Coherency Control in Power Systems

TL;DR

This paper introduces a technology-agnostic coherency control strategy for inverter-based resources in power systems, enhancing dynamic stability and damping through a novel current equivalence approach.

Contribution

It presents a new coherency control method based on complex frequency equivalence, applicable to any resource type, and demonstrates its effectiveness through case studies.

Findings

Improved damping and dynamic behavior in case studies

Control is robust to delay and noise effects

Trade-offs between oscillation mitigation and disturbance propagation

Abstract

This paper proposes a coherency control strategy for Inverter-Based Resources (IBRs) to establish coherence among power system devices. Using the equivalence of the Complex Frequency (CF) of the injected currents as the definition for coherency among devices, the control enforces an output current with a proportional magnitude and a constant phase shift relative to a reference. This formulation makes the control technology-agnostic, enabling coherency with any type of resource. Case studies based on the two-area and IEEE 39-bus systems demonstrate the controller's potential to improve damping and overall dynamic behavior. The paper further evaluates practical implementation aspects including delay/noise sensitivity and the trade-off between oscillation mitigation and disturbance propagation. This work establishes coherency as a viable direct control objective for IBRs in modern power systems.