Research On High Speed Control Schemes For Traction Motors Based On Domestic TCU Of CRH5 High Speed Trains

Control technology of traction motor is one of the core technology of high speed train traction drive system, its control performance will directly affect the safety and comfort of the vehicle. Due to the traction drive system itself is a complicated system, there still exists many research difficulties. This thesis mainly studies multi-mode pulse width modulation technology under low switching frequency and field-weakening control strategy in high-speed square wave zone.Firstly, this paper analyzes the control and modulation strategies of the traction motor in full speed range from macro perspectives in depth, and points out the corresponding motor control strategy should be adjusted reasonably when adopting different modulation methods. And this paper gives out the hybrid control scheme that the rotor field orientation closed-loop vector control in the motor low speed area and voltage feedforward scalar control in the high-speed square wave region. Considering the actual traction controller with the characteristics of DSP+FPGA structure, in order to solve the problem that control and modulation are non-synchronous, phase angle regulator is added to improve the responsiveness of control.Aiming at the high power and low switching frequency characteristics of the traction drive system of the high-speed train, the two current commonly used kinds of synchronous modulation strategies with low frequency, SVPWM and SHEPWM, are compared and analyzed. Comparing the voltage harmonic, WTHD, and so on, under the two kinds of modulation strategy with the same frequency, the conclusion that with the harmonics performance of 3 pulses SVPWM is better, is obtained. So in different applications, modulation modes and types need to be selected reasonably to achieve the optimal modulation performance. At the same time, the smooth switching experiment adopting SHEPWM between different modulation modes in the full speed range is completed base on CRH5 domestic TCU platform.In the high speed field-weakening region, the traction torque decreases with the increase of the rotating speed, and the motor torque output capacity depends largely on the field-weakening control strategy. The traditional field-weakening control method leads to the rotor flux be inversely proportional to rotating speed, this control method requires the amplitude and phase of the stator voltage are controllable. Because of the voltage amplitude saturation in the square wave zone, motor torque capacity can not fully play, the motor torque can’t satisfy the requirements of mechanical characteristics.Aiming at the problem in the traditional field-weakening control, by analyzing the optimal operating trajectory of the motor at different stages, this paper introduces q axis voltage close-loop control accordingly, coordinates and allocates the excitation current component and the torque component reasonably, achieves full playing of torque performance with limited voltage and current. Simulation results and small power motor platform experiments verify that the field-weakening control strategy is feasible and effective.