Experimental Validation of Feedback Optimization in Power Distribution Grids

TL;DR

This paper experimentally compares local Volt/VAr control, centralized OPF dispatch, and a novel feedback optimization controller for voltage regulation in power distribution grids, demonstrating the robustness and practicality of the proposed method.

Contribution

The paper introduces a feedback optimization controller that achieves voltage regulation without load measurements or detailed grid models, unlike existing methods.

Findings

The local droop control is suboptimal for voltage regulation.

The OPF-based strategy can violate voltage constraints due to model mismatch.

The proposed FO controller reliably satisfies voltage constraints and is robust to noise.

Abstract

We consider the problem of controlling the voltage of a distribution feeder using the reactive power capabilities of inverters. On a real distribution grid, we compare the local Volt/VAr droop control recommended in recent grid codes, a centralized dispatch based on optimal power flow (OPF) programming, and a feedback optimization (FO) controller that we propose. The local droop control yields suboptimal regulation, as predicted analytically. The OPF-based dispatch strategy requires an accurate grid model and measurement of all loads on the feeder in order to achieve proper voltage regulation. However, in the experiment, the OPF-based strategy violates voltage constraints due to inevitable model mismatch and uncertainties. Our proposed FO controller, on the other hand, satisfies the constraints and does not require load measurements or any grid state estimation. The only needed model knowledge is the sensitivity of the voltages with respect to reactive power, which can be obtained from data. As we show, an approximation of these sensitivities is also sufficient, which makes the approach essentially model-free, easy to tune, compatible with the current sensing and control infrastructure, and remarkably robust to measurement noise. We expect these properties to be fundamental features of FO for power systems and not specific to Volt/VAr regulation or to distribution grids.