Study on overhead transmission line magnetic field harmonics of VSC-HVDC

Wind farm connected to local power system through VSC-HVDC is better than AC transmission, but harmonics current from converter station will have effect on electromagnetic environment around both AC and DC transmission line. This paper presents a method to evaluate overhead transmission lines magnetic field harmonics produced by harmonics currents which are from PWM based converter stations of VSC-HVDC. The analysis is completed in the framework of quasi-static field. The magnetic field harmonics distributed characteristics of VSC-HVDC overhead transmission lines are calculated by the harmonics currents which are obtained through PSCAD/EMTDC simulation. The magnetic field harmonics are separately computed and evaluated according to the public safe exposure to magnetic field reference levels of ICNIRP. The calculated results show that some high order magnetic field harmonics will exceed the reference magnetic field level. The results can be applied to the design and reconstruction of AC and DC overhead transmission lines and can be extended to study magnetic field harmonics environmental effects on residents along the transmission line, which are generated by harmonics of high voltage overhead transmission lines.