Design and Simulation of a Three-Level NPC Rectifier for Wind-Energy Applications

Abstract

This paper presents an integrated modulation, control, neutral-point balancing, and open-circuit fault-diagnosis framework for a three-level neutral-point-clamped (3L-NPC) rectifier in a wind-energy conversion system. A simplified third-harmonic-injection space-vector pulse-width modulation (SVPWM) scheme is combined with zero-sequence voltage injection for neutral-point-voltage (NPV) balancing. Under unbalanced-grid conditions, positive- and negative-sequence currents are regulated by dual PI loops synchronized through a dual second-order generalized integrator phase-locked loop (DSOGI-PLL). Continuous-wavelet-transform (CWT) features of the DC-link voltage are processed by a backpropagation neural network (BPNN) for open-circuit fault diagnosis. MATLAB/Simulink results show a DC-link-voltage rise time below 0.025 s, 3.75% overshoot, approximately 1% input-current THD, and effective NPV balancing. The BPNN achieved an output-vector RMSE below 0.05 on the random test partition.