Lauren Sabine 2015-11-12 NordLink - Weekly Meetings December 16, 2015 Slide 1
NordLink Basic data Ertsmyra-Vollesfjord-Wilster Bipole VSC at ±515 kv, 1400 MW. Each pole at each station is configured as an asymmetric monopole. 50 km DC OH line 571 km subsea cable, 54 km land cable December 16, 2015 Slide 2
Introduction Why do we use HVDC Light? Connect AC networks asynchronously Support the AC networks (SVC) Black start capability Fast and accurate power flow control Slide 3
Nordlink Monopole vs Bipole Converter Asymmetrical monopole: A single converter that is connected between the positive or the negative pole and the d.c. side neutral. The other pole is used as metallic return path. Asymmetrical monopole converter. Bipole: An HVDC system consisting of two poles, which during normal operation, exhibit opposite d.c. voltage polarities with respect to earth. Bipole. December 16, 2015 Slide 4
NordLink General concept Bipole with earthed neutral on only one converter Ertsmyra Vollesfjord Wilster Pole 2 ( ) Pole 1 (+) Pole 1 (+) Pole 2 ( ) December 16, 2015 Slide 5
Nordlink Single Line Diagram December 16, 2015 Slide 6
NordLink Some Challenges Isolated converter neutral on Norway side Transition between Bipole to monopole operation DC OH line o o Earth faults Interference from parallell AC OH line Operation at 80% DC voltage Transport of Transformers December 16, 2015 Slide 7
Nordlink Transition between bipole to monopole operation December 16, 2015 Slide 8
Nordlink Interference from AC OH lines December 16, 2015 Slide 9
Valve Basics VSC converter I V X V Active and Reactive power flow controlled by controlling the amplitude and phase angle of U v. I V + U d U AC -U d U C U V + U d U C Fundamental of U V -U d Two-level converter phase-to-neutral voltage Slide 10
Nordlink Technology 2-level converter + U d -U d + U d 300 M9 version 2.2, 320kV, M2LC, P=3.37, N=35, C=1mF, no 2nd harm 200 1 Cell 100 Uv(t) [kv] 0-100 -200-300 0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02 time s VSC Toolbox version 2.4. 05-Dec-2008 10:22:05 December 16, 2015 Slide 11 -U d
NordLink ML2C principle
Valve Basics VSC converter +U d A cell can be switched in three modes. U cp1a C T1 D1 T2 D2 C T1 D1 L v I vpa T2 D2 I v L v I vna U v T1 D1 C Turning T1 off and T2 on -U d T1 T2 D1 D2 C T2 D2 Turning T2 off and T1 on Both valves are turned off, the cell becomes blocked. Current is conducted only through the diodes. Slide 13
Valve Basics VSC converter Id Id/3+Iac/2 Iac Id/3+Iac/2 Id Slide 14
Electrical Design Cell capacitor charge and discharge U cp1 C T1 D1 U dp a T2 D2 C T1 D1 L v I vpa T2 D2 I v L v I vna U f T1 D1 C T1 D1 C T2 D2 T2 D2 U cn1 a Slide 15
Electrical Design Cell capacitor charge and discharge U cp1a C T1 D1 U dp T2 D2 C T1 D1 L v I vpa T2 D2 I v L v I vna U f T1 D1 C T1 D1 C T2 D2 T2 D2 U cn1 a Slide 16
Mechanical Design Valve arm 29 30 29 30 Slide 17
NordLink Layout Ertsmyra Converter Station
NordLink Layout Wilster Converter Station
Mechanical Design Slide 20
HV areas Slide 21 PowDoc id
NordLink Vollesfjord Transition Station December 16, 2015 Slide 22
Nordlink Converter Transformers Single phase units Y-Delta (delta on converter side) DC component on converter side Tap changer on line side Line side neutral solidly earthed December 16, 2015 Slide 23
Nordlink Ertsmyra Site December 16, 2015 Slide 24
Nordlink Ertsmyra Site December 16, 2015 Slide 25
December 16, 2015 Slide 26