Distribution Grid Optimal Power Flow with Adaptive Volt-VAr Droop of Smart Inverters

Abstract

Distribution Grid Optimal Power Flow (DOPF) based Volt-VAr Optimization (VVO) provides a systematic and holistic approach to utilize Volt-VAr functions of smart inverters (SIs). Integration of such SI functionalities in DOPF can facilitate the fast-acting and adaptive VVO applications in response to voltage fluctuations caused by photovoltaic (PV) generation. Since DOPF uses complete network model and measurements, and can include SI control functions; this approach not only improves the feeder voltage response but also eliminates the control uncertainties stemming from non-smart inverters and other local controllers. Dynamic Reactive-Current Control (DRCC) function of SIs extents the existing Volt-VAr droop function, and provides adaptive control support on voltage regulation. In this context, we propose a DOPF model which can be implemented by enabling DRCC function of SIs. The proposed DOPF model makes use of adaptive Volt-VAr function complementing the Volt-VAr droop function as constraints in the DOPF-based VVO formulation. We combine a well-known second-order cone programming (SOCP) version of DOPF and SIs’ Volt-VAr droop functions, and the resulting VVO is casted as an efficient mixed-integer SOCP (MISOCP) formulation. The efficacy of the proposed VVO models are tested on a 33-node distribution feeder with 4 SIs with adaptive Volt-VAr droop functions set as per the IEEE-1547. Our findings show that the adaptive Volt-VAr droop based DOPF model is more effective in mitigating voltage fluctuations caused by PV intermittency compared to a regular Volt-VAr droop based approach.