In order to make full use of the reserve reactive power resources to improve the dynamic reactive power compensation capability of the receiving end of the power grid and improve the voltage stability better, this paper proposes the control strategy of the switching capacitor based on the automatic switching capacitor automatic device. The switching control strategy includes fault identification logic, low-voltage switching capacitor logic and over-voltage switching capacitor logic. The simulation platform builds a real-time simulation model of 220 kV and above based on RTDS, and connects DC protection devices and fast-switching capacitor automatic devices respectively, to form a double closed-loop real-time simulation system. By setting up a variety of test projects, an experimental study of basic switching strategies for automatic devices under different fault conditions is carried out to check the correctness and effectiveness of the switching strategy, which provides important technical guidance for the implementation and application of the device.