Weak Magnetic Locomotive Auxiliary Transmission System Control Strategy Research

Auxiliary transmission system is an important part of locomotive systems, its performance has a direct impact on the economy, reliability of locomotive. As a result of locomotive auxiliary driving system of cooling fan, air compressor and fan are driven by asynchronous motor, usually with the disadvantages of energy waste, bad economic. In this paper, through the study of the auxiliary transmission system for field weakening operation of induction vector control strategy, in order to improve at the weakening region load capacity, and improve the utilization rate of energy of induction motors.This paper introduces the auxiliary transmission system on the structure and control strategy of locomotive systems in detail. According to their operation principle, the paper introduces the relevant concepts of the field oriented vector-controlled strategy, speed identification method base on the integral sliding-mode observer and the flux-weakening control algorithm. Based on the comprehensively deep research on the induction motor’s mathematic model and control theory, this paper analyses the operation conditions under the limits of voltage and current based on the induction motor mathematical model and presents flux compensation and phase compensation control method through analyzing the operating characteristics of induction motors in different region. The flux compensation control coordinates d, q axis current so as to produce the maximum torque by changing the flux curve form while the phase compensation control changes the phase of stator current.Simulation model of speed sensorless vector-controlled on induction motors is built based on MATLAB/Simulink platform, and a proposed flux-weakening control algorithm is embedded into the control system and simulation, speed identification results of simulation show not only that the proposed scheme provides high-performance speed identification, but also that this scheme is robust with respect to the variations of machine parameters and operating conditions. On the premise of accelerating to the same speed based on flux compensation control strategy, the output torque is much larger while the time for speed-up or slow-down are remarkably shorter, compared with traditional control strategy. simulation results show that the proposed methods are effective for increasing motor output torque, and the results verify the validity of the theoretical analysis.