With the development of economy and society, the requirements for the reliability of distribution network power supply are increasing day by day. It has important application value to study the problem of power grid closure with voltage phase difference and to suppress the circulation problem during the loop closure process. In order to investigate the problem of 35kV power grid closing with a phase difference of 30°, a series transformer and a four-quadrant converter are used for static and dynamic voltage compensation. Based on the principle of voltage vector superposition, a series of phase-shifting transformers are designed to compensate for the voltage difference between the two input terminals. Compared with traditional full-power phase-shifting transformers, the required transformer capacity is halved, which greatly reduces costs. At the same time, a four-quadrant converter is used for dynamic voltage compensation to achieve online and precise adjustment of voltage and phase. Design an online loop-closing strategy, find the best loop-closing point, and automatically close the loop to achieve online uninterrupted load reversal, effectively improve the power quality and power supply stability of the power grid, and increase the level of intelligence in the power grid closure process.