Compared with L-type filter, LCL filter has the advantages of stronger harmonic suppression ability and smaller volume and weight, but LCL filter contains resonance, which leads to the risk of instability in the system. Feedback-type AD can effectively suppress resonance and has the advantages of flexible control and strong robustness. The differential feedback grid-side inductor voltage and the second-order differential feedback into the grid current can increase the output impedance of the inverter, and the latter can save a sensor. However, since the differential link is prone to amplify high-frequency noise and the existing differential implementation methods all aim to equivalently realize ideal differential links in the entire frequency band, it is easy to reduce the quality of the grid current when feedback is applied, which affects the application of feedback AD. To solve this problem, this chapter first uses the idea of PPD control to realize differentiation and solves the problem that the conventional differential implementation method also reduces LCL filter performance when differential feedback parasitic resistance voltage is lowered in the feedback network inductance voltage. Then, by looking for equivalent elements that can be equivalently realized as ideal differentials or second-order differentials near resonance and have lower amplitude gains in other frequency bands, differential feedback AD can be effectively realized, which improves the practicality of differential feedback AD.