Research On The Fault Tripping Criteria Of Security And Stability Control Device Adapting To AC/DC Hybrid Grid

The security and stability criterion of traditional AC transmission system is being perfected, but with the high-voltage direct current infeeding, when various types of short-circuit faults occur, the changing electrical characteristics of AC transmission line nearby converter station are quite different from those when traditional pure AC fault occurs. The traditional fault tripping criterion of stability control device based on current condition may cause maloperation or misstrip. Therefore, putting forward a new fault tripping criterion in stability control device which adapts to the fault characteristics of AC power grid nearby converter station has a great significance. This thesis relys on the State Grid Corporation Technology Project "The research and application of grid security and adequate control technology adapting to the development of intelligence ", which includes new grid security stability control criterion research, experimental prototype development and demonstration.In this article, a ±500kV AC/DC hybrid simulation model containing three DC transmission line based on the electromagnetic transient simulation software PSCAD/EMTDC is built and the modeling of main HVDC components and DC control systems is introduced in detail. Taking single-phase short circuit fault occurred in AC transmission line nearby converter station as an example, according to analyzing the conduction and extinction state of the thyristors during commutation failure and giving the conducting loop of abnormal operating state, the relationship between the short-circuit current and short starting time is put forward. In the model, the change law of the electric quantity where the protection devices installed is presented and consistent with the theoretical analysis. Thus, it is considered that the main reason for the failure of the traditional fault tripping criterion is that the short-circuit current amplitude increases too little or the duration is too short.A new fault tripping criterion in stability control device is proposed according to the phase-sequence voltage of AC transmission line when short circuit fault occurs nearby converter station. The criterion is configured in the distributed stability control device SCS-500E and verified its effectiveness by RTDS experiments.