# Power System Supplementary Damping Controllers in the Presence of Saturation

## TL;DR

This paper analyzes the impact of saturation nonlinearities on power system damping controllers and proposes a method to design controllers that enlarge the domain of attraction, improving stability and damping performance.

## Contribution

It introduces a novel approach to estimate and enlarge the domain of attraction for power system controllers considering saturation effects.

## Key findings

- Enlarged domain of attraction with the proposed controller
- Improved critical clearing time (CCT)
- Enhanced damping performance in simulations

## Abstract

This paper presents the analysis and a method to design supplementary damping controllers (SDCs) for synchronous generators considering the effects of saturation limits. Usually such saturations of control signals are imposed in order to enforce practical limitations such as component ratings. However, to guarantee the stability in the presence of saturation limits, the state trajectories must remain inside the domain of attraction (DA). In this paper, the domain of attraction of a single-machine infinite-bus (SMIB) power system with saturation nonlinearity is estimated and compared with the exact description of the null controllable region. Then, state-feedback controllers are designed to enlarge the DA. Our analysis shows that nonlinear effects of saturation should be considered to guarantee stability and satisfactory performance. Simulation results on a detailed nonlinear model of a synchronous generator indicate that the DA enlarges with the proposed controller. The results also indicate that Critical Clearing Time (CCT) and damping of the system with saturation can be improved by the proposed method.