Abstract: The paper proposed a design scheme of 6 kV chain static synchronous compensator. The compensator uses H-bridge cascade main circuit structure and carrier phase shifted sinusoidal pulse-width modulation, the AC side uses feed forward decoupling control and harmonic divide control strategy for high-power STATCOM. The compensator uses three-level balance control idea to solve problem of BUS capacitive voltage imbalance at DC side. The simulation results demonstrate superiority of the structure of STATCOM and feasibility of the control strategy.