Voltage Source Active Damper Applied to Resonance Suppression of Multi-inverter Grid-connected Systems

Multi-inverter grid-connected systems are usually in the weak grid environment where the grid impedance changes greatly, which results in a strong coupling between the inverter and the grid impedance in the grid-connected power generation system, causing the resonance problem. A lot of researches have been conducted on current source active damper, but it is difficult to achieve a small virtual harmonic impedance. So its ability to suppress resonance in grid-connected systems is limited. Regarding the issues above, this article presents a control strategy for a voltage source active damper. The voltage source active damper can virtualize the smaller harmonic impedance to reshape the impedance of the point of common coupling, which effectively suppresses the harmonic and resonance of the system from the system level. Finally, taking dual-inverter system as an example, the resonance suppression effect is theoretically analyzed, and the feasibility and effectiveness of the proposed voltage source active damper control method are verified through experiments.