An Novel Deadbeat Control Method for Active Power Filters with Three-Level NPC Inverter

Three-level NPC inverter has been put into practical use for years especially in high voltage high power grid. This paper researches three-level active power filters(APF). In this paper the mathematical model in d-q coordinates is presented for 3-phase 3-wire APFs. The deadbeat control scheme is obtained by using the state equations. Canceling the delay of one sampling period and providing the predictive value of the harmonic current is key problem of the deadbeat control. Based on this deadbeat control, the predictive output current value is obtained by the state predictor. The delay of one sampling period is remedied in this digital control system by the state predictor. The predictive harmonic command current value is obtained by the repetitive predictor synchronously. The repetitive predictor can achieve better prediction of the harmonic current with same sampling frequency, thus improves the overall performance of the system. The experiment results indicate that the steady-state accuracy and dynamic response are both satisfying when the proposed control scheme is implemented.