Universal dual-port grid-forming control: bridging the gap between grid-forming and grid-following control
Irina Subotić, and Dominic Groß
TL;DR
This work addresses stability challenges in hybrid ac/dc power systems with converter-interfaced renewables, storage, HVDC, and legacy generators. It introduces universal dual-port GFM control based on a PD $v_{\text{dc}}-f$ droop, implemented in a derivative-free PI form to unify grid-forming and grid-following functions without mode switching. The paper provides an end-to-end linearized model, concise stability conditions for VSC gains and ac-topologies, and a steady-state analysis that yields quasi-synchronous behavior under typical HVDC conditions, along with case studies on a IEEE 9-bus-inspired network and a large-scale system. Through simulations, it demonstrates grid-support from curtailed renewables, approximate MPP tracking, and robust performance under severe contingencies, highlighting reduced complexity and improved interoperability across diverse technologies.
Abstract
We analyze a dual-port grid-forming (GFM) control for power systems containing ac and dc transmission, converter-interfaced generation and energy storage, and legacy generation. To operate such a system and provide standard services, state-of-the-art control architectures i) require assigning grid-following (GFL) and GFM controls to different converters, and ii) result in highly complex system dynamics. In contrast, dual-port GFM control (i) subsumes common functions of GFM and GFL controls in a simple controller, ii) can be applied to a wide range of emerging technologies independently of the network configuration, and iii) significantly reduces system complexity. In this work, we provide i) an end-to-end modeling framework that allows to model complex topologies through composition of reduced-order device models, ii) an in-depth discussion of universal dual-port GFM control for emerging power systems, and iii) end-to-end stability conditions that cover a wide range of network topologies, emerging technologies, and legacy technologies. Finally, we validate our findings in detailed case studies.