Research On3-Phase And4-Leg Urban Rail Train Auxiliary Inverter

In recent years, the rapid development of urban rail transport and power electronics technology calls for a high level quality of the train auxiliary inverter power systems. The inverter of3-phase and4-leg topology using3-dimensional space vector modulation (3D-SVM), with the advantages of small size, simple structure, high utilization of DC voltage, good capability of handling unbalance load, and so on, is quite suitable for urban rail train auxiliary power systems. The3-phase and4-leg auxiliary power system for rail vehicle is researched in this thesis in depth.The topologies of main circuit which is widely used in the current urban rail train auxiliary inverter power systems are analyzed and compared, which is in order to determine the topological type of auxiliary inverter power system for study. The development process and application situation of3-phase and4-leg inverter are summarized. Based on the comparation of SPWM and SVPWM, the Three-Dimensional Space Vector Modulation is chosen to apply in this thesis for modulation method.According to the coordinate transformation and phasors theory, the mathematical model of4-leg inverter topology is derived and the principles of unbalanced3-phase inverter and then proposed control approach is analyzed. Double closed loop PI control strategy principles with voltage and current in the rotating coordinate system is analyzed in detail and dual coordinate transformation is applied to achieve the separation of positive, negative and zero sequence of voltage. Also current feed-back decoupling is applied to improve dynamic performance of the system. The quasi proportion resonant control in the two-phase static coordinate system is discussed and the principles and concrete realization method of3D-SVM in the static coordinate system is fully analyzed.The design process for parameters of main circuit and filter circuit in the auxiliary inverter system is discussed in detail, according to the design requirements. Based on the theoretical analysis, the simulation models are built and verified using Matlab and Simulink computer software. The functional modules in proposed Digital Control System are introduced then. Especially the peripheral protection circuits and the system control panel, which is based on FPGA and DSP technology, are introduce in detail in aspect of hardware and software.At last, the35kVA auxiliary inverter power system for urban rail train is proposed. The software design is based on PI control strategy and3D-SVM technology, the closed-loop experiment is carried under the condition of balanced load, unbalanced load and mutational load, whose results proved the correctness of the system and the effectiveness of control strategy proposed in this thesis.