Jun Imaizumi

Unit Commitment by Column Generation

The unit commitment problem is to determine the schedule of power generating units and the generating level of each unit. The decisions involve which units to commit at each time period and at what level to generate power to meet the electricity demand. We consider the heuristic column generation algorithm to solve this problem. Previous methods used the approach in which each column corresponds to the start–stop schedule and output level. Since power output is a continuous quantity, it takes time to generate the required columns efficiently. In our proposed approach, the problem to be solved is not a simple set partitioning problem, because the columns generated contain only a schedule specified by 0–1 value. It is shown that the proposed heuristic approach is effective to solve the problem.

Optimal location problem for the installation of power flow controller

In power delivery systems, the use of dispersed generation and security control to improve network utilization requires the optimal use of system control devices. The installation of loop controller allows the distribution system to operate in a loop configuration, achieving effective management of voltage and power flow. In the investment planning process, it is important to identify the optimal location and installed capacity of the equipment such that all operational constraints are satisfied. This paper presents a method for identifying the optimal location and capacity with the minimum installation cost. Our novel approach uses an economic model that considers the fixed costs. A slope scaling procedure is presented, and its efficiency is demonstrated using numerical experiments.

Optimization of Railway Timetable by Allocation of Extra Time Supplements

We consider the allocation of a running time supplement to a railway timetable. Previously, Vekas et al. developed a stochastic programming model. In this paper, their optimization model is improved by adding bound constraints on the supplements. It is shown that the probability of delays decreases when using the proposed model. In addition, an effective L-shaped algorithm is presented.

Train Platforming at a Terminal and Its Adjacent Station to Maximize Throughput

To cope with growing passenger demand and to provide better services, increasing the number of trains is desired for certain lines. Maximum possible throughput of a line is often limited due to the limited number of platforms at the terminal, which was the case with two bullet-train lines originating from Tokyo. In these lines, there exists an intermediate station in the close vicinity of the terminal. This paper proposes a network-based optimization model to analyze the throughput of a line when turn-backs at the adjacent station are introduced to increase the line capacity.

Optimization Models for Multi-period Railway Rolling Stock Assignment

It is necessary for railway companies to construct daily schedules of assigning rolling stocks to utilization paths. A utilization path consists of a series of trains that a particular rolling stock performs in a day. A mixed integer programming model based on Lai et al. [1] is presented and is shown that straightforward applications of the model result in too much computational time and also inappropriate assignment schedules due to end effects. We show that the model can be modified to alleviate these difficulties, and also show that the repeated applications of the optimization model in the rolling horizon allow to generate a feasible assignment schedule for a longer period of time thus indicating the feasibility of the optimization approach.