Simulation of the active filter with a multilevel NPC inverter

Due to the overvoltage limitation of the power devices, it is very difficult to mitigate harmonic produced from the nonlinear loads in high voltage grids with the help of a traditional active power filter (APF) with two-level inverter. An approach using an active power filter with a multi-level NPC inverter is therefore proposed. As the basic principles of the APF described, a repetitive predictor based deadbeat control scheme is given to predict harmonic current. The repetitive predictor can achieve a better prediction of the harmonic current with same sampling frequency, thus improves the overall performances of the system. The simulation results illustrate that the proposed APF is suitable for mitigating harmonic under conditions of a high voltage and a large capacity.