Study on Control Strategy of Three-level PWM Rectifier

The three-level PWM rectifier topology has been studied in this paper,and the decoupled state-space equations in synchronous rotating reference frame(d-q frame) were derived.The hierarchical controller structure is adopted,namely,the inner current-loop is responsible for reference current tracking and the outer voltage-loop is responsible for load regulation.The design methodologies for proportional-integral(PI) controllers are presented for the inner current-loop and outer voltage-loop respectively.The proposed three-level PWM rectifier based on space vector pulse-width-modulation(SVPWM) strategy is simulated using MATLAB/SIMULINK.Simulation results demonstrate that the proposed three-level PWM rectifier provides excellent performance both in steady-state and dynamic load variations.Pure sinusoidal waveforms can be achieved in grid currents with a unity power factor.Besides,energy feedback is realized.