Research Of Series Connected IGBT Medium Voltage Inverter's Key Problems

Based on the analysis of the series IGBTs'damage mechanism and after the discussion of the static voltage balance, dynamic voltage balance, RCD snubber, this paper proposes a new structure of dynamic voltage balancing circuit used in series connected IGBTs. The design method and parameters calculation of this circuit are also proposed, the simulation results and the experimental results prove that the ideas and methods of this paper are all completely correct, and this circuit can be applied to series IGBT applications.Focused on features of the DC converter without a midpoint, and the voltage reflection phenomena of long-distance transmission lines, based on the quantitative analysis of inverter output harmonic, this paper proposes a new inverter output filter structure under the guideline of unifying the inverter output filter topology, and then completed the inverter output du/dt filter's design, simulation results show that the filter designed in this paper can not only effectively overcome the voltage reflection phenomenon, but also can restrain the du/dt.The third task of this paper is to keep speed synchronization and power balance for multi-motor synchronous system, combined with constant voltage and constant frequency control method's principle of the inverter, and took the feature of non speed sensor into account; this paper analyzes the feasibility of the synchronization compensation control algorithm based on current feedback.A simplified simulation model is built in order to verify the synchronization compensation control algorithm based on current feedback, simulation data show that the effect of the control algorithm can achieve predetermined goals. Finally, the paper designs an experiment system based on TMS320LF2406 so as for the further testing of the algorithm. Experimental data show that the algorithm can effectively control the synchronization of speed and power balance of the multi-motor synchronous system.