South Australia currently has the highest penetration of residential rooftop PV of all the NEM regions and capacity continues to grow strongly, with the rate of applications for new rooftop PV systems in the mid-sized (30 – 200kW) commercial sector tripling from 2016 to 2017.
The market for residential battery storage is also starting to accelerate with several Government schemes that could see up to 90,000 new batteries with up to 400MW of controllable storage connected to the SA distribution network within the next 5 years.
As the power system was never designed to accommodate the significant reverse power flows that results from high penetrations of DER, network operators are facing escalating challenges meeting customer expectations and ensuring the network remains within its technical operating limits.
In the face of these challenges, SA Power Networks sought to develop new capabilities that would permit the efficient integration of these new resources while maintaining network security, reliability and quality of supply.
SA Power Networks, working with consultants EA Technology, developed the LV Management Strategy. The piece of work involved categorising each of the 77,000 LV circuits in the network into prototypical circuits, conducting power flow simulations on representative circuits to determine hosting capacity and then entering them in a complex techno-economic model to determine the optimal solutions.
A key innovation was a comparison of three distinct strategic options for managing DER integration:
1. Augmentation: upgrade the network to resolve the capacity constraint
2. Static limit: limit the application of new DER on constrained networks
3. Dynamic management: actively manage DER operating limits only when the network is constrained
Today’s approach, which is to allow any rooftop PV system to connect that has a maximum export power of 5kW, is not sustainable, or at least not without significant new investment in network infrastructure. Hosting capacity limits are already being exceeded in some areas of our network and by 2025, if no action is taken, voltage limit exceedances are expected to be widespread in most of our network types.
The modelling suggests that dynamic management of DER will provide the optimal solution, allowing significant additional DER to connect while only limiting exports a small percentage of the year. To do this SAPN will need to develop new capabilities to accurately model and monitor the LV network, calculate time varying export limits and develop new standard interfaces (APIs) to communicate the operating envelopes.