Design And Research Of DC Feedback Type DC Electronic Load On The Locomotive Power Supply Test

With the development of rail transit in our country and increase of the energy crisis, in view of the locomotive power test with simulated load cause energy waste, taking the locomotive power DC600 V 120V/10 kW DC charging machine as test object, a kind of DC feedback type DC electronic load is designed.By consulting literature of DC electronic load at home and abroad, analyzing the characteristics of the power under test and the environment of the workshop, a kind of DC feedback type DC electronic load consisting of the boost chopping circuit and the phase-shift full bridge circuit is designed based on the AC grid feedback type electronic load. Compared with the AC grid feedback type electronic load, the DC feedback type electronic load is simpler to control and easier to implement. It also can cycle the test power directly to the input side of the power under test, get rid of the energy transformation links, such as the inverter and rectifier, so it can avoid the power loss and harmonic pollution in the process of the energy transformations.Through the analysis of the basic working principle of boost chopping circuit and phase-shift full bridge circuit, the circuit topology and device parameters for the DC feedback type DC electronic load is designed. According to the testing requirements of the power supply under test, the control mode of the energy feedback type electronic load is analyzed and designed through the modeling method of the system small signal model. In the part of load simulation, the paper respectively discusses the PI control and one-cycle control, based on which a new hybrid control method is proposed. In the part of energy feedback, the paper adopts double closed-loop control structure and PI control method. Then, combining with the working characteristic of digital control chip TMS320F2812, the software part is designed. Finally, through the simulation software MATLAB and a 10 kW experiment platform to verify the feasibility of the design. The simulation and experimental results show that the design of DC feedback type DC electronic load can accurately follow the given test current, make the test current ripple is less than 5% of the rated current, adjusting time is less than 2ms and overshoot is within 10% of the rated value, and it can accomplish the test requirements of the power supply under test before delivery, and it can cycle the energy of test efficiently to the input side of the power under test, for the use of the cycle.