考虑双馈风电接入的电网故障特性及保护策略研究

发布时间：2018-03-02 07:28

本文关键词： 双馈感应风力发电机 DFIG机端相位跳变网侧变流器控制定转子故障电流风电场保护策略　出处：《华北电力大学》2014年硕士论文　论文类型：学位论文

【摘要】：风力发电与传统火力发电的机理不同,故障后风机电磁暂态特性发生较大变化。双馈风电的接入,使得电网结构愈加复杂,可靠性与安全性难以得到有效的保障。因此,本文通过对电网对称以及不对称故障下双馈风电机组电磁暂态特性的研究;得到双馈风机在电网故障下定转子电流瞬时表达式；并通过PSCAD仿真进行验证。同时考虑到大规模双馈风电场接入电力系统时对电网中传统保护的影响,提出针对风电场汇流线路和风电场送出线路的改进保护策略,并通过PSCAD进行故障仿真验证。本文首先建立了双馈发电系统不同坐标系下的暂态数学模型,重点阐述了同步旋转轴系下双馈感应电机的暂态模型及其常用坐标变换；推导了DFIG网侧与转子侧变流器的数学模型,分析了双馈感应风力发电机的发电特性及运行原理,并搭建了DFIG的PSCAD模型进行仿真验证。其次,本文在电网对称和不对称故障下,充分考虑DFIG机端电压相位跳变、DFIG转子侧与网侧变流器控制以及直流母线电压的波动对故障电流的影响。利用DFIG暂态数学模型分别推导出对称与不对称故障下DFIG能够反映出暂态输出特性的DFIG定转子电流时域表达式并通过PSCAD仿真和动模实验验证公式的正确性,并分析DFIG机端相位跳变以及双馈风机网侧与转子侧变流器控制对故障电流的作用机理与影响程度。由于双馈风电场自身的弱电源和故障特性,当风电场汇流线路或送出线路发生故障时,传统保护己不能可靠动作。本文提出基于双馈风电场故障特性的汇流线路自适应电流保护策略,基于故障稳态量的风电场送出线路电流纵联差动保护策略以及自适应距离保护策略。并搭建含双馈风电场以及电网联络线的PSCAD模型分别对传统保护和改进保护策略进行仿真验证与分析。为大规模双馈风电场接入电网时风电场汇流线路以及送出线路保护新原理的研究和应用提供了理论基础。
[Abstract]:The mechanism of wind power generation is different from that of traditional thermal power generation, and the electromagnetic transient characteristics of the fan change greatly after the fault. The connection of double-fed wind power makes the power network structure more complex, and the reliability and security are difficult to be effectively guaranteed. In this paper, the electromagnetic transient characteristics of doubly-fed wind turbines under symmetrical and asymmetric faults are studied, and the transient expressions of stator and rotor currents are obtained. Considering the influence of large-scale doubly-fed wind farm on traditional protection in power network, the improved protection strategy for wind farm confluence line and wind farm output line is put forward. The fault is verified by PSCAD. In this paper, the transient mathematical model of doubly-fed induction motor in different coordinate systems is established, and the transient model of doubly-fed induction motor under synchronous rotation axis system and its common coordinate transformation are described. The mathematical models of DFIG grid-side and rotor-side converters are derived, and the generation characteristics and operation principle of doubly-fed induction wind generators are analyzed. The PSCAD model of DFIG is built for simulation verification. Secondly, in this paper, under the symmetrical and asymmetric fault of power network, The control of rotor side and grid side converter of DFIG machine and the influence of DC bus voltage fluctuation on the fault current are fully considered. Using the DFIG transient mathematical model, the DFIG energy under symmetric and asymmetric faults is derived, respectively. The time-domain expression of DFIG stator and rotor current can reflect the transient output characteristics, and the correctness of the formula is verified by PSCAD simulation and dynamic simulation. The effect mechanism and influence degree of the phase jump at the end of DFIG and the control of grid-side and rotor side converter of doubly-fed fan on the fault current are analyzed. Due to the weak power supply and fault characteristics of the doubly-fed wind farm itself, when the wind farm confluence line or the outgoing line fails, Traditional protection can not operate reliably. In this paper, an adaptive current protection strategy for confluence circuit based on fault characteristics of doubly-fed wind farm is proposed. Based on the fault steady-state value of wind farm, the current longitudinal differential protection strategy and adaptive distance protection strategy of wind farm are proposed. The PSCAD model with doubly-fed wind farm and power network tie line is built to protect the traditional protection and improve the protection strategy, respectively. It provides a theoretical basis for the research and application of the new principle of wind farm confluence line and transmission line protection when a large-scale doubly-fed wind farm is connected to the power grid.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM614

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