Power Quality Measurement And Analysis Of Offshore Wind Farms Based On PSCAD/EMTDC

Energy and the environment has become an important problem restricting human survival and sustainable development, thus making wind power system receive high attention for its low consumption of conventional energy like coal and oil and low environmental pollution. Offshore wind farms have many advantages towards onshore wind farms in some respects. Therefore, the offshore wind farm has a great development all around the world.The most economical way of using wind power is integrating it into the grid. The power output of wind farms should satisfy the certain expectations of quality. Power quality is one of the most important factors of offshore wind farm operation and grid connection. This thesis first discusses about the definition of power quality indices, the reason of power quality problems and the corresponding compensation measures in detail, then the thesis introduces the power quality standards at home and abroad, and discusses the measurement and analysis methods of power quality.On account of the characteristics of wind speed and the running environment of offshore wind farms, this thesis sets up the offshore wind farm model connected with the grid on PSCAD/EMTDC. The wind turbine used is one of the mainstream models, variable speed constant frequency doubly-fed inductor generator. Control of the generator can realize the maximum wind power tracking and decoupling control of active power and reactive power. Wind farm usually contains many wind generators, capacity equivalent method is used to get wind farm equivalent model.A set of indices, including harmonics, voltage fluctuation and flicker, voltage deviation, frequency deviation, three-phase voltage unbalance, and voltage sag is measured and analyzed at the grid connected point. Wind speed models considering the wake effect, wind shear and tower shadow are set up. Under different offshore wind speed and operating conditions, the measurement data of power quality indices is gained and discussed. The influence of wind farm capacity and power grid short circuit capacity on the power quality is analyzed. Finally, according to the simulation data related to power quality, relative control measures are put forward for the power quality of offshore wind farm.