Studies On UHVDC Operation Fault Characteristic And Impact On Its Receiving System

With the launching of Yunnan-Guangdong ultra-high voltage direct current (UHVDC) demonstration project, China will lead the world into an era of constructing a strong smart grid. More and more UHVDC projects being planned and constructed, makes it a technical approach to solve the contradiction of regional differences between energy distribution and productivity. For UHVDC's higher voltage level and transmission power, higher requirements are brought out in equipment, control protection strategy and its reliable operation. Studies on UHVDC operation fault characteristic and impact on its receiving system have great significance to UHVDC itself and its receiving system stability.In the thesis,studies on UHVDC operation fault characteristic and impact on its receiving system depending on the background of Yunnan-Guangdong UHVDC project, relies on the RTDS based multi-infeed HVDC real-time simulation platform in power system technology research center of China southern grid and power system electromechanical transient analysis software PSD-BPA. Specific studies include the following aspects:RTDS based simulation and analyses of UHVDC current commutation and control & protection strategies of block/deblock the second valve-group in one pole. From theoretical discussion and simulation, analyze the interaction between series twelve-pulse inverters. But Focus on the characteristic of UHVDC unique technology, which is blocking/deblocking the second valve-group in a pole and its control & protection strategies. Simulation and analysis are carried out in two different states, communication available and communication faulty between rectifier and inverter stations.Then control & protection strategy and RTDS simulation on commutation failure of UHVDC is considered. Fistly discussing the mechanism of commutation failure, communication failure by AC fault and criterion to commutation failure, then analyzes control & protection strategies related to commutation failure.Finally simulate and analyze three inducements of commutation failure by valve short-circuit, trigger system failures and single phase short-circuit to illustrate their dynamic characteristics after commutation failure.Construct UHVDC Theoretical evaluation model based on subsystem division.Propose a method by adopting subsystem division and statistical reliability parameters of major components involved. Establish a theoretical evaluation model by fault tree analysis (FTA) and time frequency method (FD) based on based subsystem division to assess the theoretical reliability of UHVDC. The proposed model is adopted to evaluate the operation reliability of Yunnan-Guangdong UHVDC project. In 2010 and 2012 fengda model of China southern Power Grid, PSD-BPA software is employed to study the impact of serious fault of Yunnan-Guangdong UHVDC (including two valve groups forced outage and bipoles forced outage) on China southern power grid, also discuss different control measures and check corresponding dynamic recovery characteristics of Guangdong power grid. In 2012 fengda model, evaluate stability states and corresponding dynamic recovery characteristic under different load models of Guangdong power grid when serious faults of Yunnan-Guangdong UHVDC occur.