Black-Start and Hot-Swap Performance Assessment and Improved Control Strategy for Grid-Forming VSC and CSC-Based PV Systems

The grid-forming (GFM) control of voltage-source converter (VSC)-based photovoltaic (PV) systems has shown promise in supporting the grid frequency and inertia. However, the literature lacks GFM control development for current-source converter (CSC)-based PV systems and comparisons with the VSC counterpart. In particular, previous studies did not address dynamic performance assessment and comparison under critical operating conditions, such as black-start (autonomous power system restoration) and hot-swap (the transition between isolated and grid-tied modes). Furthermore, previous research did not address the dc- and ac-side stability differences among VSC- and CSC-based GFM PV systems. This article addresses these research gaps by differentiating the dynamic performance and stability of GFM VSC- and CSC-based PV systems under different operating conditions. Furthermore, this article presents active compensators for both GFM systems to enhance their dynamic performance and stability. Compared to the GFM VSC, the GFM CSC provides a better frequency profile under black-start and hot-swap conditions, improved robustness under grid impedance variation, and inherent fast current limitation under faults. Detailed offline and real-time simulation results validate the comparative analysis and the effectiveness of the proposed active damping methods for both GFM systems.