Distributed Optimal Frequency Control Considering a Nonlinear Network-Preserving Model

TL;DR

This paper presents a distributed control method for power system frequency regulation that handles nonlinear dynamics, requires minimal load measurement, and only needs communication among controllable generators, ensuring stability and optimality.

Contribution

It introduces a novel distributed control strategy considering nonlinear power flows and partial controllability, with a virtual load demand concept and local frequency-based estimation.

Findings

System stability is proven under the proposed control.

Simulations show effective frequency regulation during disturbances.

The method achieves optimal economic dispatch.

Abstract

This paper addresses the distributed optimal frequency control of power systems considering a network-preserving model with nonlinear power flows and excitation voltage dynamics. Salient features of the proposed distributed control strategy are fourfold: i) nonlinearity is considered to cope with large disturbances; ii) only a part of generators are controllable; iii) no load measurement is required; iv) communication connectivity is required only for the controllable generators. To this end, benefiting from the concept of 'virtual load demand', we first design the distributed controller for the controllable generators by leveraging the primal-dual decomposition technique. We then propose a method to estimate the virtual load demand of each controllable generator based on local frequencies. We derive incremental passivity conditions for the uncontrollable generators. Finally, we prove that the closed-loop system is asymptotically stable and its equilibrium attains the optimal solution to the associated economic dispatch problem. Simulations, including small and large-disturbance scenarios, are carried on the New England system, demonstrating the effectiveness of our design.