Study On Small-signal Modeling Of HVDC System And Optimization Of The Control System's Parameters

As the scale of power system in our country becomes more enormous and have more generating capacity, transmission of large amounts of power over long distances and interconnection between regional power grids such as the transmission of three-gorges hydraulic power, southwest hydraulic power and"Three-West"(Shangxi, Shanxi, and western region of Inner Mongolia) coal power have become a trend, because of national economic development and future strategy. High Voltage Direct Current (HVDC) transmission system has been used widely in our country with its advantages of transmission of large amounts of power over long distance, asynchronous link between two AC system and ability to rapid control. And control system is an important part of HVDC system, the selection of its pattern and the setting of its parameters has a direct influence on the performance of control system, furthermore the characteristic of HVDC system. Especially when some specific fault or disturbance occurred, the performance of control system could be very important to the stability of the system. So it's quite necessary to study HVDC system and the optimization of parameters of the control system.Firstly, the basic concept and theories of small signal stability analysis are studied, and then the eigenvalue analysis methods are described in this thesis. Secondly, the principle of HVDC systems and their control systems are studied, then small-signal models of HVDC system and their control systems are intensively studied, models of HVDC systems and their control systems are established, which are precise enough in small-signal analysis and the parameters are easy to obtain. In the end, the theories of the optimization of control system's parameters are studied, and then niche immune algorithm (NIA) is introduced. It is applied in the parameter optimizing process, based on the small-signal models built before-mentioned. The result showed that the performances of control system and the small-signal stability of HVDC system have been greatly improved, and so do the efficiency of parameter optimization of control system.