VSC-HVDC Converter System Modeling And Lightning Over-voltage Calculation

Distributed power, renewable energy, as well as the rapid development of smart grid is becoming a new trend in today’s grid development, which also makes VSC-HVDC technology more application prospects. In this paper, the AC part of a VSC-HVDC converter has been measured,the internal voltage distribution has been analyzed while the converter system under lightning over-voltage.A new method for three-phase equipment broadband model has been proposed,thereby the broadband model of the filter,reactor, transformer and even the entire AC part of converter system has been established.Time-domain measurement data can be obtained by the impulse response of the device,the frequency domain broadband model parameters of each branch can be obtained by the time-frequency transform and the corresponding matrix computing,then the broadband model for over-voltage computing of a device have been established.Matching the voltage transfer characteristic of a device using vector fitting to a rational function,and finally the time-domain voltage response could be obtained by recursive convolution calculation.Contrast model simulation and experimental results,it shows that this model can accurately reflect the over-voltage conduction properties of three-phase equipments.For AC part of VSC-HVDC converter system,broadband model composed by each device can also accurately reflect its internal key points voltage response waveform.Finally,according to the the experimental data the voltage waveforms of converter valve and each key equipment were analyzed when suffered lightning invasion;With the broadband model the resonance point of the AC part can be calculated and there may be subjected to over-voltage response of lightning cut waves.This research was supported in part by National Natural Science Foundation of Chin a(Grant No. 51207054, No.51177048), and Fundamental Research Funds for the Central Universities(Grant No. 13MS75).Experimental measurement equipment used include EMS61000-5A lightning surge generator, Agilent 33220 A signal generators, Agilent DS05340 digital storage oscilloscope.