Modeling, Control And Modulation Of The Post-Fault Grid-Connected Three-Phase PWM Converter

As a compact and high-efficiency solution to power conversion, the grid-connected three-phase pulse width modulation (PWM) rectifiers play a central role in utility interfaces with renewable energy resources, flexible AC transmission, adjustable-speed drives, and electric or hybrid electric vehicles. However, with the integration of power rectifiers into these application fields, the reliability of the overall system is challenged. Faults that occur in the power rectifiers endanger the operation of the overall system and, under certain circumstances, lead to the shutdown of the entire system. The reliability of the power rectifiers has gained increasing attention in the past decades.In this paper, the three-phase four-switch (TPFS) PWM converter is adopted as the post-fault topology to address the situation where the switch faults occurs in one of the three legs of the three-phase six-switch (TPSS) PWM converter. The contents discussed in this paper consist of two sections:modeling and control of the three-phase six-switch PWM converter, the modulation, modeling and control of the post-fault PWM converter, which is aimed to achieve the excellent uninterrupted operation of the gird-connected PWM converter.Considering the TPSS PWM converter, the space vector modulation (SVM), system modeling and controller design are discussed in detail in this paper. A detail small signal model is developed to facilitate the controller design, which gives sufficient insight into the steady and dynamic behave of the TPSS PWM converter. Using the proposed model based controller, the TPFS converter exhibits the excellent steady and dynamic performance. In addition, a SVM strategy is proposed in this paper, where sector identification and trigonometric functions are not required.The researches on the post-fault PWM converter in this paper are focused on the space vector modulation (SVM) and the AC current quality improvement. The detailed analysis of the fundamental of the TPFS converter reveals that the capacitor voltage oscillation is inherent. In addition, the effect of the capacitor voltage oscillation on the AC current is investigated and a novel SVM strategy is proposed, where sector identification and trigonometric functions are not required. Furthermore, the effect of various SVM strategies on the AC current ripple is analyzed. Based on the presented analysis, the optimized SVM strategy is selected to guarantee the excellent performance of the AC current.Finally, the simulation and experiment results validate the correctness and effectiveness of contents discussed in this paper.