Busqueda tabú multi-objetivo para la localización y dimensionamiento óptimos de generación distribuida y FACTS en redes eléctricas

Desde la apertura del mercado eléctrico a compañías privadas, las redes de transmisión y distribución de potencia se han visto afectadas en la calidad de onda, perfil y/o estabilidad de voltaje, armónicos, desbalances, entre otros. En un principio, la localización de generación distribuida a lo largo del sistema de potencia ayudó a los operadores a mantener la estabilidad, aunque el uso excesivo puede provocar saturación y por tanto, problemas a la hora de operar la red eléctrica. La combinación de las unidades de generación distribuida y FACTS ha demostrado en esta investigación que es capaz de reducir el costo total del sistema de potencia, mejorando la estabilidad de voltaje y los límites térmicos de las líneas. Aquí se presenta un modelo multi-objetivo basado en búsqueda tabú para la localización y dimensionamiento óptimos de generación distribuida y FACTS considerando la inversión mínima en dispositivos, incluyendo el coste de instalación, operación y mantenimiento, anualizando los costes mediante un factor de recuperación de capital a 25 años de vida útil. Las soluciones se han evaluado con un código abierto de flujo de cargas (PSAT, Power System Analysis Toolbox), el algoritmo heurístico se ha programado en lenguaje Matlab. La validación del modelo propuesto se lleva a cabo en una red de 300~nodos perteneciente a la IEEE, donde la generación distribuida es simulada como un generador diésel y los FACTS considerados son el HVDC, SSSC, STATCOM, SVC, TCSC y el UPFC. Los resultados son comparados con las soluciones de la frontera óptimo de Pareto para dos variables: costo de inversión y costo de generación de potencia. Los resultados obtenidos consideran tres metodologías: concatenación de atributos, indicadores predictivos y la combinación de ambos; tres estrategias de instalación: solo generación distribuida, solo FACTS y la combinación de los dispositivos. Los resultados demuestran que la adición de generación distribuida es la más económica, mientras que añadir solo FACTS no representa una mejora de la estabilidad en los nodos y, combinar los dispositivos reduce el costo total de la red eléctrica.<br /

Optimal Coordinated Operation of Distributed Static Series Compensators for Wide-area Network Congestion Relief

Relieving network congestions is a critical goal for the safe and flexible operation of modern power systems, especially in the presence of intermittent renewables or distributed generation. This paper deals with the real-time coordinated operation of distributed static series compensators (DSSCs) to remove network congestions by suitable modifications of the branch reactance. Several objective functions are considered and discussed to minimize the number of the devices involved in the control actions, the total losses or the total reactive power exchanged, leading to a non-convex mixed-integer non-linear programming problem. Then, a heuristic methodology combining the solution of a regular NLP with k-means clustering algorithm is proposed to get rid of the binary variables, in an attempt to reduce the computational cost. The proposed coordinated operation strategy of the DSSCs is tested on several benchmark systems, providing feasible and sufficiently optimal solutions in a reasonable time frame for practical systems

Utility Applications of Smart Online Energy Systems: A case for Investing in Online Power Electronics

The backbone of any power grid, the transmission and sub-transmission networks, should be flexible, robust, resilient and self-healing to cope with wide types of network adverse conditions and operations. Power electronic applications are making a major impact on the present and future state of power systems generation, transmission and distribution. These applications include FACTS (Flexible Alternating Current Transmission), HVDC (High Voltage Direct Current) in transmission and Custom Power devices in distribution. FACTS devices are some of the advanced assets that network planners can use to make the transmission grid become more flexible and robust. Many established research ideas to advance operations of these devices have been published in the open literature over the last ten years. The most recent publications in this field are reviewed in this thesis. A critical analysis of literature and existing conditions reveals a range of potentials that are ideal for development in Qatar’s increasingly strained electricity network. As a result of demand surge in Qatar in recent years and the forecast to grow in the same rate, the need for improvement in Qatar Power Transmission System (QPTS) is great and significant. Conventional planning and operational solutions such as conductor up-rating, and fixed series capacitors (FSC) are considered. However there are growing challenges on getting new rights of ways for new overhead lines and even corridors for new cables. Advanced FACTS devices are considered for dynamic control of power flows and voltages, such as TCSC (Thyristor Controlled Series Capacitor) and GUPFC (Generalized, Unified Power Flow Controller). The research in this thesis examines the potential for QPTS to improve and develop, with emphasis on increased output through integrated online energy systems, online FACTS and HVDC controllers based on synchrophasor measurements. The devices are modelled in Siemens PTI’s PSS®E software, through steady-state mode case study to investigate power flow control and voltage support. Comparison between similar FACTS technologies, such as SVC and STATCOM, is also presented. The improvement in power flow imbalance between transmission lines with different ratings and lengths is studied. The FACTS devices are tested for voltage support to enhance the network voltage profile and hence increase security and reliability to important industrial customers. Optimization techniques of the FACTS devices allocation and rating are generally discussed considering the voltage improvement and optimal power flow control. The results achieved showing the network improvement with using the FACTS are presented in the case studies. In a separate case study, applying medium voltage custom power devices to convert DC battery storage and photovoltaic energy into AC energy using a power conversion system is discussed. The dynamic mode of the STATCOM is modelled in QPTS in the succeeding case study using the same software and compared with the capacitor banks. This is followed by another case of HVDC analysis modelled with and without STATCOM present. The thesis discussed the real time operation and control of power system physical parameters in QPTS using capacitors, FACTS and HVDC. The key contribution of this thesis is the application and resting of all sorts of FACTS and HVDC in QPTS. The system wide area, coordinated control of FACTS (Online Power Electronics-OPE) is a new concept. Another major contribution is being able to look at a system wide approach for a transmission smart grid application. The results of thesis are presented in international conferences in USA, Hong Kong, France, Portugal, and locally in the Arabian Gulf (Dubai, Oman and Qatar). The thesis’s papers are listed in the ‘References’ section and in Appendix-F

A fast-acting protection scheme for series compensators in a medium-voltage network

In recent 20 years medium voltage networks have been becoming one of the important interfaces between the power plants and loads due to the increasing load demand as well as number of distributed generators connected to the network. This is the reason, managing the power flow, and voltage profile of the network at the lowest possible power losses and also price are of the utmost importance. The series compensators such as a static synchronous series compensator are of the most cost effective power compensators that also have the high efficiency in controlling the power flow and voltage profile. However, their drawback is their vulnerability against the short circuit. This thesis presents a new protection scheme for an SSSC in an MV network by using a varistor and thyristors to eliminate this weakness. The DC offset phenomenon is one of the main uncertainties that has been studied in the thesis. This phenomenon could cause a delay in the circuit breakers’ performance. In this thesis, the parameters of the machines that have most influence on the time when the fault current will pass the zero point have been analysed. Besides, the impact of the DC offset in the medium voltage network has been studied. Furthermore, the thermal issues have always been one of the most challenging problems for the power electronics devices. This thesis investigates a new packaging style by using the phase change material to improve the thermal managing of a press-pack thyristor during a short circuit. This packaging style is able to absorb the heat as much as required and also could decrease the thermal resistance

Benefit analysis of using soft DC links in medium voltage distribution networks

Soft DC Links are power electronic converters enabling the control of power flow between distribution feeders or networks. This thesis considers the use of Soft DC Links in Medium Voltage (MV) distribution networks to improve network operation while facilitating the integration of distributed generators (DGs). Soft DC Links include Soft Open Points (SOPs) and Medium Voltage Direct Current (MVDC) links. An SOP can be installed to replace mechanical switchgear in a network, providing controllable active power exchange between connected feeders, as well as reactive power compensation at each interface terminal. The deployment of an MVDC link enables power and voltage controls over a wider area, and facilitates the effective use of available capacity between adjacent networks. The benefits of using SOP and MVDC link in MV distribution networks were investigated. A multi-objective optimisation framework was proposed to quantify the operational benefits of a distribution network with an SOP. An optimisation method integrating both global and local search techniques was developed to determine the set-points of an SOP. It was found that an SOP can improve network operation along multiple criteria and facilitate the integration capacity of DGs. A Grid Transformer-based control method of an MVDC link was proposed, which requires only measurements at the grid transformers to determine the operation of an MVDC link. Control strategies considering different objectives were developed. The proposed control method is used in the ANGLE-DC project, which aims to trial the first MVDC link in Europe by converting an existing AC circuit to DC operation. It was found that an MVDC link can significantly increase the network hosting capacity for DG connections while reducing network losses compared to an AC line. An impact quantification of Soft DC Links was carried out on statistically-similar distribution networks, which refer to a set of networks with similar but different topological and electrical properties. A model was developed to determine the optimal allocation of Soft DC Links. It was found that a Soft DC Link can reduce the network annual cost under a wide range of DG penetration conditions. The statistical analysis provides distribution network planners with more robust decisions on the implementation of Soft DC Links

Large Grid-Connected Wind Turbines

This book covers the technological progress and developments of a large-scale wind energy conversion system along with its future trends, with each chapter constituting a contribution by a different leader in the wind energy arena. Recent developments in wind energy conversion systems, system optimization, stability augmentation, power smoothing, and many other fascinating topics are included in this book. Chapters are supported through modeling, control, and simulation analysis. This book contains both technical and review articles

Advanced Communication and Control Methods for Future Smartgrids

Proliferation of distributed generation and the increased ability to monitor different parts of the electrical grid offer unprecedented opportunities for consumers and grid operators. Energy can be generated near the consumption points, which decreases transmission burdens and novel control schemes can be utilized to operate the grid closer to its limits. In other words, the same infrastructure can be used at higher capacities thanks to increased efficiency. Also, new players are integrated into this grid such as smart meters with local control capabilities, electric vehicles that can act as mobile storage devices, and smart inverters that can provide auxiliary support. To achieve stable and safe operation, it is necessary to observe and coordinate all of these components in the smartgrid

Long-Run Incremental Cost Pricing for Improving Voltage Profiles of Distribution Networks in a Deregulated Environment

Electricity network pricing approaches play a fundamental role in establishing whether providing the network service function is economically beneficial to both the network operators and other stakeholders, namely, network users. Many pricing methodologies have been developed since the late 80‟s. The earlier approaches were not based on economic principle while the latest are directed to being more based on economic principle as the shift is towards deregulated and privatized electric power industry as opposed to the earlier vertically regulated regime. As a result, many such methodologies based on economic principle have emerged and these reflect the investment cost incurred in circuits and transformers to support real and reactive power flow. However, to reflect investment cost incurred for maintaining network voltages in network charges has received very little attention in network charges. Therefore, this research work is aimed to create a charging approach to recover investment cost, by the network operator, for maintaining the network voltages. This thesis presents a new long-run incremental cost (LRIC) pricing approach for distribution networks and demonstrates the course of action of evaluating and allocating the network asset cost in the context of maintaining network voltages. Also, it should be noted that this approach can be used for transmission networks. Firstly, the LRIC-voltage network pricing approach for reflecting the future network VAr compensation assets is proposed. Then, this approach is extended to consider n-1 contingency situation as per statutory requirement that the network should be able to withstand such contingencies in order to enhance reasonable security and reliability in its network. Lastly, this LRIC-voltage network charging methodology is again extended to reflect the charges for existing network VAr compensation assets. In addition, this LRIC-voltage network pricing approach is improved to reflect better the nodal charges as the respective nodal voltage degradation rates, given corresponding load growth rate, are determined based on the P-V curve concept. The advantages of all these incorporate the ability to reflect correct forward-looking charges, to recognize both real and reactive powers, to provide locational charges and to provide charges for both generation and demand customers. In addition, two fundamental studies were conducted to demonstrate the trend in which the LRIC-voltage network charges would follow given different networks and different load growth rates. What set apart the LRIC-voltage network charges are those two parameters. Moreover, with regard to different networks, this was a defining moment as to how the aforementioned charges should be sought given transmission and distribution networks. A pricing software package utilizing load-flow has been developed implementing the proposed LRIC-voltage network pricing methodology and, its extensions. This software can well be utilized by transmission and distribution companies for analyzing their cost. The LRIC-voltage network pricing methodology and its extensions, are all demonstrated on the IEEE 14-bus test system and a practical distribution test network in the South Wales area of England, UK.EThOS - Electronic Theses Online ServiceGBUnited Kingdo