| The traditional auxiliary power inverter for locomotive, featuring open-loop control scheme, cannot meet the requirements of modern locomotive on auxiliary power performance. It is imperative to upgrade and reform the traditional auxiliary power inverters. Under this circumstance, the paper carried out the research on a new auxiliary inverter for modern locomotive.Fisrtly, exiting topologys and control schemes of three-phase voltage source inverters are compared. According to the requirements of locomotives on the auxiliary power, a three-phase topology with three legs is chosen and Space-vector and dual-loop control scheme are employed. Mathematic models of the inverter are derived in ABC coordinate,α-βcoordinate and d-q coordinate respectively; the mathematical model in d-q coordinate is verfied by the circuit model setup in Simulink. Next, this paper analyzes the basic time delay elements existed in digital control systems and the influence of time delay on design of control parameters and system stability. Meanwhile, design procedures for both voltage loop and current loop are given.Several issues on designing key parameters for power stage circuit are discussed in this paper. To choose a reasonable switching frequency for the system, two relationships between switching frequency and power losses/ system bandwidth are established, which could offer a basis for the determination of switching frequency. This paper gives the design guidelines on how to choose power swithes and LC filter. In the software realization chapter, the software flow chart is given. Soft start with variable frequency scheme is presented in detailed. A comparison between software implementation of SVPWM and hardware implementation is also given.Finaly, system model is established and verifed in Matlab. A 35kVA prototype based on TMS320F2812 digital control platform is built. The experimental results varified the correctness of the theoretical analysis.
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