Dynamic modeling and simulation of 5 kW synchronous generator

Number of pages: 127 File Format: word File Code: 32115
Year: 2014 University Degree: Master's degree Category: Electrical Engineering
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  • Summary of Dynamic modeling and simulation of 5 kW synchronous generator

    Dissertation for Master's Degree

    Field of Study: Electricity-Power

    Preference: Electric Machines

    1.1 Introduction:

    In a synchronous generator, a dc current is applied to the rotor coil to A magnetic field is generated. Then the rotor of the generator is rotated by a prime mover, to create a rotating magnetic field in the machine. This magnetic field induces a three-phase voltage in the stator windings of the generator.

    In this machine, two terms are widely used to describe the windings: one is field windings and the other is armature windings. In general, the term field coils refers to the coils that produce the main magnetic field in the machine. The term armature windings refers to the windings in which the main voltage is induced. For synchronous machines, the field windings are in the rotor.
    The rotor of a synchronous generator is essentially a large electromagnet. The magnetic poles in the rotor can be prominent or non-prominent. A salient pole is a magnetic pole protruding from the surface of the rotor. On the other hand, a salient pole is a magnetic pole flush with the surface of the rotor. A non-prominent or flat rotor is usually used for 2- or 4-pole applications. While salient rotors are used for 4 or more poles. Because the magnetic field in the rotor is variable, to reduce losses, it is made of thin layers. A constant current must be applied to the field circuit in the rotor. Because the rotor rotates, it needs a special arrangement to deliver DC power to its field coils. There are 2 ways to do this:

    1- From an external source to the rotor with sliding rings and brushes.
    2- Providing DC power from a DC power source, mounted directly on the shaft of the synchronous generator.

    The slip rings completely surround the machine shaft but are separate from it. One end of the DC coil is connected to each of the two ends of the slip ring on the shaft of the synchronous motor, and a fixed brush slides on each slip ring. The wipers are a block of graphic-like compounds that conduct electricity easily, but have very little friction and therefore do not cause corrosion on the rims. If the positive end of the DC voltage source is connected to one sweep and the negative end to the other. A constant voltage is then applied to the coil throughout, regardless of its location and angular velocity, the field. Slip rings and brushes create several problems for synchronous machine field windings when DC voltage is applied. They increase maintenance on the machine, as the brush must be checked frequently for wear. In addition, the sweep voltage drop may result in significant power losses along with the field currents. Despite these problems, slip rings are used on all smaller synchronous machines. Because there is no more economical way to apply the field current.

    In larger motors and generators, brushless actuators are used to deliver the DC field current to the machine. The generator is rectified and the direct current is obtained by a three-phase rectifier circuit mounted on the generator shaft, which is directly applied to the main DC field circuit. By controlling a small DC field current from the drive generator (which is mounted on the stator), the field current can be set on the main machine without using slip rings and brushes. Because there is never a mechanical connection between the rotor and the stator, a brush drive requires less maintenance than slip rings and brushes. In order for the generator excitation to be completely independent of external excitation sources, a small pilot actuator is often included in the system. A pilot drive is a small AC generator with permanent magnets mounted on the shaft.The pilot drive is a small AC generator with permanent magnets mounted on the rotor shaft and a winding on the stator. This actuator provides energy for the actuator field circuit, which in turn controls the main machine field circuit. If a pilot drive is mounted on the generator shaft, then no external electrical power is required to operate the generator.

    Many synchronous generators that have brushless drives also have slip rings and brushes so an additional source of DC field current is available in emergencies. The stator of synchronous generators is usually made in two layers: the winding itself is distributed and has small steps to reduce the harmonic components of output voltages and currents.

    Because the rotor rotates at a speed equal to the speed of the magnetic field, the electric power with a frequency of 50 or 60 Hertz is produced and the generator must rotate at a constant speed depending on the number of poles, for example, to produce 60 Hz power in a two-pole machine, the rotor must rotate at a speed of 3600 rpm. To produce 50Hz power in a 4-pole machine, the rotor must rotate at a speed of 1500 rpm. The required speed of an assumed frequency can always be calculated from the following equation [1]:

    1- Frequency

    2- Mechanical speed

    3- Number of poles

     
    The induced voltage in the stator depends on the flux in the machine, the frequency or speed of rotation, and the construction of the machine. The internal generated voltage is directly proportional to the flux and speed, but the flux itself depends on the current in the rotor field circuit.

    The internal voltage is not equal to the output voltage. There are several factors that cause the difference between the two:
    1- The distortion in the magnetic field of the air gap due to the current in the stator, which is called armature reaction.
    2- Self-inductance of armature coils
    3- Resistance of armature coils
    4- Effect of the shape of the salient poles of the rotor
    When a generator works and feeds the loads of the system then:
    1- Power The direct and reactive power produced by the generator is equal to the amount of power demanded by the load connected to it.
    2- The governor setting points of the generator controls the working frequency of the power system.
    3- The field current (or the setting points of the field regulator) controls the terminal voltage of the power system.
    This is a situation that exists in separate generators and far apart.
  • Contents & References of Dynamic modeling and simulation of 5 kW synchronous generator

    List:

    1 Chapter 1: An introduction to synchronous machine. 7

    1.1 Introduction: 8

    2 Chapter Two: Synchronous machine dynamic equations. 12

    2.1 Voltage equations in machine variables: 13

    2.2 Torque equation in machine variables: 19

    2.3 Voltage equations in rotor reference device variables - Park equations: 20

    2.4 Synchronous: 27

    3 Chapter 3: Numerical integration method. 28

    3.1 Euler's method. 29

    3.2 Rang-Kuta method 30

    3.3 The trapezoid base integration method. 32

    3.4 An overview of Newton-Raphson method. 34

    3.5 Simultaneous solution of DAE equations by explicit integration. 36

    4 Chapter 4: The results of the simulation of the linear model of the synchronous machine. 40

    4.1 Examining the simulation results in the biaxial model. 41

    4.2       Synchronous generator performance in different areas. 46

    4.2.1 Second state: overload conditions. 47

    4.2.2 Third mode: less than the base loading. 49

    5 Chapter Five: Synchronous machine parameters. 52

    Synchronous machine parameters. 52

    5.1 Introduction. 53

    5.2 Operating parameters of synchronous machine. 53

    6 Chapter Six: Synchronous machine models. 58

    Synchronous machine models: 58

    6.1 Various synchronous machine models: 59

    6.2 Application of different models: 60

    6.3 Analyzing synchronous machine models to determine basic parameters: 60

    6.3.1 Model (2.1) 60

    6.3.2 Model(0.0) 66

    6.3.3 Equivalent circuit of model(0.0) 66

    6.3.4 Circuit equations of model(0.0) 67

    6.3.5 Model(2.2) 67

    6.3.6 Equivalent circuit of model(2.2) 67

    6.3.7 Orbital equations of the model (2.2) 68

    7      Chapter Seven: Simulation results of determining basic parameters for different models. 70

    7.1 Model simulation results (0.0): 71 Model simulation results (2.1): 71 Model simulation results (2.2): 72 References. 99

    9      Appendices 101

    9.1       Appendix one: Synchronous machine behavior simulation. 101

    9.2      Appendix Two: Determination of basic machine parameters: 113

    Source:

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Dynamic modeling and simulation of 5 kW synchronous generator