International Journal of Scientific & Engineering Research Volume 4, Issue3, March-2013 1

ISSN 2229-5518

Improvement of Input-Side Current of a Single Phase Rectifier with Variable Output Voltage Range using Boost Converter and Investigation of Harmonic Minimization

Ahmed Al Mansur, Abdullah Al Bashit, A.S.M. Mahfuzur Rahman, Md. Shahinur Alam,Hasina Begum

Abstract— In order to reduce the Total Harmonic Distortion (THD) in a single phase boost rectifier, active switching & passive filters are incorporated in this work. A constant frequency switching is used for active filtering & pulse width modulation is used to regulate the output voltage. A passive LC filter is used in the input side to suppress the unwanted high frequency harmonic components generated by the active switching and output filtering. Using passive filtering the THD could be made less than one percentage, which is a great improvement over the earlier rectifiers that have only Electro-Magnetic Interference (EMI) filter. In the earlier types of rectifiers, the THD value was as high as three percentages. The efficiency of the module is also studied. As the output voltage has the nonlinear relation with duty cycle, the efficiency is also nonlinear with output voltage variation. But up to certain range of duty cycle it could be made linear in nature with output voltage. The efficiency versus duty cycle and THD versus duty cycle curve for the proposed rectifier circuit is given for a clear understanding of the model. The conventional Power Factor Correction (PFC) circuit has a fixed output voltage. However, in some applications, a PFC circuit with a wide output voltage range is needed. A single phase power factor correction Boost rectifier circuit with wide output voltage range (150V to 300V) and efficiency more than 95% is developed in this work using passive filter and boost rectifier.

Index Terms— Active Switching, Electro Magnetic Interference, Power Factor Correction, Single Phase Rectifier, Total Harmonic Distortion

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1 INTRODUCTION

HE input stage of any AC-DC converter comprises of a full-bridge rectifier followed by a large filter capacitor. The input current of such a rectifier circuit comprises of
large discontinuous peak current pulses that result in high input current harmonic distortion. The high distortion of the input current occurs due to the fact that the diode rectifiers conduct only for a short period. This period corresponds to the time when the mains instantaneous voltage is greater than the capacitor voltage. Since the instantaneous mains voltage is greater than the capacitor voltage only for very short periods of time, when the capacitor is fully charged, large current pulses are drawn from the line during this short period of time. Fig. 1 shows the schematic of a typical single phase di- ode rectifier filter circuit while Fig. 2 shows the typical simu- lated line voltage and current waveforms. The typical input current harmonic distortion for this kind of rectification is usually in the range of 55% to 65% and the power factor is about 0.6 [1]. The actual current wave shape and the resulting harmonics depend on the line impedance. Conventional AC

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 Ahmed Al Mansur is currently pursuing PhD degree in Electrical and Electron- ic Engineering (EEE) in Islamic University of Technology, Bangladesh, E-mail: mansur.iut@gmail.com

 Abdullah Al Bashit is working as a lecturer in the Dept. of EEE, Prime Univer-

sity, Bangladesh, E-mail: eeebashit@gmail.com

 A.S.M. Mahfuzur Rahman is with the dept. of EEE in Prime University, Bang-

ladesh, Email: mahfuz.pbtl@gmail.com

 Md. Shahinur Alam is with the dept. of EEE in Prime University, Bangladesh,

Email: shahinur.alam9@gmail.com

 Mrs. Hasina Begum is with the dept. of EEE in Prime University, Bangladesh,

Email: hasina.pu@gmail.com

rectification is thus a very inefficient process, resulting in waveform distortion of the current drawn from the mains. A circuit similar to that shown in Fig. 1 is used in most mains- powered AC-DC converters. At higher power levels (200 to
500 watts and higher) severe interference with other electronic equipment may become apparent due to these harmonics sent into the power utility line. Another problem is that the power utility line cabling, the installation and the distribution trans- former, must all be designed to withstand these peak current values resulting in higher electricity costs for any electricity utility company [2],[3].

Fig. 1. Schematic diagram of a single phase diode rectifier with capacitor filter circuit [2],[3]
The power factor correction (PFC) technique has been gaining increasing attention in power electronics field in recent years. For the conventional single-phase diode rectifier, a large electro- lytic capacitor filter is used to reduce dc voltage ripple. This capacitor draws pulsating current only when the input ac volt- age is greater than the capacitor voltage, thus the THD is high

International Journal of Scientific & Engineering Research Volume 4, Issue3, March-2013 2

ISSN 2229-5518

and the power factor is poor. To reduce THD and improve power factor, passive filtering methods and active wave- shaping techniques have been explored [4],[5],[6],[7].

Fig. 2. Typical line current and voltage waveforms [2],[3]

2 RECTIFIERS THD IMPROVEMENT

2.1 Rectifier with output filter Capacitor

Fig. 4. Input current at capacitor C1=10uF, 50uF, 100uF

VAMPL = 325

VOFF = 0

FREQ = 50

Vin

0. 0001

D1N4007

D 3

D 1N4007

D 2

D 1N4007

50uF

48.4

The effects of output filter capacitor on the THD and the input current and output voltage are analyses by changing the val- ues of the output capacitor, C1 in Fig. 3. When the capacitor, C1 is increasing than the output voltages, Vo are becoming more pure dc but input currents are distorting due to harmon- ics generated by the filter capacitor, C1 [8],[9] shown in Fig. 4 and the summarized results are shown in the Table 1.

2.2 Rectifier with input inductive filter

Fig. 3. A simple diode bridge rectifier with filter capacitor

TABLE 1

EFFECTS OF FILTER CAPACITOR ON EFFICIENCY AND THD

VAMPL = 325

VOFF = 0

FREQ = 50

Vin

0.0001

1 2

10mH

D1N4007

100uF

48.4

Fig. 5. Single-phase rectifier with input inductance
Input side filter is a must to reduce the harmonics contain in the input current. Passive filters are always very much cost effect than active filters [10],[11]. Because of that an inductive filter, L1 is used as a passive filter in the input side of the recti-

International Journal of Scientific & Engineering Research Volume 4, Issue3, March-2013 3

ISSN 2229-5518

fier shown in Fig. 5. The effects of the inductor, L1 on the out- put voltage, input current and THD has been analyzed and shown in Table 2. It is clear that THD are minimizing with increasing the values of input filter L1 but the output voltage level are decreasing which is a drawback of the inductive fil- ter.

TABLE 2

EFFECTS OF INPUT FILTER L1 ON EFFICIENCY AND THD

filter, C2 on the output voltage, input current, efficiency and THD can determine from Table 3. From the Table it is clear that when inductive filter, L1 increases and capacitive filter, C2 decreases than output voltage, Vo decreases. The efficiency also decreases at this condition. But the THD values are not like that, it has different values at different L1, C1 combina- tion. At L1=100mH, C1=100uF THD is less than 1% and Vo is
295Volt which is a great achievement.

VAMPL = 325

VOFF = 0

FR EQ = 50

Vin

0.0001

1 2

100mH

C 2

100uF

D1N4007

D 3

D 1N4007

D 2

D 1N4007

C 1

100uF

48.4

Fig. 7. Rectifier with input LC passive filter.

TABLE 3

EFFECTS OF L1, C2 FILTERS ON EFFICIENCY AND THD

L1	C2	Vo (Volt)	Iin (peak)	η (%)	THD (%)
50mH	220uF	515	64	98	0.54
70mH	150uF	405	37	99	0.79
100mH	100uF	295	20	97	0.969
170mH	60uF	176	9	98	1.05
215mH	47uF	140	6.5	98	1.06
340mH	30uF	90	4.5	97	0.96
1H	10uF	32	1	93	0.64

2.4 Proposed Boost Rectifier with LC filter

Boost rectifier is the combination of boost converter with a single phase rectifier [12]. An N-channel MOSFET IRF540 [13] is used in the boost converter and to drive this MOSFET with variable duty cycle a PWM [14] driver circuit is used also shown in Fig. 8. To make the rectifier with a variable output

Rs L2 D5

n13 1 2 N2

15H

Fig. 6. Input current at L1= 10mH, 100mH, 500mH
From Fig. 6 it can be visualized that with increasing the value of the input side inductive filter, L1 from 10mH to 500mH, the current wave shapes are gradually improving means becom-

VAMPL = 325

VOFF = 0

FREQ = 50

0.0001

Vin

n7 3

1 2

100mH

100uF

D1N4007

IRF540

D1N4007

1000uF C1

48.4

ing more sinusoidal but the output voltage and the peak value

U1A AD648A 1 n6

OUT

U2 1k

A4N25

of the input current both are decreases shown in Table 2.

V1 = 0 V2

V2 = 15

TD = 0

TR = 0.01m

TF = 0.235m

2 -

Q2N2222

10Vdc

2.3 Rectifier with input LC filter

PW = 0.0001m V3 V4 V5

The effects of input side inductive filter, L1 with capacitive

PER = 0.25m

3Vdc -20Vdc

20Vdc

500k

http://www.ijser.org

International Journal of Scientific & Engineering Research Volume 4, Issue3, Marc

ISSN 2229-5518

Fig. 8. Proposed model of the single phase boost rectifier

TABLE 4

INVESTIGATION OF THD AND EFFICIENCY AT DIFFERENT BOOST

INDUCTOR, LBOOST & CAPACITOR, COUT

Fig. 9. THD versus duty cycle of the proposed model

Fig. 10. Efficiency versus duty cycle of the proposed model.

TABLE 5

PROPOSED MODELS THD AND EFFICIENCY AT DIFFERENT DUTY

CYCLE (COUT= 50UF AND LBOOST= 0.005H)

voltage range boost converter is added here. But after analyz- ing the total circuit it has been found that the boost inductor has a great contribution to improving the input side current of the rectifier shown in Table 4. The investigation of total har- monic distortion and efficiency has been done at different val- ues of the boost inductor, L2=LBoost and capacitor, C1=Cout in the proposed boost rectifier. From Table 4 it has been found that for the same value of L2 when C1 increases then THD increases and efficiency decreases because output voltage, Vo also decreases. Again at fixed filter, C1 when boost inductor, L2 decreasing THD also decreasing but efficiency increasing. From Table 4 it has been found that the harmonic distortion is
0.966% and efficiency is 96% at L2= 0.5mH, C1= 50uF.
To verify the effect of the active switching on the THD, differ- ent duty cycle is used at the MOSFET shown in Table 5. When duty cycle, k is increases then the THD are decreases and al- ways have the values less than 1% shown in Fig. 9. Again the efficiency is increasing when k is decreasing, which means the switching loss is minimized due to small duty cycle shown in Fig. 10. From Table 5 it has been found that the THD is 0.65% to 0.97% for duty cycle 0.42 to 0.1 when the rectifier output voltages range is 155V to 300V and efficiency 93% to 98%

3 DISSCUSSION AND CONCLUSIONS

First of all it had been studied the uncontrolled single phase

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ISSN 2229-5518

rectifier with and without output filter capacitor. Without fil- ter capacitor the THD value of the rectifier is 0.33% with rip- pled output voltage. To get pure dc output voltage large ca- pacitor is included at the output but THD rise to 200%. Anoth- er drawback of this circuit is that it does not have any voltage control option. To minimize the input current THD, an induc- tive filter is used in series at the input-side of the rectifier. This inductive filter can minimize input-side THD but it makes more rippled dc voltage at the output-side. To overcome this filtering problem a capacitive filter is used in parallel with the inductor. This LC filer combination makes the THD less than
1% and output voltage becomes pure dc. Now to regulate the output voltage a boost converter in added between the load and rectifier but its high frequency switching makes distortion in the input current. To solve this problem an analysis has been done with different values of boost inductor and capaci- tor. And get an optimum condition at which again THD be- comes less than 1%.
Finally, boost rectifier with active switching has been studied
for different duty cycle. The best operating point is at the
range of duty cycle 0.482 to 0.068. At this range the output
voltage can be regulated from 155V to 300V, efficiency from
93% to 98% and THD is always less than 1%. ORCAD 9.2 re-
lease version [15], very powerful Electrical & Electronic design
software is used to design all the circuits for this work.

tifier with Input Power Factor Correction", IEEE transactions on power electronics, Vol. 11, no. 2, March 1996.

[12] I. Barbi and S. Silva, "Sinusoidal line current rectification at unity power factor with boost quasi-resonant converters", IEEE Applied Power Electronics Conf (APEC), pp 553-562, 1990.

[13] N-Channel MOSFET IFR540 [online], Available:

http://www.datasheetcatalog.org/datasheet/stmicroelectronics/9387.pdf

[14] Pulse Width Modulation [online], Available:

http://en.wikipedia.org/wiki/Pulse-width modulation. [15] OrCAD Capture user manual available from:

www.seas.upenn.edu/~jan/spice/PSpice_CaptureGuideOrCAD.pdf

REFERENCES

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[3] Basu, S. 2006 Single Phase Active Power Factor Correction Convert- ers: Methods for Optimizing EMI, Performance and Costs. M.Sc. Thesis. Chalmers University of Technology – Sweden.

[4] S.B. Dewan, "Optimum input and output filters for a single-phase rectifier power supply", IEEE Trans. Industry Appl., vol. IA-17, no. 3, pp. 282-288,June 1981.

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