Time-synchronization-based constant-frequency grid-forming technology for power electronics-dominated systems

Abstract

With rising penetration of distributed energy resources, power systems are becoming increasingly power electronics-dominated. Constant-frequency control ensures a fixed system frequency and mitigates frequency instability risks, but existing schemes cannot intuitively and flexibly set the droop reference operating point, with a relatively complex overall control structure, and the system lacks the capability of accurate active power flow regulation. To solve these issues, this paper proposes a time-synchronization-based constant-frequency grid-forming control framework for low-voltage DER-integrated power electronics-dominated systems. Based on voltage/current orientation, four droop strategies are constructed: d / q -axis current-voltage magnitude ( I d / I q - U s ) and d / q -axis voltage-current magnitude ( U d / U q - I s ) droop, alongside a universal active power dispatch method adapted to this framework. Small-signal stability analysis is conducted, and the feasibility and effectiveness of the proposed strategies are verified via Simulink simulations and RT-LAB hardware-in-the-loop tests. Comparative simulations are conducted to analyze the natural power sharing characteristics of different strategies and system responses to large disturbances. The results demonstrate that the constant-frequency grid-forming converters can reliably establish system voltage and frequency, flexibly adjust the droop reference operating point, and support system-level active power dispatch, while also exhibiting favorable fault ride-through and steady-state recovery capabilities.