Research on Realization Technology of Active Damping Method with Differential Feedback of Filter Capacitance Voltage for LCL Filter Based Grid-connected Inverters

Active damping(AD) methods based on LCL filter state variables feedback have the advantages of flexible control and strong robustness. Among these methods, the filter capacitor current proportional feedback algorithm is widely used because it is easy to implement, but the filter capacitor current has a large pulsation, only high-precision current sensors can accurately measure. The theoretical derivation shows that the differential feedback of the filter capacitor voltage can achieve the same damping effect and does not need to be equipped with a high-precision sensor, but the differential link easily brings high-frequency noise into the control system, which affects the quality of the grid current. Moreover, conventional differential implementation methods do not consider the influence of leakage current of the filter capacitor, which affects the high frequency characteristics of the LCL filter. Therefore, based on the vector relationship between the filter capacitor current and its leakage current, a new differential realization method is proposed, which has high frequency noise suppression capability and does not affect the performance of the LCL filter compared with the conventional differential realization method. Simulation and experimental results prove that the proposed control strategy can achieve satisfactory results in all aspects compared with traditional methods.