Abstract: Under the background of parallel connection of photovoltaic power generation units to the power grid, the DC-link voltage oscillation caused by the maximum power point tracking (MPPT) control leads to the increasingly serious problem of low-frequency interharmonic current, which greatly affects the power quality. In this regard, this paper introduces the common forms of multiple photovoltaic power generation units connected in parallel to the grid. It establishes a model with two photovoltaic units connected in parallel to the grid. Then, the model of interharmonic current is established by using the perturbation MPPT oscillation characteristics. The influence of the disturbance step size on the interharmonic characteristics of the photovoltaic grid-connected system is analyzed, and the interharmonic content is defined. Then, an interharmonic current suppression method for the photovoltaic grid-connected system based on DC-link voltage equivalent compensation is proposed. This method makes the DC voltage oscillation of multiple parallel photovoltaic power generation units offset each other and has both MPPT dynamic performance and suppression effect. Finally, the effectiveness of the proposed method in reducing the amplitude of interharmonic current and improving power quality is verified by simulation analysis.