Coupled model for three-phase three-wire grid connected inverters through LCL filters

This paper proposes a state-space modeling for a three-phase three-wire voltage source inverter (VSI) connected to the grid through an LCL filter. The main feature of this model is to fully represent the coupling among the phases. The proposed model can be employed to develop controllers for dealing with power-grid unbalance with more accuracy using the natural reference frame. The results demonstrate that, under unbalance conditions, the currents injected into the grid are quite different from those obtained from the traditional single-phase decoupled model approach, which is usually applied to design controllers for VSIs connected to the grid through LCL filters.