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Design and implementation of high step up DC to DC converter using flipped Cockcroft Walton voltage multiplier.

INTRODUCTION

In generally to get high DC output voltage, Voltage multipliers, Inverters and step-up transformers are used. But these methods cause more cost and some drawbacks are occurred. While using Transformer to generate high voltage it occupy more space and voltage ripples are occurred. In 1932, British physicists John Douglas Cockcroft and Irish physicists Ernest Thomas Sinton Walton were in vented the Cockcroft Walton voltage multiplier. The Cockcroft Walton voltage multiplier is used for generating high voltage in various fields. The Cockcroft-Walton (CW) generator [2], or multiplier, which is an electronic circuit it generates a high voltage from a low level input voltage. It is made up ladder connections of capacitors and diodes to generate high voltage. Now a days Cockcroft-Walton (CW) circuits are still used in many electronic devices and many research fields where high voltages require. The Applications are x-ray machines, television, and photocopiers. The biggest advantage of CWVM is that the voltage across each stage of the cascade is equal to twice the peak input voltage. It has the advantage of requiring relatively low cost components and easy to insulate. The possibility of taking output from any stage, like a multi tapped transformer.

But the Cockcroft Walton voltage multiplier (CWVM) failed to continually raise the value of output voltage when the number of stages increases or when the operating frequency and capacitance are not sufficiently high to avoid voltage drop in coupling capacitors at each stage and it also have the disadvantage Output current of the circuit decreased while increasing number of stages. So that to overcome this issue, the concept of flipped circuit is introduced here. This combination is mainly helpful for increasing the output current value of the parallel connection of the loops.

Existing System:

The existing converter (Transformerless Cockcroft-Walton (CW) generator, or multiplier) [1] [3] [4] consists of one inductor Ls (boost inductor), four switches (Sm1, Sm2, Sc1, and Sc2) the rating of all switches are same as well as voltage stress across each switch are same, and one n-stage CW voltage multiplier The four switches are divided into two groups Sm1 (Sc1) and Sm2 (Sc2) which operate in two different frequencies of Sm1 and Sc1 are defined as fsm and fsc, respectively. The both fsm and fsc frequencies should be as high as possible so that we can use smaller inductor and capacitors.

The both fsm and fsc frequencies should be as high as possible so that we can use smaller inductor and capacitors in this circuit. CW voltage multiplier is constructed by a cascade of stages with each stage like in Fig. 1. But this circuit have the disadvantage the Output current of the circuit decreased while increasing number of stages. For very high voltage the number stages were increased means the output current value become very low. The current value is very low means the output voltage is not a valid one.

The simulation diagram of the existing Cockcroft Walton Voltage Multiplier is given in Fig. 2. It is a simple two stage transformerless Cockcroft Walton circuit. This circuit containing four capacitors (C1, C2, C3, C4) and four diodes (D1, D2, D3, D4). In an n-stage CW voltage multiplier, there are N (= 2n) capacitors and N diodes n=2 (2-stage). The input voltage for Cockcroft-Walton (CW) generator is 230V, Output voltage is 1800V, output current is 1.8Amp, and Output power is 3500W.

Proposed System:

The proposed circuit is based on the Flipped circuit concept. It is shown in Fig. 3.

As shown in Fig.3, the proposed CW voltage multiplier is constructed by a flipped cascade connection of the stages. It consists of DC voltage source, one inductor, four Switches (sm1, sm2, sc1, and sc2) and eight diodes (D1, D2, D3, D4, D5, D6, D7, and D8) and six capacitors (C1, C2, C3, C4, C5, and C6). Where the diodes D5, D6, D7, D8, Capacitors C1, C3, C5, C6 are formed the loop 1 and the diodes D1, D2, D3, D4, Capacitors C1, C2, C3, C4 are formed the loop 2. In this circuit the loop 1 and loop are worked simultaneously.

In general the Cockcroft Walton circuit contains transformer it causes more disadvantages. The space consumption is the major issue, while increasing the voltage range to very high means the transformer size also increased. Another important issue is maintenance of the transformer. While using transformer in Cockcroft Walton circuit separate maintenance is required. To avoid these problems we develop this project from the transformerless [5] [6] [7] Cockcroft Walton circuit. In the existing Cockcroft Walton circuit the output current value is decreased while increasing stages for increasing voltage. This was overcome by the proposed circuit. In this circuit the current value was increased the parallel operation of the flipped circuit. (i.e.), the loop 1 and loop 2 are operated separately and simultaneously.

Operation:

The operation of the modified Cockcroft Walton circuit is continuous charging and discharging of the capacitors. It is quite similar to the normal CWVM. But in the modified circuit two loops are available. The capacitors C1, C2, C3, C4 and the diodes D1, D2, D3, and D4 are form the loop one. The capacitors C1, C3, C5, C6 and the diodes D6, D7, D8, and D9 are form the loop two. Both the loops are operate simultaneously. Due to this parallel operation of this loops we got more high voltage and more current. The Operation of the proposed circuit is divided into four modes.

A. Mode 1:

In mode 1 the switches Sm1 and Sc1 are turned on, and the switches Sm2, Sc2 are turn off, and all diodes are turned off. The boost inductor is get charged by the Vin, the capacitors C2, C4, and C5, c6 are discharged and give supply to the load, the capacitors C1 and C3 are not in conduction.

B. Mode 2:

In mode 2 Sm2 and Sc1 Switches are turned on, Sm1 and Sc2 Switches are turned off. The boost inductor (Ls) and input Vin dc source are in series the boosted energy transfer to the CW voltage multiplier through different diodes. The diodes D4 and D8 are in conduction. The diode D4 is used to charge the capacitors C2 and C4 and the diode D8 is used to charge the capacitors C5 and C6. At the same time the capacitors C1 and C3 are discharged. After this the diodes D2 and D6 are conducting. The diode D2 is used to charge the capacitor C2 and diode D8 is used to charge the capacitor C5. At the same time the capacitor C1 is discharged.

C. Mode 3:

After that the switches Sm2 and Sc2 are turned on, and the switches Sm1, Sc1 are turn off, and all diodes are turned off. The inductor is get charged by the input voltage, the capacitors C2, C4, and C5, c6 are discharged and give supply to the load, the capacitors C1 and C3 are not in conduction.

D. Mode 4:

Sm1 and Sc2 Switches are turned on, Sm2 and Sc1 Switches are turned off. The boost inductor (Ls) and input Vin dc source are in series the boosted energy transfer to the CW voltage multiplier through different diodes. The diodes D4 and D8 are in conduction. The diode D4 is used to charge the capacitors C2 and C4 and the diode D8 is used to charge the capacitors C5 and C6. At the same time the capacitors C1 and C3 are discharged. After this the diodes D2 and D6 are conducting. The diode D2 is used to charge the capacitor C2 and diode D8 is used to charge the capacitor C5. At the same time the capacitor C1 is discharged.

Output comparison:

The operation of the modified Cockcroft Walton circuit is continuous charging and discharging of the capacitors. It is quite similar to the normal CWVM. But in the modified circuit two loops are available. The capacitors C1, C2, C3, C4 and the diodes D1, D2, D3, and D4 are form the loop one. The capacitors C1, C3, C5, C6 and the diodes D6, D7, D8, and D9 are form the loop two. Both the loops are operate simultaneously. Due to this parallel operation of this loops we got more high voltage and more current. The Operation of the proposed circuit is divided into four modes.

A. Output Voltage:

The output voltage of the proposed circuit to the input voltage of 230V is 1800V (1.8KV). Where, the output voltage is 8 times multiplied by the input voltage.

V out = 8 Vin

The proposed circuit is designed for 2 stage, for more high voltage value by increasing the no of stages the required high voltage was obtained.

B. Output Current:

1) Output current of Existing Circuit_

Output current of the existing circuit is 1.8A. 2) Output current of Proposed Circuit

Output current of the proposed is 18A. It is 10 times greater than the output current of the existing circuit's output current.

C. Output power:

1) Output power of existing system

The output power of the existing circuit is 3500W. 2) Output power of Proposed system

The output power of the proposed circuit is 35000W. It is 10 times greater than the output power of the existing circuit's output power.

Conclusion:

In this paper, a high step-up DC-DC converter based on flipped Cockcroft Walton Voltage Multiplier has been presented to obtain a high output voltage gain with increased output current and high output power. Finally, the simulation results are proved using MATLAB SIMULINK. In future, by modifying this circuit in matrix format very high voltage can be generated.

REFERENCES

[1.] Nileena, P., Subhash, 2014. "A High Step-Up Converter Using Transformerless Cockcroft-Walton Voltage Multiplier for a PV System", IJIRSET, 3.

[2.] Chitra Sharma1, 2014. "Low Cost High Voltage Generation: A Technique for Educational Laboratory" IJSETR., 4.

[3.] Prince, R., 2013. "DC-DC Converter Based On Cascade Cockcroft-Walton Voltage Multiplier for High Voltage Gain without Using Transformer", IJESIT., 2.

[4.] Meghana, G Naik, 2014. "Transformerless DC-DC Converter Using Cockcroft -Walton Voltage Multiplier to Obtain High DC Voltage", IJERA., 4.

[5.] Li, W. and X. He, 2011. "Review of nonisolated high-step-up dc/dc converters in photovoltaic gridconnected applications," IEEE Trans. Ind. Electron., 58(4): 1239-1250.

[6.] Leu, C.S., P.Y. Huang and M.H. Li, 2011. "A novel dual-inductor boost converterwith ripple cancellation for high-voltage-gain applications," IEEETrans. Ind. Electron., 58(4): 1268 -1273.

[7.] Chi-Chih Huang, Kuo-Ching Tseng, and Wei-Yuan Shih, 2013. "A high step-up converter with a voltage multiplier module for a photovoltaic system,". IEEE transactions on power electronics, 28: 6.

(1) Mathiyazhagan. R, (2) Prasad D, (3) Elavarasan. T

(1) Department of Electrical and Electronics Engineering, PG Scholar, Sona College of Technology Anna University, Salem, Tamilnadu, India.

(2) Department of Electrical and Electronics Engineering, Assistant Professor, Sona College of Technology Anna University, Salem, Tamilnadu, India.

(3) Department of Electrical and Electronics Engineering, PG Scholar, Sona College of Technology Anna University, Salem, Tamilnadu, India.

Received 28 March 2017; Accepted 7 June 2017; Available online 12 June 2017

Address For Correspondence:

Mathiyazhagan. R, Department of Electrical and Electronics Engineering, PG Scholar, Sona College of Technology Anna University, Salem, T amilnadu, India.

Caption: Fig. 1: Existing System

Caption: Fig. 2: Simulation of Existing Circuit

Caption: Fig. 3: Proposed System

Caption: Fig. 4: Simulation of Proposed Circuit

Caption: Fig. 5: Output Voltage

Caption: Fig. 6: Output Current of existing circuit.

Caption: Fig. 7: Output current of Proposed Circuit

Caption: Fig. 8: Output power of existing system

Caption: Fig. 9: Output power of Proposed system
Table 1: Simulation Configuration

Input Voltage        230V          Switching        IGBT
                                   Device

Capacitors [C1-C6]   470[micro]F   Diodes           PN junction
Inductor [Ls]        1.5 mH        Output voltage   1800V
Switching            1kHz          Output Current   18A
  Frequency [fsc]
Switching            60kHz         Output Power     35000w
  Frequency [fsm]

Table 2: Output Comparison

Parameters       Results of   Results of
                 Existing     Proposed
                 Circuit      Circuits

Output Voltage   1800V        1800V
Output Current   1.8A         18A
Output Power     3500W        35000W
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Article Details
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Author:Mathiyazhagan, R.; Prasad, D.; Elavarasan, T.
Publication:Advances in Natural and Applied Sciences
Geographic Code:9INDI
Date:Jun 1, 2017
Words:1985
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