Self-Synchronising Stationary Frame Inverter-Current-Feedback Control for LCL Grid-Connected Inverters

Current regulation of inductive-capacitive-inductive (LCL) grid-connected inverters usually requires multiple current sensors to actively damp the filter resonance. Inverter side current regulation avoids this issue because of its inherent LCL filter damping properties, but does not accurately control the grid side current, particularly with distorted grids. Furthermore, both strategies typically require high quality voltage sensors to maintain precise grid synchronization. This paper proposes a novel current control strategy for LCL grid-connected inverters that only requires inverter side current sensors. The strategy uses the resonator output states of a Stationary Reference Frame (SRF) Proportional Resonant (PR) current regulator to estimate the grid voltage phase and filter capacitor current, and thus achieve self-synchronized indirect regulation of the grid-side current. The effectiveness of the approach has been verified using simulation and matching experimental investigations.<p></p>