access icon free Feedforward phase compensation method of LCL grid-connected inverter based on all-pass filter in weak grid

Inverter-side current feedback control (ICFC) has been extensively adopted in distributed generation systems because of its simple implementation and better consistency with actual operating conditions. At the same time, when there are a large number of background harmonics in the grid, capacitor voltage feedforward (CVF) is usually added to the system for its suppression. This method could make the system keep the first-order characteristics under the analogue control. However, under digital control, due to the digital control delay, a reverse resonance peak will be generated in the loop gain, which makes the system unstable in the weak grid. In order to solve the aforementioned problems, this study proposes a feedforward phase compensation method of LCL grid-connected inverter based on the all-pass filter (AF). By introducing AF into the CVF channel, the phase lag in the range of reverse resonance peak frequency is compensated, so as to enhance the robustness of the system in the weak grid. At the same time, this study gives the detailed design process of the proposed method. Experimental results on a 3-kW prototype are provided, and the effectiveness of the proposed control method is verified..

Inspec keywords: compensation; power filters; feedforward; digital control; power grids; invertors; distributed power generation; electric current control; feedback

Other keywords: phase lag; actual operating conditions; weak grid; control method; reverse resonance peak changes; all-pass filter; distributed generation systems; analogue control; feedforward phase compensation method; reverse resonance peak frequency; inverter-side current feedback control; capacitor voltage feedforward; grid impedance; digital control delay; LCL grid-connected inverter

Subjects: Other power apparatus and electric machines; Distributed power generation; Control of electric power systems; Current control; Power convertors and power supplies to apparatus

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