Measurement Of Harmonic Current In HVDC Based On Rogowski Coil

In recent years, high voltage direct current system (HVDC) is rapidly developed, but harmonic pollution is produced and becomes badly, harmonic measurement by true is the precondition and sticking point of restraining harmonic. At present, measure instrument in power system is almost designed to use sine for 50Hz frequency. When signal contains harmonic, the error of measurement result will be increased. Traditional instrument in harmonic measurement is the transformer with circularity form core coil, but it is influenced by direct current and saturated, so it could not be used to measure direct harmonic current. An Optic-electric Current Transformer(OCT) based on Rogowski is discussed in detail here, it isn't influenced by direct current. This paper discusses the characteristic of HVDC harmonic, analyses the harmonic current measurement system in theory, studies the result of experimentation, accomplishes the sample of OCT. As the basis of the measurement system, the accuracy of Rogowski coil affects the whole system directly. This paper expatiates the principle of Rogowski coil measuring direct current harmonic current, completes simulation analysis based on coil performance , points out the designing rules of common Rogowski coil, and points out the especial design of Rogowski coil for HVDC. This paper designs the inside high voltage circuit, the optical transmission system, the inside low voltage circuit. The integral of differential signal at the high voltage is important, several integrators are discussed, and one integrator is choosed for direct harmonic current measurement. The optical transmission system chooses the best combination of light source, optical fiber, and PIN, in an attempt to be with the characteristics of low power, good linearity, little attenuation. It is mainly discussed inside low voltage proportion circuit detecting low light level signal and extracting effective harmonic current. Calibration is the precondition of the utility of Rogowski coil harmonic current transformer. Error of sensor and measurement system is analyzed separately by "equal-ampere"simulation high current, then performances of sensor and measurement system are tested.