Multi-energy systems may contain integrated energy networks such as electrical, gas and heating networks. The differences in the physical characteristics of each energy network make it difficult to solve power flows o...
详细信息
The aging behavior of single lap joints(SLJ) in hygrothermal cycles was investigated and compared by using a shearing strength test, Fourier transform infrared spectroscopy(FTIR), thermogravimetric analysis(TG/DTG), e...
详细信息
The aging behavior of single lap joints(SLJ) in hygrothermal cycles was investigated and compared by using a shearing strength test, Fourier transform infrared spectroscopy(FTIR), thermogravimetric analysis(TG/DTG), energy dispersive spectrometry(EDS) and scanning electronic microscopy(SEM). The temperature/relative humidity was set at 80 ℃/95% and –40 ℃/30% for 20 cycles, 40 cycles, and 60 cycles(one cycle was 12 hours), respectively. The experimental results show that hygrothermal aging significantly decreases the failure strength of adhesive joints. However, the failure displacement increases as the number of aging cycles increases. In addition, hygrothermal aging changes the failure mode of the adhesive joints from a cohesive fracture in un-aged adhesive layers to an interfacial failure of aged adhesive joints.
Security evaluation has become a hot topic in the research field of water resource management. In this paper, we established a novel water resource security indicator system based on the Pressure-Status-Response (PSR)...
详细信息
Security evaluation has become a hot topic in the research field of water resource management. In this paper, we established a novel water resource security indicator system based on the Pressure-Status-Response (PSR) framework using gray relation analysis (GRA) and technique for order preference by similarity to ideal solution (TOPSIS). A case study of Beijing from 1996 to 2007 was conducted to verify the evaluation system. Results showed that the gray relative closeness degrees of water resource security to the positive ideal solution were low, with the least one of 0.360 in 1999 and the largest one of 0.527 in 2007, implying that Beijing was facing severer challenges with water resources during the concerned time. Also, the analysis of water resource security indicated that the pressure of water resource was constantly increasing. Finally, factor analysis was employed to calculate the gray relation degrees of evaluating indices with the ideal solutions so as to reveal the relativity of water resource security of Beijing, which may contribute to a better understanding of the urban water resource management and regulation.
This paper presents a measurement-based solution for low frequency oscillation(LFO) analysis in both real time monitoring and off-line case study. An online LFO property discrimination method is developed first,which ...
详细信息
This paper presents a measurement-based solution for low frequency oscillation(LFO) analysis in both real time monitoring and off-line case study. An online LFO property discrimination method is developed first,which alternately uses empirical mode decomposition(EMD)/Hilbert transform(HT) and square calculation to process the measurement data. The method magnifies the variation trend of oscillating variables to accurately discriminate the property of the oscillation. Subsequently, an oscillation source locating method for the forced oscillation(FO) and a strongly correlated generator identification method for the weak damping oscillation(WDO) are proposed. Finally, numerical study results on a test system of the isolated Changdu grid in Tibet validate the proposed methods.
Navigable flow condition simulations can provide detailed information on water depth and velocity distribution, simulation speed is one of the key factors which influence real-time navigation. In this paper, a navigab...
详细信息
Navigable flow condition simulations can provide detailed information on water depth and velocity distribution, simulation speed is one of the key factors which influence real-time navigation. In this paper, a navigable flow condition simulation system is developed to provide useful information for waterway management and shipping safety. To improve the simulation speed of 2-D hydrodynamic model, an explicit finite volume method and Open MP are used to realize parallel computing. Two mesh schemes and two computing platforms are adopted to study the parallel model's performance in the Yangtze River, China. The results show that the parallel model achieves dramatic acceleration, with a maximum speedup ratio of 34.94?. The parallel model can determine the flow state of the navigable channel in about 4 min, efficiency is further improved by a flow simulation scheme database. The developed system can provide early warning information for shipping safety, allowing ships to choose better routes and navigation areas according to real-time navigable flow conditions.
The effects of manganese dioxide (MnO 2 ) additives on the electrical characteristics of the Al-doped ZnO varistors are investigated. The leakage current densities of the samples decrease first and then increase again...
详细信息
The effects of manganese dioxide (MnO 2 ) additives on the electrical characteristics of the Al-doped ZnO varistors are investigated. The leakage current densities of the samples decrease first and then increase again with the increase of the amount of MnO 2 additives. Correspondingly, the nonlinear coefficients of the samples keep on increasing and then decrease. In addition, the donor densities increase monotonously with the amount of the doped MnO 2 increasing. The effects of MnO 2 additives on the electrical characteristics of the samples are different from the conclusion of previous literatures. The reasons of the distinct effects are supposed to be related with the donor and interface state densities of the samples.
Distributed integrated multi-energy systems(DIMSs)can be regarded as virtual power plants to provide additional flexibility to the power *** paper proposes a robust active dynamic aggregation model for the DIMSs to de...
详细信息
Distributed integrated multi-energy systems(DIMSs)can be regarded as virtual power plants to provide additional flexibility to the power *** paper proposes a robust active dynamic aggregation model for the DIMSs to describe the maximum feasible *** aggregation model includes the power constraints,energy constraints,and ramping constraints to aggregate different types of resources in the *** proposed generator-like and storage-like model does not depend on the ancillary service market and can be directly incorporated into the economic dispatch model of the power system.A novel algorithm based on the column-and-constraint generation algorithm and convex-concave procedure is proposed to solve the two-stage robust optimization problem,which is more efficient than the KKT-based ***,a case study of an actual DIMS is developed to demonstrate the effectiveness of the proposed model.
In this paper, the impact of stochastic time delay on wide-area damping networked controlsystems is analyzed. A disintegrate method of time-delay upon sampling period is approved. Furthermore, the expectative model o...
详细信息
ISBN:
(纸本)9781467355339
In this paper, the impact of stochastic time delay on wide-area damping networked controlsystems is analyzed. A disintegrate method of time-delay upon sampling period is approved. Furthermore, the expectative model of networked controlsystems with long and stochastic time delay, whose variance extent is larger than one sampling period, is theoretically proved and calculated. Finally, the effectiveness of this expectative model is confirmed on the simulation of a power system with 8 generators and 36 nodes.
Establishing a suitable closed-loop transfer function model for the grid-connected PMSG system is the key basis in performing inter-harmonic characteristics *** closed-loop transfer functions can be constructed when d...
详细信息
Establishing a suitable closed-loop transfer function model for the grid-connected PMSG system is the key basis in performing inter-harmonic characteristics *** closed-loop transfer functions can be constructed when different components of the converter controller are taken into ***,the effect of different components of the converter controller on inter-harmonic stability analysis is not *** this paper,the complete transfer function,considering different loops,is first *** on the complete closed-loop transfer function,the DC-link,PLL and voltage forward-feed are removed step by step to derive different closed-loop transfer *** inter-harmonic related poles of different closed-loop transfer functions are further calculated to analyze the effect of closedloop transfer functions on inter-harmonic characteristics ***,by performing time domain simulation,the correctness of the theoretical analysis results is *** results show that under the conditions of a weak AC system,each loop of the converter control system will reduce the stability of the interharmonic in the sub-synchronous frequency range and influence the inter-harmonic oscillation *** transfer function needs to consider the influence of each loop to accurately calculate the inter-harmonic stability of the system.
The power system now is a typical complex system, which has inherent characteristics of SOC. Studying on cascading failures are necessary and meaningful to insure the grid's safety, national security and economic ...
详细信息
ISBN:
(纸本)9781479947249
The power system now is a typical complex system, which has inherent characteristics of SOC. Studying on cascading failures are necessary and meaningful to insure the grid's safety, national security and economic development. This paper firstly establishes the indices of power system development diagnosis, which are closely relevant to the trigger of power system evolution. Then a cascading failure model is proposed, considering planning and evolution of the power system. This model is based on OPA model, including both fast dynamics and slow dynamics. The slow dynamic process simulates the evolution of power system, which represents the functions of the planning department, while the fast dynamic process simulates power flow and cascading failures, which takes the effects of dispatch, relay protection and automation into consideration. Moreover, simulations are tested on the case of Kaifeng-Shangqiu power system in Henan Province of China, and evolution results are presented.
暂无评论