Analysis and modeling of supraharmonic coupling among multiple inverters in renewable energy systems

Purpose In renewable energy systems, supraharmonics as a new type of power quality problem generated by power electronic devices have received extensive attention. Taking three-phase grid-connected inverters with multiple different switching frequencies for this study, a supraharmonic coupling analysis method is proposed, and a supraharmonic coupling model is established to solve the frequency coupling phenomenon caused by supraharmonic propagation among multiple inverters in the renewable energy system. The purpose of this study is to analyze the coupling characteristics of supraharmonics during the propagation process among multiple grid-connected inverters with different switching frequencies. Design/methodology/approach By studying the propagated supraharmonics during parallel operation of inverters with different switching frequencies and analyzing the coupling mechanism of supraharmonics in the inverter A/D sampling and sinusoidal pulse width modulation (SPWM) process, a coupling analysis model of supraharmonics, including the control system, is established to reveal the frequency coupling characteristics of supraharmonics in multiple inverters. Findings The supraharmonic coupling among multiple inverters is mainly affected by the A/D sampling and SPWM modulation process of the inverter control loop, and supraharmonics will generate additional sideband supraharmonic frequency components in the control loop. Originality/value In this paper, a supraharmonic coupling model is established to solve the frequency coupling phenomenon caused by parallel operation of inverters with different switching frequencies in renewable energy systems. The model can accurately describe the coupling characteristics of supraharmonics among inverters and the simulation cases and experimental results show that the accuracy of the established model is about 90%, which can provide theoretical guidance for improving the safety of new energy grid-connected electronic devices.