Research And Implementation Of Single-Phase PWM Rectifier For The Locomotive

The Single-phase PWM Rectifiers in electric locomotives are usually divided into locomotive auxiliary converter and main converter. Although based on the same topological structure, they should have great differences about control strategy and switching frequency in the control system as the different power levels and power semiconductor devices. This thesis mainly studies the control strategies about how to control input current phase effectively and achieve unity power factor for the control systems of varied switching frequencies.The control strategies can be divided into two parts: direct current control strategy which is suitable for small and medium-sized power auxiliary inverter of high switch frequency, and indirect current control strategy which is suitable for the high power main converter of the low demand about the switch frequency. For the small and medium-sized power rectifier of high switching frequency, classical direct current control strategy can well solve the problem of input current phase tracking; due to the fluctuations of input side resistance parameter, the traditional indirect current controller could not control input current phase preferably in the high power rectifier system of low switching frequency. This thesis analyses the characteristics of these two kinds of control strategies and describes the control modeling.Aimed at the defect of traditional indirect current control strategy, this thesis puts forward a phase compensator. In the D-Q coordinate, with the input current decoupled into active current and reactive current, the phase compensator gets the corresponding phase compensation through analysis and calculation. The compensation contributes to the calculation of the modulation wave and dynamically adjusts the phase, so as to control the phase difference of input current and input voltage and the reactive current effectively.On the basic of related simulations and specific experiments, it is proved that classic direct current control strategy is good with current phase control in the control system of high frequency; and the phase compensator could well solve the problem of reactive power fluctuation which is caused by the unsuitable input resistance parameters in the traditional indirect current control strategy.