Study Of Transient Harmonic In Typical Faults And Harmonic Instability In Filter Commutated Converter

With the development of power electronic devices technology, HVDC got into a new period of vigorous advancement. The harmonic problem brought by a large number of power electronics technology applications is becoming the increasingly prominent and severe. Within all those problem, transient harmonic and harmonic instability bring up many issues. FFT analysis, which is commonly applied in harmonic analysis of HVDC power system, is uncapable for detection and measurement of those non-characteristic harmonic in transient state such as sub-harmonic and inter-harmonic. Harmonic instability caused harmonic oscillation doesn't attenuate or even amplifies seriously in the converter station. This paper, relys on the power transmission new-technology research and development platforms of Hunan University, combines with a special major science and technology of Hunan Province"A new-type HVDC converter transformer development"(06GK1003-1), discussed problems caused by transient harmonic and harmonic instability on building DC transmission system exploitation platform based on the Filter Commutated Converter, and described certain solutions include measurement algorithm. The main job of this paper includes the following:A brief introduction of today's domestic and abroad research of transient harmonic and harmonic instability, which aiming at the disadvantage of current filter plan, suggested that in order to minimum the damage caused by transient harmonic, and decrease the probability of harmonic instability and guaranteeing the safety and stability of HVDC's operation, it is necessary to research the effective suppression methods of transient harmonic and harmonic instability.Brief introduction of the operating principle of Filter Commutated Converter is presented, and an DC transmission system exploitation platform based on the FCC. presents was built; an enhanced measurement scheme of harmonic, which combines the concept of group energy and spectral leakage elimination algorithm is presented; the result of simulation study under classic fault of HVDC power system shows that the new scheme could reveal more characteristic and information of the original harmonic signal when it was being applied on analysis of transient harmonic.A new method is introduced for judging harmonic transformer core saturation instability. Then base on the former research platform, an simulation of the core saturation instability caused by three-phase grounding fault is processed, thus the new judgment method is validated.Certain solution for suppression of harmonic instability is presented, the result of simulation on the platform shows that the contents of 2nd,3th non-characteristic harmonic currents and 11th,13th characteristic harmonic currents in AC net side are decreased significantly, and the harmonic instability is controlled effectively, as well as the capacitors provides the reactive-power compensation to the converter, thus suggests that new scheme has nice application prospects.