Sensorless active damping method of LCL-filter in grid-connected parallel inverters for battery energy storage systems

In this paper, a sensorless active damping scheme of LCL-filter is proposed in grid-connected parallel inverters for battery energy storage systems. The proposed damping method is superior to the conventional notch filter and virtual damping methods with respect of robustness on the variation of resonance of the filter and unnecessary additional current sensors. The theoretical analysis of the proposed damping method is explained in detail, along with the characteristic comparison to the conventional active damping methods. Through the performance verification of the proposed sensorless active damping method, it is noted that the performance is comparable to the conventional virtual damping method even without additional current sensors. Finally, informative simulation and experimental results are provided to examine the overall characteristics of the proposed method.