Maximising Distributed Energy Resources using State Estimation

MAXIMISING DISTRIBUTED ENERGY RESOURCES

USING STATE ESTIMATION

by Energy Queensland Every Australian state has a net zero emissions target by 2050 and the rapid growth of rooftop solar is creating a range of challenges for the distribution networks.

Energy Queensland has a number of strategies and technology solutions to meet these challenges and it sees existing poles and wires being a critical enabler of a distributed energy future, where distribution networks enabled by new technology are the platform for sharing solar generated electricity and batteries, and also enabling the electrification of transport.

Part of the solution has come from a project led by engineers from Energy Queensland’s Ergon Energy Network and Energex, and software company GridQube.

They have developed a powerful tool that enables the network to generate an accurate picture of real-time operation from limited data.

Using this information, networks can interact with customers or aggregators to communicate additional opportunities for export or charging for Distributed Energy Resources (DER) such as rooftop solar or batteries.

It’s been recognised as a game changer for the industry and won the Energy Networks Australia 2021 Industry Innovation Award.

The tool analyses the two-way flow of electricity on the network and determines optimal ranges for export or import at a customer connection point such that DER operation remains within network limits.

Energex and Ergon Energy Senior Technology Development Engineer, Terese Milford, said the power flowing through the grid changes every minute of every day depending on how much energy people are using or generating.

“We’re aiming to offer customers a dynamic connection that will support greater installation of renewables, batteries and electric vehicles for customers wanting them without putting excessive pressure on the network,” Ms Milford said.

“Customers can choose their own individualised experience. At times, customers will export surplus power to the grid. At other times, customers will benefit from using the power they generate within their home or business to charge an electric vehicle or run the washing machine. This will become set and forget based on a customer’s energy preferences.

“It’s a paradigm shift from the existing approach of fixed export limits, unlocking network capacity where and when it’s available.”

DYNAMIC CONNECTION AGREEMENTS

Ergon and Energex have been working towards this objective for some time. In December 2020, a consultation paper was released

EQL TEAM MEMBERS (L – R) GREG MARTIN (RENEWABLE ENERGY & DEMAND MANAGEMENT CONSULTANT), TIM LEWSEY (MANAGER INTELLIGENT GRID ENABLEMENT) EGM ENGINEERING PETER PRICE, TERESE MILFORD (SENIOR FUTURE TECHNOLOGY DEVELOPMENT ENGINEER) AND PETER KILBY (SENIOR GRID TRANSFORMATION ENGINEER).

titled Enabling Dynamic Customer Connections for DER, to engage with industry on the concept of dynamic connection agreements and the corresponding interoperability requirements for small scale DER to ensure inverter manufacturers and installers design systems with compatible communication standards.

“A case study was simultaneously developed by directly engaging with recently connected customers with zero export agreements, to help us understand any constraining circumstances and limitations to offering them a future dynamic connection agreement,” Ms Milford said.

“We confirmed that without state estimation, DOEs would largely need to be conservatively based on zone substation telemetry, given the relatively low penetration of downstream monitoring.”

The innovative solution provides network visibility by cost-effectively avoiding extensive physical monitoring, an important advance on previous system demonstrations that required actively monitored distribution transformers. It also delivers the means to manage DER via DOEs with the flexibility to execute various optimisation strategies.

Energy Queensland’s production-ready system performs a comprehensive near real-time assessment of the local network via state estimation, evaluating network voltages and available capacity, and computes an optimal operating envelope for each customer connection point which is published securely via the internet. Customers' systems receive the signal and then choose how their site responds to ensure operation within the envelope.

GridQube’s capacity constrained optimisation (CCO) technology allows the transition from a basic rules-based DOE to a more advanced approach, translating the gap between current network state and network technical limits to the amount of additional export/import the network can accommodate.

Additional capacity can be allocated to customers as a DOE with no further coordination required between parties. Networks can avoid sub-optimal augmentation as power quality and capacity issues can be successfully managed, despite an ever-increasing output from distributed renewables.

“This has enormous potential to improve the affordability, reliability and sustainability of the energy system,” Ms Milford said.

ENABLING TWO-WAY ENERGY FLOWS

The technology is currently being trialled across a small number of sites in south-east Queensland with a goal of making it available for customers with larger or more complex systems in late 2022.

Ergon Energy Network and Energex recently published a follow-up consultation, Enabling Dynamic Customer Connections for Distributed Energy Resources, on their Talking Energy webpage. This engagement will support the forthcoming dynamic standards for small inverter energy systems and low voltage embedded generation. Standards are critical to ensure the customer-side installations can correctly connect to, and interface with, the distribution network and benefit from a dynamic connection approach.

“Our work is currently focused on using these advanced analytics tools as a more reliable, scalable, equitable and economical means to increase network-connected DER,” Ms Milford said.

“However, there is immense scope for networks to employ these analytical capabilities to improve and automate other parts of their businesses to reduce costs.

“We’re able to run scenario analyses to quantify additional DER hosting capacity opportunities associated with network augmentations.

“We can also use detailed historical asset performance data for asset lifecycle modelling, automate planning processes and support targeted demand management programs.

“Reducing network costs benefits all customers and that’s a really important part of what Energy Queensland is striving for – to enable two-way energy flows on the network and energise Queensland communities with safe, reliable and affordable electricity.”

IMPROVED OUTCOMES FOR ENERGY NETWORK CUSTOMERS INCLUDE: • Potential for additional revenue from solar exports and connection of larger systems • Reduced network expenditure required to manage DER impacts • Efficient network augmentation gained by understanding binding network constraints and quantifying benefits of standard mitigation actions through simulations • Increased network utilisation and renewable generation connected • Improved power quality – managing solar to mitigate high voltages • Improved equity – network capacity shared so end-of-line customers don’t bear as much potential curtailment from inverter response modes • Displacement of higher cost fossil fuel generation by renewables