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International Journal of Advanced Research in Electrical, Electronics and Instrumentation Engineering

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Modeling and Study of Switched Reluctance Generator Feeding A DC Bus with Psim

Subhashini M1, Chellamuthu2
  1. ME scholar, Department of Electrical Engineering, RMK Engineering College, Kavaraipettai, India
  2. Professor, Department of Electrical Engineering, RMK Engineering College, Kavaraipettai, India
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International Journal of Advanced Research in Electrical, Electronics and Instrumentation Engineering

Abstract

The growing interest in switched reluctance machines (SRMs) for automotive and industrial purposes because of its adjustable speed applications due to its unique mechanical structure. The Torque developed under various rotor positions and for various inductances can be generated. In recent years, the multilevel inverter has drawn tremendous interest in high and medium power energy control. Several control strategies have been developed for multilevel inverters. In this paper simulation is carried out for cascaded H bridge inverter. The study of three level and five level cascaded H bridge inverter has been carried out. The simulation of multilevel inverter is performed using the elements available in the Psim.

Keywords
Multilevel Inverter, Torque Developed, SRM, Modulation Techniques.

INTRODUCTION
The growing interest in switched reluctance machines (SRMs) for automotive and industrial applications leadsto the study and modeling of SRM. The switched reluctance generator (SRG) is an energy conversion device that has advantages in both renewable and alternative transportation systems. With the absence of excitation on the rotor, the SRG provides a robust, compact and efficient generator system. The absence of permanent magnet in the machine is a big cost and material availability is the advantage over the other permanent magnet machines. The nonlinear behavior of the SRG poses a good challenge to the control of the machine. This paper addresses and mitigates the complexities of torque developed so that the advantage of SRG can be utilized effectively.
Numerous industrial applications require higher power apparatus in recent years. Some medium voltage motor drives and utility applications require medium voltage and megawatt power level. For a medium voltage grid, it is troublesome to connect only one power semiconductor switch directly. As a result, a multilevel power converter structure has been introduced as an alternative in high power and medium voltage situations subsequently; several multilevel converter topologies have been developed. A multilevel converter not only achieves high power ratings, but also enables the use of renewable energy sources. The term multilevel began with the three-level converter. The advantages of three-level Inverter topology over conventional two-level topology are 1)The voltage across the switches is only one half of the DC source voltage 2)The switching frequency can be reduced for the same switching losses 3)The higher output current harmonics are reduced by the same switching frequency. The modulation methods used in multilevel inverters can be classified according to the switching frequency. They are 1) Sinusoidal PWM 2) Selective Harmonic Elimination 3) Space Vector PWM. The existing system uses the Sinusoidal PWM
Technique to control the total harmonic distortion. Fig.1 shows the block diagram of SRG system connected to the battery forcharging

SINUSOIDAL PULSE WIDTH MODULATION (SPWM)
In sinusoidal PWM instead of maintaining the width of all pulses the same as in the case of multiple PWM, the width of each is varied in proportion to the amplitude of a sine wave evaluated at the same pulse. The distortion is reduced significantly compared to multiple PWM (Figure 2).
The number of pulses per half cycle depends on the carrier frequency. Within the constraint that two transistors of the same arm cannot conduct at same time, the instantaneous output voltage. This method is preferable and easier to implement. The output voltage can be varied by varying the modulation index ‘m’. The area of each pulse corresponds approximately to the area under the sine wave between the adjacent mid points of off-periods on the gating signals.
Five level cascaded H bridge inverter voltage level and its switching states:
image

MATHEMATICAL MODELING OF SRM
The mathematical modeling of Switched Reluctance Motor is derived using the basic voltage equation. And by using the voltage equation, the torque equation is derived.
BASIC VOLTAGE EQUATION OF SRM
From Fig.
image
Where ψ is a function of θ and L
iR is the ohmic drop
image
image
L di/dt –Emf due to incremental inductance
i(w)dL/dθ– Self-induced Emf or e
image
Self-induced Emf e is proportional to current speed and rate of change inductance with rotor angle.
DERIVATION FOR TORQUE EQUATION OF SRM:
On the basis of the magnetic circuit theory, the stored energy in a magnetic field
image
Power due to change in stored energy
image
Mechanical power developed
image
image
Eqn 3.9 is known as Mechanical Power Equation.
Pm = ωT
Where image
image
Torque developed in SRM image

SIMULATION & RESULTS
Fig.a shows the graph between various rotor positions Vs. Inductance.
image
Fig. b shows torque profile and it is between various rotor positions and current
image
Normalized harmonic amplitude of the voltage waveform of two-level inverter with fundamental frequency of 50Hz
image
Tabulation for THD values
image

RESULTS AND DISCUSSIONS
The main aim of any modulation technique is to obtain variable output having maximum fundamental component with minimum harmonics. The objective of Pulse Width Modulation techniques is enhancement of fundamental output voltage and reduction of harmonic content in three level and Five level Cascaded H- Bridge Inverter. In this paper usage of Switched Reluctance Motor has been enhanced.

Figures at a glance
Figure Figure Figure Figure
Figure 1 Figure 2 Figure 3 Figure 4

References