Hybrid Controller for Wind Turbine Generators to Ensure Adequate Frequency Response in Power Networks

TL;DR

This paper proposes a hybrid control strategy for wind turbine generators that uses a region of safety and barrier certificates to ensure adequate frequency response and system stability during mode switching, supported by theoretical analysis and simulations.

Contribution

It introduces a novel mode switching approach based on a region of safety and barrier certificates for wind turbines to improve frequency support in power networks.

Findings

The proposed method effectively enlarges the safe operating region.

Critical switching instants ensure system stability.

Simulations validate the theoretical approach.

Abstract

Converter-interfaced power sources (CIPS) are hybrid control systems as they may switch between multiple operating modes. Due to increasing penetration, the hybrid behavior of CIPS, such as, wind turbine generators (WTG), may have significant impact on power system dynamics. In this paper, the frequency dynamics under inertia emulation and primary support from WTG is studied. A mode switching for WTG to ensure adequate frequency response is proposed. The switching instants are determined by our proposed concept of a region of safety (ROS), which is the initial set of safe trajectories. The barrier certificate methodology is employed to derive a new algorithm to obtain and enlarge the ROS for the given desired safe limits and the worst-case disturbance scenarios. Then critical switching instants and a safe recovery procedure are found. In addition, the emulated inertia and load-damping effect is derived in the time frame of inertia and primary frequency response, respectively. The theoretical results under critical cases are consistent with simulations and can be used as guidance for practical control design.