IST control system based on sliding mode variable structure and control method of IST control system

The invention relates to an IST control system based on a sliding mode variable structure and a control method of the IST control system. The method comprises the following steps: firstly, collecting voltage and current of a system circuit, comparing the voltage and the current with target voltage and current, and determining the active power and the reactive power to be input by the IST according to the calculation of a calculation module (DSP (digital signal processor)); secondly, calculating a position where an ST to be put through a sliding mode variable control module compared to a position where the ST is currently located, and controlling a switching tap of the ST to switch to the target position; and finally, after the ST is switched to the target position, calculating the residual capacity to be switched by a UPFC (unified power flow controller) and controlling the UPFC with a PI (proportional integral) controller to trace the switching in real time. The system and the method realize the closed-loop control of the IST, the ST in discrete variation can reach a compensation point more quickly and more accurately under the sliding mode variable control, and then, the UPFC controlled by the PI can trace and control in real time. The system and the method can not only make full use of the advantages of large capacity and low price of the ST, but also can quickly and accurately control the power flow.