Voltage Stability Analysis of Power Systems with Doubly-fed Induction Generators Based Distributed Generation
Voltage Stability Analysis of Power Systems with Doubly-fed Induction Generators Based Distributed Generation

Author: Ayub Machiri Wanjala

Publisher:

Published: 2016

Total Pages: 226

ISBN-13:

DOWNLOAD EBOOK

The increasing energy demand over the last few decades has led to more stresses on the power system. With the demand being equal to the available supply capacity and in some cases exceeding it, there is a need to increase the capacity of the electric system ensuring that the network security is maintained. Distributed Generation located in the Distribution Network provides the ability to meet the growing demand. With increasing concerns on the environmental impacts of conventional power stations, initiatives such as the Kyoto Protocol for Climate Change have encouraged the diversification and development of energy efficient systems. These systems rely on renewable energy sources such as wind, solar and tidal energy. However, the existing power system was not designed to include generating systems on the distribution network. As a result, the unplanned integrations of Distributed Generating Systems might cause some technical problems to the grid. Wind-based Distributed Generation Systems offer an economical and efficient solution. However, the incorporation of wind energy on the Distribution Network not only alters the power flow but in some cases results in imbalanced voltages at specific points in the network. Advances in technology has resulted in increased capacity of the Wind Energy Conversion System with some having the capability to generate more than 1MVA from a single turbine resulting in the possibility of higher Distributed Generation penetration levels on the Distribution Network. The main focus of this research is to analyse the impact of high Distributed Generating Systems penetration on the voltage stability of the network under various loading conditions. It will also analyse the control strategies to be employed to deal with any effects on the stability of the network.

Modeling, Stability Analysis, and Control of Distributed Generation in the Context of Microgrids
Modeling, Stability Analysis, and Control of Distributed Generation in the Context of Microgrids

Author: Ehsan Nasr-Azadani

Publisher:

Published: 2014

Total Pages: 121

ISBN-13:

DOWNLOAD EBOOK

One of the consequences of competitive electricity markets and international commitments to green energy is the fast development and increase in the amount of distributed generation (DG) in distribution grids. These DGs are resulting in a change in the nature of distribution systems from being "passive", containing only loads, to "active", including loads and DGs. This will affect the dynamic behavior of both transmission and distribution systems. There are many technical aspects and challenges of DGs that have to be properly understood and addressed. One of them is the need for adequate static and dynamic models for DG units, particularly under unbalanced conditions, to perform proper studies of distribution systems with DGs (e.g., microgrids). The primary objective of this thesis is the development and implementation of dynamic and static models of various DG technologies for stability analysis. These models allow studying systems with DGs both in the long- and short-term; thus, differential and algebraic equations of various DGs are formulated and discussed in order to integrate these models into existing power system analysis software tools. The presented and discussed models are generally based on dynamic models of different DGs for stability studies considering the dynamics of the primary governor, generators, and their interfaces and controls. A new comprehensive investigation is also presented of the effects of system unbalance on the stability of distribution grids with DG units based on synchronous generator (SG) and doubly-fed induction generator (DFIG) at different loading levels. Detailed steady-state and dynamic analyses of the system are performed. Based on voltage and angle stability studies, it is demonstrated that load unbalance can significantly affect the distribution system dynamic performance. Novel, simple, and effective control strategies based on an Unbalanced Voltage Stabilizer (UVS) are also proposed to improve the system control and the stability of unbalanced distribution systems with SG- and DFIG-based DGs.

The Stability Analysis for Wind Turbines with Doubly Fed Induction Generators
The Stability Analysis for Wind Turbines with Doubly Fed Induction Generators

Author: Baohua Dong

Publisher:

Published: 2019

Total Pages: 0

ISBN-13: 9781392823828

DOWNLOAD EBOOK

The quickly increasing, widespread use of wind generation around the world reduces carbon emissions, decreases the effects of global warming, and lowers dependence on fossil fuels. However, the growing penetration of wind power requires more effort to maintain power systems stability.This dissertation focuses on developing a novel algorithm which dynamically optimizes the proportional-integral (PI) controllers of a doubly fed induction generator (DFIG) driven by a wind turbine to increase the transient performance based on small signal stability analysis.Firstly, the impact of wind generation is introduced. The stability of power systems with wind generation is described, including the different wind generator technologies, and the challenges in high wind penetration conditions. Secondly, the small signal stability analysis model of wind turbines with DFIG is developed, including detailed rotor/grid side converter models, and the interface with the power grid. Thirdly, Particle swarm optimization (PSO) is selected to off-line calculate the optimal parameters of DFIG PI gains to maximize the damping ratios of system eigenvalues in different wind speeds. Based on the historical data, the artificial neural networks (ANNs) are designed, trained, and have the ability to quickly forecast the optimal parameters. The ANN controllers are designed to dynamically adjust PI gains online.Finally, system studies have been provided for a single machine connected to an infinite bus system (SMIB), a single machine connected to a weak grid (SMWG), and a multi machine system (MMS), respectively. A detailed analysis for MMS with different wind penetration levels has been shown according to grid code. Moreover, voltage stability improvement and grid loss reduction in IEEE 34-bus distribution system, including WT-DFIG under unbalanced heavy loading conditions, are investigated. The simulation results show the algorithm can greatly reduce low frequency oscillations and improve transient performance of DFIGs system. It realizes off-line optimization of MMS, online forecasts the optimal PI gains, and adaptively adjusts PI gains. The results also provide some useful conclusions and explorations for wind generation design, operations, and connection to the power grid.

Voltage Stability Problem in a Distribution System with Distributed Generator
Voltage Stability Problem in a Distribution System with Distributed Generator

Author:

Publisher:

Published: 2008

Total Pages: 138

ISBN-13:

DOWNLOAD EBOOK

With difficulties in building new transmission lines and power plants, due to environmental and political issues, while electricity demand is continuously increasing, it is expected that, in the near future, more distributed generations will penetrate into power systems, especially into the distribution system. As several competitive advantages of an induction generator compared to a synchronous generator such as durability, low investment cost and etc., it is possible that many of very small power producers may connect this type of generators into the distribution system. However, as we know, rather than generate reactive power, the induction generator consumes it. Thus, impact of the induction generator on voltage stability should be carefully investigated. We focus on this aspect in this thesis. Both static and dynamic analyses were performed in this thesis. In static analysis, the degree of voltage instability based on PQVSI index is used as the main tool to assess how close the present operating condition to the voltage instability point. In addition to the static analysis, the dynamic voltage stability was conducted as well. The dynamic voltage characteristics were observed, which is eventually used to verify the results obtained from the static analysis. It provides clearer and more accurate figure of the actual dynamics of voltage instability process following a disturbance in the system, which in this case is a load change. The studies indicating an unhealthy impact of induction generators on the system's voltage stability are shown in this thesis, especially when the system is intended to serve large inductive loads. These phenomena lead to both unstable of the induction generator itself, and unstable of the entire distribution system through voltage instability. As a consequence, special treatment should be implemented in the case of utilizing induction generators in the distribution system. An example treatment in this study, which is disclosing the advantage of installing capacitor at the induction generator terminal in enhancing the utilization of the induction generator, had been presented.

Fundamentals of Distributed Generation Systems
Fundamentals of Distributed Generation Systems

Author: Zivan Zabar

Publisher:

Published: 2022

Total Pages: 0

ISBN-13: 9780735425378

DOWNLOAD EBOOK

This textbook addresses the fundamentals of employing distributed generation systems. The content is based on the development, changes, and needs of electric utility companies in restructuring the prevailing electrical grids. The material, the order of the chapters, and the practice problems are based on years of teaching experience, including students' reactions and their knowledge acquisition. It is divided into three main parts: -- Principles of operation of commonly used distributed generators: Fuel Cells, Solar Cells, Gas Turbines, Microturbines, Reciprocate Internal Combustion Engines, and Wind Turbines. -- Detailed analysis of three major components: the induction generator (including its doubly-fed configuration), the synchronous generator (including dynamic volt-ampere reactive control), and the power static converters (including DC/DC and self- and line-commutated units). -- Interaction with electric utility lines, including the effects of harmonic distortion, voltage stability, volt-ampere reactive control, and fault conditions. The book also includes many practice and drill problems and is an ideal text for graduate students and an invaluable handbook for engineers working in electrical power systems.

Voltage Stability Analysis with High Distributed Generation (DG) Penetration
Voltage Stability Analysis with High Distributed Generation (DG) Penetration

Author: Rashid Al-Abri

Publisher:

Published: 2012

Total Pages: 121

ISBN-13:

DOWNLOAD EBOOK

Interest in Distributed Generation (DG) in power system networks has been growing rapidly. This increase can be explained by factors such as environmental concerns, the restructuring of electricity businesses, and the development of technologies for small-scale power generation. DG units are typically connected so as to work in parallel with the utility grid; however, with the increased penetration level of these units and the advancements in unit's control techniques, there is a great possibility for these units to be operated in an autonomous mode known as a microgrid. Integrating DG units into distribution systems can have an impact on different practices such as voltage profile, power flow, power quality, stability, reliability, and protection. The impact of the DG units on stability problem can be further classified into three issues: voltage stability, angle stability, and frequency stability. As both angle and frequency stability are not often seen in distribution systems, voltage stability is considered to be the most significant in such systems. In fact, the distribution system in its typical design doesn't suffer from any stability problems, given that all its active and reactive supplies are guaranteed through the substation. However, the following facts alter this situation: - With the development of economy, load demands in distribution networks are sharply increasing. Hence, the distribution networks are operating more close to the voltage instability boundaries. - The integration of distributed generation in distribution system introduces possibility of encountering some active/reactive power mismatches resulting in some stability concerns at the distribution level. Motivated by these facts, the target of this thesis is to investigate, analyze and enhance the voltage stability of distribution systems with high penetration of distributed generation. This study is important for the utilities because it can be applied with Connection Impact Assessment (CIA). The study can be added as a complement assessment to study the impacts of the installation of DG units on voltage stability.