Grid-Forming Static Power Generator with Coordinated Control of Two-Stage Converters

Abstract

Grid-forming (GFM) control is an important technical solution for addressing the declining voltage-support capability and inertia level of modern power systems. By integrating a high-voltage directly connected grid-side converter with supercapacitors, the grid-forming static power generator (GFM-SPG) can provide active- and reactive-power support to high-voltage power grids. This paper investigates a GFM-SPG with a two-stage converter topology and proposes a coordinated control strategy for the two-stage converters. The transient response characteristics of the GFM-SPG are classified into three operating regions, and the effects of key control parameters are analyzed to establish basic parameter design guidelines. To simultaneously enhance grid inertial support and transient voltage-support capability, a variable inertia time-constant control strategy is further proposed. Under normal operating conditions, a relatively large inertia time constant is adopted to provide inertial support, whereas a small inertia time constant is employed during voltage ride-through to enable rapid phase synchronization and prioritize reactive-power support. The proposed control strategy is validated through electromagnetic transient simulations and hardware-in-the-loop (HIL) experiments. The results demonstrate that the two-stage GFM-SPG can achieve stable DC-bus voltage regulation and provide effective inertia and transient voltage support under different grid operating conditions.