Static var Generator（SVG）is used widely in power systems to solve the problem of three-phase imbalance. The adoption of the method of constructing a rotating phasor without delay to improve the current detection part of the static reactive power generator in order to solve the error due to the delay caused by the phase-shifting operator and improve the real-time performance of current detection. The feedforward decoupling control is adopted for the current inner loop of the control part to solve the coupling problem between DC variables on the dq axis. In view of such shortcomings of PI control system as difficulty in determining parameters and in solving the time varying complex system

it is proposed to use the scheme of output voltage waveform which is controlled by the super spirals second order sliding mode in the in the feedforward decoupling controller to replace the PI control. Based on this method

the static var generator model is designed in Matlab to simulate and analyze the dynamic three-phase unbalanced load.It is know by the simulation result that this kind of method

compared to the traditional PI control

has better control effect.