| In recent years, kinds of power electronic equipment and chemical battery are widelyused, such as UPS, drive power of LED, APF, lead storage battery, lithium battery,nickel-cadmium battery, etc. Before they put into use, they need to be examined with variousloads to assess their output characteristics, discharge characteristic and so on. The traditionalstatic load is made up by the resistance, inductance and capacitance. There is obviousweakness to use these load. The value and type of the loads are hard to modify, and can notimitate special load, for example constant voltage load, constant current load and constantpower load. When tested the energy was dissipated in the form of the heat, so they wasteenergy seriously, and not be suitable for high power applications. It needs a new kind powerelectronic load test device to over come problems.The emergence of electronic load can overcome the shortcomings of the traditional load.It is the combination of power electronic technology, computer control technology and theautomation technology. Not only has strong flexibility, can simulate all kinds of loadcharacteristics, but also will feedback the absorbing energy to network with no pollution.Therefore, energy-feedback electronic load has become the hot spot of laboratory and powerproduction enterprise, and has a broad market prospect.This paper made the following several aspects:1. The design of the23kVA energy-feedback electronic load includes the introduction oftechnical indicators and the choice of main circuit topology. The main circuit chooses thetopology of common DC bus in the double PWM structure as the main circuit topology. Theformer is a single-phase rectifier, and the latter is a three-phase active inverter. Then analysisthe operation principle and control strategy of the PWM rectifier side and PWM inverter side.In addition, in view of the performance index this paper introduces the selection of severalimportant parameters in the circuit.2. To realize the intelligent operation of electronic load, this paper studies the PCinterface design. First, establish the load model library in the database system to manage allkinds of load type. Then write the man-machine interface, realize the model library of allkinds of operations, including query, add, delete, etc. In addition, the man-machine interfacesparameter setting module can the user set load parameter directly and conveniently. Finally,write communication program to realize the information exchange up and down a machine.3. Electronic load rectifier side simulates arbitrary load and the inverter feeds back theenergy in unit power factor. The control strategy has been the focus of electronic load projectresearch. This paper studies a new three-level hysteretic tracking control strategy. It canaverage the switch frequency, response fast and be realized easily. In this paper the method is used in rectifier side, and gets the ideal results by alternative model. In addition, for theinverter this paper also carries out some analysis, and gives the control block diagram and thedigital implementation process.4. Finally, do some experiment on the experimental platform and give the experimentalresults... |
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