风电场直流并网系统静态电压稳定分析方法研究

发布时间：2018-09-06 06:47

【摘要】：传统能源的日益枯竭及其带来的全球环境恶化,使得具有可再生、无污染、储量丰富、分布广等优点的风能备受各国重视。而我国主要的风力资源远离负荷中心,需并网远距离输送到负荷中心。电压源型的高压直流输电(VSC-HVDC)与交流输电和传统直流输电相比,有诸多优点,比如具有独立控制有功和无功、可为无源网络供电、占地面积小、可发出无功、在分散性的小型可再生能源发电并网方面具有经济性等,因此,VSC-HVDC更适合风电并网。而风电场规模的日益扩大使得风电并网对系统电压稳定性的影响越来越严重,因此,很有必要分析基于VSC-HVDC的风电并网系统的静态电压稳定性。首先,针对现有交直流联合系统潮流统一迭代法对纯交流程序继承性差、程序编写工作量大以及交替迭代算法没有考虑交、直流之间的耦合而导致收敛性差、精度低的缺陷,结合直流网络方程及VSC控制方程实现交流、直流子系统完全解耦及独立求解,从而形成了一种AC/VSC-MTDC混联系统潮流解耦快速算法。其次,针对线路换相换流器(LCC)与电压源换流器(VSC)的结合成的混合直流输电系统特别适合多风电场同时并网,这样就形成了交流/混合多端直流输电(AC/Hybrid-MTDC)系统。论文在实现交流、直流子系统解耦的基础上,通过在交流子系统雅可比矩阵中分别追加了LCC和VSC的耦合项来独立、交替求解交流子系统、直流子系统潮流,算法收敛性好、计算速度快。然后,论文研究了AC/VSC-MTDC混联系统的静态电压稳定性分析方法。提出以AC/VSC-HVDC混合系统潮流解耦快速算法为基础、局部参数化的连续潮流算法来分析AC/VSC-MTDC混联系统静态电压稳定性。算法计算速度快,且能够方便计及VSC-MTDC系统运行方式转换。最后,论文针对传统连续潮流算法分析风电场直流并网系统静态电压稳定过程中,在移去直流系统后出现孤立风电场交流节点,无法进行迭代这一现象,提出将风电场等效成变PQ节点,在建立节点无功功率与节点电压、有功功率函数关系基础上,应用前述AC/VSC-MTDC混联系统静态电压稳定性分析方法来分析基于VSC-HVDC的风电场并网系统静态电压稳定性分析。论文提出的研究方法对AC/VSC-MTDC混合系统潮流计算、静态电压稳定性分析、AC/Hybrid-MTDC潮流计算以及基于AC/VSC-HVDC的风电场并网系统静态电压稳定分析方法都具有较好的参考价值。
[Abstract]:With the depletion of traditional energy and the deterioration of the global environment, wind energy, which is renewable, pollution-free, rich in reserves and widely distributed, has attracted much attention. The main wind resources in China are far away from the load center and need to be transported to the load center. Compared with AC transmission and traditional DC transmission, voltage source HVDC transmission (VSC-HVDC) has many advantages, such as independent control of active and reactive power, power supply for passive network, small area and reactive power. So VSC-HVDC is more suitable for wind power grid. With the increasing scale of wind farm, the influence of wind power grid connection on system voltage stability is becoming more and more serious. Therefore, it is necessary to analyze the static voltage stability of wind power grid connected system based on VSC-HVDC. First of all, the current unified iterative method of AC / DC power flow has poor inheritance to pure AC program, large program writing workload and alternating iteration algorithm without considering AC, and the coupling between DC and DC leads to poor convergence and low precision. Combined with DC network equation and VSC control equation, DC subsystem is completely decoupled and independently solved, thus a fast algorithm for power flow decoupling of AC/VSC-MTDC hybrid system is formed. Secondly, the hybrid DC transmission system based on the combination of the line commutator (LCC) and the voltage source converter (VSC) is especially suitable for the simultaneous grid connection of multi-wind farms, thus the AC / hybrid multi-terminal direct current transmission (AC/Hybrid-MTDC) system is formed. Based on the decoupling of AC and DC subsystems, the coupling terms of LCC and VSC are added to the Jacobian matrix of AC subsystem separately to solve the AC subsystem alternately, DC subsystem power flow and convergence of algorithm are good. The calculation speed is fast. Then, the static voltage stability analysis method of AC/VSC-MTDC hybrid system is studied. Based on the fast power flow decoupling algorithm for AC/VSC-HVDC hybrid systems, a locally parameterized continuous power flow algorithm is proposed to analyze the static voltage stability of AC/VSC-MTDC hybrid systems. The algorithm is fast and convenient to take into account the operation mode conversion of VSC-MTDC system. Finally, aiming at the traditional continuous power flow algorithm, this paper analyzes the static voltage stability process of DC grid connected system of wind farm. After removing DC system, the isolated AC node of wind farm can not be iterated. The wind farm is equivalent to a variable PQ node. The relationship between reactive power, voltage and active power function of the node is established. The static voltage stability analysis of wind farm grid-connected system based on VSC-HVDC is analyzed by using the AC/VSC-MTDC hybrid system static voltage stability analysis method mentioned above. The research method proposed in this paper has good reference value for power flow calculation of AC/VSC-MTDC hybrid system static voltage stability analysis AC / hybrid-MTDC power flow calculation and static voltage stability analysis method for wind farm grid-connected system based on AC/VSC-HVDC.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM614;TM712

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