By Phil Kreveld
The Australian Energy Market Operator (AEMO) is seriously worried—worried about the loss of inertia—worried about the loss of system strength—worried about operating the NEM grid with little or no synchronous generation.
Publicly, AEMO is restrained in its commentary—as is to be expected. Confidence in the electricity system is important—important to participants in the market—important to the Commonwealth Government. For the Opposition, stirring the pot seems to be its main business.
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Technical problems—the ones AEMO is concerned about, in essence the replacement of synchronous generation with asynchronous generation—are given the ‘silver bullet treatment’. For example, ‘don’t get rid of coal’, ‘put in small nuclear reactors’ comments pepper the media—all suitable ‘wedging’ at the political level but dangerous distractions from what is urgently required—strong, engineering-directed solutions to:
- preventing voltage collapse
- allowing regions to operate as self-sustaining islands
- restarting after blackouts, when synchronous generators are ‘history’.
Meanwhile social licence isn’t forthcoming for new transmission line projects and the gravity of the delays combined with investors switching out of CO2 belching clunkers is potentially setting us up for serious grid failures. Potentially, because somehow that probably won’t happen. More likely we will muddle through with power demand restrictions, more market interventions by AEMO, a slowing in project completions and abandonment of projects. And a revival of climate wars, because we should really accept that we cannot meet the renewable target of 82% renewables by 2030! We should switch our attention to the above threesome of serious issues—by examining what engineering need be done to address each one. Right now, that is made really tough because we lack a central, coordinated authority to implement an all-encompassing, engineering plan.
Posturing over progress in technology terms has us facing a ‘con’—an ‘asynchronous con’. It involves populating the grid with synchronous condensers! South Australia started the fashion and we are led to believe that battery ‘firming’ plus 40 or so syncons will ‘hold op the sky’. There is just one niggly issue: some stable voltage and frequency source (or two or three or more, etc.) better be permanently available because no one has figured out in practical terms how to run an extensive radial grid, the size of Australia’s with only inverter-based generation. South Australia is a good example because if it weren’t for the Heywood interconnector and the planned Energy Connect link (pumping synchronous power from Victoria and New South Wales), there would be a shortfall in keeping SA’s syncons running and all those domestic solar inverters. Remember November 16, last year when the Heywood connection was lost when domestic solar inverters had to be switched off in order to preserve network frequency stability.
The recently held international CIGRE meetings in Cairns (4-7 September) illustrate the ‘energy band gap’ between electrical engineering and the energy ‘meddlers’ (for want of a better word). The latter are ‘designing’ Australia’s electricity grid in the full confidence that an engineering team will clean up after them with the proverbial brush and pan. Our problem is that there is no such engineering team—instead we have engineering siloes who painfully communicate via ‘legalled’ (commercial in confidence) routes and long-winded, very complicated generator connection approvals.
Let’s review a few engineering aspects that should be solved on a ‘whole of network’ basis. Transmission lines in existence, and those being planned will have battery energy storage system-inverter based resources connected to sending and receiving buses. Voltage stability will depend critically on power flow-voltage curves (P-V) and which are in turn dependent on the actual voltages at the buses. AEMO has some control over network design in Victoria but nowhere else. The nature of the IBR (PLL-based or droop-controlled), the BESS rating, whether charging or discharging, should be considered on as near a complete system basis as possible. Instead, a piecemeal approach is adopted, using AEMO 4.6.6 connection requirements.
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Self-sustaining islands and cranking path design are two areas urgently requiring whole of system design and the specification of geographical distribution of generator capacities. This will certainly require the retainment of synchronous capacity and the conversion of existing synchronous machines into clutched ones, capable of conversion from generator to synchronous condenser operation.
We should cease being conned, and accept that national grid security and stability is too important to make it subservient to climate targets. A wholistic approach, at a detailed engineering level, is urgently required. There are no easy fixes, and not enough syncons available within the time required for the 82% renewable target projected to 2030.
There is no time to be wasted.
