Accurate Power Loop Design of a Single-Phase Grid-Forming Power Converter via Modeling of SOGI-Based Power Calculation

The second-order general integrator (SOGI)-based power calculation method is generally used to calculate single-phase average power owing to its capability to eliminate double-frequency components with limited delay. It is important to identify the transfer function of this power calculation method to facilitate the closed-loop design of a single-phase grid-forming (GFM) power converter. This article investigates the periodic time variability introduced by the SOGI-based power calculation method. We use the phasor domain representation of power to establish the small-signal linearization model and obtain the linearized transfer function of the power calculation part. The linearized transfer function is used for accurate closed-loop pole placement design of a single-phase virtual synchronous generator (VSG). An adaptive state feedback (ASF) pole assignment design scheme is proposed to deal with the periodic time variability. Simulation and experiment results verify the effectiveness of the linearized model in accurately designing the closed loop of a single-phase GFM power converter.