| According to the situation of our country,it is necessary to develop the railway transportation system with the purpose of alleviating pressure of the railway and improving speed and quality of the railway transportation meanwhile.Therefore,the development of high-speed train has become an inevitable demand.Traction auxiliary system is one of the most important components of the high-speed train,which is mainly supplied by auxiliary converter.And the auxiliary converter consists of DC-DC buck converter and inverter.In this paper,two kinds of zero current shutdown DC-DC converter topologies are presented;which are suitable for DC-DC buck part of the auxiliary system on the high-speed train.The paper also introduces their working principles and output characteristics,then their parameters are selected according to the resonant cycle and switching frequency.At the same time,aiming at one kind of the two,the state space average method is used to write state equation of the converter for each period of time,then small-signal model and transfer function of the circuit are gained after weighing time,which are certified by the relevant simulation.Through the feedback of output voltage and inductive current of the circuit,the circuit can realize to keep stable outputs by the closed-loop control of duty cycle,afterward parameters of the PI compensator are calculated and correctness of the calculation is verified by circuit simulation.Finally,building the circuit experiment platform and pulse control board,researching in closed loop control strategy for PWM drive pulse of the switch,then completing the experiment.The output voltage and current can be kept stable under closed loop control,and the circuit achieves turn off switch in zero current state;it also verifies the output voltage and current remaining stably in theoretical value under the load switching condition,and when the circuit is operated under the light load condition,it can automatically change the control mode to realize a stable output voltage. |
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