Harmonic extraction method, controller and harmonic extraction system

The invention provides a harmonic extraction method, a controller and a harmonic extraction system. The method comprises the steps of obtaining a target electric signal of an alternating-current source; a target extraction signal of a target period is obtained, the product of the target extraction signal and the first parameter A is calculated to serve as a first feedback signal, the product of the target extraction signal and the second parameter B is calculated to serve as a second feedback signal, and the first parameter A and the second parameter B meet the relation: A2 + B2 = 1; and determining a target extraction signal of the current period according to the target electric signal, the first feedback signal and the second feedback signal, and determining a target harmonic wave of the AC source of the current period according to the target extraction signal of the current period. The reliability of harmonic compensation can be improved. 本申请提供一种谐波提取方法、控制器及谐波提取系统。该方法包括：获取交流源的目标电信号；获取目标周期的目标提取信号，并计算目标提取信号和第