Oscillation Suppression Strategy of Three-Phase Four-Wire Grid-Connected Inverter in Weak Power Grid

As the penetration of renewable energy increases year by year, risk high-frequency oscillation instability when a three-phase, four-wire split capacitor inverter (TFSCI) is connected to grid with complementary capacitors in weak grids. Compared three-wire inverter, TFSCI has an additional zero-sequence current loop. To improve accuracy modeling and stability analysis, effect loop needs be considered impedance-based analysis. Therefore, correlation model considering multi-perturbation variables first established, based on which positive, negative, zero sequence admittance models are derived, solving difficult problem impedance under small perturbations. Secondly, remodeling strategy negative third-order differential element second-order generalized integrator (SOGI) damping controller proposed, can systems simultaneously. Finally, effectiveness suppression verified simulation experiment.