Topics. HVDC Fundamentals

Transcription

1 Topics HVDC Fundamentals Conventional Converters Capacitor Commutated Converters Voltage Source Converters Reactive Power Requirements System Configurations Tapping Control basics High Power Transmission

2 Evolution...

3 AC Core HVDC Technologies HVDC-CSC CSC HVDC-VSC VSC AC Outdoor Indoor AC Filters Outdoor Indoor Converter Transformers DC Filters DC Thyristor Valves IGBT Valves DC HVDC Classic Current source converters Line-commutated thyristor valves Requires 50% reactive compensation (35% HF) Converter transformers Minimum short circuit capacity > 2x converter rating HVDC Light Voltage source converters Self-commutated IGBT valves Requires no reactive power compensation (15% HF) Standard transformers No minimum short circuit capacity, black start

4 The HVDC Classic Converter Station Converter station Transmission line or cable Converter Smoothing reactor AC bus DC filter Shunt capacitors or other reactive equipment AC filters Telecommunication ~~ Control system

5 The CCC* Station *Capacitively-commutated converter Transmission Line, Cable or Back-Back Converter Smoothing reactor AC bus Commutation capacitors DC filter Contune AC filters Telecommunication ~~ Control system

6 Modular Back-toBack CCC Asynchronous Tie

7 Improved Stability and Higher Power Transfer HVDC Classic HVDC CCC

8 The HVDC Light Converter Station Converter station Indoor Voltage Source Converter - VSC AC bus Phase Reactor Transmission Cable Dry DC Capacitor AC filters DC Capacitor Control system IGBT Valves

9 Comparison of Reactive Power Characteristics Active Power (p.u.) P-Q Diagram Operating Area Conventional HVDC HVDC Classic (~ SVC with TCR+FC, -0.5Pd / +0 MVAr) VSC Based HVDC HVDC Light (~ STATCOM, -0.5Pd/+0.5Pd MVar) Reactive Power (p.u.) HVDC VSC Operating Range

10 HVDC Converter Arrangements Thyristor Module HVDC Classic Thyristor valves Thyristor modules Thyristors Line commutated Single Valve Double Valve Quadruple Valve Thyristors HVDC Light Submodule IGBT valves StakPak Chip IGBT valve stacks IGBT Valve Stacks StakPaks Submodules Cable Pair Self commutated

11 HVDC Operating Configurations and Modes

12 Tapping OVHD HVDC with Large VSC Converters HVDC Tap Reverse power by polarity reversal Electronic clearing of dc line faults Fast isolation of faulty converters Reactive power constraints Momentary interruption due to CF at tap Limitations on tap rating, location and recovery rate due to stability HVDC Light Tap Polarity reversal if main link is bidirectional Cannot extinguish dc line fault current contribution without special provision, e.g., diode coupling for inverter No interruption to main power transfer due to CF at tap Less limitations on tap rating and location Cascade VSC connection for lower tap rating No reactive power constraints Improved voltage stability

13 HVDC Classic Control I d IR IS IT u α u R u S u T IR IS IT U d

14 Control of VSC Based HVDC Transmission K K K K AC Line Voltages OPWM u DC1 u DC2 - u AC-ref1 + q ref1 u AC1 AC voltage control i PWM internal current control + DC voltage control - u - u DC-ref2 DC-ref1 + p ref1 p ref2 DC voltage control PWM internal current control i u AC2 u AC-ref2 AC voltage control q ref2 Principle control of HVDC-Light

15 Comparison - AC, HVDC, HVDC CCC and HVDC Light Attributes Power flow control Reactive power demand Reactive power compensation & control AC voltage control Voltage stability 3 I^2 X -3 V^2 B Static AC Cable None unless PST or series reactor Shunt reactors Dependent on P, Q and Z HVDC - Conventional Continuous ±0.1Pr to ±Pr Reactive power demand = 50% power transfer Switched shunt banks 35% in filters + 15% in capacitors Slow - switched filters, capacitors & reactors + LTC Degraded, special control HVDC Capacitor Commutated Continuous ±0.1Pr to ±Pr Reactive power demand reduced by series cap Filters + series compensation of 3 I^2 Xcc Slow - switched filters, capacitors & reactors + LTC Improved, CF lower probability HVDC Light Continuous 0 to ±Pr No reactive power demand STATCOM + 15% in fixed filters Dynamic virtual generator Superior, no CF AC system limitation Cable derated with distance by charging current Min SCC>2x converter rating Min SCC>1.3x converter rating None black start, passive load, induction generators OK

16 Running Underground 500 kv EHV 1500 MW ± 500 kv HVDC 3000 MW ± 320 kv HVDC Light 1000 MW

17 Power Ranges HVDC-Classic and HVDC-Light HVDC 1000 Power in MW 100 Back to back HVDC Light Voltage in kv

18 Comparison of overall line design 800 kv ±600 kv 1000 kv ±800 kv

19 Itaipu 765 kv AC Line Performance Note:, =. 800 kv AC ± 600 kv DC

20 Itaipu 600 kv HVDC Line Performance Note:, =. 800 kv AC ± 600 kv DC