Research On Traction Network Voltage Compensation Of High-speed Railway Under Long And Large Ramps Conditions Considering On-board Energy Storage

With the expansion of the high-speed railway operation range,many railway lines are opened in mountainous sections.When the train runs in the long ramp section,the larger traction under uphill conditions and the larger braking power under downhill conditions of the EMU and the injection of harmonics into the traction network will be in this section.These problems make a bad influence on the voltage of the traction network.So,it is important to effectively suppress voltage fluctuations when train running on the long slope section for the safety and stable operation of railway.In this thesis,the model of the high-speed railway traction power supply system and EMU are established.The operating characteristics and voltage fluctuation mechanism of the train running on the long ramp section are analyzed.A traction network voltage fluctuation suppression scheme based on the on-board energy storage system is given,the corresponding control method and energy management strategy are studied,and simulation analysis verifies the effectiveness of the proposed scheme.The main research contents are as follows:(1)Build the model of the high-speed railway traction power supply system and EMU.The structure and control method of the rectifier and inverter of the traction drive system are construed.The transient current control is employed to control the rectifier,in the same time,the rotor field-oriented vector control is employed to get command of the inverter.In order to study the whole operation process of the train,the traction and braking characteristics of the train are construed.The model analyzes the whole process of train traction and braking,and verifies the correctness of the model,which is the basis of this thesis.(2)The voltage fluctuations caused by working conditions and the voltage fluctuations caused by harmonic injection when the train is running on a long ramp section are studied.The load torque is used to simulate the change of line conditions,and the operation of the train on the long ramp section is simulated.The generation mechanism of voltage fluctuations caused by climbing and downhill conditions and voltage fluctuations caused by harmonic injection are studied,and the regular patterns of voltage fluctuations are analyzed.The results express that the greater the traction and braking power of the train,the farther the train is from the traction substation,and the greater the voltage fluctuation of the traction network.What’s more,since the resonance frequency of the traction network of long scope section is lower when it is compared to the ordinary traction network,so the voltage harmonic content of the traction network of the train running on the long ramp section is higher than that of the ordinary line.(3)Considering the negative influence when the train is running caused by the fluctuation of traction network voltage,a solution according to the on-board energy storage system is proposed.The compensation mechanism of the on-board energy storage for two types of voltage fluctuation problems is studied.According to the compensation target of the energy storage system,the converter control strategy of the energy storage system based on M-PR control is studied.The results show that the scheme can effectively suppress the two types of voltage fluctuations mentioned.(4)The energy management strategy of the energy storage system is analyzed,and a rule-based energy management strategy is studied to setting the power of the energy storage system.Furthermore,a superior energy management strategy based on fuzzy control is proposed which can optimize the power of the energy storage system.Simulation analysis has obtained the traction network output power and energy storage SOC change curve under two energy management strategies.According to the results,we can draw a conclusion that the energy storage system under the fuzzy control energy management strategy can adjust the output power adaptively according to the train operation,and the voltage fluctuation of the traction network is reduced after compensation.Finally,the capacity configuration of the energy storage system is studied.