Rolf Grünbaum, Power Systems – FACTS, 201206- … stability, i.e. the maintaining of synchronism;...

© ABB Group May 20, 2013 | Slide 1

FACTS-Intelligent solutions for meeting challenges in power transmission IEEE PES PowerAfrica 2012, Johannesburg

Rolf Grünbaum, Power Systems – FACTS, 2012-06-18


Grid improvements: options

Building new transmission lines is always a safe way to improve power transmission capability in a grid.

Considering FACTS already at the planning stage considerably lowers the investment cost.

Improving already existing grids may be much more attractive in many cases, however. This can be true from more than one aspect:

Economically: Less costly.

Legally: Right of way permits, land purchases unnecessary.

Environmentally: Less impact on the landscape; forest and land saving.

Time expenditure: Time consuming permits and building of lines can be avoided.

This is where FACTS is coming in.


Power transmission issues

In long HVAC interconnectors, several kinds of system stability are required:

Angular stability, i.e. the maintaining of synchronism;

Synchronous stability, i.e. the absence of sustained power oscillations;

Voltage stability, i.e. the avoiding of voltage swings, dips or collapses.

These stability issues can all be addressed and improved by means of FACTS


SVC (Static Var Compensator): Dynamic voltage control

Common SVC configuration:

TCR/TSC/Harmonic Filters Large Mvar range feasible

Low harmonic emission

Low losses at 0 Mvar point

Voltage stabilization at a load busbar:

Smooth voltage control over the entire Mvar range

The SVC should be rated large enough to cope with the most severe load case


System voltage correction by means of SVC

VT

VREF IQ 3 1 2

Vo

Xs VT

VREF

Thyristor valve, water cooled (one phase of three)

Grid characteristics:

1: Nominal voltage and load

2: Undervoltage, e.g. due tp generator outage

3: Overvoltage, e.g. due to load rejection

I


Wind application, Western Texas: Background

West central Texas: plenty of wind power McCamey area: 750 MW and growing; Central area: 1.000 MW

Very high wind power penetration (up to 80%).

Variations in import/export of active power due to rapid swings of wind farm output require continuous voltage regulation.

During grid faults, induction generators lose synchronism at low voltages and thus increase their reactive power demand, further dragging down the system voltage until protection intervenes.

Dynamic voltage control is achieved by means of SVCs located in a number of key points in the grid.

Rio Pecos SVC


Wind application, Western Texas: SVCs for stabilization of grid voltage

Customer’s need

To improve system stability, e.g. due to connections of wind farms.

Supplier’s response

Five SVCs, each rated at -40/+50 Mvar

Three SVCs are directly related to wind power

Connected directly to 35 or 69 kV

Customer’s benefits

Improved system stability for steady state as well as fault ride-through conditions

Modularized, transformer-less SVC design

7th 15th

69 kV

TCR

90 Mvar

5th

20 Mvar 17 Mvar 13 Mvar 69 kV directly connected SVC


Juna Downs ore mining complex, Australia Mining complexes are often forced

to operate in remote areas where power supplies are weak or inadequate, and with elevated or high isokeraunic activity

Juna Downs is a large iron ore mining complex, fed from a long, weak 220 kV grid.

Degraded availability of the 220 kV OH line due to lightning strikes. Voltage dropping to 0.8-0.85 p.u., causing serious disturbances in production.

SVC installed to stabilize the 220 kV voltage, as well as accomodate future plans for increased ore extraction.

The SVC is rated at -75/+75 Mvar at 220 kV, with an overload capability of -100/+100 Mvar for one hour.

75 MVA

220 kV

TCR 70 Mvar

TCR 70 Mvar

TSC 60 Mvar

7th 10 Mvar

3rd 15 Mvar

5th 15Mvar

MSC 25 Mvar

MSC 25 Mvar


Juna Downs ore mining complex, Australia

Operational experience:

Excellent correlation between load drops which would have caused voltage rises, and the SVC going inductive to keep the grid voltage at its set point.

Likewise excellent correlation between load increases which would have caused voltage drops, and the SVC going capacitive to support the voltage.


Series compensation: Basic mechanisms

The flow of active power, P, can be increased by a decrease of the effective series reactance of the line (XL-XC)

Also, the transfer stability can be increased by a decrease of the angular separation of the end voltages (δ)

Further, the reactive support yielded by the SC adds to the transfer capability of the line

δsin21 ×−×

=CL XX

UUP


Series Capacitors: Main design features

SCs need to be protected against overvoltages in the grid. This is achieved by means of a scheme as seen to the left.

The MOV acts as primary protection

The FPD acts as back-up protection1)

With B, the SC is by-passed

1) Consisting of two parts: - Arc Plasma Injector (API) - Fast Mechanical Contact (FC)

API FC


765 kV series capacitors: Cape Corridor

A total of six SC coming on line in the 765 kV Cape Corridor:

Alpha 1&2, 2x446 Mvar

Beta 1&2, 2x1340 Mvar

Mercury, 1119 Mvar

Perseus, 893 Mvar

Purposes: Increased power transmission

capacity over the 765 kV interconnector

Less need for reliance on local power generation

Mercury 765 kV

Zeus 765 kV

Alpha 765 kV

Perseus 765 kV

Beta 765 kV

Gamma 765 kV

Hydra 765 kV


Site views, Cape Corridor 765 kV Series Capacitors

Perseus 765 kV SC (One phase of three)

Beta 765 kV SC (One phase of three)


SVC Light : Voltage Source Converter based

U1 Bus voltage

U2 VSC voltage

With U1 and U2 in phase, only reactive power is exchanged.

A reactive power compensator

SVC Light U-I characteristic:

Full reactive output even for small system voltages.


Improved transmission capability over long intertie: Cerro Navia SVC Light, Chile

Background: An increasing demand for power within the

country’s economy

Increasing opposition to constructing new power transmission lines

A demand for better utilization of existing facilities

Solution: An SVC Light installed at Cerro Navia in the

Central Interconnected System, the largest power system in Chile.

Purpose: Increase the power transfer from south Chile up to

the capital of Santiago over the long power corridor

Yield dynamic voltage control for steady-state and transient grid conditions

Contribute reactive power during faults in the grid

SVC Light, 220 kV, -65/+140 Mvar


DynaPeaQ - SVC Light with Energy Storage UK Power Networks, UK

Customer’s need A dynamic wind energy storage

demonstrator operating on a 2 MW wind farm connected to an 11 kV grid

ABB’s response An SVC Light with Energy Storage

11 kV - 600 /+725 kvar 200 kW / 1 h 600 kW / a few minutes

State of the art Li-ion batteries

Customer’s benefits Storage of surplus energy from wind

farm during low demand, to be released into the grid during peak periods

Level out active power variations from wind farm (absorb power peaks, fill out power dips)

Dynamic grid voltage support


Conclusion With FACTS such as SVC, Series Capacitors and STATCOM, a number of

benefits can be obtained in power transmission, such as: Dynamic voltage control, to limit over-voltages over lightly loaded lines, as

well as prevent voltage dips or even collapses in heavily loaded or faulty systems.

Increased power transmission capability and stability of power corridors, without any need to build new lines. This is a highly attractive option, costing less than new lines, with less time expenditure as well as impact on the environment.

Facilitating connection of renewable generation by maintaining grid stability and fulfilling grid codes. By means of Dynamic energy Storage, wind power can be stored during low demand, to be released into the grid during high demand.

Maintaining power quality in grids dominated by heavy industrial loads such as large mining complexes.

In this presentation, several examples have been given of FACTS devices such as SVC, Series Capacitors and STATCOM in operation for power transmission in Africa and elsewhere in the world.

It can be expected that in coming years, FACTS will find additional uses where there are needs for long power interconnectors, between countries as well as between regions inside countries, not least in Africa.

Rolf Grünbaum, Power Systems – FACTS, 201206- … stability, i.e. the maintaining of synchronism;...

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