NPC three-level series active power filter with neutral-point voltage self-restraining

Series active power filter (SAPF) improves power quality as a key technology, which has been highly valued and widely used at present. NPC (neutral point clamped) three-level SAPF enables to compensate harmonic voltage in the field of high voltage, but traditional NPC three-level SAPF has a problem of neutral-point voltage excessive fluctuation which will cause switch devices damage. In order to solve this problem, a NPC three-level SAPF with neutral-point voltage self-restraining function is proposed. A controllable voltage source will be put in series between the neutral point of the DC-side capacitors and point O in traditional NPC three-level SAPF. To obtain better control effects, sliding mode control method is used to control the compensation voltage generated. Neutral-point voltage will be compensated in the real-time. Simulation results show that the proposed SAPF has good performances.