With the continuous improvement of the manufacturing level of power electronic elements and the increasing demand of power quality by the people

the static synchronous compensator（STATCOM）based on the voltage re-injection converter has a fast dynamic response speed

does not require filtering devices and outputs low voltage harmonic contents and is suitable for high-voltage and high-power transmission systems. The main circuit re-injection topological structure of the DC voltage re-injection type STATCOM consists of two three-phase full bridges in series and an additional re-injection branch

and the re-injection branch adopts a cascaded H-bridge structure. The zero-crossing interval generated by the re-injection voltage can achieve the zero-voltage on-off of the three-phase full-bridge switch. The construction method of the re-injection branch pulse sequence is designed and an improved cycle logic trigger sequence is proposed. The simulation shows that the re-injection branch can effectively suppress the capacitor voltage unbalance in the re-injection cascaded H-bridge under the specific cyclic trigger pulse. The advantages of the converter in terms of zero-crossing turn-off and harmonic elimination are verified by the simulation platform. The reactive current is taken as a direct control command

a closed-loop control system is set up to verify that the STATCOM can effectively reduce the harmonic content and switching frequency in high-voltage and high-power systems

improve the operation reliability of devices and systems

and is especially suitable for high-voltage and high-power environments.