A Novel Sliding-Mode Current Controller in On-Grid NPC Converter

This paper proposes a model based on robust control for three-phase three-level Neutral Point Clamped (NPC) power converters. Based on the continuous averaged model of the power system, a Sliding Mode Control (SMC) technique is applied to implement in the control system. The nonlinear SMC based on Gao’s reaching law has been utilized to control the grid current in order to inject desired amount of active and reactive power to the grid. Using a single dc source at the NPC inverter dc bus, neutral point voltage is controlled through redundant switching states and instantaneous dc voltage feedback integrated into proposed controlling technique. There is no external voltage controller involved, since no associated fine-tuning issues are existed. Simulation results are provided to verify the fast-dynamic performance, low content of line current THD, and good voltage balancing of dc bus capacitors of NPC inverter.