Simulation Study of Voltage & Current Commutated Chopper


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International Journal of Science and Research (IJSR)
ISSN (Online): 2319-7064 Index Copernicus Value (2013): 6.14 | Impact Factor (2013): 4.438
Simulation Study of Voltage & Current Commutated Chopper
Manoj Meena1, V. Siva Brahmaiah Rama2
1, 2Mewar University, Department of Electrical Engineering, Chittorgarh, Rajasthan, India

Abstract: In this project we study the simulation of Current Commutated Chopper and Voltage Commutated Chopper. We also study the control strategies of Current &Voltage Commutated Chopper. This control techniques are working by two types;-1). Pulse width modulation controller constant frequency operation. 2). Variable frequency control

Keywords: Power Quality, inductor, capacitor, Switch mode power supply (SMPS), chopper

1. Introduction

2.1 Principle of Step-down Chopper

Converting the unregulated DC input to a controlled DC output with a desired voltage level. A chopper is a static device which is used to obtain a variable dc voltage from a constant dc voltage source. A chopper is also known as dc‐to‐dc converter. The thyristor converter offers greater Efficiency, faster response, lower maintenance, smaller size and smooth control. Choppers are widely used in trolley cars battery operated vehicles, traction motor control, control of large number of dc motors, etc.

Figure 2.1: Step‐down Chopper
Fig. 2.1 shows a step‐down chopper with resistive load. The thyristor in the circuit acts as a switch. When thyristor is ON, supply voltage appears across the load and when thyristor is OFF, the voltage across the load will be zero.
2.2 Principle of Step-up Chopper

Figure 1.1: General Block Diagram
1.1 Applications
Switched-mode power supply (SMPS), DC motor control, battery Charger.
2. Classification of Choppers
Choppers are of two types: 1) Step‐down choppers 2) Step‐up choppers In step down chopper output voltage is less than input Voltage In step up chopper output voltage is more than input voltage.

Figure 2.2: step-up chopper
Step-up chopper is used to obtain a load voltage higher than V0 . The input voltage V. The values of L and C are chosen depending upon their requirement of output voltage and Current. When the chopper is ON, the inductor L is connected across the supply. The inductor current ‘I’ rises and the Inductor stores energy during the ON time of the
chopper, tON. When the chopper is off, the inductor current
I is forced to flow through the diode D and load for a period,

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Paper ID: SUB156701

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International Journal of Science and Research (IJSR)
ISSN (Online): 2319-7064 Index Copernicus Value (2013): 6.14 | Impact Factor (2013): 4.438

tOFF. The current tends to decrease resulting in reversing
the polarity of induced EMF in L .Therefore voltage across load is given By:-
3. Control Strategies

Figure 3.2: Variable frequency waveform
4. Voltage Commutated Chopper

Voltage Commutated choppers are widely used in high

power circuits where load fluctuation is not large. This

chopper is also known as

1)

Parallel capacitor turn-off chopper

2)

Impulse Commutated chopper

3)

Classical chopper.

The output dc voltage can be varied by the following methods. 1. Pulse width modulation control or constant frequency
operation. 2. Variable frequency control
3.1 Pulse Width Modulation
TON is varied keeping chopping frequency f & chopping period „T‟ constant Output voltage is varied by varying the ON time tON

To start the circuit, capacitor ‘C’ is initially charged with polarity (with plate „a‟ positive) by triggering the thyristor
T2 Capacitor ‘C’ gets charged through Vs, C, T2 and load.
As the charging current decays to zero thyristor T2 will be turned off. With capacitor charged with plate „a‟ positive the circuit is ready for operation. Assume that the load current remains constant during the commutation process

Figure 3.1: Pulse width modulation Waveform
3.2 Variable Frequency Control
Chopping frequency ‘f’ is varied keeping either tON or tOFF constant. To obtain full output voltage range,
frequency has to be varied over a wide range. This method
produces harmonics in the output and for large tOFF load
current may be come discontinuous

Figure 4.1: Circuit diagram of voltage commutated chopper

For convenience the chopper operation is divided into five

modes:-

1)

Mode-1

2)

Mode-2

3)

Mode-3

4)

Mode-4

5)

Mode-5

Choppers are classified as follows

1)

Class A Chopper

2)

Class B Chopper

3)

Class C Chopper

4)

Class D Chopper

5)

Class E Chopper

5. Simulink Model & Result

Volume 4 Issue 7, July 2015

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Paper ID: SUB156701

Licensed Under Creative Commons Attribution CC BY

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International Journal of Science and Research (IJSR)
ISSN (Online): 2319-7064 Index Copernicus Value (2013): 6.14 | Impact Factor (2013): 4.438

Figure 5.1: Output Waveform of Voltage commutated chopper

Figure 5.2: Simulink diagram of voltage commutated chopper

Volume 4 Issue 7, July 2015

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Paper ID: SUB156701

Licensed Under Creative Commons Attribution CC BY

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International Journal of Science and Research (IJSR)
ISSN (Online): 2319-7064 Index Copernicus Value (2013): 6.14 | Impact Factor (2013): 4.438

Figure 5.3: Simulink diagram of current commutated chopper
Zainal Salam, UTM-JB [4] Power Electronics Laboratory (EE33006) [5] Applications conference, 1996. 31st IAS Annual
Meeting, Conference record of the 1996 IEEE. [6] IEEE Task Force, “Effects of harmonics on equipment,
” IEEE Transactions on Power Delivery, Vol. 8, Apr.1993, pp. 672-680. [7] DC-DC Converter (DC-Chopper)- Asnil Electro FTUNP [8] Rahman, M.A.Radwan, T.S.Osheiba, "Analysis of current controllers for voltage-source inverter" Volume 44, Issue 4, Aug. 1997 Page(s): 477–485 [9] S. Ogasawara, H. Akagi and A .Nabae: “A Novel PWM Scheme of Voltage Source Inverter based on Space Vector Theory”. Proceedings of European conference on power Electronics Applications, EPE-89, Aachen, Oct.1989, pp. 1197-1202.

Figure 5.4: Output Waveform of current commutated chopper

6. Conclusion

In this paper we successfully study the simulation of Current Commutated Chopper and Voltage Commutated Chopper on Matlab. We also study the control strategies of Current & Voltage Commutated Chopper. The discharging and charging time of commutation capacitor are dependent on the load current and this limits high frequency operation, especially at low load current Chopper cannot be tested without connecting load.

References

[1] Delivery, Vol. 16, no. 4, Oct. 2001, pp.782–780. [2] V. Arun, B. Shanthi S.P. Natarajan “Performance
Analysis of Multicarrier SPWM Strategies for Three Phase Z-source Seven Level Cascade Inverter ”International Journal Of Modern Engineering Research (IJMER) Vol. 3, Issue, Jan-Feb 2013. Pp. 204-211 ISSN2249-6645. [3] Power Electronics and Drives (Version 3-2003) Dr.

Volume 4 Issue 7, July 2015

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Paper ID: SUB156701

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Simulation Study of Voltage & Current Commutated Chopper