Control Strategy Analysis Of Reclosing At Unknown Speed In Electric Locomotive Auxiliary Transmission System

Auxiliary Transmission System(ATS) ensures the safety and reliability of the equipments on the locomotive, thus it directly affects the performance of locomotive. The cooling fan, air compressor and fan in Alternating Current(AC) ATS are driven by asynchronous motor but not the hybrid of traditional mechanical and hydraulic ways, which dramatically exerts the characteristics of AC speed governor and improves the overall performance. Considering the particularity of the rail transport locomotive traction transmission system, the problem of monitor restarting at unknown speed after passing phase becomes an extremely urgent problem and an international topic in the electric traction drive field. Since there are not many published researches at present, a corresponding control strategy is proposed to promote the monitor restarting success rate and realize the locomotive dependable circulation.After analyzing the structure and control strategy of ATS systems in detail, a mathematic model of asynchronous motor and dc-to-ac converter is presented and direct torque control strategy based on circular flux is proposed. This method uses full-order speed identification based on MRAS to build a speed sensorless control system and the closed-loop flux is applied to improve the control accuracy. Meanwhile, instantaneous power and Residual Voltage(RV) in stator side of asynchronous motor is introduced and analyzed. A self-optimizing fuzzy search method is given to estimates the restarting speed and a phase correction algorithm based on RV is proposed. It combines current control loop and serial and parallel link restarting way, rendering a high success rate, a quick speed and a credible reliability.Simulation model of asynchronous motor speed sensorless DTC control system is built based on MATLAB/Simulink platform and the proposed phase correction algorithm based on RV control algorithm is embedded into the control system and simulation. The experiments shows that the proposed control strategy significantly reduced the impact of current and torque, furthermore, it highly enhances both the restarting success rate and circulation reliability.