Performance Comparison of Cascade Control Systems for Single-Phase Grid-Forming Converters with LCL Filter

Universal operation of a Distributed Power Generation System (DPGS) implies the presence of a grid-forming power converter in the plant. The grid-forming converter achieves power and voltage control when the system operates in island mode. Several multiloop control systems have been proposed in literature focusing on three-phase applications. Differently the focus of this paper is on single-phase DPGSs. Three cascade control systems are compared in terms of stability, dynamics, power quality. The first control system is based on resonant controllers. The second and the third method are based on traditional three-phase control systems which are extended to single-phase applications in d-q synchronous reference frame. In these cases, an Orthogonal Signal Generator (OSG) is required to provide a fictive q-axis. It is demonstrated that the control system based on a Second Order Generalized Integrator (SOGI) OSG allows some advantages in comparison with the others.