| With the rapid increase in the proportion of China’s urban population,in order to alleviate the pressure of commuting citizens,urban rail transit with large capacity and high speed is being built at a high speed,and trams,with their advantages of low construction cost and short cycle time,have become one of the main in-process formats.In recent years,in order to realize the de-contacting of modern trams,two new power supply technologies,Wireless Power Transfer(WPT)and Hybrid Energy Storage System(HESS)have been widely discussed,and studies have been conducted to combine the two technologies to fully utilize their advantages.Most of the current energy efficiency optimization control strategies for Dynamic Wireless Power Transfer(DWPT)systems are complex and rarely consider the impact of HESS on the load characteristics of trams in dynamic environments.A grid-connected DWPT system circuit topology and a simple and easy system power control method based on this topology are designed in this thesis,and the efficiency of the DC/DC link in the system are also optimized.Firstly,based on the active impedance matching principle,the energy efficiency characteristics of DWPT systems based on SS,LCC-S,and LCC-LCC topologies are compared and analyzed.Then,the electrical energy flow of the train energy network during tram operation is analyzed,and the load characteristics under the joint action of HESS and traction system are summarized.Finally,based on the LCC-LCC topology,a grid-connected DWPT system topology is designed by cascading DC/DC links between the rectifier bridge and the on-board DC bus,under which the power supply of the system is easily controlled and the transmission efficiency is less affected by the power variation,and a control strategy is proposed to control the power supply of the DWPT system by adjusting the voltage of the supercapacitor bank.Secondly,the secondary Buck/Boost bidirectional converter is controlled in critical mode based on the complementary PWM strategy to reduce the transmission loss of the cascaded DC/DC link.And after a detailed analysis of the duty cycle and the limit range of the transfer power of the converter in the critical mode,the Buck/Boost bi-directional converter transfer power control strategy based on the resistance parameters is proposed,which is more accurate,stable and linear than the direct adjustment of the duty cycle to control the transfer power of the converter,and the design of the voltage fuzzy controller of the supercapacitor bank is completed based on this strategy.Then,based on the aforementioned research,a rail coupling structure with a DD-type coil on the primary side and a U-type core on the secondary side is designed by Maxwell,and the hardware circuit design of the control board with DSP28335 chip as the core,and the power board of the full-bridge inverter,uncontrolled rectifier bridge and Buck/Boost bidirectional converter is completed.Finally,the feasibility of the DWPT system power supply control strategy is verified by MATLAB/Simulink simulation,the control effect of the fuzzy controller on the supercapacitor group voltage is tested,and a small power experimental platform is built to verify the simulation conclusions.The experimental results show that the dynamic and steady-state performance of the supercapacitor bank voltage is better under the control of this fuzzy controller,and the amplitude of the DWPT system power supply change reaches 50% when the supercapacitor bank voltage power changes 59%,which is an obvious regulation effect,while the transmission efficiency of the DC/DC link is above 98%. |
PDF Full Text Request