Study On Measurement Method Of Harmonic Current In HVDC

In recent years, high voltage direct current system(HVDC) has been rapidly developed, but harmonic pollution was produced and became more and more badly, Safe and stable electric system operation was effected by more and more elements . harmonic measurement by true is the precondition and sticking point of restraining harmonic. At present, measuring instrument in power system was almost designed to use sine wave for 50Hz frequency. When the singal contains harmonic, measuring accurate degree facts challenge. Traditional instrument in harmonic measurement was the transformer with circularity form core coil, but it has been influenced by direct current and saturated, so it could not be used to measure harmonic current in HVDC. It submittes a measuring method with Optic-electric Current Transformer(OCT) based on Rogowski coil in the paper. The system was an integral whole new model harmonic electric current measurement system gather the fibre-optical technology , electron technology and USB communication. The author carry out analysis on Rogowski coil performance data , digital signal acquisition system , USB communication system and designed that in the paper.As the basis of the measurement system, the accuracy of Rogowski coil was affected the whole system directly. The paper describes the principle of Rogowski coil measuring harmonic current, completes simulation analysis based on coil performance, point out the designing rules of common Rogowski coil, and point out the especial design of Rogowski coil for HVDC.It designes analog the data acquisition for analog signal circuit,photoelectricity change system in high voltage circuit and serial signal to parallel signal convertion system ,USB communication system and signal simulation output in low voltage circuit. Several integrator were discussed ,and one integrator was choosen for derect harmonic current measurement for this system. The sample-taking system was based on MSP430 and ADS8325 digital sample-taking circuit. Optical fibre was used intransmission system between diffirent circuit , overcoming effectively the problem that the signal was disturbed by the environment. Serial signal to parallel signal conversion system,USB communication system and signal simulation output system based on DSP in low voltage circuit was designed in the paper .