To improve the power quality of the bus voltage, the bus harmonic voltage feed-forward is often added to the original control of the inverter. However, in the traditional design process of the bus harmonic voltage feed-forward control, the coupling effect of the phase-locked loop (PLL) and the bus harmonic voltage extraction is ignored, which causes design error of system parameters and weakens the power quality. To deal with this problem, this paper explores the coupling relationship between PLL and bus harmonic voltage feed-forward process in detail and proposes an approach of bus harmonic voltage extraction that can eliminate the mentioned coupling. The small signal model of PLL and bus harmonic voltage coupling is established, effectively revealing the coupling mechanism of PLL and the extraction process of the bus harmonic voltage. It is found that when the bandwidth of PLL is increased, the accuracy of bus harmonic voltage is seriously reduced, which further worsens the control accuracy and performance of the inverter. To solve the above harmonic coupling problem, a bus harmonic voltage and frequency extraction method based on αβ axis is proposed. Finally, the simulation model is built in MATLAB /Simulink to prove the correctness of the theoretical analysis.