This paper presents a feedforward scheme to improve system stability in grid-connected inverter with LCL filter. It is found that the delay time in feedforward path has a significant impact on system stability when the converter-side current is used for feedback control and capacitor voltage is used for feedforward control. Theoretical analysis is presented to explain the instability mechanism. A delay suppression method is then proposed to improve system stability margin. A single-phase inverter laboratory prototype is used to verify the theoretical analysis.
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