Description
ABSTRACT
Gas turbines inherently show unique frequency response characteristics compared to other conventional synchronous generation technologies as their active power output is not entirely determined by the governor response during frequency deviations of the power network. In this study, a model suitable for studying the short-term dynamic response of a combined-cycle gas turbine (CCGT) to a system frequency deviation is developed. The model is used in conjunction with a larger system model to study the impact of increasing levels of CCGT generation on frequency control of a small system. The study considers single contingencies and does not consider severe cascading-type events. A consequence of the results is that as the number and proportion of base-loaded CCGTs increases, frequency control may become more challenging. The results indicate that with additional CCGTs on the system large frequency departure will be more likely, and the transmission system operators on the station should review their frequency control strategies in the future to avoid the shedding of customers.
TABLE OF CONTENTS
COVER PAGE
TITLE PAGE
APPROVAL PAGE
DEDICATION
ACKNOWELDGEMENT
ABSTRACT
CHAPTER ONE
INTRODUCTION
1.1 BACKGROUND OF THE PROJECT
- AIM OF THE PROJECT
- OBJECTIVE OF THE PROJECT
- SCOPE OF THE PROJECT
- SIGNIFICANCE OF THE PROJECT
- LIMITATION OF THE PROJECT
- METHODOLOGY
- PROJECT ORGANISATION
CHAPTER TWO
LITERATURE REVIEW
- REVIEW OF THE STUDY
- REVIEW OF PROEVOUS WORK
- OVERVIEW OF GAS TURBINE
- OPERATION OF GAS TURBINE
CHAPTER THREE
METHODOLOGY
- GAS TURBINE MODELLING
- THE CCGT DYNAMIC SIMULATION MODEL
- THE OCGT DYNAMIC SIMULATION MODEL
- EXCITATION SYSTEM MODEL
CHAPTER FOUR
- TEST
- GAS TURBINE DYNAMICS DURING FREQUENCY EVENTS
- GAS TURBINE DYNAMIC DURING FREQUENCY INCREASE EVENTS (LOAD REDUCTION)
- DYNAMIC BEHAVIOUR OF GAS TURBINES DURING SHORT-CIRCUIT
CHAPTER FIVE
- CONCLUSION
- REFERENCES
CHAPTER ONE
1.0 INTRODUCTION
1.1 BACKGROUND OF THE STUDY
System dynamic characteristics of combined cycle gas turbines (CCGTs) have become an issue of considerable interest over the last ten years. This is due to the increasing pro- portions of CCGT plant that are being brought online in the majority of electricity systems worldwide. Higher efficiency, greater flexibility, and lower emissions than many conventional thermal generators, combined with progressively shorter installation times and reducing installation costs, are the basis for this move toward CCGT generation. Understanding the dynamic behavior of CCGT units is crucial to maintaining system reliability and security in electricity systems. This is particularly true as the move toward competitive markets means system operators now have little or no control over the type and location of new plant investment.
Maintaining the standards of security and quality of supply of any electricity system are of utmost importance to the system operator. Recent system blackouts in countries such as the USA, Canada, the United Kingdom, and Italy highlight the importance of system security and reliability [1]–[3]. When an incident occurs on the system, maintaining the system frequency within the stipulated limits is a major priority, and if these limits are breached, then the magnitude of the excursion needs to be restricted and the frequency returned to within the limits as quickly as possible.
The behavior of gas turbines and CCGT units in response to the frequency disturbance contributed significantly to the severity of generation loss – blackout [ Kunitomi, 2011]. As a consequence of the incident, several modifications to improve the response of both gas turbine (GT) and CCGT controllers to large-frequency excursions were incorporated.
In large, interconnected electricity systems, frequency deviations from nominal tend to be small. This is due to the relatively high inertia of the system and the fact that any sudden supply/demand imbalances are generally small in comparison with the total size of the system. The largest infeed in a small electricity system is likely to be a much higher proportion of the total generation while the system inertia is considerably less. Consequently, the effect of an incident, such as the loss of generation, on the system frequency is much more notable. An understanding of the response characteristics of CCGT generators to frequency events is, therefore, essential for small systems, as their response could potentially have a relatively large influence on the severity of the event. While frequency deviations on larger systems are generally less sizeable, as the proportion of CCGTs on such systems increases, their influence will become more significant.
Therefore, the impact of the dynamic behavior of CCGTs in response to frequency events on the system needs to be assessed carefully. Furthermore, CCGT ratings tend to be large, and therefore, with the addition of CCGTs to the system, the size of the largest infeed and, as a consequence, the size of the largest possible contingency has increased. Severe frequency events are rare on the Ireland system with only one event in the past ten years resulting in the unanticipated shed- ding of normal customers [Soon et al, 2008 ]. However, as large CCGTs replace a number of smaller conventional plants, major frequency events may become more likely, and the impact on the system needs to be studied. In particular, the impact on system integrity and the possibility of interruption to customers’ needs to be assessed.
The aim of this paper is to study the impact of frequency responsive of combined cycle gas turbines on Afam VI Combine Cycle Power Plant electricity system.
1.2 PROBLEM STATEMENT
Gas turbines are generally connected to the electrical power grid/network in droop mode (4% standard) with the primary goal of supplying adequate power and maintaining the Grid frequency within set operating limits for Grid operational stability. Grid instabilities attributable to large losses or additions in connected generation or loads have a significant impact on the Grid frequency. Depending on the nature of the load or generation change, the system frequency will either increase or decrease.
Frequency deviation in a gas turbine station greatly influences the system stability during frequency events in power networks. Power system and power plant operators require improved understanding of the gas turbine characteristics during various frequency events in order to mitigate adverse impact on power system. The operation and the development of power system networks introduce new types of stability problems. The effect of the power generation and consumption on the frequency of the power system can be described as a demand/generation imbalance resulting from a sudden increase/decrease in the demand and/or generation.
This work was carried out to investigates the impact of a loss of generation due to system frequency responsive.
1.3 AIM AND OBJECTIVES OF THE STUDY
The main aim of this paper is to study the impact of frequency responsive of combined cycle gas turbines on Afam Vi Combine Cycle Power Plant electricity system. The objectives are:
- To quantify the effect that these units will have on the overall system short-term response to events on the
- To determine the response of the system to large single
- To study the characteristics of CCGTs
- To study the details of the CCGT dynamic models
1.4 SCOPE OF THE STUDY
In this study, various rates of primary frequency responses model are developed for providing a fast-reliable primary frequency response. It is concluded that generation system inertia and a governor droop setting are the most dominant parameters that effect the system frequency response after a loss of generation. Therefore, for different levels of generation loss, the recovery rate will be dependent on the changes of the governor droop setting values. The proposed model offers a fundamental basis for a further investigation to be carried on how a power system will react during a secondary frequency response.
1.5 SIGNIFICANCE OF THE STUDY
This research work will throw more light on effect of frequency deviation on combined-cycle gas turbine (CCGT) to a system. This study will also be designed to be of immense benefit to all those that works in turbine power stations
It will also serve as a guide to all power students who are privilege to write this work.
Finally, it will also serve as a useful piece of information which emphases most on turbine power generator.
1.6 LIMITATION OF STUDY
As we all know that no human effort to achieve a set of goals goes without difficulties, certain constraints were encountered in the course of carrying out this project and they are as follows:-
- Difficulty in information collection: I found it too difficult in laying hands of useful information regarding this work and this course me to visit different libraries and internet for solution.
- Financial Constraint: Insufficient fund tends to impede the efficiency of the researcher in sourcing for the relevant materials, literature or information and in the process of data collection (internet).
Time Constraint: The researcher will simultaneously engage in this study with other academic work. This consequently will cut down on the time devoted for the research work.
1.7 RESEARCH METHODOLOGY
In the course of carrying this study, numerous sources were used which most of them are by visiting libraries, consulting journal and news papers and online research which Google was the major source that was used.
1.8 PROJECT ORGANISATION
The work is organized as follows: chapter one discuses the introductory part of the work, chapter two presents the literature review of the study, chapter three describes the methods applied in this chapter, The gas turbine modelling descriptions are outlined, chapter four discusses the results of the work, chapter five summarizes the research outcomes and the recommendations.
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