双馈风力发电系统在电网不对称故障下的控制策略研究

发布时间：2018-05-11 05:09

本文选题：双馈风力发电 + 电网电压不对称故障　；参考：《西安理工大学》2017年硕士论文

【摘要】：近年来,为了积极应对环境与能源问题,清洁能源-风电快速发展,世界各地电力系统风电渗透率不断提高。由于风电占总体发电系统的份额增大及其并网处易发故障等问题,这就要求风力发电系统能够抵御故障,维持电网的稳定性。风力发电系统中较为频发的故障是三相电网电压的不对称。双馈发电机作为目前风力发电场中的主流机型,占据风电产业较大比重。而双馈风电系统中双向变换器的控制策略决定了风力发电机组的运行特性,但其设计是建立在电网电压平衡的基础上的,故障时原有的控制措施失效,致使双馈风电系统从电网解列,这将导致大面积的停电,甚至造成巨大损失。因此,就需要研究如何改进双馈风电系统的控制策略来提高其在电网故障时的并网运行能力。本课题以双馈式风力发电系统为研究对象,从其主要组成部分DFIG和背靠背式变换器的工作原理入手,建立了关于双馈风力发电机的数学模型以及并网变换器的模型和控制方案,并在仿真平台中搭建了其整体模型进行后面的仿真实验。在此基础上,对电网电压不对称故障进行分析,给出故障对双馈发电系统定、转子以及直流母线的影响,在MATLAB/simulink中再现故障电压,通过仿真分析故障过程中各电气量的变化规律。其次,给出电网电压故障时故障电压相位的检测技术,并针对在电网电压不对称故障时,由于负序分量的存在,系统不能很好的稳定直流母线电压,在网侧变换器采用比例谐振控制策略代替传统的矢量控制,给出控制算法原理以及实现框图,并在仿真软件中对其控制效果进行了仿真实验和结果分析,验证了比例谐振控制策略能有效抑制故障时直流母线电压的波动,使双馈风电系统顺利完成故障穿越。最后,针对在电网电压不对称故障时,矢量控制不能很好的消除因负序分量引起的定、转子电压的振荡以及过压,在转子侧变换器采用定子磁链跟踪控制策略代替传统的矢量控制,给出控制算法原理以及实现框图,在仿真软件中对其控制效果进行了仿真实验和结果分析,结果验证了定子磁链跟踪控制策略应用在双馈风电系统的转子侧变换器中可以抑制无功、有功功率脉动,减小定转子过流和转子过压,实现故障穿越。
[Abstract]:In recent years, in order to deal with the environmental and energy problems, clean energy-wind power rapid development, the world's power system wind power permeability is increasing. Due to the increase of the share of wind power in the total power generation system and the vulnerability to faults in the power grid, it is required that the wind power system be able to resist the failures and maintain the stability of the power grid. The more frequent faults in wind power system are the asymmetry of three-phase grid voltage. As the main type of wind farm, doubly-fed generator occupies a large proportion of wind power industry. The control strategy of the bi-directional converter in the doubly-fed wind power system determines the operating characteristics of the wind turbine, but its design is based on the voltage balance of the power network, and the original control measures are invalid when the fault occurs. As a result, the doubly-fed wind power system is decomposed from the power grid, which will result in a large area of power outages and even great losses. Therefore, it is necessary to study how to improve the control strategy of doubly-fed wind power system in order to improve its grid-connected operation ability in the event of power grid failure. Based on the working principle of DFIG and back-to-back converter, the mathematical model of doubly-fed wind power generator and the model and control scheme of grid-connected converter are established. The whole model is built in the simulation platform to carry out the simulation experiment. On this basis, the voltage asymmetry fault of the power network is analyzed, and the influence of the fault on the stator, rotor and DC busbar of the doubly-fed generation system is given. The fault voltage is reproduced in MATLAB/simulink, and the variation law of the electrical quantities in the fault process is analyzed by simulation. Secondly, the detection technology of fault voltage phase is given, and the system can not stabilize DC bus voltage well because of the existence of negative sequence component in the voltage asymmetry fault. In the grid-side converter, the proportional resonance control strategy is used to replace the traditional vector control. The control algorithm principle and the implementation block diagram are given. The simulation experiment and the result analysis of the control effect are carried out in the simulation software. It is verified that the proportional resonance control strategy can effectively suppress the fluctuation of DC bus voltage and make the double-fed wind power system complete the fault traversing successfully. Finally, the vector control can not eliminate the oscillation and overvoltage caused by the negative sequence component in the voltage asymmetry fault. The stator flux tracking control strategy is used to replace the traditional vector control in the rotor side converter. The principle of the control algorithm and the implementation block diagram are given. The simulation experiment and the result analysis of the control effect are carried out in the simulation software. The results show that the stator flux tracking control strategy used in rotor side converter of doubly-fed wind power system can suppress reactive power, active power pulsation, reduce stator and rotor overcurrent and rotor overvoltage, and realize fault crossing.
【学位授予单位】：西安理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM614

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