Optimal Distributed Control of Reactive Power via the Alternating Direction Method of Multipliers
This work provides a practical distributed control method for voltage regulation in power distribution systems, balancing communication overhead and optimality.
The authors formulate reactive power control for photovoltaic inverters as a convex optimization problem and propose a distributed ADMM-based protocol that achieves near-optimal performance with only local measurements and limited neighbor communication, outperforming dual ascent.
We formulate the control of reactive power generation by photovoltaic inverters in a power distribution circuit as a constrained optimization that aims to minimize reactive power losses subject to finite inverter capacity and upper and lower voltage limits at all nodes in the circuit. When voltage variations along the circuit are small and losses of both real and reactive powers are small compared to the respective flows, the resulting optimization problem is convex. Moreover, the cost function is separable enabling a distributed, on-line implementation with node-local computations using only local measurements augmented with limited information from the neighboring nodes communicated over cyber channels. Such an approach lies between the fully centralized and local policy approaches previously considered. We explore protocols based on the dual ascent method and on the Alternating Direction Method of Multipliers (ADMM) and find that the ADMM protocol performs significantly better.