Synchronous condensers are applying a proven century-old technology to support current operations and the transition to the power system of the future.
In a traditional synchronous generator, energy is transmitted to the power system by the rotation of a huge shaft, spinning at its nominal speed and synchronised to the power system’s frequency. So it can operate, a synchronous generator needs a steady supply of fuel such as coal, gas, diesel or water for hydro generation.
Synchronous generation technology, which is coupled electromagnetically to the network via the rotating shaft, provides the system with energy and also has inherent characteristics that support system strength, inertia and voltage control.
Much new renewable generation, however, connects to the system in a different way, via power electronics. Without the synchronous connection, the power system can experience reduced system strength in some parts of the network (making it less able to respond effectively to disturbances). Frequency and voltage can also become harder to control, and control systems rely on reference signals provided by fewer and fewer synchronous machines to operate stably.
To address these challenges, the power system requires essential services from other sources. A synchronous condenser is one of the options being used to achieve that.
This large machine has a spinning shaft, electromechanically coupled to the grid, and it can boost system strength and assist with voltage control and inertia, similar in many ways to a synchronous generator. Unlike a synchronous generator, though, it doesn’t produce energy, nor – once it has been kick-started and synchronised to the grid – does it need fuel to operate.
Widely used to help regulate voltage when electrical networks were first built in the early 1900s, synchronous condensers have been updated and are enjoying a revival. They help with reactive power needs, increasing short-circuit levels and system inertia, and assuring better dynamic voltage recovery after severe system faults in parts of networks where synchronous generation is not present or no longer provides this support. They’re also less expensive than building synchronous generation.
In Australia’s National Electricity Market (NEM), synchronous condensers have or will be installed in many places to increase system strength, especially in areas where new renewable generation is being connected and/or built a long distance from the nearest synchronous generation or large centre of demand (such as cities and large industry).
Some synchronous condensers have been or are being installed by the owners of transmission networks. In South Australia, ElectraNet will install four synchronous condensers in 2020 to help maintain system strength across the state.
Other synchronous condensers have been or are being installed by the owners of new generators, to boost system strength in their local area and help remediate the network impact of their new connections. While these machines generally tend to be smaller than transmission-connected synchronous condensers, they are getting larger – like the 190 megavolt amperes (MVA) machine being installed at the Kiamal 200 megawatt (MW) Solar Farm project in Victoria.
This isn’t the first renewable generation project in the NEM to add a synchronous condenser – for example, Musselroe Wind Farm in Tasmania has two small synchronous condensers. There are also a number of generators that can operate in ‘synchronous condenser mode’ by decoupling the generator shaft. At present there are no synchronous condensers operating in Western Australia’s South West integrated system (SWIS).
Synchronous condensers have their own limitations and aren’t the only option available to keep the system operating securely. New technologies, such as grid-forming devices (grid formation refers to the system’s ability to set and maintain frequency), are in operation and constantly being further developed as the power system continues its global transition to renewable. The recently commissioned Dalrymple ESCRI-SA battery project is an example of this technology.
Renewable generators are also increasingly finding ways to provide additional services to support the power system.
But synchronous condensers are part of the picture, and it’s encouraging to see that even amid the rapid transformation underway in our power system that there’s still a place for an old-fashioned engineering solution!*As the system and market operator, we are fuel and technology neutral. The products, services and providers in this content are for illustrative purposes only and are not endorsed by AEMO.