Comparison of current control structures for three-phase four-wire systems in natural frame

The paper presents a comparison between two current control structures in natural frame. The proposed methods were applied to a three-phase four-wire grid-connected voltage source inverter (VSI). The compared control structures are a proportional-integral (PI) controller, and a proportional-resonant (PR) controller, which is based on second order generalized integrators (SOGI). For sinusoidal references, PI controllers present steady-state error. In order to overcome this issue and to reduce the harmonic distortion, an integral predictive control (IPC) was implemented. The results will highlight the performance differences based on steady-state error, transient behaviour and harmonics compensation.