The Response Characteirstics Of FCC-HVDC With Typical Fault

The characteristic harmonics generated from the converter of the traditional HVDCsystem flux from the valve side of the transformer to the line side. Consequently, seriousharmonic pollution of the AC system is induced, and the problems of transformer loss,noise and reactive power compensation are occurred. But the converter transformer of theFCC-HVDC adopting inductive filtering theory can suppress harmonics and compensatereactive power. So the problems mentioned above will be weakened. Because there arestill a series of technical problems to be solved ahead in the process of promoting FCC’sengineering prototype. From the point of Filter Commutated Converter, several researchwork can be summarized in this thesis.(1) In order to study the response characteristics of Filter Commutated Converter (FCC)with single-phase earth fault, in the paper, referring to the CIGRE HVDC benchmarktesting model (LCC-HVDC), on the premise of non-changing the short circuit ration(SCR) and some parameters, combining the connecting features of FCC, the new testingmodel based on FCC (FCC-HVDC) is established in the PSCAD/EMTDC; based the twomodels of LCC-HVDC and FCC-HVDC, the magnetizing and harmonic characteristicsare analyzed comparatively with single-phase earth fault.(2) The definition of the strength of AC system, the steady state of the AC system andthe function of its control module are simply described. Then the characteristics of powertransmission and dynamic recovery of FCC-HVDC with different SCR are studied bycomparing with LCC-HVDC in detail with typical disturbances occurring in reality. Thesimulations show that FCC-HVDC may improve the capacity of DC transmission, andalso retain relatively satisfactory dynamic recovery characteristics following varioustypical disturbances.(3) Combing with the technique characteristic of FCC-HVDC, a new method ofsuppressing the harmonic instability is proposed. Even harmonic filters are installed at thevalve side of new converter transformer in the new method. This article derives theprinciple of even harmonic suppression using mathematical formula. Then, the harmonicsuppression model is built up, and simulation studies are carried out. The simulationresults show that this new method of suppressing harmonic instability can block thecondition of generating harmonic instability, which can also decrease the occurring ratioof harmonic instability in DC transmission system.(4) The action equations of three-phase protection and differential current expressions are deduced from the mathematical model of FCC’s converter transformer. Then thetransformer’s three-phase protection model is established. Consequently, the simulationstudies utilizing identification methods of the2nd order harmonic restraint criterion andmagnetic flux characteristics are carried out by using of the action equations, then theeffectiveness of the proposed protection scheme in distinguishing between the internalfaults and the energizations of the converter transformer is validated.This thesis makes a detail and systematic research on the the magnetizing andharmonic characteristics, power transmission and dynamic recovery characteristics,harmonic instability and so on. And the results are contributive to the greatly prospect otFCC-HVDC.