Diseño de un estabilizador de sistemas de potencia neuro-borroso adaptativo ajustado mediante algoritmos genéticos

Los sistemas eléctricos de potencia constituyen una de las realizaciones más complejas y sofisticadas que ha conseguido la ingeniería eléctrica. Los sistemas eléctricos se encargan de asegurar el suministro de energía conectando los centros productores con los centros de consumo, a través de un gran número de redes eléctricas. Para que el sistema funcione adecuadamente, todos los generadores deben estar interconectados entre sí de forma que se asegure el suministro eléctrico. La conexión sólo es posible cuando todos los generadores se mantienen girando a la misma velocidad, garantizando así el valor constante de la frecuencia de la tensión de salida. Para controlar estos sistemas se disponen de reguladores automáticos que mantienen constante los valores de tensión y frecuencia generadas por el alternador. Al realizar estas interconexiones se han observado inestabilidades en el comportamiento dinámico del sistema, apareciendo oscilaciones espontáneas de muy baja frecuencia en el margen entre 0.2 a 3 Hz. Estas oscilaciones limitan la capacidad de transmisión de potencia entre los generadores y las cargas y por ello, se han diseñado los Estabilizadores de Sistemas de Potencia (Power System Stabilizer-PSS) como elementos adicionales que permiten amortiguar y estabilizar estos sistemas. La mayor parte de los PSS utilizados en aplicaciones reales son células de adelanto-retraso de tipo analógico con parámetros fijos. El diseño y la selección de la mejor estructura del PSS, así como el valor de sus parámetros es un proceso iterativo y muy complejo, optimizándose en el punto de trabajo habitual de la máquina. El comportamiento del PSS empeora cuando, debido a cambios en la topología de la red, cambios en la demanda de carga o cualquier otro tipo de perturbaciones, se modifica el punto de funcionamiento del sistema y los parámetros del estabilizador dejan de ser óptimos. El objetivo principal de esta Tesis Doctoral consiste en diseñar un sistema de estabilización adaptativo que utilice estas técnicas de sistemas expertos. El diseño del estabilizador está dividido en dos partes: En primer lugar se diseña un PSS robusto, utilizando algoritmos genéticos, capaz de estabilizar al sistema de potencia en un amplio margen de puntos de operación y posteriormente se calculan los mejores parámetros de los estabilizadores para distintos puntos de trabajo. La relación entre estos puntos y el valor de los parámetros del estabilizador es aprendida por un sistema neuro-borroso que se encarga de ajustar los parámetros del un PSS clásico a medida que el sistema de potencia evoluciona y cambia su punto de trabajo. Con objeto de validar el correcto funcionamiento del sistema de control propuesto, se han realizado una serie de ensayos que permiten comparar este esquema de control con otros sistemas de control clásicos

Reducing the impact of EV charging on the electric grid

One of the main objectives of European Commission related to climate and energy is the well-known 20-20-20 targets to be achieved in 2020: Europe has to reduce greenhouse gas emissions of at least 20% below 1990 levels, 20% of EU energy consumption has to come from renewable resources and, finally, a 20% reduction in primary energy use compared with projected levels, has to be achieved by improving energy efficiency. In order to reach these objectives, it is necessary to reduce the overall emissions, mainly in transport (reducing CO2, NOx and other pollutants), and to increase the penetration of the intermittent renewable energy. A high deployment of battery electric (BEVs) and plug-in hybrid electric vehicles (PHEVs), with a low-cost source of energy storage, could help to achieve both targets. Hybrid electric vehicles (HEVs) use a combination of a conventional internal combustion engine (ICE) with one (or more) electric motor. There are different grades of hybridation from micro-hybrids with start-stop capability, mild hybrids (with kinetic energy recovery), medium hybrids (mild hybrids plus energy assist) and full hybrids (medium hybrids plus electric launch capability). These last types of vehicles use a typical battery capacity around 1-2 kWh. Plug in hybrid electric vehicles (PHEVs) use larger battery capacities to achieve limited electric-only driving range. These vehicles are charged by on-board electricity generation or either plugging into electric outlets. Typical battery capacity is around 10 kWh. Battery Electric Vehicles (BEVs) are only driven by electric power and their typical battery capacity is around 15-20 kWh. One type of PHEV, the Extended Range Electric Vehicle (EREV), operates as a BEV until its plug-in battery capacity is depleted; at which point its gasoline engine powers an electric generator to extend the vehicle's range. The charging of PHEVs (including EREVs) and BEVs will have different impacts to the electric grid, depending on the number of vehicles and the start time for charging. Initially, the lecture will start analyzing the electrical power requirements for charging PHEVs-BEVs in Flanders region (Belgium) under different charging scenarios. Secondly and based on an activity-based microsimulation mobility model, an efficient method to reduce this impact will be presented

Neural Networks for optimal operation of a run-of-river adjustable speed hydro power plant with axial-flow propeller turbine

This paper analyzes the regulating capabilities of both turbine speed and guide vanes position in an axial-flow propeller turbine. Two neural networks are implemented in order to simulate the turbine behavior and the turbine efficiency. A maximum-efficiency-tracking algorithm is developed to set the guide vanes position. An experimental power plant built in the Hydraulics Laboratory is described. In order to validate the proposed operation control, the dynamics of this run-of- river pilot plant has been simulated. Substantial increases in the turbine efficiency have been found

Dam seepage analysis based on artificial neural networks: the hysteresis phenomenon

Seepage flow measurement is an important behavior indicator when providing information about dam performance. The main objective of this study is to analyze seepage by means of an artificial neural network model. The model is trained and validated with data measured at a case study. The dam behavior towards different water level changes is reproduced by the model and a hysteresis phenomenon detected and studied. Artificial neural network models are shown to be a powerful tool for predicting and understanding seepage phenomenon

REDUCCIÓN DEL IMPACTO DE VEHÍCULOS ELÉCTRICOS A TRAVÉS DE UNA PLATAFORMA DE ECONOMÍA COLABORATIVA

En este trabajo se presenta una nueva forma de reducir el impacto de la recarga de vehículos eléctricos (VE), basado en aplicaciones de economía colaborativa. La propuesta consiste en que VEs con excedente de energía almacenada en sus baterías puedan vender energía a aquellos VEs que requieran recargar sus baterías durante el día y que estén aparcados en la misma zona y a la misma hora. A través del mercado propuesto, es posible reducir significativamente el coste de la recarga a aquellos usuarios que necesitan recargar fuera del horario nocturno (hasta un 70% dependiendo de la situación) y reducir también el impacto de la recarga sobre la red, puesto que dicha recarga se realiza intercambiando la energía entre vehículos aparcados en la misma zona, sin necesidad de estar conectados a la red eléctrica.Este estudio se ha realizado con fondos del Proyecto Europeo DATA science for SIMulating the era of electric vehicles, FP7-ICT-270833

Characteristic study, its identification and self-tuned approach to control hydro-power plants

The water time constant and mechanical time constant greatly influences the power and speed oscillations of hydro-turbine-generator unit. This paper discusses the turbine power transients in response to different nature and changes in the gate position. The work presented here analyses the characteristics of hydraulic system with an emphasis on changes in the above time constants. The simulation study is based on mathematical first-, second-, third- and fourth-order transfer function models. The study is further extended to identify discrete time-domain models and their characteristic representation without noise and with noise content of 10 & 20 dB signal-to-noise ratio (SNR). The use of self-tuned control approach in minimising the speed deviation under plant parameter changes and disturbances is also discussed

Nationwide impact and vehicle to grid application of electric vehicles mobility using an activity based model

This paper describes the impact of electric mobility on the transmission grid in Flanders region (Belgium), using a micro-simulation activity based models. These models are used to provide temporal and spatial estimation of energy and power demanded by electric vehicles (EVs) in different mobility zones. The increment in the load demand due to electric mobility is added to the background load demand in these mobility areas and the effects over the transmission substations are analyzed. From this information, the total storage capacity per zone is evaluated and some strategies for EV aggregator are proposed, allowing the aggregator to fulfill bids on the electricity markets

Vehicle to vehicle energy exchange in smart grid applications

This paper presents a novel vehicle to vehicle energy exchange market (V2VEE) between electric vehicles (EVs) for decreasing the energy cost to be paid by some users whose EVs must be recharged during the day to fulfil their daily scheduled trips and also reducing the impact of charging on the electric grid. EVs with excess of energy in their batteries can transfer this energy among other EVs which need charge during their daily trips. These second type of owners can buy the energy directly to the electric grid or they can buy the energy from other EV at lower price. An aggregator is responsible for collecting all information among vehicles located in the same area at the same time and make possible this energy transfer

Evaluation of the utilization of electric vehicles for building energy management in hotels

Governments are working in new policies to slow down total energy consumption and greenhouse gases (GHG) emissions, promoting the deployment of electric vehicles (EVs) in all countries. In order to facilitate this deployment and help to reduce the final costs of their batteries, additional utilization of EVs when those are parked has been proposed. EVs can be used to minimize the total electricity cost of buildings (named vehicle to building applications, V2B). In this paper an economic evaluation of EVs in the Building Energy Management System is shown. The optimal storage capacity and its equivalent number of EVs are determined. This value is then used for determining the optimal charging schedule to be applied to the batteries. From this schedule, the total expected profit is derived for the case of a real hotel in Spain

A control system for low-head diversion run-of-river small hydro plants with pressure conduits considering the tailwater level variation

This paper presents a control system for low-head diversion run-of-river small hydro plants with pressure conduits. Since these hydropower plants usually have low or null water storage capacity, the water discharged through the turbines should be adapted to the possible extent to the natural river inflow. For this purpose, a control scheme aimed at maintaining a constant water level in the head pond is normally used in these cases. As an alternative, the option of maintaining a constant water level in the surge tank is studied in this paper. Furthermore, since in low-head hydro plants the tailwater level variation may represent a relatively important contribution to total head losses, it has been explicitly considered in the proposed control system. A small-perturbation stability analysis has been carried out in order to analyze the influence of the plant design and controller parameters in the plant dynamic response. Finally, in order to illustrate the applicability of the proposed control system, several simulations have been carried out using data gathered from a real hydro plan