Investigating the dynamic stability of the expansion turbine power plant generator in the presence of power electronics

Number of pages: 107 File Format: word File Code: 32157
Year: 2013 University Degree: Master's degree Category: Electrical Engineering
  • Part of the Content
  • Contents & Resources
  • Summary of Investigating the dynamic stability of the expansion turbine power plant generator in the presence of power electronics

    Master's thesis in the field of electrical engineering, power orientation

    1-1 Introduction

    In the last few decades, the sources of energy supply have been from fossil sources, which until recently were obtained almost cheaply. The cheap sources of energy caused that the optimal use of energy and energy recycling were practically not given much attention.

    Given the crisis of energy shortage and the sense of danger from limited energy resources, increasing environmental pollution, increasing greenhouse gases, reducing the thickness of the ozone layer, and the discussion of green industry, the issues related to optimizing production processes, increasing production efficiency, managing domestic consumption reduction, and energy audits received serious attention.

    The approaches taken in this direction are in three categories:

    1- Finding new sources of energy such as (Wind P.P, Tide P.P, GeoThermal Power Plant Solar Energy)

    2- Modifying existing energy production methods (Modernization, Rehabilitation, Optimization)

    3- Recycling (Turbo) Expander)

    1-2 Expansion turbine:

    The expansion turbine is a device for converting pressure energy into gas flow with steam to mechanical work, the result of which is gas expansion. Every turbine, such as a steam turbine, is responsible for the expansion of the corresponding fluid and energy production, this word can also be applied to them, but usually expansion turbines do not include steam turbines and gas turbines, and are only referred to turbines that are placed in the path of other streams under gas pressure. In the gas transmission lines, the gas pressure is high, the main reason for the high pressure in these lines is that the gas can be transported through smaller diameter pipes. This pressure is usually much higher than the pressure required at the place of consumption. Expansion turbines are a very suitable alternative to pressure relief valves used in pressure reduction stations. Currently, gas pressure is reduced by pressure relief valves. If these valves are replaced with expansion turbines, the pressure energy in the gas will be recycled. By installing expansion turbines in the path of gas flows under pressure, the pressure energy in these flows can be recovered. A flow with high temperature and pressure is a suitable source for energy recovery by expansion turbines. Expansion turbine generator:

    Expansion turbine generators are of induction type (asynchronous) and usually have six poles. The rotor of the generator and the rotor of the turbine are co-axial, and the speed delivered to the rotor of the generator is from 1500 to 1507 revolutions per minute, with the rotation of the rotor inside the stator, the generated electricity is taken out by the terminals of the stator and entered into the grid.

    Using the squirrel cage asynchronous generator in expansion turbine power plants has many great advantages. These generators are cheap, strong, simple, and because they don't have rims, brushes, commutators, batteries, and inverters, they have very simple repairs and maintenance. Also, because of the lack of a proper and cheap control system, when the asynchronous machine works as a generator, it can provide its required magnetic (reactive) current in two ways. In the state connected to the network, this current is from the network, and in the state that it is used as self-excitation, this reactive current is provided by the capacitor bank. Of course, the presence of a capacitor even in the first case can lead to a reduction in the current of the transmission line, which in turn reduces losses and improves voltage regulation. The noteworthy point in this case is that the amount of reactive power that the asynchronous machine receives from the grid in generator mode is more than that of the motor mode, and with the increase of its active power, the amount of reactive power that the machine receives from the grid increases and its lowest value is at synchronous speed. It is noteworthy that sometimes the amount of reactive power that asynchronous generators absorb from the network may even exceed the amount of active power that they produce.It is noteworthy that sometimes the amount of reactive power that asynchronous generators absorb from the network may even exceed the amount of active power that they produce, which is an undesirable characteristic, an unnecessary imposition on the network and the synchronous units connected to it, and as a result, it may weaken the system in terms of voltage regulation conditions. To eliminate this phenomenon, the reactive power required by each asynchronous generator must be compensated locally. Since the amount of reactive power produced by the capacitor is dependent on the terminal voltage of the generator and it is not possible to continuously change its value, in different loading conditions in order to stabilize the frequency and voltage range, it is variable amounts of reactive power, which causes engineers and designers to think of solutions to compensate for the reactive power required.

    1-4 Fact tools:

    FACTS tools were initially used to solve the problems that arose due to the limitations in the construction of transmission lines and facilitated the exchange of growing transmission power with the following dual goals:

    Increasing the ability to transmit power in transmission systems

    Directing the passage of power in the desired paths

    FACTS controllers are able By providing angular stability and voltage stability, they can significantly increase the transmission power of the permanent mode.

    By controlling the line current (for example, by changing the effective impedance of the line), it is possible to control the power flow in the desired transmission line and adjust the power flow in parallel and circular paths. Also, the goal is to be able to quickly change the path of power passing from the primary system to the existing secondary system in emergency situations so that the desired power transmission is preserved in the entire system. With the fulfillment of the above basic goals, the utilization of the existing transmission system will increase significantly and these goals can play an important role in resetting with minimal need for new lines. Also, new topics are discussed in the field of electronic power technology and simultaneous control system and preventing their unwanted interference with different purposes and arrangements of the system in normal and accident conditions. These new topics are aimed at creating an optimal control strategy, telecommunication links, safety protocols. The realization of such an optimal control system can be considered as the third goal in FACTS. solve the desired problems in transmission lines.

    The first group uses reactive impedances or tap changer transformers with thyristor switches (as control elements).

    The second group uses static converters with internal commutation.

    SVC:

    Static reactive power compensators are the leading FACTS controllers today. An example of this type that includes thyristor switched capacitors (TSC), thyristor switched reactors (TSR) is shown in the figure. With proper coordination, the output reactive power can continuously change in the capacitive and inductive range. SVC usually works to adjust the voltage at the desired point in the system.

    STATCOM:

    STATCOM is capable of compensating inductive and capacitive power and is also capable of controlling its output power within the maximum current range, independent of the ac system voltage. This means that it is able to provide full capacitive output current at any system voltage, practically up to zero voltage.

    In this project, it is tried to investigate the effect of FACT devices such as SVC, STATCOM to compensate the reactive power and improve the dynamic stability of the expansion turbine generator in stable and transient conditions.

  • Contents & References of Investigating the dynamic stability of the expansion turbine power plant generator in the presence of power electronics

    List:

     

    Abstract..1

    Chapter One: Introduction

    1-1 Introduction..3

    1-2 Expansion Turbine..3

    1-3 Expansion Turbine Generator..4

    1-4 Fact Tools..5

    1-4-1 Controller FACT:..6

    Chapter Two: Expansion Turbine

    2-1 Introduction:..8

    2-2 Types of Turbine..8

    2-3 Expansion Turbine..9

    2-3-1 Advantages of using Expansion Turbine.10

    2-3-2 Structure of Expansion Turbine..10

    2-3-3 necessary features in the design of the expansion turbine. 11

    2-3-4 The main parts of an expansion turbine power plant. 12

    2-3-4-1 Ball valve..13

    2-3-4-2 Safety trip valve (STV.14

    2-3-4-3 Preheater). 2-3-4-4 Regulator. 15 5-4-3-2 Turbine. 16 2-3-4-6 Shaft and gearbox. 17 2-3-4-7 Generator. 20 2-3-4-8 Reheater. 21

    Chapter: 3-1. Introduction.. 22

    3-2. Introduction of asynchronous generator.. 23

    3-2-1 Advantages of asynchronous generator.. 25

    3-2-2 Disadvantages of asynchronous generator.. 25

    3-2-3. Speed. 26

    3-2-4 generator working point..26

    3-2-5 Asynchronous generator connected to the grid (GCIG). 27

    3-2-7 Economic advantages of asynchronous generator. Fact

    4-1 Introduction ..31

    4-2. Characteristics of static compensators. 31

    4-2-1. Ideal static compensator. 31

    3-2-2. Structure of SVC..33

    4-2-2-1. SVC dynamic model ..36

    3-2-3. STATCOM structure ..38

    Chapter Five: Stability improvement methods

    5-1 Introduction..41

    5-2 Amount of reactive power consumed by asynchronous generator.41

    5-3 Review of different methods of compensating the reactive power of the expansion turbine generator.43

    5-4 Different modes studied.43

    5-4- 1 The set of different modes examined in the project. 43

    Chapter 6: Simulation

    6-1 Introduction..46

    6-2 System assumptions for simulation. 46

    6-2-1 Parameters set for simulation elements. Fact in a stable way. 6-3-2 Network simulation with SVC next to the generator in a stable way. 6-3-3 Network simulation with a STATCOM next to the generator in a stable way.

    6-3-5 network simulation with SVC next to the generator considering a symmetrical three-phase short circuit at the generator terminal..64

    6-3-6 network simulation with a STATCOM next to the generator considering a symmetrical three-phase short circuit at the generator terminal. Fact, taking into account the momentary interruption of gas input turbine. 70 6-3-7 Network simulation with SVC next to the generator, taking into account momentary interruption of gas input turbine. Turbine..76

    Chapter Seven: Conclusions and Suggestions

    7-1 Simulation results for the steady state of the generator and turbine.80

    7-1-1 Simulation results in the steady state of the generator and turbine without the presence of fact devices and in the presence of fact devices on the generator terminal voltage..80

    7-1-2 Simulation results in the steady state of the generator and Turbine without the presence of fake devices and in the presence of fake devices on the reactive power of the generator terminal. 82

    7-2 Simulation results for the three-phase symmetrical short circuit condition at the generator terminal. 83

    7-2-1 Simulation results in the symmetrical three-phase short circuit condition at the generator terminal without the presence of devices

    Fact and in the presence of fake devices on the terminal voltage 83. 7-2-2 Simulation results in the case of three-phase symmetrical short circuit at the generator terminal in the presence of SVC on reactive power.86

    7-3-1 The results of the simulation of momentary interruption of the gas entering the turbine without the presence of fact devices and in the presence of fact devices on the generator terminal voltage. 87

    7-3-2 The simulation results of momentary interruption of the gas entering the turbine without the presence of fact devices and in the presence of

    fact devices on the reactive power. 88

    Conclusion General.

    Suggestions.

    List of references.92

     

    Source:

     

    Mirsalim, Mojtabi, "Electric machines and transformers," Amirkabir University of Technology Publishing Center, first edition, 1379.

    Qazi, Reza, "Reactive power control in systems Elektriki," Mashhad University Press, 1371

    Catalogs related to Neka Power Plant expansion turbine project

    English sources

    [4].   Mehdi Taleshian, Hasan Rastegar, Hossein Askarian Abyaneh "Modeling and Power Quality Improvement of Grid Connected Induction Generators Driven by Turbo-Expanders" International Journal of Energy Engineering 2012, 2(4): 131-137

     

    [5].   Mehdi Taleshian, Hasan Rastegar, Hossein Askarian Abyaneh "Modeling turbo-expander systems Simulation": Transactions of the Society for Modeling and Simulation International0(0) 1-15 2013 The Society for Modeling and Simulation International

    [6].   E. G. Marra and J. A. Pomilio, "Induction-Generator-Based System Providing Regulated Voltage With Constant Frequency," IEEE Trans. Industrial Electronics, Vol. 47, No. 04, August 2000. pp. 908-914. [7].   Li. Wang and R. Deng, "Transient performance of an isolated induction generator under unbalanced excitation capacitors," IEEE Trans. Energy Conversion, Vol. 14, No. 4, December 1999. pp 887-893. [8].  G. McPherson and R. D. Laramore, "An introduction to electrical machines and transformers," John Wiley & Sons, 1990.

    [9].    DSTATCOM Devices for Improvement of induction generator stability," IEEE Melecon, May 2004.

    [10].  W. Freitas, A. Morelato, W. Xu and F. Sato, "Impacts of ac generators and DSTATCOM devices on the dynamic performance of distributed systems," IEEE Trans. on power delivery, Vol. 20, No. 2, April 2005. pp. 1493-1501

    <11] S. S. S. GUPTA, "Analysis and Design Regulator for Self-Excellent Induction," IEE Trans 90.

    [12]. Turbo-Expander Driven Generators for Power System Studies,” IEEJ Transactions on Electrical and Electronic Engineering, IEEJ Trans 2009; 4: 645–653. [13] Mehdi Babaei Turkemani, Hassan Rastegar, “Flicker Assessment of Turbo-Expander Driven Synchronous Generator in Power Distribution Network,” Journal of Iranian Association of Electrical and Electronics Engineers – Vol. No.1- Spring & Summer 2010.

     

    [14].    T. Ahmad, K. Nishida and M. Nakaoka, "Static VAR Compensator-based voltage regulation implementation of single-phase self-excited induction generator," IEEE Trans. 0-7803-8486-5/04, IAS 2004, pp.2069-2076.

     

    [15].   T. Ahmad, O. Noro, E. Hiraki and M. Nakaoka, "Terminal voltage regulation characteristics by Static VAR Compensator for a three-phase self-excited induction generator," IEEE Trans. On Industry App. Vol. 40, No. 4, July/August 2004, pp. 978-988.

     

    [15].   D. Jovcic, N. Pahalawaththa, M. Zavahir and H. Hassan, "SVC Dynamic Analytical Model," IEEE Trans. On Power Delivery, Vol. 18. 4, October 2003. pp. 1455-1461.

Investigating the dynamic stability of the expansion turbine power plant generator in the presence of power electronics