Dynamic Traffic Assignment Model Based on GPS Data and Point of Interest (POI) in Shanghai

Dynamic traffic flow, which can facilitate the efficient operation of traffic road networks, is an important prerequisite for the application of reasonable assignment of traffic demands in an urban road network. In order to improve the accuracy of dynamic traffic flow assignment, this paper proposes a dynamic traffic flow assignment model based on GPS trajectory data and the influence of POI. First, this paper explores the impact patterns of POI on regional road network congestion during peak hours through qualitative and quantitative analysis. Then, based on the user equilibrium theory, a dynamic traffic flow assignment model, in which the effect of POI on links is reflected using the link-node impedance function, is proposed. Finally, the accuracy of the model is validated by the GPS trajectory data and origin–destination (OD) traffic data of motor vehicles in Xuhui District, Shanghai, China. The results show that the model can be used to coordinate and optimize the traffic assignment of the regional road network under the influence of POI during peak hours and alleviate the congestion of the road network. The findings can provide a powerful reference for developing scientific and rational traffic assignment decisions and management strategies for urban road network traffic.

Evaluation of Operating Schemes on Municipal Rail Transit with Express/Local Mode

The express/local train mode has made municipal rail more competitive in connecting the city center with its suburbs. Therefore, how to design operating schemes is of concern to decision makers. Unlike earlier line planning optimization, this paper aims to provide a quick and comprehensive evaluation of operating performance in all feasible options through reasonable reduction of the scope of the operating schemes, rather than optimization for a single objective. To achieve this, the paper constructs a travel topology network structure based on the separation of trains, which regards express and local trains running on the common line as independent competitors. Focusing on the problems of uneven departure intervals and inconsistent dwell times caused by overtaking, a generalized cost model suitable for the express/local train mode is established. To solve the express/local line problems of multi-routes and high-overlapping, the improved Multinominal Logit (MNL) Model is used to construct a passenger flow assignment model, with the solution achieved by the Method of Successive Averages algorithm. Taking a municipal rail line in Guangzhou as a case study, this paper analyzes the advantages and disadvantages of feasible operation schemes with different characteristics in the express/local train ratio, the location and number of overtaking stations based on passenger flow assignment results and also the impacts of crowdedness on passenger flow dynamics. The results verified the effectiveness of our approach in the comprehensive evaluation of the express/local train mode and shed light on potential practical applications in determining a reasonable operating scheme.

Safe Operation Conditions of Electrical Power System Considering Power Balanceability Among Power Generators, Loads, and Storage Devices

The introduction of an energy storage system plays a vital role in the integration of renewable energy by keeping a stable operation and enhancing the flexibility of the power flow system, especially for an islanding microgrid which is not tied to a grid and for a self-contained microgrid which tries to stay independent from a grid as much as possible. To accommodate the effects of power fluctuations of distributed energy resources and power loads on power systems, a power flow assignment under power balance constraint is essential. However, due to power limitations of power devices, the capacity of storage devices, and power flow connections, the power balance may not be achieved. In this paper, we proposed a system characterization which describes the relation among power generators, power loads, power storage devices, and connections that must be satisfied for a system to operate by keeping SOC limitations of power storage devices. When we consider one power generator, one power load, and one power storage device connected at a single node, the generated energy by the generator minus the consumed energy by the load from some start time will increase/decrease the state of charge (SOC) for the storage device; hence, keeping SOC max/min limitations relies on whether the difference between the generated energy and the consumed energy stays within a certain range or not, which can be computed from the capacity Ess and other parameters. Our contribution in this paper is an extension and generalization of this observation to a system that consists of multiple fluctuating power generators, multiple fluctuating power loads, multiple storage devices, and connections that may not be a full connection between all devices. By carefully enumerating the connection-dependent flow paths of generated energy along the flow direction from generators to storages and loads, and enumerating the connection-dependent flow paths of consumed energy along the counter-flow direction from loads to storages and generators, we have formulated the increase/decrease of SOCs of storage devices caused by the imbalance between generated energy and consumed energy. Finally, considering the max/min limitations of SOCs and fluctuations of power generators and power loads, the conditions that the power generators and the power loads must have for SOCs of storage devices to maintain individual max/min limitations have been derived. The system characterization provides guidelines for a power flow system that can continue safe operation in the presence of power fluctuations. That is, in order for a system to have a feasible power flow assignment, there are the issues of how large the capacity of a power storage device should be, how large/small the maximum/minimum power/demand levels of the power generators and the power loads should be, and how the connection should be configured. Several examples using our system characterization are demonstrated to show the possible applications of our results.

Optimal Capacity And Flow Assignment For Self-Healing ATM Networks Based On Path Restoration: Nonlinear Models

This thesis addresses the design of self-healing Asynchronous Transfer Mode (ATM) networks which is a special aspect of a more general problem, referred to as capacity and flow assignment (CFA) problem in self-healing ATM networks. We have proposed two nonlinear mathematical models for global reconfiguration strategy and failure-oriented reconfiguration strategy in our thesis. Our restoration strategies aim to minimize the capacity installation cost and the routing cost when a single link failure occurs in the network. A special case of the augmented Lagrangian method so-called Separable Augmented Lagrangian Algorithm (SALA) is proposed for solving the proposed nonlinear mathematical models. Numerical results are presented comparing the two restoration strategies in terms of five performance metrics which are capacity installation cost, total required capacity, routing cost, total network cost and required CPU time for convergence of the algorithms. Our results show that the global reconfiguration strategy has always performed better than the failure-oriented reconfiguration strategy for all the network scenarios, topologies and bandwidth requirements.

Optimal Capacity And Flow Assignment For Self-Healing ATM Networks Based On Path Restoration: Nonlinear Models

This thesis addresses the design of self-healing Asynchronous Transfer Mode (ATM) networks which is a special aspect of a more general problem, referred to as capacity and flow assignment (CFA) problem in self-healing ATM networks. We have proposed two nonlinear mathematical models for global reconfiguration strategy and failure-oriented reconfiguration strategy in our thesis. Our restoration strategies aim to minimize the capacity installation cost and the routing cost when a single link failure occurs in the network. A special case of the augmented Lagrangian method so-called Separable Augmented Lagrangian Algorithm (SALA) is proposed for solving the proposed nonlinear mathematical models. Numerical results are presented comparing the two restoration strategies in terms of five performance metrics which are capacity installation cost, total required capacity, routing cost, total network cost and required CPU time for convergence of the algorithms. Our results show that the global reconfiguration strategy has always performed better than the failure-oriented reconfiguration strategy for all the network scenarios, topologies and bandwidth requirements.