The Mechanism of Low-order Non-characteristic Harmonics of LCC-HVDC and The Impact on The Hot-spot Temperature of Converter Transformer

The actual operating experience of XingAn high voltage direct current (HVDC) system in China indicates that in addition to the characteristic harmonics, the negative impact of low-order non-characteristic harmonics in line commutated converter (LCC) based HVDC is also prominent. Based on the actual operation data of XingAn HVDC system, this paper investigates the generation mechanism of low-order non-characteristic harmonics and verifies the analysis resorts to the simulation model in PSCAD/EMTDC. Furtherly, according to the IEEE Std C57.91-2011, this paper proposes an improved hot-spot temperature calculation method considering the harmonics, and the impact of low-order non-characteristic harmonics on the converter transformer is thereby revealed. Some practical suggestions are provided in the end to mitigate the effect of these low-order non-characteristic harmonics.