A new joint working group between A1 (Rotating Machines) and C4 (System Technical Performance) on the use of Synchronous Condensers in power systems with a predominance of low or zero inertia generators has just been initiated. The objective of the working group is to produce an application guide dealing with rotating machine and power system issues for synchronous condensers.
This is a topic that is very relevant to the Australian power industry. For example, in South Australia, with the high level of wind and solar generation combined with the decommissioning of the coal fired Northern Power Station, AEMO studies have shown that the power system has low levels of inertia and fault levels, which can adversely affect its operation. Installation of Synchronous Condensers to provide inertia and improve fault levels is now being considered. Similar problems are starting to appear in other parts of Australia.
As part of carbon emission reduction mechanisms, many countries have adopted policies to increase the installed capacity of renewable generation, based on Solar and Wind technologies, to either supplement or replace existing thermal generation. These have been deployed en-masse at both transmission and distribution voltage levels.
The displacement of traditional synchronous machines with various forms of power electronic (PE) interfaced energy sources is contributing to fundamental changes in power system steady-state and dynamic behaviour, including:
Significant reductions in system inertia will impact network frequency control capability including observable rates of change of frequency following credible and non-credible contingency events. At low inertia levels, there is likely to be a need to increase and possibly improve primary frequency control capabilities. The ability of under frequency load shedding and/or over frequency generation shedding schemes to operate correctly following non-credible events is also likely to be impeded if ‘minimum’ levels of inertia are not maintained.
An inability to maintain adequate ‘system strength’ will have multiple negative impacts on the power system including:
One mitigation strategy is the use of synchronous condensers, which can address many of the issues outlined above as well as provide significant reactive power contributions. Modern design of synchronous condensers can be optimised to address a select or broad range of network needs. However, ‘off the shelf designs’ may not be sufficient to address specific network issues. When considering the synchronous condenser solution, it is important to understand what is technically possible as well as the trade-offs that may be present in the design and construction of plant, including the corresponding cost impacts.
The Terms of Reference for this WG can be downloaded HERE.