The low-carbon upgrading of transmission grids can be effectively realized by trend optimization techniques. This paper improves the traditional trend calculation based on the distributed power supply controlled by droops. Each node’s power balance equations are outlined based on the established distributed power supply with droop control and other models. The improved Niu La method is used to establish the trend calculation model, and the active sag coefficient and reactive sag coefficient in the droop control are normalized. Virtual impedance is utilized to regulate the reactive power classification between distributed power sources in the transmission network to minimize transmission network losses. The carbon and economic benefits of this paper’s method are analyzed using the MATLAB platform, and the carbon emissions of line and node active losses are reduced by 72.30% and 50.67%, respectively, before and after the optimal flow control. The economic benefits of saving line losses after performing optimization and control are 4.8739 × 105 yuan, 7.8593 × 105 yuan and 1.1283 × 106 yuan, respectively.