A New 500MW Frequency Converter
Station to Exchange Power Between
Uruguay and Brazil
Dr. Norman MacLeod
Co-authors – R Bonchang, C Horwill,
D Castagna, M Croce, M Artenstein
GRID
Uruguayan Power System
• Peak power demand in 2010 = 1700MW
• Growth rate = 4 – 5% per annum
• Installed generation capacity = 2400MW
• 60% hydroelectric generation
• Strong AC connections to Argentina
• Weak (70MW) HVDC connection to Brazil
IEEE PSCE- Paper 0299 - P 2
New Interconnection with Brazil
• Stage 1 = 500MW
• Stage 2 = future expansion to 1000MW
• HVDC is required as Uruguay is 50Hz, Brazil is 60HZ
• New 500kV AC line from San Carlos to Melo
• HVDC converter station at Melo (60km from the
border)
• New 525kV AC line from Melo to Candiota (in Brazil)
IEEE PSCE- Paper 0299 - P 3
Melo HVDC Converter Station
Brazil
Argentina
Rivera
70MW BtB
URUGUAY
Candiota
Buenos
Aires
Melo
Montevideo
500MW BtB
San Carlos
IEEE PSCE- Paper 0299 - P 4
Single Line Diagram – Melo Station
+DC
500kV 50Hz
525kV 60Hz
system
system
-DC
4 off 110Mvar
4 off 96Mvar
Harmonic
filters
Harmonic
filters
IEEE PSCE- Paper 0299 - P 5
Reactive Power Interchange – Uruguay side
IEEE PSCE Paper 0299 P 6
Impedance Sector Diagram – Uruguay side
IEEE PSCE Paper 0299 P 7
Harmonic Distortion Limits
Order
(%)
Order
(%)
Order
(%)
5
2.0
3
2.0
2
1.0
7
2.0
9
1.0
4
1.0
11
1.5
15
0.3
6
0.5
13
1.5
21
0.2
8
0.4
17
1.0
>21
0.2
10
0.4
19
1.0
12
0.2
23
0.7
>12
0.3
25
0.7
>25
0.5
IEEE PSCE Paper 0299 P 8
Equipment examples
Converter transformer – 1 phase / 3
winding
IEEE PSCE- Paper 0299 - P 9
AC Harmonic filters
Thyristor Valve Design
• Suspended quadri-valve structure
• Operating voltage ±79.3kV DC
• Operating current 3150A DC
• 24 thyristors per valve, including 2 redundant levels
• Thyristor devices rated at 8.5kV, 4000A DC
− 125mm (5 inch) diameter devices
• Single circuit water cooled design
− Uses mono-ethylene glycol for temperature <0°C
IEEE PSCE- Paper 0299 - P 10
Thyristor Valve Design
IEEE PSCE- Paper 0299 - P 11
Conclusions
• The 500MW Melo inter-connector will be a strategic
link in the Uruguayan transmission system
• The station is due to be commissioned in late 2011
• An innovative approach on transformer design has
allowed a common design (and spare) to be used on
the two sides, although the voltages and frequencies
are different
• An innovative approach was adopted for the filter
design, by installing part of the equipment at the
point of common coupling, 116km from the
converter station
• Phase 2 of the project will see the power rating of
the inter-connector increased to 1000MW
IEEE PSCE- Paper 0299 - P 12
www.alstom.com
Station Design
• Common design of converter transformers on both sides
− Single phase three winding units
− Wide tapping range to suit AC system voltages
− Only 1 spare transformer required
• No DC smoothing reactor required
• AC harmonic filters at Melo
− 50Hz side 4 x 110Mvar triple frequency (11/14/24)
− 60Hz side 2 x 96Mvar triple frequency (HP 13/24/36)
− 60Hz side 2 x 9Mvar triple frequency (HP 3/13/47)
• AC harmonic filters at Candiota
− 2 x 96Mvar double frequency (HP 3/11)
HP = High Pass (damped) filter
IEEE PSCE- Paper 0299 - P 14