Ramón Rodríguez Pecharromán

Energy Savings in Metropolitan Railway Substations Through Regenerative Energy Recovery and Optimal Design of ATO Speed Profiles

Traffic operation has a significant impact on energy consumption in metro lines and thus it is important to analyze strategies to minimize it. In lines equipped with Automatic Train Operation systems (ATO), traffic regulation system selects one ATO speed profile on line among a preprogrammed set of optimized speed profiles. Previous works only minimize the energy demanded by the train in pantograph without considering energy savings measured at substations due to regenerative energy in detail. The main objective of this work is to design optimal ATO speed profiles of metro trains taking into account the energy recovered from regenerative brake in order to minimize the net energy at substations. A model of a train with an on-board energy storage device as well as a network model for estimating the energy recovered by the train is presented. Different scenarios are analyzed to assess the achievable energy savings due to possible investments such as installing power inverters or storage devices and energy savings due to the optimal design of ATO speed profiles are estimated. A real line of the Madrid Underground has been considered obtaining comparative results to facilitate an evaluation of the most advantageous scenario and possible investment. A future application would be the optimal design of driving for the newest train signaling system communications-based train control (CBTC). The CBTC improves train operation and control, due to continuous communication with each train. However, its features have not been taken full advantage yet to reduce the energy consumption. The proposed method could be applied to design and execute in real time the most energy-efficient driving according to the traffic and electrical situation of the line.

Optimal underground timetable design based on power flow for maximizing the use of regenerative-braking energy

This paper deals with the design of underground rail system timetables that synchronize the movement of trains to allow the energy consumption from substations to be reduced by maximizing the use of regenerative-braking energy. Nowadays, most trains are equipped with regenerative-braking systems and any of this recovered energy not used by on-board auxiliary services can be consumed by other trains in the same rail section. A mathematical programming optimization model has been designed to synchronize the braking of trains arriving at station with the acceleration of trains exiting from the same or another station. In addition, a power flow model of the electrical network has been developed to calculate the power-saving factor for each synchronization event in order to encourage better synchronizations, particularly those which have fewer energy losses. These models were applied in the design of a schedule for line 3 of the Madrid underground system. This schedule was then trialled for a week. Energy savings were measured and a significant correlation with the synchronization of train movements was observed. It was concluded that a modification in the published timetables would result in energy savings, with no effect on the quality of service for passengers and low associated investment costs.

New design for the Spanish AGC scheme using an adaptive gain controller

This paper investigates the application of adaptive control to the Spanish load-frequency regulation scheme, Automatic Generation Control (AGC). The Spanish AGC system regulates the frequency and the power exchange between France and Spain. The system is hierarchically structured with one master regulator that coordinates four control areas. Each control area is composed of several generating units providing AGC service. Coordinating signals are sent to the control areas so that the global system response achieves the objective established by the System Operator. The participation of each control area in the service is set according to the rated share that it has obtained in the secondary-reserve market and its relative response speed compared to that of the rest of the control areas. Some problems, such as the lack of sensitivity to the quality of the reserve provided by the control areas, have been detected in the operation of the current AGC scheme. A new design, which is presented in this paper, has been developed in order to overcome these problems. This paper attempts to outline how this new design improves the global AGC system response and the distribution of the regulation effort among the control areas. The proposed strategy is compared with the present design by means of simulation.

Control Design for PID Controllers Auto-Tuning Based on Improved Identification

Abstract Every auto-tuning method for PID controllers has two steps: identification of the process and design of the controller. An identification procedure to obtain two points of the frequency response of the system was presented in (Pecharroman and Pagola, 1999). This paper develops a design method based on the ITAE index. This design procedure is then related to the results of the process identification, yielding a complete auto-tuning method that gives very good results in theory and in practice. A complete test batch is used. The main contribution is that the method is valid for integrating as well as non-integrating processes.

Energy savings in metro-transit systems: a comparison between operational Italian and Spanish lines

For transportation in large cities, new technologies that impact the operation of metro-transit systems are being developed. The energy efficiency in metro-transit systems is a key topic that is being studied in order to reduce both consumption and costs. A review on approaches to managing the energy recovered from train braking is reported. Then, energy performance indexes are presented. Their assessment is possible due to highly specialized simulation tools that have been developed at the University of Rome Sapienza and Comillas Pontifical University, Madrid. The indexes are used to perform a comparison between an operational metro-line in Spain and one in Italy. The results confirm their accuracy and significant improvements in energy efficiency and environmental effects are presented.

Optimal deployment of energy storage systems in a DC-electrified railway system

Energy Storage Systems (ESSs) represent one of the main vectors for improving railway electrical systems. Former low reliability rates and life-time are being dramatically improved in recent times due to the intensive research on battery and capacitor technologies. However, little research has been conducted on the optimization of railway system infrastructure by incorporating ESSs. This paper presents a method for designing the best possible deployment of ESSs in a DCelectrified mass rapid transport system line by means of optimization, selecting number and location of ESSs. A detailed model of system load flow and energy storage devices for a given traffic scenario in a general DC railway system has been carried out, resulting in a MINLP optimisation model that minimises total energy consumption. Then, a linearization of load flow equations has been performed in order to get a fast-approximate solution of the system by converting the MINLP problem into a MIP one. This optimization method has been applied to a realistic railway system, yielding reasonable location and number of ESSs in the system. The error due to the approximation has been evaluated by comparing the results of the linear load flow against those of the non-linear load flow. The method has demonstrated to be a powerful tool to decide how many and where to place ESSs in a DC-electrified railway system.

A variable no-load voltage scheme for improving energy efficiency in DC-electrified mass transit systems

Railway mass transit systems like subways play a fundamental role in the concept of sustainable cities. In these systems, the amount of passengers strongly fluctuates along the day. Hence, in order ...

PID AUTO-TUNING BASED ON A SECOND POINT OF FREQUENCY RESPONSE

Abstract This paper summarizes a new method for the auto-tuning of PID controllers, and extends it to take into account all the information that the process identification can give. The identification is based on two characteristic points of open-loop frequency response: the ultimate and the crossover frequencies. A 4-parameter model can be obtained and used for controller design based on the ITAE index. The main contribution is that this method makes use of all the information provided by the identification step, suppresses the need for a separation between integrating and non-integrating processes, an can address a wider set of plants.

Work in progress - Design of a new european higher education area degree in electronics and control engineering

A group of teachers from the School of Engineering at Universidad Pontificia Comillas is working in the implementation of a new degree in electronics and control engineering coherent with both the European Higher Education Area (EHEA) principles and the Spanish industrial and research environment. The first stage of this work, the conversion of one year of the study program of the existing degree to a EHEA-type framework, analyzing the work load assigned to the students, is reported in this paper.

Load-frequency regulation using an adaptive predictive control

This paper investigates the application of an adaptive-predictive control to the load-frequency regulation of the Spanish power system. The control system regulates the frequency and the power exchange with France at the power-inter-tie. The control signal distributed among the control areas is calculated so that the generated power reaches the desired power at the end of the prediction horizon. The regulation effort distribution among the control areas is established according to their relative dynamic response speed and their rated share obtained in the load-frequency market. The proposed strategy is compared with the present design by means of simulation.