Under the condition of system frequency fluctuation or offset

common harmonic compensation control methods for the active power filter（APF） are easy to lose efficiency. Based on a dq0 synchronous rotating frame

taking the three-phase four bridge APF as an application object

we compared the control structures

amplitude characteristics and stability of the three harmonic compensation methods

namely

the proportional resonant（PR）

the vector-proportional integral（VPI）

and the repetitive control（RC）

and discussed their advantages and disadvantages. Furthermore

the traditional RC was improved

and a fast repetitive control FRC method was proposed. The stability of the control system was analyzed with zero-pole

and the actual compensation effects of the three control methods were analyzed and compared through experiments. The research results show that

through shortening the repetitive period

the proposed method can be adopted to improve the RC controller response speed and to extend frequency bandwidth

therefore

it has good frequency-selection characteristics and strong anti-frequency fluctuation robustness. The test implies that the FRC has the best harmonic suppression and adaptability to system frequency fluctuations.