When it comes to DC bus voltage fluctuation, a photovoltaic grid-connected converter system is prone to suffer from unbalanced power transmission and unstable operation at the input and output. Thus an improved linear active disturbance rejection control strategy is proposed. First, the physical and mathematical models of the converter system are established, and the principle of energy transmission imbalance is analyzed. Then, a first-order linear active disturbance rejection controller is designed to replace the traditional proportional integral vector controller. Further, in order to strengthen the disturbance observation ability of the extended observer, a new parameter decoupling method is introduced to form a decoupling improved active disturbance rejection control. This improves the speed and disturbance rejection of the system. Finally, based on the frequency response characteristic curve and a variety of simulation conditions, a simulation is carried out. The results show that, compared with the traditional control strategy, the improved linear ADRC not only is superior in suppressing voltage fluctuation of the DC side bus, but also has good disturbance resistance and short-time transient fault ride-through ability. This ensures power transmission balance and normal and stable operation of the system. This work is supported by the National Natural Science Foundation of China (No. 51877152).