Commutation Failure And Static Stability Research In Multi-infeed HVDC Transmission Systems Containing Filter Commutated Converter

Converter devices have been widely used in Chemical electrolysis industry and Power transmission, which bring in both economic benefit and many troublesome problems. The Filter Commutated Converter, FCC for short, as a new type of Converters mentioned in this paper,could effectively suppress harmonic and reduce the energy loss and noise of the converter station. At the present time, research on FCC in long-distance power transmission area has just begun, and only limited in the harmonic and reactive power characteristics of single-infeed alone High Voltage Direct Current transmission systems (HVDC), which is not comprehensive enough or fact-based enough so that it need to be much intensively studied. Especially, as the Multi-infeed HVDC transmission systems(MIDC) have actually formed in power grid, The intensive research on FCC in power transmission area must directly bases on the whole MIDC structure, while not just on the single-infeed HVDC system. In this paper, the new MIDC transmission model mixed with FCC and traditional Line Commutated Converter (LCC) is built and compared with traditional MIDC model those converters in which are all LCC. The two models above are given for the purpose of finding out how FCC affect the two typical problems in MIDC, which are Commutation Failure and Static Stability, and how FCC inverters and LCC inverters interact with each other. The content and achievement of the paper can be summarized as follows:(1) The structure, principle and design method of Filter Commutated Converter is given in this thesis. Then the HVDC transmission project in operation or planned at home and abroad which result in several typical MIDC structures are summarized in detail.(2) A traditional MIDC model and a new MIDC model mixed with FCC and LCC both mentioned above are built for comparison, based on CIGRE benchmark HVDC Model. The parameters of convertor transformers, Var compensator and filter device in FCC inverters and LCC inverters of these two models are calculated.(3) Improved extinguish angle calculation model applying to both of the two MIDC models before mentioned is given. The commutation failure interaction among inverters in the two type of MIDC models are contrastively analyzed through examples and simulated based on PSCAD/EMTDC, under different electrical distance and strength of AC power system. Simulation result is identical to example and theoretical analysis. It indicates that FCC broaden extinguish angle margin, improve commutation process effectively, decrease the continuous commutation failure rate or simultaneous failure rate.(4) two type of contrastive MIDC models before mentioned are built according to the analytical and simulation method of modal maximum power curve (MMPC) in MIDC. The static voltage stability and DC power stability of these two contrastive MIDC models is simulated, with the same active and reactive power small disturbances applied at the same node in both of two models. The results indicate that FCC enhance the active strength of AC power system, improve the static voltage stability and DC power transfer limit of MIDC system.