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This paper investigates the feedforward schemes of grid voltages for a three-phase LCL -type grid-connected inverter. The full-feedforward functions of grid voltages are derived for the stationary α- β frame, synchronous d - q frame, and decoupled synchronous d - q frame-controlled three-phase LCL -type grid-connected inverters. The derived full-feedforward functions mainly consist of three parts which are proportional, derivative, and second derivative parts. The use of the traditional proportional feedforward function in the three-phase LCL -type grid-connected inverter will result in the amplification of the high-frequency injected grid current harmonics. With the proposed full-feedforward schemes, the injected grid current harmonics and unbalance caused by grid voltages can be greatly reduced. The effectiveness of the proposed feedforward schemes is verified by the experimental results.
Li et al. (2012) studied this question.