Research On Mixed Sensitivity Control Strategy Of Statcom To Restrain Voltage Fluctuation From Wind Power Integration

It is analyzed at first how the wind disturbance influences the active power and reactive power in a wind power system with a doubly fed induction generator.The thesis discusses the relations between the reactive power and the voltage fluctuation,making a conclusion that the wind disturbance distorts the voltage at PCC.Thus,a device called Static Synchronous Compensator is shunted there in order to improve the performance of voltage stability.A mathematical model is established after a basic understanding of the structure as well as the principle.The parameter rules of DC link capacitor and filter reactor are also given then.It's effective to deal with the uncertainties and distortions in the environment mentioned before when a mixed sensitivity control strategy of H? problem introduced.The design and solution method depends on control principle and mathematical derivation.With the help of frequency domain analysis,the thesis focuses on the design rules of weight functions,the key to getting the desirable controller,and researches on the effects on controller performance.So it's easy to get the optimal controller with suitable performances by means of Matlab.A performance comparison of conventional PI controller and mixed sensitivity controller is given then.Indispensible to the program to damp the voltage fluctuation in the wind farm,a synchronization algorithm based on Kalman Filter is provided,which can identify the fundamental wave information from the voltage at PCC,such as the phase,amplitude and frequency.The algorithm above is compared with Discrete Fourier Transform and Phase-Locked Loop with the help of Matlab code.With these preparations,an enormous simulation on wind power system is presented based on Matlab/Simulink.A STATCOM is shunted at PCC to damp the voltage fluctuations when happens a wind disturbance,whose simulation results may show some improvement for voltage stability at PCC.On the basis of these researches,a STATCOM experiment system is given to damp PCC voltage fluctuation caused by wind disturbance.DSP is applied in the experimental platform.The experiments contain controlling the DC link capacitor voltage,eliminating PCC voltage fluctuations,suppressing the impacts under different loading conditions.The results show a faster dynamic response as well as transient stability enhancement.The mixed sensitivity controller is validated better efficiency and superiority than traditional PI controller.