A New Wind Turbine Control Method to Smooth Power Generation. Modelling and Comparison to Wind Turbine Frequency Control.
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Typ
Examensarbete för masterexamen
Master Thesis
Master Thesis
Program
Publicerad
2012
Författare
Solberg, Olov
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Following the significant increase of world wide installed wind power during the first decade of the 21st century, transmission system operators are faced with new challenges originating from the intermittent character of renewable energy sources and their installation on low and medium voltage levels. One challenge arising from the fluctuating nature of wind is to maintain frequency stability. This thesis presents a new approach to smooth the power generation of wind turbines subjected to varying wind. An active power feedback control has been developed which feeds back the momentary power generation to the turbine pitch and speed control systems. This power feedback control has been implemented in the simulation software SIMPOW and the results have been compared to a frequency control regulator for wind turbines. The frequency control was developed by the Power System Analysis Group at A° F Industry as a part of the Swedish research initiative Elforsk. Simulation results show that the power feedback control clearly levels the active power production of wind turbines under varying wind and thereby diminishes network frequency excursions. To achieve this, turbine deloading through a pitch angle offset is found to be imperative. The effect of different deloading levels of a turbine are evaluated, clearly demonstrating the correlation between larger deloading, enhanced frequency stability and declining energy yield. Up to wind power shares of approximately 25 %, the performance of the power feedback control is on a par with the frequency control, i.e., frequency excursions are equally subdued. Above this level of installed wind power, the frequency control is superior. Usage of the wind turbine power feedback control is discouraged because of its poorer performance, its unintuitive function and the difficulty to predict its behaviour. Lastly, the frequency control is applied to a much simplified black start case, showing the expediency of the control method to improve frequency stability, but also the extended requirement on a large turbine deloading when there are no synchronously generating units in the network.
Beskrivning
Ämne/nyckelord
Elkraftteknik , Electric power engineering