High voltage (HV) cables are widely used in urban power transmission networks. The key component in HV cable, the buffer layer, has attracted lots of attention and more and more researchers are devoting to its material property evaluation and quality test techniques. A longitude water-blocking property evaluation method of buffer layer based on image processing is proposed in this paper. The microscopic images of the buffer layer are enhanced and morphologically processed. The area fraction method, entropy method, and fractal dimension method are used to evaluate the distribution characteristics of buffer layer water-blocking powder in binary images. This article innovatively proposes a more economical and convenient simulation method that can efficiently and accurately evaluate the waterproof performance of the buffer layer of high-voltage cables. With the proper use of the buffer layer, it can effectively protect the cables and improve the stability of power system operation.
With the promotion and development of China’s electricity market reform process, how to capture the maximum profits of all responding entities at the level of industrial parks to guide users to actively participate in demand response has become a new problem to be solved. Based on the situation that the market information disclosure is limited and users and aggregators freely conclude contracts in the response process, this paper proposes an optimal game strategy from the perspective of aggregators and a revenue distribution method for users. Considering the interests of users in the industrial park, a multi-agent and two-tier game structure is established with incomplete information Bayesian game as the upper layer and cooperative game as the lower layer; Secondly, in order to maximize their own interests, an algorithm combined with improved counterfactual regret minimization idea and heuristic algorithm is used to solve the game equilibrium to achieve a stable cooperative relationship in the park. Finally, a numerical example is used to verify that multiple comparison models are set up for the declaration strategy and income distribution in different scenarios. The results show that the strategy obtained under the proposed method can improve user income, and the reasonable selection of the benefit distribution mechanism can play a catalytic role in improving the enthusiasm of users to respond to their needs.
换流器作为高压交直流输电系统中的重要元件,因其存在复杂的电力电子器件而产生大量频次的谐波严重影响到输电系统的安全稳定,获取交直流输电系统交流侧谐波电流是谐波治理的基础,因此交流侧谐波电流的精确计算具有重要意义.本文基于时域分段法的思想,充分考虑到直流纹波电流的影响,提出了内外双环迭代的计算方法:内环采用时域分段法计算直流侧端口电压瞬时量、采用相量法计算直流侧纹波电流、利用直流纹波电流和直流侧端口电压耦合迭代计算的方法计算直流侧纹波电流;外环利用换相过程中退出换相的相电流在换相结束时刻电流过零的特点,结合纹波电流迭代计算换相角的方法精确获取换相角和交流侧谐波电流.与PSCAD/EMTDC模型计算结果对比表明:此方法既保证了谐波电流计算结果的精确度和计算效率,也充分计及了工频负序电压、背景谐波电压、触发角不等距、换相电感不平衡、变比误差、测量误差、纹波电流等各种非理想因素的影响,同时易于程序实现.
电流母排是中低压开关柜中主要的发热部件之一,有效抑制其温升对确保开关柜安全可靠运行具有重要意义.抑制母排温升的现有措施大多不够经济或操作、实施较为复杂.本文依据传热学理论,提出采用适当厚度、传热系数较好的绝缘材料对电流母排进行包裹,以提高母排散热效率,从而达到抑制母排温升的目的.理论推导得到了电流母排散热效率的解析模型,数值计算和有限元仿真分析均验证了所提出措施的有效性;基于解析模型分析了该措施的适用范围;并通过物理实验验证了所提出方法的有效性.研究结果表明,针对多种常用型号的母排,其温度随绝缘层厚度的增加先降低,后升高;包裹用绝缘材料的导热性能越好,散热效果改善越明显;本文提出的改善散热措施适用于采用自然对流散热的中低压开关柜.
需求响应是虚拟电厂应对电力市场交易中由不确定性因素带来交易风险的重要资源.本文提出一种计及多种需求响应资源的虚拟电厂运行机制以及控制策略.首先,通过v型支持向量回归机对虚拟电厂可再生能源出力、负荷出力、电力市场价格等不确定量进行日前预测,并利用自回归移动平均对预测误差进行典型场景生成.其次,考虑来自虚拟电厂内部直接可控负荷以及外部需求响应交换市场所购得的需求响应资源,基于多阶段随机规划优化框架,以预期利润最大化以及可再生能源未消纳率最小化为目标,构建了不考虑风险控制和考虑风险控制两种条件下的虚拟电厂竞价策略优化模型.最后,通过算例分析不确定性和风险偏好对虚拟电厂的预期收益及可再生能源消纳率的影响,验证了所提运行策略的有效性.
