WA Electricity Industry Weekly News Roundup: 19 October 2020 – 25 October 2020

alternative alternative energy close up electricity

Headlines

AEMO reports record-low demand across the NEM [22/10/2020]

New records for minimum electricity demand have been recorded across the nation as Australia’s uptake of rooftop solar systems continues to climb.

Huge $50bn Pilbara green hydrogen hub granted major project status [23/10/2020]

The Asian Renewable Energy Hub, a plan to build a massive renewable energy hydrogen project of up to 26GW of wind and solar capacity in Western Australia’s Pilbara region, is set to enjoy a fast-tracked approvals process, after securing ‘major project status’ from the federal government.

Fast-track status for Asian Renewable Energy Hub’s giant Pilbara renewables project [23/10/2020]

The ambitious hydrogen project that seeks to become the world’s largest renewable energy export facility has received major project status from the Federal Government.

Solar plus storage better than grid connection for remote households [23/10/2020]

The Western Australian government has praised the use of solar and batteries to provide power to remote households and businesses, after Western Power replaced costly 230km of costly grid connections with stand-alone power systems that slashed costs and improved reliability.

Announcements

WA Government: Minister Johnston launches sustainable home of the future [19/10/2020]

Energy Minister Bill Johnston today launched an affordable housing experiment between Mirvac, Synergy, Terrace and Keystart. The home has been built to a 9.1-star energy rating, taking into account various energy saving initiatives, including solar passive design, and water and energy efficient appliances. Synergy has provided rooftop solar panels and a battery to further reduce the energy requirements of the home and help the family better manage their electricity bills.

AEMO: Record minimum demand levels across Australia [22/10/2020]

Western Australia’s Wholesale Electricity Market (WEM) logged a new Q3 minimum demand record with operational demand reaching 999 MW on 13 September. The balancing price floor (-$1,000/MWh) in Western Australia was hit six times during the quarter – it had only been previously been reached this threshold three times before in the history of the WEM.

WA Government: Energy technology a boon for regional WA homes [23/10/2020]

Energy Minister Bill Johnston has congratulated Western Power on the successful deployment of 52 stand-alone power systems (SPS) at properties throughout the Mid-West, Goldfields, eastern Wheatbelt and Great Southern regions. It is the largest single deployment by a network business in Australia

Western Power: WA’s power digitisation recognised nationally [23/10/2020]

Western Power’s innovative Digital Substation pilot has won the national Digital Utility of the Year – Energy Award.

Publications

APA FY2020 Annual Meeting Address [22/10/2020]

Consultations

None this week

WA Electricity Industry Weekly News Roundup: 12 October 2020 – 18 October 2020

low angle photograph of black metal tower satellite during daytime

Headlines

Renewable energy to replace coal in WA’s biggest power grid as solar hollows market, report predicts [12/10/2020]

More than half of Western Australia’s remaining coal-fired electricity capacity could be phased out within five years, according to a landmark report which charts the extraordinary rise of renewable energy.

Tailwind for wind, storage [12/10/2020]

About 870 megawatts of new gas capacity, and 5,260MW of renewables, could be needed by 2030 if WA’s economy grows dramatically.

Rooftop solar and battery storage take centre stage in W.A energy transition [12/10/2020]

Western Australia has unveiled its first 20-year blueprint into how the clean energy transition may evolve in its uniquely isolated grid, and it seems clear that rooftop solar PV and battery storage will take centre stage.

Natural gas to continue powering WA’s way of life [12/10/2020]

The WA Government’s inaugural “Whole of System Plan” (WOSP) highlights the ongoing role of natural gas to power WA’s way of life.

Renewable energy to power more than 70 per cent of WA’s South West Interconnected System by 2040 [12/10/2020]

Newly released modelling predicts at least 70% of WA’s main electricity network will be fueled by renewable energy in 2040.

WA’s Whole of System Plan forecasts renewable generation on the rise [13/10/2020]

The Western Australian Government has launched the state’s first Whole of System Plan (WOSP), giving a 20-year forecast on the future of the South West Interconnected System (SWIS), which shows a huge increase in renewable generation.

WA plans a slow move to greener power [13/10/2020]

Rooftop solar will make South-West WA power greener, but there is no path outlined for Collie’s future or to net-zero by 2050, according to a WA Government study.

WA energy utility Synergy to receive more than $700 million in taxpayer subsidies as revenue slides [13/10/2020]

West Australian taxpayers will fork out almost three-quarters of a billion dollars to subsidise loss-making electricity utility Synergy, which is being battered by low prices and a renewable energy onslaught.

Massive Asian Renewable Energy Hub grows to 26GW of wind and solar [16/10/2020]

The Western Australian government has granted state environmental approvals to the massive first stage of the Asian Renewable Energy Hub, which proposes to build up to 15,000MW of new wind and solar power in the state’s Pilbara region and has expanded its long term plans to an extraordinary 26,000MW.

Announcements

McGowan Government launches Whole of System Plan [12/10/2020]

Energy Transformation Taskforce delivers inaugural Whole of System Plan. Renewable generation expected to triple by 2040, helping drive down emissions. Rooftop solar, wind generation and battery storage to play important role

AEMO welcomes inaugural WA Whole of System Plan [12/10/2020]

The Australian Energy Market Operator (AEMO) welcomes the release of the Western Australian (WA) Government’s inaugural Whole of System Plan (WOSP) – a comprehensive study of the possible changes to occur in WA’s major power system over the next 20 years.

Funding awarded for regional community partnerships [13/10/2020]

Funding awarded to support vibrant communities and thriving regions across WA. Horizon Power allocates $699,500 through its Community Partnerships Program. 73 community initiatives to benefit from funding of up to $50,000 

Publications

WA Whole of System Plan [12/10/2020]

Consultations

EPWA Foundation Regulatory Frameworks: Tranche 1 Amending Rules and Explanatory Memorandum – open from 12 – 19 October 2020

EPWA Foundation Regulatory Frameworks: Tranche 2 Amending Rules and Explanatory Memorandum – open till 16 November 2020

EPWA Foundation Regulatory Frameworks: Draft WEM Procedures – open till 6 November 2020

EPWA Cost recovery for the non-scheme gas pipeline access regime – open till 19 November 2020

WA Electricity Industry Weekly News Roundup: 5 October 2020 – 11 October 2020

photography of electric tower during sunset

Headlines


Synergy seeking 100 MW of storage to follow the sun
[05/10/2020]

The Western Australian Government is expanding its battery of solar-smoothing energy storage systems, with a 100 MW BESS proposed to move into the site of the old fossil-fueled Kwinana power station 30 km south of Perth.

Design contract for $350m renewable hydrogen plant [05/10/2020]

A decision on a $350 million renewable hydrogen plant is planned around February 2021, after Petrofac was picked for FEED work.

Large WA hydrogen project nears critical go-ahead [05/10/2020]

A “green” hydrogen project on the west coast that is set to be the country’s largest has taken a leap forward with the hiring of London-based oil and gas services company Petrofac to carry out engineering and design work.

$644m power credit praised [05/10/2020]

A $644 million package to credit electricity bills is a smart move to encourage spending, economists say, while recent retail trade data is strong for WA.

Bell windfall squandered [05/10/2020]

Premier Mark McGowan’s decision to give every household a $600 credit on their power bill will undoubtedly be a great vote winner, but comes with issues.

Grids struggle with solar splurge as records tumble [07/10/2020]

Numerous instances of record low demand for grid-based power this spring amid soaring rooftop solar use are causing headaches for the market operator and pushing network owners to trial tariff reforms and technical initiatives to help keep the lights on.

WA’s third-largest wind farm, Warradarge to reach full output by end of October [07/10/2020]

The Warradarge wind farm in Western Australia – the state’s newest and third largest wind project – will be up and running before the end of October, the state government says.

Gold Fields cleans up power supply at Granny Smith [07/10/2020]

The gold giant says the new solar-gas hybrid system at the northern Goldfields mine is one of the world’s biggest renewable energy microgrids.

Solar and battery microgrid completed at Granny Smith gold mine [08/10/2020]

Ground-breaking solar, battery and gas microgrid built to power remote W.A. gold mine is complete and cutting fossil fuel consumption by up to 13%.

Synergy in $27m loss [09/10/2020]

A freeze on disconnections, compliance rules for renewable energy generation and a court dispute have affected Synergy, as it posted a $27 million loss.

Synergy blames solar, COVID-19 for $27m loss [09/10/2020]

Energy provider Synergy lost $27.2 million last year after writing off more than $40 million in debt it expects coronavirus-impacted customers will never pay back.

Western Power lifts profit after operating uninterrupted during COVID-19 [09/10/2020]

Western Power has hiked its full-year profit by 6.8 per cent after the State-owned utility was able to continue operating at full capacity throughout the COVID-19 pandemic.

Australia’s first utility scale solar farm is now four times bigger [09/10/2020]

Australia’s first utility scale solar farm, the 10MW Greenough River solar project near Geraldton in Western Australia, is now operating at four times its original capacity as the finishing touches are put on a long-awaited expansion.

Announcements

WA Government: Warradarge powers up [07/10/2020]

The 180 megawatt Warradarge Wind Farm, near Eneabba, will power up to full capacity with all 51 turbines spinning and generating power by the end of October.

Publications

APA Climate Change Resilience Report [06/10/2020]

Western Power Electricity Licence Reporting Datasheets – NQR Code – 2020 [07/10/2020]

Western Power Electricity Licence Reporting Datasheets – Distribution – 2020 [07/10/2020]

Synergy 2020 Annual Report [08/10/2020]

WA Electricity Industry Weekly News Roundup: 28 September 2020 – 4 October 2020

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Headlines

WA Flexibility Services Pilot cues a 100MW orchestra of DER [28/09/2020]

How to get the gigawatts of distributed solar generation in the WA’s South West Interconnected System to play nicely with the network: Western Power has gathered 100 MW of resource to test its coordinated ability to stabilise the system on low demand days.

Federal Budget: Indigenous jobs to be created in remote WA communities in energy funding boost [01/10/2020]

A Federal Government funding boost to be outlined in next week’s Budget will create jobs and deliver a more reliable and more affordable energy supply to WA’s remote communities.

Large lithium-ion battery to start operating at Kwinana to stabilise WA power system [02/10/2020]

One of the world’s biggest lithium-ion batteries will be operating in Kwinana in two years’ time, under a $100 million public-private sector collaboration unveiled by Synergy today.

Synergy to investigate WA’s biggest battery [02/10/2020]

The state government has announced Synergy will investigate building a 100 MW battery.

Too much of a good thing [02/10/2020]

The WA government needs to protect the state’s power networks, with rooftop PV systems in the crosshairs.

WA plans $100M big battery to balance solar [02/10/2020]

A huge battery in Kwinana will help tame the chaos in the South-West WA power system caused by soaring output from rooftop solar panels and pave the way for more renewable energy.

WA receives $15m for 100MW ‘big battery’ [02/10/2020]

The Morrison government has allocated $15 million towards the building of a 100 megawatt “big battery” in Western Australia.

West Australia to build 100MW big battery – the first on state’s main grid [03/10/2020]

The West Australia government says it plans to build a 100MW big battery with two hours storage to ease the pressure off the state’s ageing coal and gas generators as the share of renewable energy grows.

McGowan announces $600 electricity bill bonus for every WA household [04/10/2020]

Premier Mark McGowan has announced more than a million WA households will receive a $600 credit on their electricity account before their next bill. The $600 credit is fully funded through the recent Bell Group settlement, for the losses incurred in the Bell Group collapse in the early 1990s.

WA households get pre-Christmas boost with $600 power credit from Bell Group settlement [04/10/2020]

Every West Australian household will get a $600 credit, which will not be means tested, on their next power bill with the proceeds of this year’s Bell Group Liquidation.

Announcements

WA Government: Big battery to power 160,000 homes in WA and create 100 local jobs [02/10/2020]

McGowan Government set to construct WA’s biggest battery – the size of 22 tennis courts and will be Australia’s second biggest battery. The 100 MW battery will be located at Synergy’s Kwinana Power Station. Battery will support uptake of renewables and long-term grid stability. Follows $66.3 million package, part of WA Recovery Plan, for clean energy projects.

Every WA household to receive a $600 electricity bill credit [04/10/2020]

Historic $600 one-off WA Household Electricity Credit on electricity bills to be received from November 1, 2020, helping families ahead of Christmas. In total, the average WA household will save $663.52, or 10.4 per cent, on the overall household basket of fees and charges in 2020-21.

Publications

Western Power Annual Reliability and Power Quality Report 2019/20 [01/10/2020]

Western Power Annual Reliability & Power Quality Report 2017-2020 Audit Summary [01/10/2020]

Western Power Annual Performance Report – Metering Code 2019/20 [01/10/2020]

WA Electricity Industry Weekly News Roundup: 21 September 2020 – 27 September 2020

Headlines

WA puts out call to develop 1.5 gigawatt wind and solar hydrogen hub [21/09/2020]

The West Australia government has put out a call for expressions of interest to develop a massive new 1.5GW renewable energy hydrogen hub in an industrial estate some 435kms north of Perth.

WA EPA & industry make real moves to net-zero by 2050 [25/09/2020]

Fortescue and Mitsui appear to have agreed massive emissions cuts with WA’s environmental watchdog that is now looking at Woodside and Chevron LNG projects.

Business customers offered incentives to manage solar, batteries and flexible loads [25/09/2020]

Western Power, the main network owner in Western Australia, is launching a trial this weekend with local businesses to see how incentives can be used to encourage customers to best manage their rooftop solar, battery storage and flexible loads.

Announcements

WA Government: Renewable energy solutions making a difference in Derby [21/09/2020]

$5.2 million in renewable energy upgrades for Derby Hospital and Shire of Derby Upgrade of 827 LED streetlights to reduce local crime by 10 per cent. Another important piece of the State’s transition towards a low carbon future.

Horizon Power: Renewable energy solutions making a difference in Derby [22/09/2020]

Horizon Power is pleased to announce it will deliver $5.2 million worth of renewable energy projects in Derby, which will reduce energy costs and greenhouse gas emissions, as well as help reduce night time crime and traffic incidents through better lighting.

Western Power: Charging up a hotwire [24/09/2020]

At Romina Nicoletti’s farm, keeping the roos out can be a problem if you don’t have power to the hotwires. That problem is about to be solved with Standalone Power Systems.

Synergy: Here’s what the future of solar is looking like for WA [24/09/2020]

While there’s no crystal ball, algorithm or matrix which can show us exactly what the future of energy will look like, we know that WA’s intelligent energy future is already on its way. More and more WA households and businesses are embracing new solutions. We know our collective energy future will be made of smarter, more efficient technology and solutions which adapt to what people need most.

Western Power launches flexibility services trial [25/09/2020]

Western Power, in conjunction with a number of WA business customers, will launch a trial of flexible energy services this weekend (the Flexibility Services Pilot) to learn how commercial and industrial businesses with large distributed energy resources (DER) such as solar PV and batteries, and manageable loads like heating and cooling systems, can be enabled to manage their generated load for a financial incentive.

Publications

Western Power 2020 Annual Report [23/09/2020]

WA Electricity Industry Weekly News Roundup: 14 September 2020 – 20 September 2020

Headlines

A shift to 90 per cent renewables in the West would create 5,000 jobs a year [14/09/2020]

Shifting Western Australia’s main electricity grid to 90 per cent renewables by 2030 is not only technically and economically feasible, but would create thousands of new jobs during an economic slump, a new report has found. The report, put together by Sustainable Energy Now based on data from the Clean Energy Council and the Australian Industry Group, finds that moving W.A.’s South West Interconnected System, or SWIS, to 90% renewables by 2030 would generate 5,000 jobs a year on average.

WA colours in 30 regional school rooftops with PV [14/09/2020]

Call it a school upgrade, a maintenance improvement, a learning opportunity, a right start in life. Western Australia’s Solar Schools Program was launched last week in the Pilbara town of Port Hedland to bring multiple benefits to the quality of student experiences in the state’s regions.

Sun shines on school solar plan [16/09/2020]

Five Hedland schools are set to be transformed into “virtual power plants”, as part of the State government’s $5 million solar schools program for regions.

Wesfarmers LNG arm to power Ora Banda goldmine [17/09/2020]

Ora Banda Mining has signed a long-term agreement with Wesfarmers’ liquefied natural gas business to supply power to the Davyhurst gold mine in Western Australia

South West 90% renewable power job boost plan [18/09/2020]

South West WA could have 5000 jobs a year for a decade in a race to 90% clean energy, according to a study by Sustainable Energy Now.

Announcements

EPWA: WA modern Access Code for Western Australia’s energy transformation [18/09/2020]

The Energy Transformation Taskforce has delivered the largest package of changes to the Electricity Networks Access Code since 2004.

WA Government: New MOUs ensure collaborative pathway for Muja C workers [18/09/2020]

McGowan Government ensuring smooth transition for Collie before Muja C retirement. Synergy and unions sign Memorandums of Understanding to support affected workers 

Publications

WA Electricity Consultative Forum (WAECF) 27 – Meeting Pack [16/09/2020]

WA Government Gazette No. 157 – Electricity Networks Access Code Amendments (No. 2) 2020 [18/09/2020]

WA Electricity Industry Weekly News Roundup: 7 September 2020 – 13 September 2020

Headlines

Joondalup for battery bus trial [08/09/2020]

Electric buses will be operating on Joondalup streets in a trial from early 2022, with buses from Volvo and charging infrastructure provided by ABB.

Green power coming in from the cold [09/09/2020]

A flurry of renewable projects has connected to the grid in recent months, although the pace of development could slow.

Hydrogen hopes on Horizon [09/09/2020]

Hydrogen, batteries, and standalone power systems are a major focus for WA’s regions.

Inside WA’s bet on PowerBanks [12/09/2020]

Western Australia is soaked in sunshine, and PV uptake is challenging the grid. But small numbers of medium-sized community batteries are taking the heat off the system, while helping more people to reap the dividends of rooftop solar PV.

Announcements

WA Government: McGowan Government launches solar schools program for regions [11/09/2020]

30 public schools in remote and regional WA to benefit from Solar Schools Program, with Horizon Power to supply and install rooftop solar systems at the schools.

WA Government: New agreement to supply Port of Esperance [11/09/2020]

Southern Ports Authority signs 20-year power supply agreement with Horizon Power.

Publications

Market Advisory Committee – September Meeting Papers [09/09/2020]

Benchmark Reserve Capacity Price Working Group – August Meeting Minutes [10/09/2020]

Diagnosing Load Flow Convergence Issues

Load flow studies form the basis for the steady-state analysis of power systems and are performed for a wide range of applications from planning to operations. The studies are typically conducted using computer software packages such as PSSE, DIgSILENT PowerFactory, ETAP, PowerWorld and SKM Power*Tools.

The load flow (or power flow) calculation solves for four steady-state electrical quantities (at each bus and branch element):

  • Voltage V at each bus
  • Phase angle Φ at each bus
  • Active power flow P through each branch element
  • Reactive power flow Q through each branch element

We can use these four basic electrical quantities to calculate other quantities of interest, for example:

  • Apparent power S through each branch element
  • Current I flowing through each branch element
  • Loading of branch elements (e.g. transformers, cables, etc) based on continuous and short-term equipment ratings
  • Voltage drop between buses
  • Total system load
  • Total amount of generation dispatched
  • Network losses

These calculated quantities are of interest to electrical network operators and design engineers in order to ensure that the power system operates efficiently and within limits. The rest of this article will talk about the generic structure of a commercial power flow solver / algorithm and how to debug convergence problems.

Algorithm Structure

Power flow solution algorithms are typically comprised of inner and outer loops:

  • The inner loop calculates the main iterations of the solver (e.g. Newton-Raphson, Gauss-Seidel, etc) in order to minimise the power (or current) mismatch equations.
  • The outer loop is used to check and satisfy control conditions (e.g. auto tap changer / shunt control) and limiting behaviour (e.g. generator reactive power limits).

Note that automatic tap or shunt control is sometimes included in the inner loop, but only when continuous tap/shunt steps are used. When automatic tap and shunt control is incorporated in the outer loop, the power flow algorithm will attempt to switch the positions of the taps and shunts at the end of every inner loop iteration to satisfy the control conditions (e.g. bus voltage or branch power flow setpoints).

Diagnosing Convergence Issues

When a load flow fails to converge, the first step to diagnosing the problem is to identify whether the algorithm has failed in the inner or outer loop.

An inner loop problem signifies that the Newton-Raphson equations could not be solved, which could be due to ill-conditioning, voltage stability issues, etc. This usually results in a program error message stating that the algorithm has either diverged or stagnated.

Inner loop problem (from DIgSILENT PowerFactory)

On the other hand, when the problem is in the outer loop, the Newton-Raphson equations can be solved, but control conditions can’t be met (e.g. voltage setpoint could not be reached with transformer taps at maximum / minimum settings or are hunting between two tap steps). Typically, a maximum number of outer loop iterations must be reached before an error is reported by the program.

Outer loop problem (from DIgSILENT PowerFactory)

Tackling Inner Loop Problems

As mentioned earlier, inner loop problems suggest that the system is ill-conditioned and the Newton-Raphson algorithm either diverges or is stuck in a local minimum (i.e. stagnated). Mismatches in generation, poor distribution of generator dispatch and local voltage stability issues are among the common causes for an inner loop problem:

  • Mismatches in generation and load: when there is a large mismatch in generation and load (i.e. over- or under-generation), the discrepancy in active power has to be supplied or absorbed by the slack element. Depending on the location of the slack element, this can lead to large power flows from one part of the network to another, which can cause imbalances in the voltage profile and lead to convergence problems.
  • Distribution of generator dispatch: similar to mismatches in generation, poor distribution of dispatched generation can lead to large unwanted power flows from one part of the network to another.
  • Local voltage stability: relates to busbars reaching the nose point of the PV curve (voltage collapse). This could be very localised due to large loads placed at weak radial parts of the network without sufficient reactive compensation, or could affect larger areas where multiple buses have depressed voltages.

Some approaches to resolving inner loop problems are as follows:

  • Turn off enforce reactive power limits option: most programs have an option to limit the reactive power output of PV buses (generators, SVCs, etc) so that they are within their reactive power capability curves. When a PV bus reaches limits, it is converted to a PQ bus in the outer loop with the reactive power set to its limits and the inner loop is run again, which can then fail due to voltage stability reasons (i.e. the PV bus is supporting the local voltage, but with limits enforced, voltages can go wild). Turning this option off can help diagnose which generators, SVCs, etc are supplying / absorbing large amounts of reactive power and their associated problem buses.
  • Change the location of the slack element and distribute generator dispatch: so that there are more balanced flows through the network. Some programs have a distributed slack bus option that automatically caters for mismatches in generation by distributing the slack across all in-service generators according to their nominal ratings.
  • Switch in or add shunt compensation: in order to support weak buses that may have voltage stability problems.

Tackling Outer Loop Problems

Outer loop problems are normally associated with voltage control issues from the following elements:

  • Generators – reaching their reactive power capability limits
  • SVCs – reaching their reactive power capability limits
  • Transformer automatic tap changers – reaching maximum tap settings without satisfying voltage setpoint tolerances
  • Shunt controllers – reaching maximum shunt steps without satisfying voltage setpoint tolerances

Some approaches to resolving outer loop problems are as follows:

  • Increase the maximum number of outer loop iterations: particularly for larger systems, the outer loop solution may take many iterations.
  • Change voltage control setpoints and tolerances: the bus voltage setpoints and tolerances can be adjusted to help the solution along.
  • Lock taps and/or shunts: automatic transformer tap and shunt adjustment options can be de-selected to lock the taps and shunts at their initial positions.
  • Reset taps and/or shunts: the initial tap and shunt positions may not be well configured for the particular scenario. Reset tap positions by setting all transformers to neutral tap and re-configure initial shunt positions to better control system voltages (e.g. if you know that a bus has a low voltage, put some capacitors in service).

Importance of Inertia in Island Power Systems

The accurate modelling of inertia in an islanded power system is crucial when attempting to integrate low or inertia-less generation into the network, particularly those from intermittent sources, e.g. solar PV, converter-fed wind turbines, etc.

In the context of synchronous generators, the term “inertia” generally refers to the kinetic energy in the rotating mass of a generator shaft. The inertia depends on the speed of rotation and mass of the shaft, i.e. the heavier the shaft and faster the rotational speed, the higher the inertia. Under normal operation, the instant a new load is applied to the system, rotational energy (inertia) is converted into electrical energy to supply the load. As energy is removed from the system to supply the load, the speed of rotation (or frequency) decreases. This is commonly referred to as the inertial response and occurs before primary frequency control actions (e.g. from governors) take place. As a result, inertia has a direct impact on transient frequency deviations resulting from sudden changes in generation and load.

Effects of varying inertia on system frequency

In large interconnected systems, these frequency deviations are minor since the instantaneous mismatches in generation and load are very small relative to the amount of synchronous generation dispatched. However, in small island systems, these frequency deviations are much more significant and can even lead to frequency collapse.

By virtue of their remoteness and lack of other resources, the small island power systems that are normally found in island nations and archipelagos typically have high penetration of diesel engine generation. As diesel engines generally have low inertia, the inertia constants selected during system modelling can have a large effect on frequency swings. For example, consider the load acceptance (25% load step event) of a 1.5MVA diesel generator with varying inertia constants:

The simulations show that maximum frequency swings can vary from 1.235Hz up to 3.548Hz depending on the inertia constant selected.

Small power systems are usually equipped with under-frequency load shedding (UFLS) systems to prevent network collapse during frequency swings and active power deficit events (e.g. trip of generator). Integrating inertia-less sources such as solar PV plants would displace synchronous generation and thus reduce the total inertia in the system. Grid simulation studies are performed to predict whether or not the UFLS system is at risk of operating during normal day-to-day fluctuations of the solar PV system, and this requires fairly accurate modelling of the system inertia.

Selecting appropriate inertia values

Generator inertia values are usually found in vendor / manufacturer data sheets and are often expressed as a moment of inertia quantity (e.g. in kg.m2 or slug.ft2). While some software packages can accept these quantities directly as inputs, other programs require that they are converted into per-unit inertia constants (H).

In some cases, particularly in older systems or networks with temporary generators, the inertia data is not available and must be estimated. Based on our database of actual equipment data, the following inertia values can be used as guidance:

New electricity business models: Local distribution cooperatives as market participants

Transmission and distribution networks are natural monopolies and in Australia (as in most other countries), they were once part of vertically integrated corporations comprising either the complete or significant portions of the electricity supply chain (e.g. the state electricity commissions). During the industry restructure of the mid-1990s, these corporations were broken up so that in each state, there was a single monopoly transmission company (e.g. TransGrid, Western Power, PowerLink, Electranet, etc) and one or more geographically-focused distribution companies (e.g. Ausgrid, Ergon, Citipower, etc).

Despite the unbundling process, the network businesses are still relatively large in scale, with approximately 550,000 km of poles and wires shared between just 18 network companies in the National Electricity Market (NEM). In particular, distribution companies can own assets from sub-transmission level (e.g. 132kV) all the way to the 240V meter box at a residential premises.

Thus a natural question to ask is – can present-day distribution network service providers (DNSPs) be further unbundled?

Local distribution cooperatives

One possibility is for cooperatives in a localised geographical area (e.g. a suburb or housing estate) to acquire ownership of the low voltage distribution assets in the area, connect to the distribution network at one or two points as a major customer (e.g. at kiosk substations) and participate directly in the wholesale electricity market as a single coordinated entity.

Source: Identicoin

Such a local distribution cooperative could be a microgrid with a mix of its own distributed generation and storage, or it could simply be a consumer aggregating the households in the area (e.g. Virtual Power Plant). However, to get the most out of participating in the electricity market, the cooperative needs to have some level of controllability. What this could mean in practice is an energy management system that can control discretionary household loads (such as hot water heaters, air conditioner thermostat settings, swimming pool pumps, washing machines, etc), as well as generation and storage resources, in order to optimise the kWh price on the spot market for the whole cooperative.

For example, when the spot price is high due to peak loading or a binding network constraint, the energy management system can control discretionary loads, generation and storage to either limit energy purchases or sell energy back to the market (and vice versa when spot prices are low).

The cooperative itself could be run like a body corporate or owners corporation, with a professional management company appointed to maintain and manage the local distribution assets (e.g. poles, lines, energy management system, etc) on behalf of the owners. The cooperative acts like a micro-retailer and the owners simply pay an equivalent electricity tariff to maintain the system. In some circumstances, the cooperative could even pay out a dividend from profits made trading on the wholesale electricity market.

Transferring ownership

A looming obstacle for local distribution cooperatives will be convincing (or coercing) DNSPs to sell / transfer their assets to a cooperative. Under the current regulatory scheme, networks are paid a guaranteed return on their regulated asset base (RAB), and this of course gives DNSPs very little incentive to reduce the size of their RAB.

In the United States, the recent track record for municipalising electric utilities has been mixed. In some cases, local municipalities were able to negotiate the purchase of utility assets without much pushback from the incumbent utility business, typically when the incumbent saw strategic gains from pulling out of the area. In other cases, there was significant resistance from the incumbent to municipalisation proposals and negotiations were difficult and acrimonious.

However, there is a case to be made that micro-scale municipalisation proposals like local distribution cooperatives could face less resistance since the value of the assets are relatively low.

A new role for DNSPs

If local distribution cooperatives were to emerge as viable businesses, this could signal a trend towards a widely distributed ownership of electricity network assets. Micro-scale networks owned and operated by the locals who live there would change the landscape of the electricity supply industry. Where present day DNSPs have to plan and optimise a network across large geographic areas, the local distribution cooperatives only need to worry about their own small sections of the grid. The role of DNSPs would be more akin to what transmission networks are now – a backbone for the bulk supply of power to the local networks. Two or more cooperatives could potentially build private interconnections between each other’s networks, bypassing the DNSP altogether.

Moreover, there is the possibility that local distribution cooperatives can negotiate their own terms of connection to the DNSP, for example, customising the trade-off between network reliability and use of service charges. Of course, such provisions would necessitate a fairly significant change in the rules by the AEMC, but it has the potential to give more choice and responsibility to end-users regarding their own electricity supply and how they choose to manage risks and resources.