Online Event-Triggered Switching for Frequency Control in Power Grids with Variable Inertia

TL;DR

This paper introduces an online event-triggered switching control strategy using Neural-PI controllers to maintain power grid frequency stability amid variable inertia caused by renewable energy integration.

Contribution

It proposes a novel Neural-PI controller structure and an online switching algorithm to adapt to changing inertia levels, ensuring stability and improved frequency regulation.

Findings

The Neural-PI controller guarantees exponential input-to-state stability.

The online switching algorithm effectively selects controllers for different inertia levels.

Simulations demonstrate improved frequency control performance under variable inertia.

Abstract

The increasing integration of renewable energy resources into power grids has led to time-varying system inertia and consequent degradation in frequency dynamics. A promising solution to alleviate performance degradation is using power electronics interfaced energy resources, such as renewable generators and battery energy storage for primary frequency control, by adjusting their power output set-points in response to frequency deviations. However, designing a frequency controller under time-varying inertia is challenging. Specifically, the stability or optimality of controllers designed for time-invariant systems can be compromised once applied to a time-varying system. We model the frequency dynamics under time-varying inertia as a nonlinear switching system, where the frequency dynamics under each mode are described by the nonlinear swing equations and different modes represent different inertia levels. We identify a key controller structure, named Neural Proportional-Integral (Neural-PI) controller, that guarantees exponential input-to-state stability for each mode. To further improve performance, we present an online event-triggered switching algorithm to select the most suitable controller from a set of Neural-PI controllers, each optimized for specific inertia levels. Simulations on the IEEE 39-bus system validate the effectiveness of the proposed online switching control method with stability guarantees and optimized performance for frequency control under time-varying inertia.