche und Sperrspannung in HGÜ-Anlagen All that was possible through the evolution of semiductor technology over 50 years 8

9 Preferred power flow direction - But most of the schemes are point to point links (never meshed dc grid) - However we have seen two radial schemes, each with three terminals: è Sardinia-Corsica-Italy (Sarcoi) è Quebec-New England 9

10 A pilot project of the 70s HVDC Circuit Breaker 10

11 Pilot Project - Pacific Intertie, USA Inspite of this achievement dc breakers never break through. So dc grid operation never became real. 11

12 Semiductor Technology - Transistor - Since the 80s the semiconductor technology has evolved so fast that even insulated gate bipolar transistors (IGBT) have become applicable for power conversion i.e. transmission. (bidirectional current flow!) - Also extremely fast microprocessors can control the converter and the dc scheme 40 V_1A IGBT_3300V_1200A_Mitsubishi.jpg 12

13 Capacity and voltage of Converters (LLC and VSC) By courtesty of ABB 13

14 DC Grid Operation in future We have nowadays a new generation of converters on the market with novel inherent technical features which allow new applications, especially the design and operation of an interconnected dc grid with all advantages of such a system such as: è Higher security of supply è Cost savings in grid operation and generating units è Fast fault clearing è Selective isolation of faulty elements Source: DENA Study II

15 The Challenge for Offshore Transmission: DC Grid European Transmission System Operator? - About 20 HVDC submarine links as interconnectors and offshore links - but all as point to point lines and not as offshore grid 15

16 Proposed DC Grid schemes (1) +/-500 kv, 2 bipoles, MW 16

17 DC Grids Visions everywhere claverton-energy.com wikipedia/desertec 17

18 Grid development plan 2023 Optimisation of existing routes - New AC lines: 3,400 km - Reinforcement of AC lines: 1,000 km - Conversion to DC circuit: 300 km Grid expansion in new routes - New routes: 1,700 km - 4 DC corridors transmission capacity: construction of new DC routes: 12 GW 2,100 km Investment volume: approx. 21 billion 18

19 DC Grids in Europe Europeanwide Grids need several protection zones: - New R&D necessary for dc breaker, fast protection and master controller for power flow control - Long term needs è DC/DC coupler for connecting grids of different voltages ( Edison: The missing link), CigréWG B4.52 HVDC Grid Feasibility study By courtesty of ABB 19

20 Half bridge Full bridge pros and cons in a meshed dc grid z ac1 DC Terminal 1 I dc1 I 11 R 11 I 12 I 12f DC Terminal 2 I22 R 22 I dc2 z ac2 I ac1f V ac1 Md1,Mq1 I dc1f V dc1 R 14 R 12 I 24f I 14f I 23f I 14 R 13 R 24 I 23 R 23 V dc2 Md2,Mq2 I ac2f V ac2 z ac4 I ac4f V ac4 Md4,Mq4 I dc4 I dc4f V dc4 DC Terminal 4 R 34 R 44 R 33 I 11 I 34 I 13f I dc2f I 34f I 33 I dc3 I dc3f V dc3 Md3,Mq3 DC Terminal 3 z ac3 I ac3f V ac3 20

21 HVDC Grid Evolution The evolution of a new network layer The HVDC grid option [Bryan Christie Design] Properties, advantages and challenges of meshed HVDC grids Structure of an operational management system of meshed HVDC grids [Fiends of the Supergrid] [Japan Renewable Energy Foundation] 21

22 The european perspective 1930 [Quelle:, Festschrift 50 Jahre RWE, CIGRE B4.52 DC-Grids, 3. Meeting Paris, August 2010] 22

23 The european perspective DVG 1951 UCPTE 1999 UCTE 2009 ENTSO-E 2050? [Quelle:, Festschrift 50 Jahre RWE, CIGRE B4.52 DC-Grids, 3. Meeting Paris, August 2010] 23

24 Evolution of a meshed ac overlay grid Example: Germany [VDN, FFN] [VDN, FFN] [VDN, FFN] 24

25 HVDC grid development steps p2p interc. radial multiterminal meshed multiterminal HVDC grid state of the art First embedded onshore HVDC scheme in Europe: INELFE (2014) 25

26 Potential evolution of a meshed dc overlay grid Example: Germany 2023? [FFN] [FFN] [FFN, TU Ilmenau] 26

27 Meshed dc grids Advantages and challenges Advantages N-x-Redundancy and natural power flow distribution among lines Less no. of converters for multi directional power transmission Lower costs than equivalent p2p connections In total lower space requirements for converters (dc nodes) De-meshing of underlayed ac grid possible Challenges New quality of system dynamics on the dc side Standards for multivendor grids Grid protection system (methods and components) Seamless integration with the ac operational management? 27

28 System stability and security Some Analogies to HVAC systems Category HVAC grids (classic defs.) HVDC grids Energy stability (Frequency stability) Small signal stability (rotor angle) Transient stability (rotor angle) Voltage stability Energy balance by load frequency control Control systems (generator, FACTS, HVDC) Returning to synchronism Equal area criterion Nose curve, voltage control, i.e. tap changers, RPC Energy balance by node voltage control Control systems (converter, FDCTS, HVAC) Fault ride through Nose curve but max. power far beyond thermal line limits N-1 redundancy 1 by 1 redundancy Diversified redundancy due to controllability & infeeds are dispatchable to a certain extend 28

29 Requirements for an Operational Management System HVDC grid Coordinated system control (focus on ac & dc) Provides p ac-dc (and q ac ) schedule for entire grid Replaces reference values Reschedules after major incidents Prepares input for setpoint adaption HVDC grid system control (focus on dc system) Integral character and smaller ampl. factor than node control Setpoint adaptation for unscheduled power flow changes in underlaying HVAC grid Node voltage & power balancing control Proportional control characteristic Fast and continuous acting control Ensuring energy stability Tertiary control central Secondary control local Primary control local 29

30 HVDC grid Operation management A potential structure Scheduler (OPF) [A.-K. Marten and D. Westermann, Schedule for Converters of a Meshed HVDC Grid and a Contingency Schedule for Adaption to Unscheduled Power Flow Changes in Proc. oft he IEEE PES General Meeting, Paper 535, Vancouver, Canada, July 2013] 30

31 Setpoint adaptation example: Commutation of unscheduled ac power flows Setpoint adaptation needed to react to unscheduled events in ac and dc grid Example: Load frequency control induced load flows in the ac grid w/o setpoint adapt.: dc grid would not transport these flows Approach: Adaptation based on voltage angle gradient Scheduler (OPF) Example for further setup point adaptation triggering incidents Generation volatility induced power flow changes Line trips (ac and dc) Power flow controller maloperation Voltage incidents in in ac grid [Marten A.-K., Westermann D., Load Frequency Control in an interconnected power system with an embedded HVDC Grid, Proceedings, IEEE PES GM, Paper 2012GM0296, San Diego, USA, July 2012] 31

32 Summary & Outlook Conclusion Need for a new network layer for bulk power long distance transmission HVDC technology is viable option for new network layer Meshed HVDC grids evolve from p2p interconnections for the sake of economy Need for operational management of mutual interactions between HVDC and HVAC operation Outlook Definition of detailed grid operation and design methods will develop with upcoming onshore projects Normal operation Disturbed operation Further research on operation in technical & organizational sense to fully utilize dc (grid) capabilities? 32

33 Vielen Dank für Ihre Aufmerksamkeit Merci pour votre attention Thank you for your attention 33