大容量双馈风电场送出线路差动保护的研究

发布时间：2018-07-13 12:44

【摘要】：风能以其清洁性、可再生性以及丰富的储量而得到了优先发展。风力发电机是以随机的和不可控的自然风为原动力的,这将造成风力发电具有不稳定性。当数量较多、容量较大的双馈风电机组汇集而成的大容量风电场并入系统时,必然会对送出系统的继电保护造成一定的影响。因此,研究大容量双馈风电场送出系统的继电保护性能很有必要。首先,建立了双馈风力发电机及其控制系统的数学模型,研究了低电压穿越特性及转子Crowbar保护电路的接线形式,再利用MATLAB/Simulink仿真软件搭建了双馈风电场送出系统仿真模型,通过分析风电场送出线路的各种短路故障及其故障电流,验证了双馈风电场故障电流具有频率偏移特性与弱馈特性。其次,研究了大容量双馈风电场送出线路故障选相元件的改进方法。由于双馈风电场送出线路短路电流具有频偏特性与弱馈特性,导致送出线路故障选相元件可能选相失败。为了消除频偏特性与弱馈特性的影响,采用经相模变换后的模故障分量结合形态谱分析的新方法进行故障选相。仿真结果表明,所提出的模故障分量结合形态谱进行双馈风场送出线路故障识别的方法是可行有效的。最后,研究了大容量双馈风电场送出线路电流差动保护的改进方法。在送出线路发生故障的情况下,传统傅里叶工频算法不能准确地提取故障电流工频分量,有可能导致电流差动保护元件的灵敏度降低,甚至不正确动作,为此提出了基于ESPRIT算法的电流差动保护改进方法。运用MATLAB/Simulink仿真验证了 ESPRIT算法能够准确地提取出两侧基波故障分量电流,使电流差动保护能够准确动作,同时将ESPRIT算法与Prony算法进行比较,结果表明ESPRIT算法具有更高的信号提取精度。
[Abstract]:Wind energy has been given priority because of its cleanliness, reproducibility and abundant reserves. The wind turbine is driven by random and uncontrollable natural wind, which will lead to the instability of wind power generation. When a large number of doubly-fed wind turbines with large capacity are incorporated into the system, the relay protection of the delivery system will be affected to a certain extent. Therefore, it is necessary to study the relay protection performance of a large-capacity doubly-fed wind farm. Firstly, the mathematical model of the doubly-fed wind turbine and its control system is established, and the low-voltage traversing characteristic and the connection form of the rotor Crowbar protection circuit are studied. Then the simulation model of the doubly-fed wind farm output system is built by using MATLAB / Simulink simulation software. By analyzing all kinds of short circuit faults and their fault currents of wind farm, it is proved that the fault current of doubly-fed wind farm has the characteristics of frequency offset and weak feedback. Secondly, the improved method of fault phase selection for large capacity doubly-fed wind farm is studied. Due to the characteristics of frequency offset and weak feed, the fault phase selector may fail to select the phase in a doubly-fed wind farm. In order to eliminate the influence of frequency offset and weak feed characteristics, a new method of fault phase selection based on the mode fault component after phase mode transformation and morphological spectrum analysis is proposed. The simulation results show that the proposed fault identification method based on the mode fault component and the morphological spectrum is feasible and effective. Finally, the improved method of current differential protection for large capacity doubly-fed wind farm is studied. In the case of fault of the transmission line, the traditional Fourier power frequency algorithm can not accurately extract the power frequency component of the fault current, which may lead to the reduction of sensitivity of the current differential protection element, and even the incorrect operation. An improved method of current differential protection based on Esprit algorithm is proposed. The simulation results of MATLAB / Simulink show that Esprit algorithm can extract the fault current accurately and make the current differential protection work accurately. At the same time, the Esprit algorithm is compared with the Prony algorithm. The results show that Esprit algorithm has higher precision of signal extraction.
【学位授予单位】：南京理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM614;TM773

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