Research On DC Electronic Load With AC Energy Feedback

With the rapid development of China's railway transport industry and the enhancement of people's awareness of energy saving and environmental protection,how to save energy and increase efficiency in locomotive power plant aging test becomes an important research topic of related enterprises.In this paper,taking 400 kW locomotive power as the test object,a kind of DC electronic load device with AC energy feedback which can measure the electric energy to the grid is designed.First of all,through the comparison and analysis of the topology and control strategies of the DC electronic load in domestic and foreign literatures,and combining with the working characteristics and performance technical indexes of the locomotive power supply,the basic principle of DC electronic load with AC energy feedback which consists of a phase shift full bridge converter with soft switch technology and a grid connected inverter with LCL filter is researched,and the scheme of modular parallel system program is proposed.Secondly,according to the composition of the electronic load,the power circuit and control strategy of the front and back converter are analyzed and researched.The key problems such as the realization of the ZVS of the bridge arm of the soft switch phas shifted full bridge converter,the duty cycle loss of the secondary side of the transformer and the oscillation of the rectifier diode are analyzed and researched,and on this basis the main circuit parameters of full bridge converter is designed.Based on the state space averaging method,the small signal mathematical model of the soft switching phase shifted full bridge converter is established,and the double current loop control strategy which is the phase shifted full bridge input current outer loop and the output current inner loop is proposed.According to the technical specifications of the grid connected inverter the main electrical parameters are designed.By establishing the mathematical model of grid connected inverter,the tracking effect of PI controller and PR controller on grid connected current is discussed.Aiming at the defects of PI control and PR control,a quasi-resonant PR control technique which has zero error current tracking and anti grid interference capability is researched.In order to solve the problem of LCL resonance,the active damping capacitor current feedback control is used to increase the damping of the system,and the LCL resonance suppression is realized.Finally,the hardware and software design of the control system are introduced.Through the MATLAB simulation and prototype experiment,the DC electronic load with AC energy feedback topology and control strategy is verified,and simulation and experimental results verified the feasibility of the topology and control strategies.