| CRH2EMU has already been widely applied in domestic rail transportation, also in a constant situation of reform and innovation. So the research on the transmission system of CRH2type of EMU shows a positive reference function in site maintenance. In that case, this paper is mainly focused on four quadrant rectifier and inverter of motor. It offers an overview of the operating principle, equivalent circuit, phase diagram of the single-phase three-level four-quadrant pulse rectifier; Single phase four quadrant rectifier control adopts the voltage loop and inner current closed-loop control, of which the control method is the transient current control, by the means of positive and negative inverting cascade SPWM modulation method. Rectifier neutral potential imbalance will result in the emergence of the25th harmonic of the current, affect the power quality and cause pollution to the grid. In this situation, the switch state changes to change the charging and discharging process of the capacitor while maintaining the same voltage. The design of the four-quadrant rectifier can ensure the power factor is1at traction and braking condition, in accordance with the requests to achieve the conversion of the stability of DC voltage at2600V in traction and3000V in braking, good to meet the operational requirements of the locomotive.This essay also gives a theoretical analysis to the three-level inverter circuit topology, the space voltage vector modulation method of SVPWM, the influence and solution to the neutral potential of the EMU; provides the mathematical model of the asynchronous traction motor under the rotor field-oriented; studies the basic idea and basic equations of vector control; establishes the three-level vector control system, mainly focused on the solution of the reference voltage vector and vector synthesis calculation; selects the control factor of hysteresis comparison method to solve the problem of the neutral potential caused in the capacitor charging and discharging process. Through the simulation analysis, the article verifies the feasibility of the control system and the effectiveness of the approach to the imbalanced neutral potential.According to the traction characteristics curve and braking characteristics curve of the CRH2type, the design of the traction electromagnetic torque control, traction rotor flux control, braking electromagnetic torque control, braking rotor flux control, constant speed electromagnetic torque control, constant speed rotor flux control allows the EMU a stable operation in a given speed of-1km/h, and the state conversion can be done smoothly to ensure the required acceleration and current. On the basis of each controller, this paper completes the simulation, specifies the results, and verifies the correctness and reliability of the designed control system. |
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