| China’s high-speed railways are developing by leaps and bounds,which in turn enables continuous breakthroughs and innovations in the core technology of EMU.At the same time,with the enhancement of the country’s various hard powers in high and new technology and the improvement of the people’s overall material living standards,the requirements for safe operation and ride comfort of EMU is becoming higher and higher.As the key equipment of the EMU,the charger plays two important roles: one is to charge the battery when the emergency battery is fed,and the other is to supply power to the low-voltage DC load on-board when the train is running.The wide application of technologies such as power electronics and digital signal processing has promoted the performance of chargers to be more outstanding.However,domestic chargers started late,and the core technology is still mastered by foreign companies.Therefore,the development of high-performance chargers is of far-reaching significance to the improvement of my country’s EMU technology.This article takes a certain type of domestic EMU charger as the research background and adopts the research method of semi-physical simulation to study the main circuit and control system of the charger.There is a solid theoretical basis for the parameter design of the main loop components,and a more adequate understanding of the control system and control strategy.First,analyze the working principle of nickel-cadmium batteries commonly used in EMU,and determine that nickel-cadmium batteries are very suitable for the operating conditions of EMU by analyzing its advantages and disadvantages and temperature compensation curves.Comparing several battery charging methods commonly used in the field of professional technology,comprehensively pros and cons,a two-stage charging method of first stage constant current and second stage constant voltage is selected.This charging method has fast charging speed and high charging efficiency.According to the needs of the charger,use low-voltage input as the input mode and select the corresponding main loop topology,design the circuit of the input link,DC/DC link,and output link,and calculate the parameters of the components used in each link.Then,select the single closed-loop control mode,establish the small signal model of the main circuit of the charger and derive the open-loop transfer function of the control quantity and the output voltage,write the PSO algorithm program,call the PSO optimization program through the model nesting,and determine the PID parameters.At the same time,the pre-charging module,charging process control module and fault protection module in the control system are designed.According to the functional design of the control system,the control model is written and the man-machine interface is built in Simulink.In order to connect the simulation control system with the actual main circuit,a hardware circuit is built to process the collected parameters,and the software and hardware complement each other to form a semi-physical simulation platform.Finally,the "simulation control system + simulation main loop" experiment was carried out in Simulink,and the results of each link met the requirements.The prototype realizes the working mode of "virtual controller + actual main circuit",and performs platform experiments on the prototype with functions such as pre-charging,load switching,and overcurrent protection.The final result shows that all aspects of the prototype meet the expected design requirements. |
