Bi-level Volt/VAR Optimization in Distribution Networks with Smart PV Inverters

TL;DR

This paper introduces a bi-level optimization framework for Volt/VAR control in distribution networks that coordinates mechanical devices and smart PV inverters, improving efficiency and leveraging inverter group cooperation.

Contribution

It proposes a novel bi-level optimization model that integrates mechanical devices and smart PV inverters for enhanced Volt/VAR control in distribution networks.

Findings

The framework effectively reduces network active power losses.

Cooperative inverter actions improve voltage regulation.

Case studies validate the approach's effectiveness.

Abstract

Optimal Volt/VAR control (VVC) in distribution networks relies on an effective coordination between the conventional utility-owned mechanical devices and the smart residential photovoltaic (PV) inverters. Typically, a central controller carries out a periodic optimization and sends setpoints to the local controller of each device. However, instead of tracking centrally dispatched setpoints, smart PV inverters can cooperate on a much faster timescale to reach optimality within a PV inverter group. To accommodate such PV inverter groups in the VVC architecture, this paper proposes a bi-level optimization framework. The upper-level determines the setpoints of the mechanical devices to minimize the network active power losses, while the lower-level represents the coordinated actions that the inverters take for their own objectives. The interactions between these two levels are captured in the bi-level optimization, which is solved using the Karush-Kuhn-Tucker (KKT) conditions. This framework fully exploits the capabilities of the different types of voltage regulation devices and enables them to cooperatively optimize their goals. Case studies on typical distribution networks with field-recorded data demonstrate the effectiveness and advantages of the proposed approach.