作为促进温室气体减排的新兴市场,碳交易市场逐渐成为影响发电公司收益的重要因素。碳市场中的碳排放配额具有典型的金融产品特征,碳价波动及其与电价的交互作用会给参与电力市场运营的发电公司竞标决策带来风险。在此背景下,针对由同...作为促进温室气体减排的新兴市场,碳交易市场逐渐成为影响发电公司收益的重要因素。碳市场中的碳排放配额具有典型的金融产品特征,碳价波动及其与电价的交互作用会给参与电力市场运营的发电公司竞标决策带来风险。在此背景下,针对由同一区域的火电机组、分布式发电单元、电动汽车和需求侧资源所集成的虚拟电厂(virtual power plant, VPP),首先利用条件风险价值(conditional-value-at-risk, CVaR)理论度量VPP所面临的不确定性因素。然后,采用Copula函数对电价与碳价的联合概率分布进行建模,并以CVaR最小化为目标,针对虚拟电厂构建了计及电价和碳价间风险依赖的Copula-CVaR竞标优化模型。最后,采用YALMIP/CPLEX对所建立的竞标优化模型进行求解,并用一个算例系统的4个场景说明了采用所提方法刻画VPP竞标风险的可行性与有效性。展开更多
电网中少数关键节点的故障可能会引发连锁故障,从而对电网的安全稳定运行造成巨大影响。因此,识别出电力系统的关键节点并进行重点保护对预防重大停电事故具有重要意义。在此背景下,该文提出了基于改进节点重要度贡献矩阵的电网关键节...电网中少数关键节点的故障可能会引发连锁故障,从而对电网的安全稳定运行造成巨大影响。因此,识别出电力系统的关键节点并进行重点保护对预防重大停电事故具有重要意义。在此背景下,该文提出了基于改进节点重要度贡献矩阵的电网关键节点的识别方法。首先,基于功率转移分布因子(power transfer distribution factors,PTDF)定义改进的电气距离,在此基础上提出了反映节点间连通性的节点效率指标;接着,为了更好地体现节点的局部和全局重要性,对节点重要度贡献矩阵进行改进,并提出基于改进节点重要度贡献矩阵的节点重要度评估方法;然后,为了比较不同关键节点识别方法的优劣,提出并定义了网络可供电能力和网络效能指标;最后,基于新英格兰10机39节点系统,通过模拟对关键节点的攻击以及与其他方法的比较,验证所提出的关键节点识别方法的有效性和正确性。展开更多
Glass-forming ability is a long-standing concern in the field of metallic glasses(MGs),which greatly limits their maximum casting size and extensive applications.In this work,we report an ultrasonic-assisted rapid col...Glass-forming ability is a long-standing concern in the field of metallic glasses(MGs),which greatly limits their maximum casting size and extensive applications.In this work,we report an ultrasonic-assisted rapid cold welding of bulk MGs without using any additives.MGs with various compositions are welded together under a 20,000-Hz highfrequency ultrasonic vibration without losing their amorphous nature.The ultrasonic technology offers the advantages of rapid bonding(<1 s)at low temperature(near room temperature)and low stress(<1 MPa).According to the phenomenon observed in the experiment,the activated fresh atoms diffuse through the broken channel port under continuous rupture of the oxide layer,and the ultrasonic vibration accelerates the atomic-diffusion process.Finally,stable bonding of the MG interface is realized.This universal ultrasonic-assisted welding process can realize the composition design of dissimilar MGs as well as tuning of new materials with new performance.展开更多
文摘作为促进温室气体减排的新兴市场,碳交易市场逐渐成为影响发电公司收益的重要因素。碳市场中的碳排放配额具有典型的金融产品特征,碳价波动及其与电价的交互作用会给参与电力市场运营的发电公司竞标决策带来风险。在此背景下,针对由同一区域的火电机组、分布式发电单元、电动汽车和需求侧资源所集成的虚拟电厂(virtual power plant, VPP),首先利用条件风险价值(conditional-value-at-risk, CVaR)理论度量VPP所面临的不确定性因素。然后,采用Copula函数对电价与碳价的联合概率分布进行建模,并以CVaR最小化为目标,针对虚拟电厂构建了计及电价和碳价间风险依赖的Copula-CVaR竞标优化模型。最后,采用YALMIP/CPLEX对所建立的竞标优化模型进行求解,并用一个算例系统的4个场景说明了采用所提方法刻画VPP竞标风险的可行性与有效性。
文摘电网中少数关键节点的故障可能会引发连锁故障,从而对电网的安全稳定运行造成巨大影响。因此,识别出电力系统的关键节点并进行重点保护对预防重大停电事故具有重要意义。在此背景下,该文提出了基于改进节点重要度贡献矩阵的电网关键节点的识别方法。首先,基于功率转移分布因子(power transfer distribution factors,PTDF)定义改进的电气距离,在此基础上提出了反映节点间连通性的节点效率指标;接着,为了更好地体现节点的局部和全局重要性,对节点重要度贡献矩阵进行改进,并提出基于改进节点重要度贡献矩阵的节点重要度评估方法;然后,为了比较不同关键节点识别方法的优劣,提出并定义了网络可供电能力和网络效能指标;最后,基于新英格兰10机39节点系统,通过模拟对关键节点的攻击以及与其他方法的比较,验证所提出的关键节点识别方法的有效性和正确性。
基金supported by the Key Basic and Applied Research Program of Guangdong Province,China(2019B030302010)the National Natural Science Foundation of China(51871157,51971150 and 51775351)+2 种基金the Science and Technology Innovation Commission Shenzhen(JCYJ20170412111216258)the National Key Research and Development Program of China(2018YFA0703605)Shenzhen Basic Research Project(JCYJ20190808152409578).
文摘Glass-forming ability is a long-standing concern in the field of metallic glasses(MGs),which greatly limits their maximum casting size and extensive applications.In this work,we report an ultrasonic-assisted rapid cold welding of bulk MGs without using any additives.MGs with various compositions are welded together under a 20,000-Hz highfrequency ultrasonic vibration without losing their amorphous nature.The ultrasonic technology offers the advantages of rapid bonding(<1 s)at low temperature(near room temperature)and low stress(<1 MPa).According to the phenomenon observed in the experiment,the activated fresh atoms diffuse through the broken channel port under continuous rupture of the oxide layer,and the ultrasonic vibration accelerates the atomic-diffusion process.Finally,stable bonding of the MG interface is realized.This universal ultrasonic-assisted welding process can realize the composition design of dissimilar MGs as well as tuning of new materials with new performance.
