Optimal Droop Settings of Smart Inverters

In active distribution grids, smart inverters (SI) can provide grid support functionalities through the control of active and reactive power. However, SIs operate based on droops as per the IEEE-1547; therefore, the dispatch setpoints obtained from the distribution grid optimal power (DOPF) models should lie on SIs’ droops and abide by the IEEE-1547. Moreover, instead of following rule-based methods or arbitrarily selected settings, the SI settings have to be optimally configured in order to enhance the network performance. The objective of this work is to obtain optimal droop settings of SIs using DOPF formulation for Volt-VAr and Volt-Watt grid-support functions. The non-convexity of the DOPF model as well as the inclusion of droops as constraints into the DOPF model makes this a computationally challenging problem to solve. The problem is formulated as a nonlinear programming problem to minimize the total system losses and voltage deviation. The efficacy of the model is validated on the IEEE 123-node feeder with 15 photovoltaic systems. Case studies demonstrate that optimal SI settings can improve grid performance compared to the recommended default settings.