•Three organization schemes are compared and aggregation is the most efficient.•Sharing scheme can achieve near optimal efficiency without a central organizer.•Concrete bilevel models for energy hub ...management in multi-energy system.•An approximated mixed-integer linear program for computing the market equilibrium.
The interdependency across natural gas, power and heating systems is increasingly tightened due to the wide development of cogeneration plants and electrified heating facilities. Multi-energy integration is a prevalent trend and the energy hub, which acts as an intermediary agent between providers and consumers, is expected to play a central role in allocating energy resources more efficiently. However, uncertainties originating from multiple kinds of energy demands challenge the operation of energy hubs and may compromise system efficiency. Energy trading and sharing among individual hubs offer a unique opportunity to increase system flexibility and reduce the cost under demand uncertainty. In this paper, three quintessential schemes for organizing a cluster of energy hubs at demand side, i.e., individual, sharing market, and aggregation, are studied under a stochastic framework with probabilistic load forecasts. First, we perform theoretical analysis and compare their economic efficiencies from a maximum-utility (or minimum-cost) perspective. Utility curves of respective schemes are given, and several important phenomena are revealed from the economic analysis. Then we discuss the concrete decision-making models of energy hubs under the three schemes, taking into account the change of electricity price in response to the total demand, which give rise to bilevel optimization problems and are technically transformed into mixed-integer linear programs. Finally, we conduct numerical experiments, which validate the theoretical outcomes, and reveal that the sharing scheme can achieve nearly optimal efficiency without a central organizer, and hence appears to be a promising direction for future multi-energy systems.
Abstract
Organizing nonstop train is one of the effective ways to organize traffic flow. This article introduces the conditions, principles and schemes of the nonstop transport organization. On this ...basis, this paper establishes a mathematical model with the goal of minimizing the total consumption of traffic in the loading and unloading areas and during operation. This model is constrained by the uniqueness of the plan and the restriction of direct traffic flow. This paper constructs an example to test the actual application of the model, verify its effectiveness, and explain the advantages of organizing nonstop train.
This paper addresses the train organization problem of a small-size metro network during the peak hour, with a special consideration of transfer coordination. The problem is formulated as a ...multi-objective programming (MOP) model, where the economic cost, capacity utilization, and transfer coordination are considered together based on the routing selection analysis. Train marshaling number and headway on different routes are key decision variables in the model. The economic cost consists of generalized trip cost, operation cost, and external benefits, and the capacity utilization describes the remaining section capacity expressed by a difference quadratic sum. The proposed model highlights the transfer coordination, which targets at minimizing the number of left-behind passengers on platforms, considering the time-varying arrival rate and the remaining train capacity. Based on the sequencing method, an integration of genetic algorithm and ant colony optimization is devised to solve the MOP model. Finally, a real-world case study of Xi’an metro network has been conducted. Results show that the number of left-behind passengers in the network decreased 55.3
%
, the total remaining capacity decreased 15.3
%
and the number of trains decreased 8.5
%
, while the total time cost increased 1.6
%
. To further check the passenger distribution density on the platform, a simulation of
Beidajie
transfer station has been elaborately designed via Viswalk 7.0. Both theoretical results and simulation data have validated the feasibility and reliability of presented method.
Because of a high proportion of renewable energy sources (RESs) access, the establishment of a "photovoltaic, energy storage, DC, flexible" distribution system (PEDFDS) has great value, such as ...reducing power loss and saving construction costs. This paper investigates the organizational scheme of the PEDFDS and its voltage sag mechanism. First, the fundamental functions and control strategies of crucial components in the PEDFDS are elucidated. Then, the voltage sag mechanisms are studied by various transient disturbances, and the propagation characteristics of the voltage sags under different voltage levels are explored. Finally, a detailed simulation model of the PEDFDS is built in MATLAB/Simulink, and the goal is to analyze the voltage sag mechanisms caused by the instantaneous load change and single-pole grounding faults. From the simulation results, the voltage sag-blocking effect of the DC solid-state transformers (DCSSTs) can be confirmed, and the correctness of the theoretical analysis is verified.
To formulate a scientific and reasonable road organization plan in the course of the construction period of roads in Lhasa city, the current traffic organization scheme during construction period is ...firstly evaluated and studied by combining AHP and entropy method. Secondly, the evaluation index system for the traffic organization scheme of the construction section is constructed from the three aspects of the regional road network, traffic facilities and driving, and road intersections. Finally, based on the analysis results, some feasible measures are proposed for the current transportation organization scheme of Najin Township during the construction period.
The scientific and reasonable ship traffic organization scheme is an important guarantee to improve the channel's passage capacity and maintain the channel's navigation safety. Firstly, the ...simulation model for channel passage capacity based on the NaSch model was proposed to calculate the passage capacity of the channel under different organization schemes. The model considered several restrictive conditions such as ship speed, safety distance, channel layout Scheme, and ship overtaking rules. Then, the optimal selection model for the ship traffic organization scheme based on the serial number sum theory is proposed. Taking the Nacao Channel of the Yangtze River Estuary as an example, 24 ship traffic organization schemes were simulated and preferred. The results show that the proposed model can quantitatively simulate the passage capacity in the Nancao Channel under different organization schemes and preferably select a reasonable scheme. The results can provide decision support for the development and optimization of the navigational organization scheme of the ship channel.
West Germany is densely populated, averaging 245 inhabitants/km2, but varying widely between urban agglomerations and rural areas. Transport volume has increased by 40% since 1970, with virtually all ...growth due to private automobiles. Since 1981 public transit has been suffering from decreasing demand.A 1964 Expert's Report to the German federal government was the stimulus for initiating an effective funding mechanism for new public transit construction In 1965 Germany's first federated transit authority was founded for the region of Hamburg.Principal among the goals of any cooperative agreement among transit companies are improvements for the passengers and improvement of revenues for the companies To attain these ends, two distinct forms of transit aggrements have been developed in Germany: transit cooperative (Verkehrsgemeinschaft) and transit federation (Verkehrsverbund). The former is more suitable for smaller to medium-sized towns, while the latter is more suitable for larger cities. The two types are described in this article.German transit federations during the 1970s succeeded in significantly increasing ridership, while during the 1980s patronage has either remained steady or has declined. Yet transit federations showed much better perfomance than did public transit in general. In terms of costs and revenues, no public transit organization in Germany is able to break even; deficits vary between 42% and 55%. The author concludes, however, that hidden subsidies for automobile traffic are far higher, because of environmental damage and the high social cost of traffic accidents.
PDF
