Research Of Programmable Energy Feedback Type DC Electronic Load

With the development of power electronic technology, automatic control technology and other relative technology, coupled with the growing demand to high performance test load and energy conservation and emissions reduction, energy feedback type electronic load becomes the inevitable development of test load. The programmable energy feedback type DC electronic load was taken as research object. This paper focused on the research of high precision load simulation, test electric energy feedback in high quality and programmable function. The hardware system and software algorithm were studied in detail. A prototype of 600 W programmable energy feedback type DC electronic load was implemented, which verified the correctness of the theoretical analysis and design.Firstly, the research background and significance were introduced. The research situation of key technology, including load simulation topology, grid-connected inverter topology, energy feedback structure, remote control, human machine interface and load simulation control algorithm were analysed.The basic principle of energy feedback type DC electronic load was introduced. The “Synchronous Rectification Boost+Dual Push-Pull Step Up+Full Bridge High Frequency Inverter” were selected as the main topology. The micro-controller TMS320F28035 was taken as control core, and load programmable control was implemented with PC upper computer. The work modes of synchronous rectification boost load simulation circuit, dual push-pull step up circuit and full bridge high frequency inverter were studied systematically.The hardware parameters of energy feedback type DC electronic load were analysed and calculated in detail. The magnetic components of the main topology, including CCM Boost inductance, dual push-pull transformer, push-pull converter output filter and grid-connected output filter were analysed and calculated. The analog signal conditioning circuits, including precision resistance divider detection circuit, grid voltage detection circuit, grid-connected current detection circuit and grid voltage zero-crossing detection circuit, were analysed and designed. The hardware of programmable load, including communication and memory circuit and the TFT-LCD human machine interface based on “STM32+FPGA” framework, was designed.The software framework of digital control power supply based on state machine control was adopted, and system control state machine was built. The control task timing sequence of energy feedback type DC electronic load was researched systematically, which elaborated how to arrange the control tasks properly to achieve optimal design. The “Start-up State+Grid-connected State” two state type Boost load simulation control strategy was proposed, and the load simulation control algorithm based current mode was researched. Combined with deadbeat grid-connected control and advance one beat control method, the prediction algorithm based on Newton interpolation was proposed. Finally, deadbeat grid-connected control algorithm based on Newton interpolation was proposed. The basic control process of load programmable control was elaborated, and load curve simulation method by the lines approach to curves was proposed.The experiment platform was set up. The diver circuit, analog signal circuit, soft start-up function, load simulation function, grid-connected electric power quality and system efficiency were tested. The experiment results verified the theoretical research and technology solution of this paper were feasible and workable.