The early detection of cascading failure plays an important role in the safe and stable operation of the power system with high penetration of renewable energy. This paper proposes a fault propagation dynamic model based on the epidemic model, and further puts forward a method to detect the development of cascading failures. Through the simulation of the IEEE 39-bus and 118-bus systems, this model is proven to be valid and capable of providing practical technical support for the prevention of cascading failures in power systems with high penetration of renewable energy. This paper also provides an analysis method for the choice of different protection and control measures at each stage of cascading failure, which has critical significance and follow-up value.

Due to low inertia and restricted frequency regulation resources, isolated system frequency may deviate from nominal operating conditions easily. The conventional solution is to install energy storage or curtail PV power, which is quite costly. This paper proposes a closed-loop feedback control strategy to provide quick frequency support based on conservation voltage reduction effect of voltage-sensitive loads. The power of different loads is regulated coordinately and continuously considering the difference in CVR effect and voltage state between each load. Thus, a two-stage adaptive control method based on the adjustable margin of each load is proposed to achieve online optimization of feedback coefficients. Voltage quality of each load can be guaranteed in the control process while system transient nadir can be minimized. The proposed scheme enables fast and continuous power support through the supply-side to respond to fast power fluctuation caused by PVs. Simulation is performed on the RTDS based on a real system in China, and results verify effectiveness of the proposed method.