Enhancing reliability in passive anti-islanding protection schemes for distribution systems with distributed generation

This thesis introduces a new approach to enhance the reliability of conventional passive anti-islanding protection scheme in distribution systems embedding distributed generation. This approach uses an Islanding-Dedicated System (IDS) per phase which will be logically combined with the conventional scheme, either in blocking or permissive modes. Each phase IDS is designed based on data mining techniques. The use of Artificial Neural Networks (ANNs) enables to reach higher accuracy and speed among other data mining techniques. The proposed scheme is trained and tested on a practical radial distribution system with six-1.67 MW Doubly-Fed Induction Generators (DFIG-DGs) wind turbines. Various scenarios of DFIG-DG operating conditions with different types of disturbances for critical breakers are simulated. Conventional passive anti-islanding relays incorrectly detected 67.3% of non-islanding scenarios. In other words, the security is as low as 32.3%. The obtained results indicate that the proposed approach can be used to theoretically increase the security to 100%. Therefore, the overall reliability of the system is substantially increased

Evolution of microgrids with converter-interfaced generations: Challenges and opportunities

© 2019 Elsevier Ltd Although microgrids facilitate the increased penetration of distributed generations (DGs) and improve the security of power supplies, they have some issues that need to be better understood and addressed before realising the full potential of microgrids. This paper presents a comprehensive list of challenges and opportunities supported by a literature review on the evolution of converter-based microgrids. The discussion in this paper presented with a view to establishing microgrids as distinct from the existing distribution systems. This is accomplished by, firstly, describing the challenges and benefits of using DG units in a distribution network and then those of microgrid ones. Also, the definitions, classifications and characteristics of microgrids are summarised to provide a sound basis for novice researchers to undertake ongoing research on microgrids

Application of Power Electronics Converters in Smart Grids and Renewable Energy Systems

This book focuses on the applications of Power Electronics Converters in smart grids and renewable energy systems. The topics covered include methods to CO2 emission control, schemes for electric vehicle charging, reliable renewable energy forecasting methods, and various power electronics converters. The converters include the quasi neutral point clamped inverter, MPPT algorithms, the bidirectional DC-DC converter, and the push–pull converter with a fuzzy logic controller

Investigation of methods for loss of mains detection for domestic scale distributed generation

PhD ThesisThe drive to lower the environmental impact of power generation has underlined the importance of distributed generation (DG). DG allows a multitude of dispersed renewable technologies to be included within the energy supply network. The energy generation of a DG installation doesn’t necessarily coincide with local power consumption; grid connec- tion allows surplus local power to be distributed using the wider power network. This results in a variety of DG units requiring grid connection. A power electronics interface is commonly needed to achieve connection between the DG unit and the distribution network. Whilst DG units are available in a multitude of sizes, the focus of this work is domestic scale DG. Single phase power inverters are commonly used to connect DG units to the utility. An issue associated with the interconnection of generators within the distribution network is the formation of power islands. A power island is defined as a section of the power network, consisting of generators and loads, which becomes electrically isolated from the wider power network. The majority of grid connection standards stipulate that the grid con- nection power electronics interface must include a robust loss of mains (LOM) detection routine. Once a LOM event has been detected the output power of the DG unit must be reduced to zero to guarantee no power island exists. This thesis details the work carried out during the completion of an En- gineering Doctorate (EngD) Degree in Power Electronics, Machines and Drives. A low voltage laboratory test bench and associated simulation model have been designed and constructed to allow multiple in-the-loop based LOM detection methods to be presented, analysed and compared. A new LOM detection technique has been created, referred to as the proposed technique. The proposed technique is a hybrid LOM detection technique which uses a passive routine to signal when a LOM event may have occurred and an active technique to confirm the LOM event. The passive routine uses Fourier analysis to constantly monitor the magni- tude and spread of high frequency voltage components present at the DG unit connection point. The active confirmation routine is an active power shift function. A fully rated 500W laboratory test bench was created which allows the proposed technique to be verified at power levels more realistic for a standard DG unit installation.Narec: EPSRC

Loss allocation in a distribution system with distributed generation units

In Denmark, a large part of the electricity is produced by wind turbines and combined heat and power plants (CHPs). Most of them are connected to the network through distribution systems. This paper presents a new algorithm for allocation of the losses in a distribution system with distributed generation. The algorithm is based on a reduced impedance matrix of the network and current injections from loads and production units. With the algorithm, the effect of the covariance between production and consumption can be evaluated. To verify the theoretical results, a model of the distribution system in Brønderslev in Northern Jutland, including measurement data, has been studied

State-of-the-art of design and operation of power systems with large amounts of wind power, summary of IEA Wind collaboration

An international forum for exchange of knowledge of power system impacts of wind power has been formed under the IEA Implementing Agreement on Wind Energy. The task “Design and Operation of Power Systems with Large Amounts of Wind Power” is analysing existing case studies from different power systems.There are a multitude of studies made and ongoing related to cost of wind integration. However, the results are not easy to compare. This paper summarises the results from 15 case studies