Control Strategy of Electrolytic Capacitor-Less Multi-Port Converter for Suppressing the Influences of Low-Frequency DC-Link Current Ripple

Multi-port converter (MPC) gets growing applications due to its advantages of flexible control and high power density. But the fluctuation low frequency DC bus current ripples could degrade the operational stability of the system. In this paper, a frequency-adaptive repetitive control method is proposed to eliminate the effect of variable low frequency ripples. The virtual variable sampling (VVS) instead of traditional fixed sampling is used to achieve integral sampling number during the variable ripple period. Then a frequency-adaptive repetitive control strategy is adopted to suppress the ripples. Compared to the traditional methods designed for reducing fixed frequency ripples, the proposed one can eliminate the fluctuation low frequency ripples, showing better suppression ability and dynamic response speed. Moreover, the mechanism of DC chain current ripple is also analyzed, and the current ripple frequency identification method is improved. Finally, simulations and experiments are performed to verify the proposed strategy and analysis.