Study On The Charging Ununiformity Of Impulse Voltage Generators

Impulse voltage generator is one of the most important high-voltage test equipments. During the charging process of impulse voltage generator, ununiform phenomenon comes into being during the charging process of stage capacitor voltages for the reason of the generator circuit structure. However, the charging voltage'ununiformity of stage capacitor voltages will directly influence the accuracy of output forecast and control setting of the generators. And for multi-stage large generators with high output voltage, the phenomenon of charging ununiformity of stage capacitor voltages is particularly prominent. Therefore, it is necessary to make an analysis of the factors which have influence on the charging ununiformity of stage capacitor voltages.This paper first analyzes the charging process of uniform distributed parameter circuits charged by DC voltage supply, then analyzes rectifying voltage supply to charge the charging circuit, and calculates the ununiformity of the charging voltage of stage capacitors. According to the structure of impulse voltage generator, the EMTP simulation software is used to build a 36-stage charging circuit model of impulse voltage generator. By way of simulating and calculating this model,the impact of component parameters of charging circuit, charging methods and the charging time on the ununiformity is investigated. With the results of simulating calculation,an analysis of the effects which some technical measures, such as constant current charging, reducing the chargeable resistance value, and reasonable manipulative strategies have on improving the charging voltage ununiformity is made.Finally, in the experiment, I employ my own R&D fiber-optic measurement system to measure the voltage capacitor of first and final stage,and make four PLC control programs so as to respectively carry out constant current charging in impulse voltage generator. By comparing the simulation results with actually measured charging ununiformity, I verify the effects of different charging current value and control strategies, which leads me to put forward some measures to improve as follows:(1) Carry out constant current charging and meanwhile try best to choose high current value to charge.(2) Reduce the charging resistance value to improve the ununiformity in the charging process.(3) Strategy use high current to charge the first capacitor so as to set the voltage value and then replace with a lower current to charge by means of controllable switch.In conclusion, all these measures above can effectively lessen the charging ununiformity of impulse voltage generators so that they can help improve the accuracy of measurement and control during the process of charging and discharging impulse voltage generators.