| Along with the formation of multi-infeed HVDC system, the interaction between multi harmonic sources has became more and more serious. Shanghai multi-infeed HVDC system is taken as an example in this paper. ETAP built the model of AC system is built based on EATP. The transfer of Harmonic which is generated by the multi harmonic sources in AC system is analysised and the mathematical derivation and validation is given. As a result the function relationship between transfer ratio with harmonic frequency, transmission distance and transmission line is obtained. The resonant frequency of 500kV substation, power plant and the AC bus of the inverter station in Shanghai grid is analysised by the impedance - frequency scan, which points out some danger of harmonic amplification.Multi-infeed HVDC system model is built based on the platform of PSCAD/ EMTDC to analysis the influence of the operation situation of multi infeed HVDC on harmonic ransferration between each inverter station. The effect between the harmonic distortion of the inverter in multi-infeed DC system and the electric contact strength, transmission power and filter switching is drawn. In addition the interaction of harmonics between DC and AC system in multi-infeed model is analysised, namely the interaction from DC to AC side and the transfer from the AC to the DC side. The relationship between the harmonic interaction and the electrical connection is resulted eventually. |
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