The Application Of Large-Scale Power Electronic Devices In Wind Power Systems

Wind power is a kind of clean energy and turns into a popular research field of power systems. However, connection of a large-scale wind farm with power grid can result in some problems, such as, voltage drop, transmission power exceeding heat limits, increasing of short circuit capacity and the change of transient stability. It is urgent to carry out some solutions to decrease or eliminate the negative influence described above. Flexible AC Transmission System (FACTS) and VSC-HVDC, based on large-scale power electronic devices, therefore, become a new research focus.FACTS, including SVC, TCSC, STATCOM, SSSC and UPFC, can enhance controllability, stability and reliability of AC system by direct control of voltage and power flow of transmission lines. FACTS can act as reactive power compensators to improve voltage stability in a wind power system. This paper mainly studied the control strategy of SVC and STATCOM and their characteristics as compensators for wind farms. Connection mode of wind farm and power grid is another important issue. Until now, the general mode is AC connection. Compared to it, the cost and expenditure of DC transmission line is lower and the latter is possible to use cable underground or on seabed. VSC-HVDC, a new type of DC transmission technology, is suitable for off shore wind parks. In this paper, firstly, control system of VSC-HVDC is designed according to the specific demand of wind power. Then stability analysis and simulation for VSC-HVDC in parallel to an AC line are completed.The main task is study of application of FACTS and VSC-HVDC in wind power systems by using MATLAB/SIMULINK tool.