基于改进级数展开的含风电电力系统概率潮流计算方法

我国正在构建新能源占比较高的新型电力系统,新能源风电的大规模并网和电动汽车等随机用电负荷的接入加剧了电力系统的不确定性,也给常规的半不变量概率潮流分析方法带来了挑战。在概率潮流计算中提出了一种利用最大熵原理改进的C型Gram-Charlier(C-type Gram-Charlier,CGC)级数展开法,并根据风速的Weibull分布特性推导了双馈风机出力的概率,同时利用双馈风机无功出力特性修正了用以计算系统状态量的半不变量的雅可比矩阵。在分析含新能源的电力系统时,既提高了传统CGC法的计算精度,也保留了较高的计算效率。最后,利用含双馈风场的IEEE测试系统验证了上述方法的准确性和有效性。算例结果表明,综合考虑计算精度和效率,所提出的方法具有较明显的优势。

Probabilistic Load Flow Algorithm with the Power Performance of Double-Fed Induction Generators

Probabilistic load flow(PLF)algorithm has been regained attention,because the large-scale wind power integration into the grid has increased the uncertainty of the stable and safe operation of the power system.The PLF algorithm is improved with introducing the power performance of double-fed induction generators(DFIGs)for wind turbines(WTs)under the constant power factor control and the constant voltage control in this paper.Firstly,the conventional Jacobian matrix of the alternating current(AC)load flow model is modified,and the probability distributions of the active and reactive powers of the DFIGs are derived by combining the power performance of the DFIGs and the Weibull distribution of wind speed.Then,the cumulants of the state variables in power grid are obtained by improved PLF model and more accurate power probability distributions.In order to generate the probability density function(PDF)of the nodal voltage,Gram-Charlier,Edgeworth and Cornish-Fisher expansions based on the cumulants are applied.Finally,the effectiveness and accuracy of the improved PLF algorithm is demonstrated in the IEEE 14-RTS system with wind power integration,compared with the results of Monte Carlo(MC)simulation using deterministic load flow calculation.

城市配电网中电缆大规模接入条件下的无功优化方法研究

目前大型城市电网负荷低谷时段容性无功倒送现象日益凸显,危及电网安全稳定运行。基于此背景,研究了城市配电网中电缆大规模接入条件下的无功优化方法。首先,分析无功倒送对节点功率因数的影响,建立了考虑功率因数约束的含电抗器和电容器的综合无功优化模型,模型以有功网损最小为目标函数,在传统无功优化约束基础上增加了节点功率因数约束和电抗器投切容量约束;然后,利用基于网损无功灵敏度的改进遗传算法求解所建模型,求得的优化方案通过协调配电网感性和容性无功补偿设备投切以解决电缆大规模接入时的无功倒送和功率因数越限问题;最后,以典型的高压配电网作为算例验证模型和算法的有效性。

新形势下如何做好工程造价的管理与控制

在新形势下，根据前一阶段工程造价工作中遇到的问题，结合新的设计理念、管理理念以及造价工作中总结的经验去解决所遇 到的问题，本文将从当前工程造价管理工作的现状出发，并总结出有针对性的控制措施，以期为工程造价的管理与控制的不断优化起到一 定的助推作用。

Optimal Reactive Power Compensation of Distribution Network to Prevent Reactive Power Reverse

The capacitive reactive power reversal in the urban distribution grid is increasingly prominent at the period of light load in the last years.In severe cases,it will endanger the security and stability of power grid.This paper presents an optimal reactive power compensation method of distribution network to prevent reactive power reverse.Firstly,an integrated reactive power planning(RPP)model with power factor constraints is established.Capacitors and reactors are considered to be installed in the distribution system at the same time.The objective function is the cost minimization of compensation and real power loss with transformers and lines during the planning period.Nodal power factor limits and reactor capacity constraints are new constraints.Then,power factor sensitivity with respect to reactive power is derived.An improved genetic algorithm by power factor sensitivity is used to solve the model.The optimal locations and sizes of reactors and capacitors can avoid reactive power reversal and power factor exceeding the limit.Finally,the effectiveness of the model and algorithm is proven by a typical high-voltage distribution network.

感恩与大学生网络成瘾的关系:核心自我评价和生命意义感的中介作用

为探讨核心自我评价和生命意义感在感恩与网络成瘾之间的中介作用,采用感恩量表、核心自我评价量表、生命意义感量表和网络成瘾量表对吉林省3所高校大一到研三的1072名大学生进行调查。结果表明:(1)感恩、核心自我评价和生命意义感三者之间呈显著两两正相关,且三者分别与网络成瘾呈显著负相关;(2)感恩对网络成瘾的直接效应和间接效应均显著,间接效应包含了两条路径:通过生命意义感的部分中介作用和通过核心自我评价—生命意义感的链式中介作用。本研究揭示了感恩与网络成瘾的关系及其作用机制,对预防及减少大学生网络成瘾具有一定的现实意义。

东北地区3所高校大学生网络成瘾与自尊、生命意义感的关系研究

目的:探讨大学生网络成瘾与自尊、生命意义感之间的关系,为预防和控制大学生网络成瘾提供科学依据。方法:采用网络成瘾量表、生命意义感量表和自尊量表对东北地区3所高校1092名大学生进行调查。结果:大学生网络成瘾者占调查总人数的8.33%。自尊和生命意义感与网络成瘾呈负相关(P<0.01),自尊与生命意义感呈正相关(P<0.01)。生命意义感在自尊和网络成瘾间起中介作用。结论:提高大学生自尊水平和生命意义感有助于降低网络成瘾率。