CYG's Power Grid Security and Stability Control Solution establishes a complete system centered on the "Three Lines of Defense." The first line of defense uses relay protection devices to quickly isolate faults. The core of the second line of defense is the QWD series security and stability control devices, which, through a three-layer architecture of master station, substation, and execution station, coordinate to monitor the grid's operating state in real time. When a significant disturbance, such as an N-1 contingency, is detected that may cause power angle instability, the system can make rapid decisions based on a preset strategy table and execute emergency control measures—such as generator tripping and load shedding—to prevent system instability. The third line of defense is equipped with devices for out-of-step islanding, low-frequency/undervoltage load shedding, etc. It employs final measures like system separation and load disconnection when the system has become unstable, preventing grid collapse and widespread blackouts. This solution provides comprehensive security protection for the power grid, encompassing prevention, control, and ultimate defense.