Research on Harmonic Suppression of Single-phase LCL Inverter Based on Full Feedforward of Grid Voltage

With the development of new energy technologies, the performance of grid-connected inverters in distributed power generation systems is of vital importance. This paper conducts research on the grid-connected inverter system based on virtual impedance. Although the traditional LCL filter can suppress high-frequency switching noise, its resonant characteristics pose challenges to the stability of the system. Therefore, this paper proposes a fully feedforward control strategy for power grid voltage. Through decoupling and analysis of the system structure, the influence mechanism of grid voltage on the output grid-connected current is clarified. A second-order low-pass filter is connected in series in the secondary differential term. Without increasing the cost of the sensor, the grid voltage interference is effectively eliminated, the total harmonic distortion of the grid-connected current is reduced, and the grid-connected power factor is improved. A single-phase grid-connected inverter with a rated power of 5kW was designed. Experiments were conducted on the Matlab/Simulink platform to compare the distortion of the inverter's output grid-connected current when the 5th harmonics were injected with or without feedforward control. The results show that in the system adopting this strategy, when different harmonics are injected The THD was significantly reduced by 73.21%, and the error fluctuation range was small. This proved the good anti-interference ability of the proposed inverter system, provided new ideas for the development of grid-connected inverter control technology, and promoted the efficient and stable operation of distributed power generation systems.