Managing residential prosumers using operating envelopes: An Australian case study

The volume of system-level services procured from aggregators that manage residential prosumers, i.e., consumers with distributed energy resources (DER) such as solar photovoltaic (PV) and batteries, has been increasing over the past few years. Due to the relative scarcity of residential prosumers in the portfolio of aggregators today, the distribution network can handle the resulting power flows. However, with the rising adoption of DER and the willingness of prosumers to engage with aggregators, the volume of services is expected to increase even further. Consequently, distribution companies will soon have to start imposing restrictions on aggregators so that the voltage and thermal constraints of distribution networks, particularly at the low voltage (LV) level, are not violated.

To incorporate distribution network constraints in the operation of aggregators, this paper proposes an architecture which uses day-ahead, time-varying export limits (henceforth referred to as “operating envelopes”) for aggregator-managed prosumers. Using information such as the inverter capacity at each household, household demand forecasts, and network information (i.e., topology, impedances and phase connections), the distribution company first determines the maximum feasible exports for each time period in the day-ahead timeframe. The maximum feasible exports for each time period are then combined (for all time periods) to create the day-ahead operating envelope at the connection point of each prosumer. The distribution company then provides the aggregator with the operating envelope for each prosumer in the aggregator’s portfolio, allowing the aggregator to incorporate distributing network constraints when performing their corresponding optimization of the controllable DER.

A real Australian LV network from Victoria with 465 single-phase customers is used as a case study. Operating envelopes are calculated by solving a convex, three-phase AC optimal power flow (OPF) with the objective of maximising the aggregated exports. Economic assessments are also carried out to quantify the benefits that the proposed approach brings when compared with the currently enforced firm 5kW export limit per phase in Australia. The results demonstrate that the use of operating envelopes can be effective in facilitating the provision of services whilst satisfying network constraints. Furthermore, the proposed approach brings substantial benefits to prosumers when compared with the current practice (5kW export limit). Moreover, the proposed architecture better aligns with current regulation in Australia (and many countries around the world) where distribution companies and aggregators are separate entities with different roles, i.e., the distribution company is responsible for managing the network assets while the aggregator is responsible for managing prosumers’ DER.