Several Key Techniques for Large Capacity STATCOM

This paper introduces several key techniques for large capacity STATCOM from three aspects: main circuit topology,converter chain DC voltage optimization control and synchronization soft phase-locked technology.Firstly,the structural characteristics and development tendencies of STATCOM main circuit topology are analyzed in detail;secondly,the converter chain DC voltage control methods are compared by means of principle analysis,emphatically the method of three-level DC voltage control;finally,working principle of soft phase-locked technology in synchronously rotating reference frame is presented based on the analysis of system positive sequence voltage soft phase-locked loop technology.In conclusion,cascaded H-bridge topology is easy to realize structural compaction and to be formed as relocatable structure,convenient for achieving flexible configuration of dynamic power supply;three-level DC voltage control is effective to achieve DC voltage balance of the converter chains;soft phase-locked technology based on synchronously rotating reference frame is more conducive to improving the transient compensation performance of STATCOM.