Synchronous Condensers: One Tool to help powering Australia's Renewable Future

The following article has been produced by Fabian Spescha from Australian Panel A1 who was an Australian member of a Joint Working Group (JWG) A1/C4.66 which has produced Technical Brochure (TB) 885, “A guide on the assessment, specification and design of synchronous condensers for power systems with a predominance of low or zero inertia generators”. The article illustrates the importance of this topic in relation to power systems in Australia and the energy transition.  The JWG also had members from Australian Panel C4, Lingxiao Situ who was the secretary of the WG, and Peter Wiehe.

With Australia leading the charge in renewable energy integration over a vast geographical area with a low population density, ensuring grid stability and security becomes paramount. In order to help accelerate the change, synchronous condensers (SC’s) are a fundamental tool in the toolbox of developers, regulators and service providers and emerge as a key facilitator of the transition to a cleaner energy system.

What are Synchronous Condensers?

Think of SC’s as giant spinning machines, similar to traditional generators, but without directly producing electricity. Instead, they act as grid guardians or ankers, injecting or absorbing reactive power to maintain voltage stability and improve system strength. This stability is crucial for inverter-based renewables like solar and wind, which are predominantly grid-following and can be highly variable and unpredictable.

Current Use in Australia:

Australia has been at the forefront of renewable integration and to a certain extent installation of SC’s, particularly in South Australia. Facing grid instability due to conventional plant closures and a high uptake of inverter-based renewables, ElectraNet installed four large SCs with flywheels in 2021 at Robertstown and Davenport. These "spinning reserves" provide crucial support, allowing for higher penetration of renewables without compromising reliability and the need to direct conventional generators to come online for grid stabilisation purposes. Furthermore, with the recent updates to the System Strength Framework in mid-2023 and the introduction of System Strength obligations, Network Service Providers and developers are considering SC’s as one of the technologies to either remediate potential System Strength Charges or to provide System Strength Services for the benefit of the grid.

Benefits for Renewables:

SC’s offer several advantages for integrating renewables:

• Voltage Regulation: They provide reactive power, essential for maintaining stable voltage levels when renewable generation fluctuates.
• Improved System Strength: SC’s mimic the inertia of traditional generators, ensuring the grid remains stable during sudden changes in power flow.
• Transmission Congestion Relief: By managing reactive power flow, SC’s can optimize transmission lines, allowing for more renewable energy to be delivered.

Future Potential:

The future for SC’s in Australia is multifaceted:

• Repurposing Generators: Research is investigating the repurposing of existing coal or gas generators as SC’s, leveraging existing infrastructure and providing a faster, cheaper solution for renewable transition.
• Strategic Placement: Targeted placement of greenfield SC installations across the National Electricity Market can maximize their impact on grid stability and support further renewable expansion.
• Advanced Technologies: Development of smaller, modular SC’s could offer flexible solutions for specific grid challenges and distributed renewable generation.

Challenges and Considerations:

While promising, SC’s also come with certain challenges:

• Cost: Compared to some renewable technologies, SC’s can be expensive to install and maintain.
• Environmental Impact: Their reliance on traditional generators raises concerns about emissions, though repurposing existing infrastructure could mitigate this.
• Long-term Role: As battery energy storage system (BESS) technologies advance very rapidly, especially with the introduction of grid-forming BESS, the long-term need for SC’s might need re-evaluation.

Conclusion:

Synchronous condensers are playing a vital role in enabling Australia's renewable energy transition. Their ability to stabilize the grid, improve system strength, and facilitate higher renewable penetration makes them invaluable tools in the toolbox of a power system engineer. While challenges exist, ongoing research and innovation, along with strategic investments, can ensure SC’s continue to be a key player in powering a clean and reliable future for Australia. 

A detailed guide to the use of synchronous condensers, including a number of case studies from around the world is provided in TB 885.  It is free to members of CIGRE and 220€ for non-members.