Robust Decentralized Secondary Frequency Control in Power Systems: Merits and Trade-Offs

TL;DR

This paper introduces a fully decentralized leaky integral controller for power system frequency restoration, balancing performance and robustness through tunable parameters, and compares it with existing control methods.

Contribution

It proposes a novel decentralized leaky integral control approach derived from a classic lag element, with comprehensive stability and robustness analysis.

Findings

Leaky integral control achieves a good trade-off between robustness and transient performance.

Tuning DC gain and time constant optimizes disturbance rejection and convergence.

Compared to traditional methods, it offers improved stability and noise rejection.

Abstract

Frequency restoration in power systems is conventionally performed by broadcasting a centralized signal to local controllers. As a result of the energy transition, technological advances, and the scientific interest in distributed control and optimization methods, a plethora of distributed frequency control strategies have been proposed recently that rely on communication amongst local controllers. In this paper we propose a fully decentralized leaky integral controller for frequency restoration that is derived from a classic lag element. We study steady-state, asymptotic optimality, nominal stability, input-to-state stability, noise rejection, transient performance, and robustness properties of this controller in closed loop with a nonlinear and multivariable power system model. We demonstrate that the leaky integral controller can strike an acceptable trade-off between performance and robustness as well as between asymptotic disturbance rejection and transient convergence rate by tuning its DC gain and time constant. We compare our findings to conventional decentralized integral control and distributed-averaging-based integral control in theory and simulations.