摘要
Abstract
Aiming at the problem of insufficient research on the nature and key influencing factors of high-fre-quency resonance in parallel system consisting of static var generator(SVG)and cluster doubly-fed induction generator(DFIG),this paper aims to reveal the mechanism of high-frequency resonance of wind farm system caused by no-load line input,and quantitatively analyze the influence of wind speed change and the number of wind turbines on system stability.The harmonic linearization method is employed to establish a sequence imped-ance model of the SVG under constant power factor control and the cluster DFIG considering the power outer loop.The accuracy of the model is verified by the frequency sweep method.Based on the impedance analysis method combined with the stability criterion,the equivalent circuit of the system is derived,the influence of the no-load line input on the impedance characteristics of the system is analyzed,and the variation of the phase mar-gin and damping characteristics of the system under different wind speeds and the number of fans is explored.The frequency sweep results of the model are in good agreement with the theoretical calculation,which verifies the accuracy of the modeling.The analysis shows that after the no-load line is put into operation,the system im-pedance intersects with the grid impedance near 1 225 Hz and the phase margin is negative,which leads to high frequency resonance.Reducing the wind speed can shift the impedance intersection to high frequency,make the phase characteristics move forward,and shrink the negative damping area.Increasing the number of DFIGs can increase the resonant frequency and improve the phase margin,both of which are helpful to improve the system stability.The high-frequency capacitive impedance characteristics of SVG and the capacitance effect of no-load lines lead to the system impedance falling into the negative damping region,which is the root cause of high-fre-quency resonance.Low wind speed and parallel operation of multiple wind turbines are beneficial to shrink the negative damping area of the system and improve the phase margin,so as to effectively suppress the resonance risk caused by the input of no-load lines.The electromagnetic simulation results verify the correctness of the above mechanism and factor analysis.关键词
双馈风力发电机/高频谐振/静止无功补偿器/阻抗分析法/风速变化Key words
doubly-fed induction generator(DFIG)/high frequency resonance/static var generator(SVG)/im-pedance analysis method/wind speed change分类
信息技术与安全科学
