Abstract: Medium-voltage direct-linked photovoltaic power generation system does not need line frequency step-up transformers and reactive power compensation device and it has no loss at night, which has attracted wide attention in recent years. A large number of photovoltaic strings are collected in series through the output of the isolated DC-DC converter, and then are connected to the grid to send power through the MMC converter, forming a two-stage medium voltage direct-linked PV power generation topology. This topology has high operating efficiency, but it is difficult to control the maximum power point tracking (MPPT) of each PV string. Parallel the input side of the isolated DC converter, and insert the MPPT converter between the photovoltaic string and the isolated DC converter, which is beneficial to MPPT control, but increases the system loss. Oriented to two-stage power conversion medium voltage direct-linked photovoltaic power generation system, the paper proposed a voltage-power self-tracking control method of the isolated converter, so that the converter can realize the automatic distribution of the output voltage of each power module without communication and closed-loop control while achieving MPPT control of the PV string. Therefore, the power conversion level can be reduced and the operation efficiency and robustness can be improved. A low power experimental system was constructed to verify the effectiveness of the proposed inter-module power control strategy.