Distribution Grid Optimal Power Flow with Volt-VAr and Volt-Watt Settings of Smart Inverters

High penetration of photovoltaic generators in active distribution networks (ADNs) causes overvoltage due to reverse power flow. Smart inverter (SI) functionalities can be configured to provide efficient voltage regulation and reactive power support in ADNs. Distribution grid optimal power flow (DOPF)-based models are typically employed to obtain setpoints of inverters and/or legacy control devices. However, existing works do not consider Volt-VAr and Volt-Watt droop functionalities of SI in a system-wide optimization framework, making the inverter dispatch solutions potentially unsuitable at the local inverter controller level. Therefore, in this work, we propose the inclusion of local piecewise Volt-VAr and Volt-Watt droop functions (as per the IEEE-1547) as constraints in the DOPF formulation. We adopt a well-known LinDistFlow version of DOPF and with the inclusion of piecewise Volt-Watt and Volt-VAr droop functions, the resulting DOPF becomes a mixed integer linear programming (MILP) problem. Simulations on a 730-node MV/LV feeder with 20 utility-scale inverters validate the efficacy and scalability of the proposed formulation. The simulation results confirm the capability of SI droop functions to provide reactive power and voltage regulation support in ADNs.