The Research Of Former Stage Of High Power Frequency Conversion And Three-level PWM Rectifier

The Former Stage of High Power Frequency Conversion system using the traditional6-pulsediode rectifier is not only low power factor but also harmonic pollution will be caused to the powergrid. The multi-pulse rectifier technology can effectively reduce the harmonic pollution. This paperresearch and design the self-coupled12pluses rectifier of500kW inverter.We analyse the self-coupledphase-shifting transformer and balanced reactor in-depth. Simulation and experimental results verifythe feasibility of the theory.PWM rectifier can work as high power factor and four quadrant and minimized harmonicpollution, so the research become hot at the high power system. This paper is the research of themidpoint of the diode-clamped three-level PWM rectifier.First, according to the voltage-type three-level PWM rectifier topology, we analyse of the basicworking theory. The three-level PWM rectifier model in three-phase static coordinate system andtwo-phase rotating coordinate system mathematical modeling is analysed. Combined the space vectorpulse width modulation we analyse the direct current control method with the voltage and currentring double-loop structure.Researched a way to solve the effect of dead time; studied the effects of the efficiency ofswitching devices narrow pulse problem; to achieve three-level PWM rectifier control of midpointbalance, researched a method of balance factor. Designed a three-level PWM rectifier MATLABsimulation and finished the completion of a prototype platform experiment.