| Auxiliary converter is an important part of electric locomotive,which supplies power for different auxiliary equipments of train.Their stable operation of the converter ensures the normal operation of the train.Based on the school-enterprise cooperation project,this paper studies the principle and designs the control strategies of each part in electric locomotive auxiliary converter in the project.The paper focuses on solving the problems encountered.The study was concentrated on the following parts:Auxiliary converter has semi-controlled thyristor rectifier,three-phase inverter and half-bridge DC-DC converter in the project.This paper studies the principle and the control strategies of each part.The semi-controlled thyristor rectifier adopts closed-loop control strategy of DC side capacitor voltage.Three-phase inverter adopts voltage and current double closed-loop decoupling control in the synchronization reference frame.Half-bridge DC-DC converter adopts closed-loop control strategy of output capacitor voltage.Simulation verifies the performance of control strategy.When the converter is cascaded,the DC side of the inverter oscillates due to impedance mismatch.This paper analyzes the oscillation mechanism and the system stability by impedance matching principle in simple model.In small-signal model,the paper analyzes system stability by Nyquist steady-state criterion,and introduces active damping compensation controller,which makes the system satisfies the Nyquist steady-state criterion and makes the system stable by changing the structure of three-phase inverters.Based on the theoretical analysis of the auxiliary converter,this paper designs the control cabinet of the auxiliary converter to achieve the control target of the auxiliary converter which meets the requirements of the project.The hardware control cabinet takes DSP+FPGA as the core control board,and also includes functional blocks such as AD sampling board,PWM pulse board,CAN communication board.Software control mainly includes system state machine control logic,different converter control algorithm,fault judgment protection mechanism and other functions.The working waveforms of different parts and the effect of DC-side oscillation suppression are simulated in Matlab/Simulink.The control algorithm and the basic functions of the control cabinet are tested on the hardware-in-the-loop simulation platform;The output of the auxiliary converter is verified whether the auxiliary converter output meets the project requirements by high-power experiments.The experimental results show that the auxiliary converter has good steady state and dynamic output performance.It can operate reliably under complex conditions and the output meets project standards.54 figures,3 tables and 62 references are given. |
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