Research on LCL Filters for Photovoltaic Grid-Connected Systems

In renewable energy generation systems, the output power quality of photovoltaic grid-connected inverters is crucial. LCL filters have become key components connecting inverters to the grid due to their superior harmonic suppression capabilities.

The LCL filter consists of two-stage inductors (inverter-side inductor and grid-side inductor) with a parallel capacitor in between. Compared to traditional L-type filters, it achieves high-frequency harmonic attenuation with smaller physical size. However, its third-order characteristics introduce resonance peaks, requiring coordinated control strategies to suppress oscillation risks.

Proportional-Integral (PI) control serves as a classic solution to this challenge: The current inner loop employs PI regulators to track reference signals, controlling grid-connected current by adjusting inverter output voltage Special attention must be paid to phase abrupt changes at resonant frequencies, often combined with capacitor current feedback or active damping methods to enhance stability Parameter tuning requires balancing dynamic response speed against harmonic suppression effectiveness

This research provides valuable references for improving grid-connected power quality in photovoltaic systems. Future work could explore advanced control strategies like resonant control and model predictive control for integrated applications.