New constraints imposed to cover for sudden loss of rooftop solar PV

The Australian Energy Market Operator has introduced new “contingency” constraints on power flows from Victoria to South Australia to cover what it says is the risk of a large gas generator in Adelaide tripping off, and then having a contagion effect on rooftop solar in the state.

The new constraint effectively means that capacity that can be exported from Victoria to South Australia is reduced by up to 180MW – depending on the time of day and amount of solar generation – to allow for a quick response as a back-up should the modelled impact on rooftop solar PV in South Australia actually occur.

South Australia has one of the highest penetrations of rooftop solar in Australia and the world, with more than 1,100MW of installed capacity – still growing rapidly. It has contributed up to 64 per cent of instaneous underlying demand, and contributed 12 per cent of the overall generation over the last year.

However, AEMO and the local transmission company ElectraNet say they are worried about what will happen to rooftop solar systems should a large generator trip, and provoke voltage issues with the solar inverters, and say it needs to be addressed.

“AEMO and Electranet have analysed the impact of a trip of a large generator on subsequent rooftop PV disconnection,” the market operator said in a market notice published on Friday morning.

“This analysis indicated that up to an additional 180MW of generation may be lost (net result of PV and load loss across the SA region) following the loss of the largest generator in the Adelaide metro area.

“As such the contingency size in the constraint equations for Victoria to South Australia power flow will increase by up to 180MW, dependent on PV output at the time (considering field measurements from SA solar plants), to model the possible PV tripping during daylight hours.”

The move is part of a series of initiatives being taken around the grid, including the upgrading of solar inverter standards in Western Australia and the launch of a distributed energy roadmap, and efforts in the main grid to gain more “visibility” and “control” over rooftop solar to help the operator manage a distributed energy resource that could account for nearly half of total demand within a few decades.