A new control method for neutral-point-clamped three-level PWM rectifiers

A neutral-point-clamped three-level PWM rectifier is studied in the paper. The naturally decoupled state-space equations in stationary reference frame (α-β) were derived. Furthermore, a new PWM method for input current harmonic of rectifier is presented including asymmetrical regular sampling and DC-bus voltage balancing. The hierarchical controller structure is adopted and can be divided as the inner current-loop and the outer voltage-loop. Besides, a proportional sinusoidal signal integrator method, namely proportional-resonant (PR) controllers in two phase stationary reference frame is proposed. The presented PWM control method for three-level PWM rectifiers is simulated using Psim8.0. Simulation and experimental results based on a rectifier of a 75kVA three-level NPC converter prototype show that the provided control scheme provides preferable performance in steady-state.