GRID

Dr. Norman MacLeodCo-authors – R Bonchang, C Horwill,

D Castagna, M Croce, M Artenstein

A New 500MW Frequency Converter Station to Exchange Power Between

Uruguay and Brazil

IEEE PSCE- Paper 0299 - P 2

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 3

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 4

Melo HVDC Converter Station

Montevideo

BuenosAires

Rivera

70MW BtB

URUGUAY

Melo

500MW BtBSan Carlos

Candiota

BrazilArgentina

IEEE PSCE- Paper 0299 - P 5

Single Line Diagram – Melo Station

500kV 50Hz

system

525kV 60Hz

system

+DC

4 off 110Mvar

Harmonic filters

4 off 96Mvar

Harmonic filters

-DC

IEEE PSCE Paper 0299 P 6

Reactive Power Interchange – Uruguay side

IEEE PSCE Paper 0299 P 7

Impedance Sector Diagram – Uruguay side

IEEE PSCE Paper 0299 P 8

Harmonic Distortion Limits

0.5>25

0.725

0.3>120.723

0.2121.019

0.4100.2>211.017

0.480.2211.513

0.560.3151.511

1.041.092.07

1.022.032.05

(%)Order (%)Order(%)Order

IEEE PSCE- Paper 0299 - P 9

Equipment examples

Converter transformer – 1 phase / 3

winding

AC Harmonic filters

IEEE PSCE- Paper 0299 - P 10

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 11

Thyristor Valve Design

IEEE PSCE- Paper 0299 - P 12

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

www.alstom.com

IEEE PSCE- Paper 0299 - P 14

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