Active power decoupling now is commonly used in single phase converter for the purpose of replacing bulky electrolytic capacitors, which is usually install in dc side of inverter to mitigate the second harmonic ripple in the single-phase converter. One possible way is to using half-bridge and split dc capacitor to realize power decoupling, but the conventional power decoupling control scheme for this half-bridge circuit is developed with equal storage capacitances, which may vary in practice and degrade the ac and dc performance. The intention of this paper is to quantify ac and dc imperfections when storage mismatch occurs, which may break the standard requirement such as IEEE 1547. As a consequence, a robust control scheme is then proposed for half-bridge circuit, which realized power decoupling by generating second order harmonic voltage on the split dc decoupling capacitor instead of fundamental voltage with using the conventional method. By doing so, the converter performance can be promised with uncertainly mismatched capacitance. Finally, experimental results are presented to confirm the effectiveness of the proposed approach.