Seamless Integration of Grid-Forming and Grid-Following Capabilities in a Single VSI within a Unified Hybrid Control Framework under Islanded Conditions

To achieve seamless integration of grid-forming (GFM) and grid-following (GFL) capabilities in a single voltage-source inverter (VSI) under islanded conditions, this study introduces a unified hybrid control (UHC) scheme with minimal control parameters and measurement sensors.The UHC scheme enables a single voltage-controlled VSI to effectively emulate the behavior of two virtual parallel VSIs, each functioning independently as a GFM and GFL inverter, ensuring system stability and reliability.This innovative approach significantly enhances the functionalities of voltage-controlled inverters in islanded mode, allowing them to perform various operational tasks simultaneously, including voltage and frequency regulation, provision of grid support services, and accurate tracking of reference powers using output current control, without relying on a phase-locked loop.Additionally, a VSI equipped with a UHC scheme can mimic virtual inertia, ensuring stable voltage and frequency maintenance under varying operating conditions with rapid and desirable dynamic and transient responses.Comprehensive simulation studies on single-and multiinverter systems operating in the islanded mode rigorously validate the effectiveness and feasibility of the UHC scheme for practical implementation in power systems.