Study of Three-Level APF Control Methods Based on Kalman Filter

The accuracy of harmonic current detection and the current tracking control is key performance of active power filter (APF). Signal sampling, digital operation and transmission are typical processes in extracting harmonic current signal. The accuracy will be lost during these processes due to the signal transferring lag or interference. De-noising, fast tracking the current, extracting fundamental active current component are realized by utilizing the recursive algorithm of Kalman filter. The compensation current can be predicted to compensate the influence of signal delay and achieve real-time tracking compensation. A shunt active power filter (SAPF) based on the main circuit topology of three-level inverter is adopted and a proposed simple current tracking control method is used to eliminate the harmonic distortion. The filtering system and the algorithm are verified in MATLAB/Simulink. The simulation results show that the recursive algorithm based on Kalman filter can accurately track the power load current, effectively extract the reference current for compensation, and the inverter can provide good tracking control performance. It is proved that the proposed methods are feasible and effective.