The chain static reactive compensation device (SVG) is of great significance for enhancing the security and stability of power grid, the chain structure that is facilitated to modulate has brought great convenience to expand capacity, But the scattered DC voltage control solution is difficult to be solved. This article embarks from the double closed-loop control, the inner current control realize the reactive current real-time following accurately; the outer DC voltage control is not only control the single phase voltage level as a whole, but also control the modulation signal of each power unit directly from various modulation wave, so realize the hierarchical control strategy of the outer ring. Under the environment of Matlab Simulink, taking 2KV voltage level for example, simulate the three-phase system that its power unit of single-phase three series , proving the compensation effect of SVG and the reliability of the control system.