Investigation And Simulation Verification Of Single-Phase Three-Level Controlled Rectifier

In order to improve the efficiency of railway and changing existing patterns of transportation, China has attached great importance to development of high speed railway. At present, China has successfully developed a number of high speed trains and high power electric locomotives, they have autonomous intellectual property and combine the most advanced AC drive technology in the world. As the key technology of AC drive system, three-level controlled rectifier is significant for theory and engineering design.The three-level structure of CRH2 high-speed EMU is the research object in this paper. The operation principle of single-phase three-level neutral-point-clamped(NPC) controlled rectifier is discussed. Through switching function definitions, mathematical modeling is established. On basis of modeling above, two close-loop controllers of the rectifier are designed and derived from the classical control theory point of view. To improve tracking performance of sinusoidal input current, a proportional-resonant(PR) controller is proposed. Which resonates at fundamental frequency of input current, the system can obtain a high gain to improve performance.Predictive current control scheme is analyzed in this paper. Modulation algorithms of SPWM and SVPWM for single-phase three-level rectifier is discussed. In the field of SPWM algorithms, the research object is single-phase three-level uni-polar SPWM algorithm. Considering the unbalance problem of neutral point voltage for three-level rectifier, feed-forward of capacitor voltage balancing method is proposed. In the field of SVPWM algorithms, neutral point voltage control method is embedded in SVPWM modulation algorithms by arranging basic vector sequence and function of time.A simulation model based on predictive current control is established and analyzed by using the PSIM software. PR controller is designed in the inner-current-loop. Switching between traction working or switching between traction working and regeneration conditions is discussed. The simulation results show that SPWM modulation and SVPWM modulation both can achieve stable DC voltage and AC current tracking. But SVPWM modulation has better performance. When SPWM modulation is used, the neutral point voltage balancing controller is necessary.With the theoretically analyzed above, the hardware and software of experiment system are designed. A single-phase three-level NPC controlled rectifier system is based on TMS320F28335. And IGBT drive circuit and master control conditioning circuits are designed in this paper. Finally, the software design flowchart is shown.