Accurate Power Loop Design of a Single-Phase Grid-Forming Power Converter Via Linearization of SOGI-Based Power Calculation

Second order general integrator (SOGI)-based power calculation method is generally used to calculate single-phase average power owing to its ability to eliminate double frequency component with limited delay. It is important to identify the transfer function of the power calculation to facilitate the closed-loop design of a single-phase grid-forming power converter. In this paper, we investigate the nonlinearity and periodic time variability introduced by the SOGI-based power calculation method. To address this issue, we propose a method to identify the optimally linearized transfer function of the power calculation part through the system identification method based on numerical subspace state space system identification algorithm and particle swarm optimization algorithm. The optimally linearized transfer function is used for closed-loop pole placement design of a single-phase virtual synchronous generator. Simulation results verify the effectiveness of the proposed linearization method in accurately designing the closed loop of a single-phase grid-forming power converter.