Control Strategy of Grid-Connected Inverter Suppressing Grid-Voltage Background Harmonics Based on the Improved Passive Damping Method

The traditional LCL-filter third-order system grid-connected inverter may cause the resonance phenomenon without damping. Also, it will be affected by the distorted grid-voltage background harmonics. In order to overcome the problem, a new control strategy is proposed. The chapter analyzes the current waveform performance of grid-connected inverter in the condition of grid-voltage background harmonics, which derive the feed-forward function for grid-connected inverter. The disadvantages of passive damping could be well solved by damping resistor virtualization of the original system, which realizes the active damping suppression of resonance. Simulation results based on the Heric single-phase transformerless grid-connected inverter verify the correctness of the theoretical analysis.