SA Power Network flexible export limit and how it affects SmartShift™ curtailment

1. What are the SAPN flex export limits?

SA Power Networks (SAPN) uses flexible export limits to manage how much solar can be exported to the grid based on real-time grid capacity. These dynamic limits are communicated directly to your inverter, which means the amount of energy you’re allowed to export can change throughout the day (e.g. from 1.5kW to 4.5kW), depending on grid conditions.

If you have a Sungrow, Fronius or AlphaESS system, the inverter receives these commands directly from SAPN and for the time being is prioritising them above any other control systems - including Amber’s SmartShift™ automation and manual controls.

2. What does this mean for SmartShift™ curtailment?

You may have observed irregular curtailment behaviour in the past few weeks leading to some exports during times of negative Feed-in tariffs (FiT). The reason for this is that the Amber SmartShift curtailment commands are at times overwritten by the network's flexible export limits. This is because your inverter is directly connected to the SAPN export limit server, so the kW (rate of energy) limit set by the network will take priority over the Amber curtailment command. 

In more detail, while we're sending a command for the site exports to be set to 0kW during negative FiT to stop any exports to the grid, SAPN will send a command to set the site exports to match the SA grid’s capacity to take on solar power at that time (e.g. 4.5kW). This dynamic export limit takes priority over the Amber control in the Fronius inverter command structure. The site exports will revert back to the SAPN dynamic export limit which can lead to spillovers to the grid if their command is set above 0kW. 

For example this is what happens during SAPN flexible export periods with negative pricing:

1. Amber send 0kW export limit
2. SAPN send 0.5kW export limit
3. Inverter adheres to SAPN export limit so will be leaking 0.5kW to the grid during negative FiT

3. What is being done to solve this issue?

We've been liaising with our partners at Sungrow, Fronius and AlphaEss on fixing this issue but they've advised this will require development work on their end to adjust the inverter’s command response. At this stage, they don't have a clear timeline for when this can be completed. While their team works on this update, unfortunately, there is no workaround on the Amber side, so you may experience some exporting during negative FiT.

We're sorry for any inconvenience the irregular curtailment behaviour is causing. In the meantime, please feel free to check out this explainer on: Managing times when wholesale FiT turns negative.

If you have further questions, please reach out to our support team.