RHEOSTATIC STABILISATION OF A CHOPPER-CONTROLLED BRAKE FOR TRACTION DRIVES.

Means of dealing with and compensating for line-voltage decreases in chopper-controlled regenerative-brake equipment are described. The method of correction involves using a rheostatic brake resistor which is commonly available in such equipment and requires no extra power electronic circuit components. Electric braking can be maintained under all specified line-voltage conditions, as well as with a short circuit on the power supply line. With this arrangement full protection of the traction and chopper equipment is provided. A fast acting controller is proposed consisting of a closed-loop peak-current inner feedback loop with an outer loop controlling average armature current. Results of practical tests on a 250 A 400 v chopper are supported by numerically predicted results, obtained using a digital computer.link_to_subscribed_fulltex

Dynamic coast control of train movement with genetic algorithm

The railway service is now the major transportation means in most of the countries around the world. With the increasing population and expanding commercial and industrial activities, a high quality of railway service is the most desirable. Train service usually varies with the population activities throughout a day and train coordination and service regulation are then expected to meet the daily passengers' demand. Dwell time control at stations and fixed coasting point in an inter-station run are the current practices to regulate train service in most metro railway systems. However, a flexible and efficient train control and operation is not always possible. To minimize energy consumption of train operation and make certain compromises on the train schedule, coast control is an economical approach to balance run-time and energy consumption in railway operation if time is not an important issue, particularly at off-peak hours. The capability to identify the starting point for coasting according to the current traffic conditions provides the necessary flexibility for train operation. This paper presents an application of genetic algorithms (GA) to search for the appropriate coasting point(s) and investigates the possible improvement on fitness of genes. Single and multiple coasting point control with simple GA are developed to attain the solutions and their corresponding train movement is examined. Further, a hierarchical genetic algorithm (HGA) is introduced here to identify the number of coasting points required according to the traffic conditions, and Minimum-Allele-Reserve-Keeper (MARK) is adopted as a genetic operator to achieve fitter solutions