交直流电网可靠性评估方法的研究

发布时间：2019-01-24 17:59

【摘要】：随着大规模可再生能源和直流负荷接入电网等问题的出现,直流输电的优势越来越突出。而“五交三直”西电东送新格局的形成,也促进了交直流并联系统和交直流混联系统的发展。针对交直流电网的开展,其可靠性问题也引起了越来越多的关注。目前,交流系统和两端直流系统的可靠性评估已经日益成熟,而针对规模不断增大,结构日益复杂的直流电网和交直流混联电网的可靠性评估还刚起步。本论文在对已有的可靠性评估方法进行对比分析的基础上,根据直流电网以及交直流混联电网的特点,选取了频率与持续时间法(FD法)和最小割集法作为基础方法,对直流电网和交直流混联电网的可靠性评估模型和评估方法进行了综合性研究。首先基于FD法提出一种适用于直流电网的可靠性评估等效模型,该模型避免了由于元件众多而出现的维数灾,减少了计算量；还可以计算除稳态概率以外的可靠性指标,如故障频率指标、持续时间指标等。简单直流电网算例的可靠性计算结果证明了本方法的正确性和有效性。对系统薄弱环节的计算和参数灵敏度分析表明海底电缆和海上换流器是影响系统可靠性的薄弱环节。然后结合FD法和最小割集法提出一种适用于交直流混联电网的可靠性评估方法。该方法对直流系统和交流系统分别建立等效模型,然后再对整个电网进行可靠性计算,得到了电网内各节点的失负荷概率、失负荷频率、失负荷持续时间以及电力不足期望值等可靠性指标。通过对负荷点可靠性指标的分析,可以找出电网的薄弱环节。以含两端直流输电系统和多端直流输电系统的混联电网为例,对上述可靠性评估方法进行验证,计算结果可以反映出系统中网络节点的可靠性水平,很好的证明了本方法的正确性和可行性。
[Abstract]:With the emergence of large-scale renewable energy and DC load connected to the power grid, the advantages of DC transmission become more and more prominent. The formation of a new pattern of "five AC and three straight" power transmission from west to east also promotes the development of AC / DC parallel system and AC / DC hybrid system. For the development of AC / DC power network, its reliability has attracted more and more attention. At present, the reliability evaluation of AC system and DC system has become more and more mature, but the reliability evaluation of DC network and AC / DC hybrid network with increasing scale and complex structure is still in its infancy. On the basis of comparing and analyzing the existing reliability evaluation methods, according to the characteristics of DC network and AC / DC hybrid network, the frequency and duration method (FD) and minimum cut set method are selected as the basic methods. The reliability evaluation model and evaluation method of DC and AC / DC hybrid networks are studied. Firstly, based on FD method, an equivalent model for reliability evaluation of DC network is proposed, which avoids the disaster of dimensionality due to the large number of components and reduces the amount of calculation. Besides the steady state probability, the reliability index, such as fault frequency index, duration index and so on, can also be calculated. The reliability calculation results of a simple DC network example show that the method is correct and effective. The calculation of weak links and the sensitivity analysis of parameters show that submarine cables and offshore converters are the weak links that affect the reliability of the system. Then a reliability evaluation method for AC / DC hybrid networks is proposed by combining the FD method and the minimum cut set method. The equivalent models of DC system and AC system are established by this method, then the reliability of the whole power network is calculated, and the load loss probability and frequency of each node in the power network are obtained. Reliability indicators such as the duration of load loss and the expected value of insufficient electricity. By analyzing the reliability index of load point, we can find out the weak link of power network. The reliability evaluation method mentioned above is verified by the example of the hybrid power network with both ends of HVDC transmission system and multi-terminal HVDC transmission system. The calculated results can reflect the reliability level of the network nodes in the system. The correctness and feasibility of this method are well proved.
【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】：TM732

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