Control Technology And Experimental Research Of The Energy-Fed DC Electronic Load

Considering of multiple shortcomings in the traditional power-source out-of-factory test methods,inclusive of lower energy utilization rate and single loading pattern,more modern electronic loads have been widely applied in practical power-source tests.Targeting to various problems in the current energy-feedback electronic loads,such as lower load-simulation accuracy,slower dynamic-response speed,weaker inverter gridconnection quality and lower energy-feedback efficiency,by taking typical electronic loads used for locomotive power-supply out-of-factory tests as research objects,this paper provided a series of control strategies and experimental researches around the existing energy-feedback electronic loads.And based on the achieved reviews around the current research status of the electronic-load field,this paper firstly discussed the two-level grid-connected topology of electronic loads using DC/DC load simulation + DC/AC energy feedback,loadsimulation unit constituted of LC+ phase-shifted full-bridge topology structure and energy-feedback unit composed of LCL grid-connected inverter,for further solve commonly-seen loss problems existing in power devices under the development background of high frequency and high power density,this paper attempted to apply the advanced soft-switching technologies into actual phase-shifted full-bridge converters.In addition,it analyzed corresponding main-parameter design methods,as well as some key problems and relevant solutions in practical project-designing work.Secondly,aiming to some input-current control problems in DC/DC load simulations,it’s suggested to establish corresponding small-signal models in entire system.And this paper further discussed a series of secondary ripple disturbances of bus voltages in twostage grid-connected structures and corresponding bus-current ripple problems occurred,as well as further analyzed a series of feasible control strategies for input current control+ bus current feed-forward control for purpose of achieving better simultaneous suppressions of analog-load input-current controls and DC-bus current ripples in future.Thirdly,targeting to a series of output-unit power-factor control problems existing in LCL grid-connected inverters,it discussed corresponding control strategies for busvoltage outer loop + output-current inner loop.And by Frequency Response Method,it further discussed the resonance characteristics of LCL link and analyzed specific schemes of applying passive-damping and active-damping devices to practical suppress resonances.And it further explored and designed a series of effective PI+ grid voltage feed-forward dual-loop controls for establishing specified analog-current automatic tracking and good performances when injecting grid currents accordingly.Finally,based on the achieved design schemes,this paper conducted a series of simulation analysis and experimental verifications.It shows the result that when load simulation accuracy is higher,corresponding dynamic adjustment speed would be faster to achieve quicker grid-connection by inverter unit-power factor.After a series of experiments,it turns out that,when entire system operates at 60 KW,grid-connected power factor of inverter would reach 0.98,total grid-current harmonic distortion would not exceed 1.9% and overall prototype energy-transmission efficiency would be up to0.87 respectively.It concluded that all the simulation results and the test results further verified the correctness of the previous theoretical designs.