A Control Strategy of LCL-Type Grid-Connected Inverters for Improving the Stability and Harmonic Suppression Capability

The conventional inverter-side current single-loop feedback control scheme is weak in suppressing the grid-side harmonics, posing a challenge for an inverter to inject high-quality under distorted grid voltage. With capacitor compensation added, achieves controllability of harmonics so that it can effectively suppress some specific harmonic components. However, due stability requirements, only few low-order resonance controllers be applied, which limits mitigation high-order harmonics. To tackle this problem, with inductor–capacitor–inductor (LCL) damping proposed paper. In case, higher LCL frequency set compared scheme. Thereby, more applied active method proportional plus voltage adopted because its high robustness impedance variations. Furthermore, paper reveals has limitation considers single inductive impedance, cannot eliminate risk caused by interaction multiple inverters and grid. address issue, phase lead compensator (PLC) proposed, eliminating removing non-passive region output admittance. retain advantage scheme, i.e., measuring devices are required, digital differentiator used calculate from difference between measured calculated taken approximate control. performance comparable using feedback. Simulation experimental results demonstrate endows good quality without extra measurement devices.