Fast Control Strategy of APF Based on Improved DFT Algorithm and Repetitive Control with Multiple Control Frequency in Synchronous Rotation Coordinates

Traditional DFT harmonic detection algorithm and repetitive control both have certain inherent delay, which seriously affects the dynamic performance of active power filter (APF). To quicken the dynamic response performance, as well as reduce the calculation amount and memory space occupied by the algorithm, characteristics of load harmonics in synchronous rotation coordinates are analyzed and an improved DFT algorithm with six-fold computing frequency is proposed. Secondly, a quasi-internal model with six-fold base control frequency in synchronous rotation coordinates is established. Detailed design of novel repetitive control (RC) and system stability check are carried out. Kinds of experiments are conducted to validate the feasibility and effectiveness of proposed methods.