Increasing Renewable Transfer

B4 International Colloquium
1st
– 4th
October 2019
Johannesburg, South Africa
B4 – 21
paul.harrington@smartwires.com
Increasing Bulk Power Transfer of Renewable Generation with Modular FACTS
to Lower Wholesale Costs to Consumers
J. BRIDGE A. KINGSMILL H. KLINGENBERG B. KELLY P. HARRINGTON
AusNet Services TransGrid ElectraNet Smart Wires Smart Wires
Australia Australia Australia Ireland Australia
SUMMARY
As global power systems transition to a new energy future, transmission networks are
increasingly required to enable renewable generation to integrate into energy markets.
The changing generation mix is driving changes to power flow patterns which increase
transmission constraints and curtailment of zero fuel cost and emissions-free
generation.
Developing transmission infrastructure to relieve network constraints involves capital
intensive investment and significant costs to end users. By improving line utilisation,
utilities can reduce generation curtailment, provide increased sharing of geographically
diverse renewable energy resources while saving considerable capital investment by
deferring or eliminating augmentation costs. Modular Flexible Alternating Current
Transmission System (M-FACTS) devices are one such technology that can be
employed to optimise line power flows, allowing utilities to enhance the capability of
existing networks, whilst minimising overall network investment cost and risk.
Recent developments leverage Static Synchronous Series Compensator (SSSC)
technology to provide a modular solution to improving network utilisation. The modular
SSSC (M-SSSC) is a member of the M-FACTS product family whose modular nature
enables a flexible, no-regrets approach to network investment. These solutions are
economic and allow incremental network augmentation, removing the stumbling block
of high cost-of-entry for many projects, in much quicker timeframes than traditional
network investments. Standard components come off-the-shelf, enabling shorter
project lead-times, matching the timeline of renewable generation developments, for
example.
Sharing renewable generation across regional interconnections reduces the reliability
risks associated with the intermittent nature of renewable technologies and enables
more efficient operation of energy sources. This paper describes how three Australian
network owners, TransGrid, AusNet, and ElectraNet, plan to leverage M-FACTS

1st
– 4th
October 2019
B4 – 21
paul.harrington@smartwires.com
technologies to improve utilisation of existing networks and facilitate bulk transfer of
renewable energy across regional boundaries, while achieving the following benefits:
 Reduced curtailment of wind generation;
 Increased market access for hydro generation;
 Greater sharing of wind and solar generation sources across broader
geographic regions;
 Reduction of forecast probability of unserved energy following retirement of
legacy fossil fuel generators.
KEYWORDS
Power Flow Control, SSSC, Modular FACTS, Regional Transfer Capacity, Renewable
Integration, Sub-synchronous Resonance, Series Compensation, Series Reactance,
Series Capacitors, Voltage Injection

1st
– 4th
October 2019
1. INTRODUCTION
The Australian power system is currently experiencing a transformational change as
renewable energy sources proliferate, displacing large thermal coal-fired generators
from the market. An increasing mix of grid scale non-synchronous solar and wind
generation, and distributed energy resources (predominantly in the form of roof-top
solar PV), are disrupting the energy market and contributing to the increased
complexity of managing the planning and operation of the high voltage transmission
network.
Over the next 20 years, it is anticipated that a substantial portion of the conventional
generation fleet in eastern Australia will retire, with a significant number of coal-fired
generators advising they are closing or are expected to reach end-of-life in this period.
This expectation is underpinned by a history of generator retirements that have
occurred over recent years as refurbishment of older stations is deemed uneconomic
in light of the new renewable energy economy. Presently, coal fired generation is
responsible for generating almost one-third of the total energy consumption in the
Australian National Energy Market (NEM).
Figure 1 – Australian coal-fired power station expected retirement dates
Source: (AEMO 2018 ISP)
This change is causing a fundamental alteration to power flows across the Australian
transmission network. Historically planned and built to transfer large amounts of power
from large thermal generators located near coal fields to major city load centres, the
network is now experiencing high levels of power flow in weaker rural parts of the
network that were originally designed to supply modest sized country load centres.
These rural locations are now subject to injection of large amounts of power from
renewable generators connecting in these areas. As a result, renewable generators
are experiencing increasing levels of curtailment as sub-transmission networks
constrain their output.
The change in generation mix also has implications for supply reliability, as the
constant base load support provided by traditional fossil fuel generation is supplanted

1st
– 4th
October 2019
by the variable output of renewable generation sources that rely on variable or
intermittent solar and wind resources.
Figure 2 – Forecast unserved energy against 0.002% reliability standard1
(committed projects)
Source: (AEMO 2018 Electricity Statement of Opportunities)
The emerging risk of an increase in the probability of unserved energy events occurring
as a consequence of the emerging supply-demand imbalance has been met by the
development of an Integrated System Plan (ISP) by the Australian Energy Market
Operator (AEMO). The ISP serves the primary objective of identifying a national
strategic plan to support development of the power system to deliver a safe, reliable,
and secure electricity supply. A key aspect of the ISP is the recognition of the increased
role that transmission capability has to play in enabling access to geographically
diverse sources of renewable generation to enhance supply reliability.
In this regard, a range of strategic transmission developments have been identified
that would reduce network congestion in critical locations to deliver increased transfer
capacity between trading regions of the NEM with a resulting improvement in supply
reliability and reduce energy costs for consumers through better sharing and utilisation
of existing infrastructure and increased competition in the energy market.
2. MODULAR FACTS DEVICE POWER FLOW CONTROL TECHNOLOGY
The modular FACTS device power flow control technology considered here is a
modular implementation of static synchronous series compensator (M-SSSC). Based
on established voltage-source convertor technology, and connected in series with the
circuit, it allows the series reactance of a line to be effectively increased or decreased
by injecting a sinusoidal voltage waveform in series with the line. The voltage is injected
at 90 degrees to the line current, leading or lagging, to produce an apparent series
inductance or capacitance. By adjusting the magnitude of the injected voltage, the
amount of series reactance injection can be continuously varied, allowing the flow of
1 The reliability standard for the National Electricity Market in Australia requires 99.998% of customer
demand within a region to be supplied each year.

1st
– 4th
October 2019
power amongst parallel circuits to be controlled and the transfer capacity of a set of
lines to be increased, resulting in the overall utilisation of the transmission network
benig maximised. When used for series compensation of transmission lines, the
negative effects of physical series capacitors, such as SSR, SSCI, and high fixed
installation costs can be avoided.
The modular nature of the M-SSSC allows a flexible approach to network investment.
The devices are installed in banks or arrays, and unlike most traditional network
augmentations can be installed incrementally. This allows the solution to be right-sized
to meet the immediate need, while maintaining the option to expand, or reduce, the
size of the installation as required in future. Lead times are considerably shorter than
other solutions due to the ‘off-the-shelf’ nature of the equipment, allowing the decision
to commit to network investment to be made closer to the need date and reducing the
risk of untimely investment when needs are uncertain. The short time to deploy also
means that solutions can be put in place in timeframes that align with renewable
generation developments, facilitating faster integration of renewable energy into
constrained areas of a network without the delay or prohibitive cost of more traditional
solutions. Being an “off the shelf” technology, which is voltage agnostic and easily
scaled, means that the equipment can be redeployed elsewhere as a network evolves
over time.
The devices can be configured to operate autonomously, or can be remotely controlled
by EMS, via SCADA. Management of line loading over a wide area network can be
achieved through coordinated control of a number of distributed installations to achieve
optimal load balancing between lines to maximise the power transfer capability across
a parallel set of lines or transmission corridor.
3. INCREASED ACCESS TO HYDRO GENERATION IN NEW SOUTH WALES
Supplying the NEM with around 4GW of hydroelectric generation capability, the Snowy
Mountains Scheme is strategically located between the states of New South Wales
and Victoria, harvesting snow melt from the Australian alps through a complex system
of sixteen major dams supplying seven hydroelectric power stations. It is an important
source of generation for the eastern Australian states, playing a key role in meeting
peak system demand.
The Snowy Mountains Scheme is connected to the New South Wales transmission
system through a set of four parallel 330 kV lines. Due to the different lengths of the
four line routes, the lines have different impedances and do not share load evenly in
proportion to their thermal ratings. The longest line, Upper Tumut to Yass tends to be
lightly loaded, while the shortest lines, Upper Tumut to Canberra and Lower Tumut to
Canberra, tend to constrain first. This leaves the other two lines with unused capacity
when power transfers into New South Wales from the Snowy Scheme are constrained.
When this import constraint occurs at time of peak demand in New South Wales, gas
turbine peaking plant is often required to be run to meet the supply need, at significant
cost to end users.
An installation of the modular FACTS devices described above, (M-SCCC), is planned
to be installed on the Upper Tumut to Yass 330 kV line in mid-2020. The installation
will consist of 8 x 1 MVAr M-SCCC modules being installed on each phase, 24 MVAr

1st
– 4th
October 2019
in total, and will be operated in capacitive mode to relieve thermal constraints across
the four-line Snowy transmission corridor. By sharing load more evenly between the
parallel lines, the transfer capacity of the transmission corridor is improved by
approximately 42 MW, providing both fuel cost savings by reducing the level of gas
peaking generation required and a reduction in the expected value of future unserved
energy, yielding a payback of the investment in around 4 years.
Figure 3 – Snowy Hydro to Canberra/Yass 330 kV transmission corridor
Since the commencement of the project, the focus on the capability of the Snowy
transmission corridor has increased as the ISP has identified the important role it plays
in enabling the sharing renewable generation supply between states, and further
improvement in its transfer capability has been given priority status. This is expected
to become increasingly important following the planned retirement of the 2GW Liddell
coal-fired power station in 2022, after which an increased risk of load shedding is
expected unless additional dispatchable capacity is made available. By increasing the
size of the installation on the Upper Tumut to Yass line, and also installing on the Upper
Tumut to Canberra line, around 200 MW of latent capacity in the network could be
released.
A unique aspect of this solution is that it can provide this benefit over a broad range of
operational scenarios due to the ability of the M-SCCC to operate in both capacitive or
inductive modes. Depending on the ratio of the hydroelectric generation output at the
Lower Tumut and Upper Tumut locations, and dependent on which line outages occur,
the 45 MVAr M-SCCC installation being considered on the Upper Tumut to Canberra
line would operate in inductive mode to address overloads on the Upper Tumut-
Canberra line, or else would operate in capacitive mode to address overloads on the
Lower Tumut to Canberra line. A wide area control scheme that monitors the loading
on the lines would co-ordinate the response of the M-SCCC banks, via SCADA, to
Upper Tumut
(Hydro)
Lower Tumut
(Hydro)
Murray
(Hydro)
Canberra
Yass
SYDNEY
Power flow control
operated in series
capacitive mode
Power flow control
operated in series
inductive or capacitive
mode

1st
– 4th
October 2019
distribute load evenly between the remaining in-service lines following a line outage.
The modular nature of the M-SCCC means that this additional capacity could be
achieved within a much shorter scale than many alternative solutions, with potential to
deliver the benefits of greater market access to renewable generation within a year.
4. ENHANCED ENERGY SECURITY FOR VICTORIA
The ability to transfer power between the states becomes increasingly important as
traditional base load thermal power stations are removed from the NEM. The
retirement of the 1.6 GW Hazelwood coal fired power station in 2017 was particularly
significant for the state of Victoria, raising concern for the security of supply in the state
over the ensuing summers, and requiring special Reliability and Emergency Reserve
Trader (RERT) provisions to be activated to enable sufficient generation reserves to
be made available. Additionally, the Australian Energy Market Operator (AEMO)
reported that there was a 1-in-3 chance of an unserved energy event occurring over
the Australian 2018/19 summer, and forecast a reliability gap that requires an
additional 130 MW of generation to be available to meet the reliability standard under
10% POE demand conditions for the 2019/20 summer.
Figure 4 – Probability of unserved energy exceeding reliability standard (committed projects)
Source: (AMEO 2018 Electricity Statement of Opportunities)
The Victorian transmission network owner responded to this need by instigating a
number of projects that each delivered a modest increase in generation and supply
capacity to the state, that when combined would contribute significantly to meeting the
supply needs of the region. One of these projects was to enable an increase in the
amount of power that could be exported from New South Wales to Victoria through the
use of M-SSSC technology. The New South Wales to Victoria 330 kV interconnection
comprises three parallel 330 kV lines that converge at the Dederang 330 kV terminal
station. Of these, the two lines that make up the Murray to Dederang 330 kV double
circuit constrain, while the western 330 kV route from Wagga to Dederang remains
underutilised. By installing and operating M-SCCC on the Jindera to Wodonga section
of this route, operated in capacitive mode, the loading on the Murray to Dederang
circuits is reduced, allowing an extra 15 MW to be exported south across the New

1st
– 4th
October 2019
South Wales to Victoria border. This project is planned to be in place for the 2019/20
summer peak load.
Figure 5 – Snowy Hydro to Canberra/Yass 330 kV transmission corridor
This installation will also provide further benefits when, in 2022, the Liddell power
station is expected to retire in New South Wales. By this time Victoria is forecast to
have significantly more renewable generation sources in place due to the Victorian
Renewable Energy Target (VRET) – a target that requires 25% of electricity generated
in Victoria to come from renewable energy resources in 2020, and 40% by 2025.
Victoria will then be expected to be a net exporter of energy to New South Wales.
Again, the western interconnector route via Jindera to Wodonga will be underutilised
as the eastern line route constrains, and operation of the M-SCCC installation on the
Jindera to Wodonga 330 kV line will increase the transfer capacity of the New South
Wales to Victoria interconnection, now in a northerly direction, allowing excess
renewable energy generated in Victoria to support summer peak demand in New South
Wales.
An installation of M-SCCC further along the western interconnection line route is being
considered for the Wagga to Jindera 330 kV line, duplicating the benefits of the Jindera
Sydney
Melbourne
Upper
Tumut
Lower
Tumut
Murray
Dederang
Wodonga
Wagga
Jindera
NSW
VIC
Power flow control
operating in
capacitive mode

1st
– 4th
October 2019
to Wodonga installation, and is proposed to be commissioned by the 2020/21 summer.
The payback of this installation due to fuel cost savings resulting from displacing gas
peaking plant with solar renewable energy, and a reduction in the expected value of
unserved energy, is expected to be around 4 years.
5. REDUCING CURTAILMENT OF WIND GENERATION IN SOUTH AUSTRALIA
South Australia has an abundance of renewable energy resources, and has reached
world-leading levels of renewable generation, driven by renewable energy policy and
rapidly evolving technology. The state no longer has any coal based thermal
generation following the closure of the Playford and Northern power stations in 2015
and 2016 respectively. As a result, over 50% of energy generated in South Australia
is now expected to come from renewable sources.
Figure 6 – South Australia energy generation sources
Source: (South Australian 2018 Transmission Annual Planning Report)
The integration of substantial volumes of renewable energy generation is significantly
altering power flows across the South Australian transmission network. Many of the
new renewable energy generators are connecting in locations that are remote from
the retired thermal generation plant that they are displacing. As a result, the
transmission system is experiencing flows for which it was not originally designed,
with congestion on transmission corridors resulting in dispatch constraints for
renewable generation that are expected to increase over time as additional generator
connections are established.
One such constraint is occurring in the Mid-North region, resulting in the curtailment
of wind generation due to a thermal constraint on the Templers-Waterloo 132 kV line,
while spare capacity remains unutilised on the electrically parallel 275 kV
transmission network. The use of modular power flow control devices to redistribute

1st
– 4th
October 2019
power flows across the meshed network was studied and found to be economically
viable. By introducing approximately 900 mΩ of controllable reactance to the
Templers to Waterloo 132 kV circuit, an additional 17 MW of wind generation was
able to be transmitted along the Mid-North to Metropolitan Region corridor, with the
additional power being routed onto the parallel Roberstown to Tungkillo and
Robertstown to Para 275 kV circuits.
Figure 7 – Templers to Waterloo 132 kV transmission constraint
The value provided to the market due to savings in fuel costs is estimated to be
$1.3M per annum, as the additional capability to dispatch wind generation on the grid
reduces the amount of gas fuel needing to be consumed by peaking plant. This is
forecast to provide a project payback of under 5 years, while the modular nature of
the solution allows for expansion of the installation if additional relief to curtailment of
the wind generation is required in future. In addition to the economic savings, this
measure is expected to save approximately 10,000 tons of CO2 emissions per
annum.
6. CONCLUSION
The experience in Australia has demonstrated the value of modular FACTS devices
as a strategic tool for enabling the integration of renewable generation into the grid and
for improving the capability of the network to transport and share that renewable power
across regional boundaries. The result has been greater market access for renewable
generators, providing fuel cost savings that will deliver cheaper power to end users
while also reducing greenhouse emissions.
The ability to deploy the equipment in short time frames is being exploited to allow the
economic benefits provided by the equipment to be realised earlier, while the flexibility
to stage incremental installations and for the equipment to provide variable power flow
control is finding practical application in a variety of intra and interregional settings.
Templers-
Waterloo 132 kV

1st
– 4th
October 2019
The projects outlined in this paper have been assessed to provide positive net market
benefits, with typically project payback periods of around 4 to 5 years. The potential
for larger scale application of the technology exists as network owners become more
accustomed to integrating the equipment into their network planning and operating
functions.
BIBLIOGRAPHY
[1] Integrated System Plan for the National Electricity Market. (Australian Energy
Market Operator, July 2018).
[2] Electricity Statement of Opportunities. (Australian Energy Market Operator,
August 2018).
[3] New South Wales Transmission Annual Planning Report. (TransGrid, June
2018).
[4] Victorian Annual Planning Report. (Australian Energy Market Operator, July
2018).
[5] South Australian Transmission Annual Planning Report. (Electranet, June 2018).

Increasing Renewable Transfer

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Increasing Renewable Transfer

Similar to Increasing Renewable Transfer (20)

More from Power System Operation

More from Power System Operation (20)

Recently uploaded

Recently uploaded (20)

Increasing Renewable Transfer