双馈风力发电系统磁链预测同步弱磁控制策略

发布时间：2018-07-08 21:18

本文选题：双馈风力发电机 + 故障检测　；参考：《河南师范大学》2017年硕士论文

【摘要】：近几年来,双馈风力发电机以其独特的结构被广泛应用在发电系统中,能够实现变速恒频发电,并且具有相对较小的励磁容量。当电网处于正常运行状态时,双馈风力发电系统的控制策略已经趋于成熟,目前主要的研究动向是从电网正常运行条件下转为电网故障运行条件下,使双馈风力发电机在故障条件下实现不脱网运行,避免造成电网大面积瘫痪。本文主要研究的是:在电网发生单一的跌落以及混合跌落故障下,采用双馈风力发电系统磁链预测同步弱磁控制策略,以保证双馈风力发电机在低电压下安全工作。本文首先分析了一种快速并且有效的电网电压故障检测方式。因为双馈风力发电机定子直接与电网挂接,一旦电网电压降落,对其影响比较大,为了保证在电网故障瞬间能够快速切换至故障下的控制策略,本文提出了电网电压的幅值和相位检测的方法,达到快速准确检测电网电压跌落的目的。其次论文采取了两相静止坐标系下双馈风力发电机的矢量模型,详细介绍了双馈风力发电系统在电网电压正常情况下采用的比例谐振控制,此控制算法简单,没有多余的补偿项,能够实现被控量的无静差控制,提高了控制系统的鲁棒性。当电网电压发生跌落故障时,双馈风力发电系统的定子磁链在电网发生对称跌落时出现的直流分量以及不对称跌落时出现的直流和负序分量,造成了很大的转差率,从而在转子回路形成较高的暂态过电流。本文依据其数学模型,分析得到了电网电压正常运行时和电网电压降低情况下的暂态电磁关系,同时结合附图对电网正常运行时和电网电压降低瞬间双馈发电机定、转子磁场的磁路路径变化进行分析,为下文控制策略的提出奠定了理论基础。为了提高双馈风力发电系统在电网电压降低情况下的安全运行能力,本文提出了一种磁链预测同步弱磁控制策略。分析了电网电压降低的情况下定转子磁链的变化规律,在此基础上,使转子磁链对定子磁链实时跟踪,实现定转子磁链同增同减,本质上减少了故障期间的转差,从而减小故障期间定转子过电流。并且推导了两相静止坐标系下的定转子磁链关系以获取最优转子磁链参考值。最后通过对转子磁链进行无差拍预测控制实现故障期间定转子磁链的快速同步,削弱定转子磁链之间的相互作用,在电网电压降低的情况下实现了双馈风力发电机的不脱网运行。本论文最后通过运行结果表明,所提磁链预测同步弱磁控制策略结构简单,具有较快的动态响应速度,可以有效抑制定、转子过电流,消除故障期间的电磁转矩大范围波动对风力机组的机械冲击,表明了双馈风力发电系统在电网电压降低的情况下仍然具有良好的运行品质。文章最后为了进一步验证控制策略的适用性,设置电网电压发生不同类型的电压跌落故障,所验证类型从电网电压出现三相对称跌落故障过渡到更为普遍出现的不对称跌落故障。对运行结果进行分析可以得到:双馈风力发电系统磁链预测同步弱磁控制策略得到的转子最大电流都可以控制在系统所允许的最大值以内。
[Abstract]:In recent years, doubly fed wind generator has been widely used in power generation system because of its unique structure. It can achieve variable speed constant frequency power generation and has relatively small excitation capacity. When the power grid is in normal operating state, the control strategy of doubly fed wind power generation system has become mature. Under the condition of normal operation, the doubly fed wind generator can not be removed from the network under the condition of fault operation and avoid the large area paralysis of the power grid. This paper mainly studies the synchronous weak magnetic control strategy using the magnetic chain of doubly fed wind power generation system under a single drop and mixed fall fault in the power grid. In order to ensure the safe operation of the doubly fed wind generator under low voltage. This paper first analyzes a fast and effective method for detecting voltage faults in the power grid, because the stator of the doubly fed wind generator is directly connected with the power grid. Once the voltage of the power grid is landed, it has a large impact on it, in order to ensure fast switching to the power grid fault. In this paper, the method of amplitude and phase detection of power grid voltage is proposed in this paper to detect the voltage drop of power grid quickly and accurately. Secondly, the vector model of doubly fed wind generator in two phase stationary coordinate system is adopted in this paper, and the ratio of the doubly fed wind power generation system under the normal voltage condition of the power grid is introduced in detail. In the case of resonant control, this control algorithm is simple and has no excess compensation. It can realize the control of the controlled quantity without static difference, and improve the robustness of the control system. When the power grid voltage falls down, the stator flux of the doubly fed wind power generation system appears when the power grid occurs symmetrically and the asymmetrical fall occurs. In this paper, the transient electromagnetic relationship between the normal operation of the grid voltage and the decrease of the voltage of the power grid is obtained. At the same time, the double feed of the normal operation of the power grid and the voltage reduction of the power grid is presented in this paper. The change of magnetic path path of the generator stator and rotor magnetic field is analyzed, which lays the theoretical foundation for the following control strategy. In order to improve the safe operation ability of the doubly fed wind power generation system under the voltage reduction of the power grid, this paper proposes a magnetic chain prediction synchronization weak magnetic control strategy. On the basis of the change law of the rotor flux, the rotor flux can track the stator flux in real time to achieve the same increase and decrease of the stator and rotor flux. In essence, the rotor flux decreases during the fault, thus reducing the over current of the rotor during the fault, and derives the relationship between the stator and rotor flux in the two phase stationary coordinate system so as to obtain the optimal rotor flux linkage. At the end of the test, the rotor flux linkage is predicted to realize the fast synchronization of the stator and rotor flux in the fault period, weaken the interaction between the stator and rotor flux, and realize the non net operation of the doubly fed wind generator under the condition of the voltage reduction of the power grid. The weak magnetic control strategy has a simple structure and a fast dynamic response speed. It can effectively suppress the fixed, overcurrent of the rotor and eliminate the mechanical impact of the large electromagnetic torque fluctuation on the wind turbine during the fault. It shows that the doubly fed wind power generation system still has a good running quality when the voltage of the power grid is reduced. The applicability of the control strategy is further verified, and the voltage drop fault of different types of power grid voltage is set up. The verification type transition from the three-phase symmetrical fall fault of the power grid voltage to the more common asymmetrical fall fault. The maximum current of the rotor obtained by the magnetic control strategy can be controlled within the maximum allowable value of the system.
【学位授予单位】：河南师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM315

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