Research On DC Microgrids Integrated Electric Vehicle Charging And Traction Power Supply System

Microgrid is an autonomous system which integrates power generation,power distribution and power consumption.It builds a new energy technology fair competition system,and has a long-term technical,economical,environmental and social significance.As a new type of power system,DC microgrid can matche the development needs of clean energy and energy internet.On the other hand,electrification railway locomotive and electric vehicles will be an important part of the future urban power grid load,which has a great significance for safe operation of the power supply system.Under the background,according to the characteristics of the traction power supply system and electric vehicle charging,a architecture of DC microgrids integrated electric vehicle charging and traction power supply system is proposed,and the basic composition and topology structure of the system is described,which the effective use of renewable energy is taken into account.In order to ensure the safe and stable operation of this system,the control strategy is mainly studied.Firstly,the traditional droop control is introduced,and the steady state analysis of the parallel distributed generations under droop control is carried out from the three aspects of the circulation size,output voltage and output current.The factors that influence the traditional droop control performance are obtained.An improved droop control strategy based on adaptive virtual impedance is proposed.The droop virtual impedance can be automatically adjusted according to the difference of power distribution among distributed generations,so as to realize power sharing.Simulation results verify the effectiveness of the improved droop control strategy.Secondly,for the case of unilateral power supply,a coordinated control strategy based on power hierarchical is proposed.The system is divided and introduced,and the constraints of system operation are determined.The energy management and power distribution of the coordinated control strategy are introduced respectively.The coordinated control process of grid-connected operation,island operation and transient operation state is described.The control method of each unit converter is analyzed,and the simulation model can verify the proposed control strategy.Finally,for the case of bilateral power supply,an improved coordinated control strategy for DC microgrid based on DBS is proposed.The system is divided into f our working modes and the switching signal of each mode is optimized through the synchronous pretreatment link of the voltage signal.The control strategy eliminates the central controller,and improves the reliability and accuracy of the system by combining the improved droop control strategy based on adaptive virtual impedance.The simulation results show that the control strategy can maintain the DC bus voltage stability and achieve the power balance of the system.