Abstract: Transformer is the hub of power grid,which is the gathering place of adverse factors such as reactive power and harmonic. Taking transformer as compensation node,a new device combining cascade hybrid reactive power compensation equipment with transformer was proposed.The hybrid reactive power compensation system was connected with the system through the tap of triangular winding on the high voltage side of DYn11 transformer,and the reactive current was injected into the tap to improve the power quality.According to the performance characteristics of reactive power compensation equipment and based on the instantaneous power theory,a method of applying power decomposition to hybrid reactive power compensation system was proposed.The high-frequency power was distributed to the static reactive power generator for compensation,and the low-frequency power was distributed to the new structure for compensation.A control strategy based on adaptive control algorithm was proposed to improve the robustness of the system.The effectiveness of the scheme was verified by simulation,which has a certain reference significance for the development of hybrid reactive power compensation system with cascade structure.