The Comprehensive Design and Optimization of the Post-Fault Grid-Connected Three-Phase PWM Rectifier

The comprehensive design and optimization, including the optimized modulation approach, detailed modeling, and reliable control algorithm, is presented in this paper to guarantee the stable operation of the post-fault three-phase pulsewidth modulation (PWM) rectifier. The effects of the space vector modulation approaches on the capacitor current are investigated. Based on the analytical results, the method introducing the smaller capacitor current is selected as the optimized modulation approach, which is of paramount importance to avoid the permanent failure of the dc-link capacitors. Then, with the optimized modulation approach, a control-oriented model for the post-fault PWM rectifiers is derived based on the $\alpha-\beta$ stationary frame, where the capacitor voltage oscillation and deviation are taken into account. The proposed model-based controllers do not require the phase-locked loop (PLL), and the elimination of the PLL means that the post-fault rectifiers can never lose synchronization with the grid. Furthermore, an equation of the required dc voltage for linear modulation is proposed, and using the proposed equation, a correct dc voltage is selected to reject the overmodulation. The experimental results validate the effectiveness of the proposed comprehensive design and optimization. Finally, a conclusion can be drawn from the experimental results—that the dc-link capacitor current and the linear modulation should be taken into account when selecting the dc voltage in the post-fault operation.