POWER FAILURE DETECTION METHOD, POWER CONVERSION DEVICE, AND ENERGY STORAGE SYSTEM

This application provides a power failure detection method, including: obtaining a first fundamental wave signal of an alternating current (AC) at a first moment and a second fundamental wave signal at a second moment, where the second moment differs from the first moment by N sampling periods, and N is a positive integer; then obtaining a target signal orthogonal to the first fundamental wave signal based on the first fundamental wave signal and the second fundamental wave signal; quickly obtaining a real-time voltage amplitude of the AC at the first moment based on the first fundamental wave signal and the target signal; and determining a power failure detection result of the AC based on the real-time voltage amplitude.