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Wang J.,Beijing Jiaotong University | Xie H.,Beijing Jiaotong University | Sun J.,Beijing Electrical Power Research Institute
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2014

Active distribution network has gradually become the important direction of the future smart power grid. It plays an important role in increasing capability of renewable energy accommodation, improving the power utilization level and realizing the flexible intelligent distribution network management. The active distribution network energy management system (DMSs), which is the highest decision-making center of active distribution network, uses effective controlling and scheduling of the distributed power to guarantee global optimization operation of distribution network. This paper aims to improve the economy and reliability of the active distribution network. As the wind power and photovoltaic power generation have uncertainty, it uses random simulation technique and the penalty function method, based on the chance-constrained programming to establish a energy scheduling mathematical model, which has wind turbines, photovoltaic power generation unit and the active power energy storage device. Considering various constraint conditions, the model uses the improved particle swarm algorithm to solve. In order to verify the correctness and effectiveness of the provided model, an actual system in a certain area is used as an example and the standard particle swarm algorithm is compared.

Wang L.,Tianjin University | Du B.,Tianjin University | Ren Z.,Beijing Electrical Power Research Institute
Gaodianya Jishu/High Voltage Engineering | Year: 2014

To obtain the degradation condition of insulation in crosslinking polyethylene (XLPE) cables which has been operated for many years, and to understand the mechanism of the degradation, we analyzed the insulation of 14 XLPE cables returned from 110 kV and 220 kV transmission lines using the thermo gravimetric method, infrared spectrum, mechanical strength test. Moreover, we researched the relationship of thermal stability of insulation materials, the material composition and mechanical properties with the degradation, and analyzed the historical operation data of the 14 samples. The results show that four of 14 cables have degradation in their insulation, and all these four cables are heated by fault current or external high temperature. It is also concluded that initial decomposition temperature, hydroxyl index, and fracture energy have good consistency in terms of characterizing the status of XLPE cables' insulation degradation: when insulation has degradation, its initial decomposition temperature and fracture energy decrease, and its carbonyl index increases. The cross-linked cable subjected to large fault current shock or external high temperature will accelerate insulation degradation.

Xiao B.,Northeast Dianli University | Cong J.,Northeast Dianli University | Gao X.,Jilin Electrical Power Company Ltd | Gu Y.,Beijing Electrical Power Research Institute
Dianwang Jishu/Power System Technology | Year: 2014

In allusion to restricted grid-connected capacity and high wind power curtailment when large-scale wind farm is grid-connected, in usual it is considered to improve power grid's ability of accommodating wind power by energy storage system, however how to evaluate the overall efficiency of the hybrid wind power-pumped storage system is the problem to be solved well. For this reason, the investment cost, economic benefit of pumped storage system and its operational constraints are analyzed, thus the follow-up mechanism between comprehensive benefits of hybrid wind power-pumped storage system and energy storage capacity under optimized operating condition of regional power grid is revealed, and a mathematical model to solve the comprehensive benefits is established and a method to evaluate the comprehensive benefits is proposed. Based on output curves of mutually matched thermal generation units, wind power and load characteristics of power grid and combining with the installation capacity of thermal generation units and utilizing the incidence relation between system frequency and load (or the change of power generation), the proposed method quantitatively analyzes the impacts of the change of such factors of pumped storage station as its capacity, service life, cost and revenue on comprehensive benefits and power grid's accommodation ability of wind power. Case analysis shows that proposed evaluation method is effective.

Xiao H.,North China Electrical Power University | Zhang Q.,Beijing Electrical Power Research Institute | Wang L.,North China Electrical Power University | Sun B.,North China Electrical Power University
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2011

The combustion-adjustment experiments for NOx emission reduction were performed on an 1025 t/h boiler. By changing the factors such as the oxygen content, top tertiary-air, overfire-air and the distribution of second-air, the regularity of NOx emissions concentration and boiler efficiency in different working conditions were studied, and the results indicates that change of average temperature of flame in furnace is very small under different oxygen concentrations. The fuel-NOx and the boiler efficiency rapidly become greater with increasing the oxygen content, but they decreases by increasing the top tertiary-air gradually. With the overfire-air increasing, average temperature of flame in furnace and NOx emission decreases, however this influence on boiler efficiency may be neglected. The experiments also confirmed that the most boiler efficient and the minimum NOx emissions occurres in constricted air distribution mode, by comparison, in uniform mode, the NOxemissions increases 14.20%. On the premise of a certain boiler efficiency, the NOx emissions can be reduced by 10%~20% through combustion-adjustment. © 2011 Chin. Soc. for Elec. Eng.

Li A.,Beijing Electrical Power Research Institute
Zhenkong Kexue yu Jishu Xuebao/Journal of Vacuum Science and Technology | Year: 2015

The flow field in the steam ejector, a key component of the equipment dedicated to low temperature multi-effect seawater desalination, was empirically approximated, mathematically modeled via modification of Sokolov design-method, theoretically analyzed and numerically simulated with software CFD to optimize its design. The influence of the structure of the newly-designed ejector, including the sizes of different sections, on the jet coefficient was investigated by simulation. The calculated results show that the optimized ejector outperforms the conventional one. For example, its jet coefficient of 1.35 is much higher than 0.96 of the old ejector. In addition, the sizes in the major sections of the novel ejector lie in the best range. We suggest that the newly-developed steam ejector may be of much technological interest. ©, 2015, Science Press. All right reserved.

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