 Open Access
 Total Downloads : 245
 Authors : Lijin K L, Sunil Kumar P R
 Paper ID : IJERTV3IS040821
 Volume & Issue : Volume 03, Issue 04 (April 2014)
 Published (First Online): 15042014
 ISSN (Online) : 22780181
 Publisher Name : IJERT
 License: This work is licensed under a Creative Commons Attribution 4.0 International License
Single Stage Power Regulator With High Power Factor using Active Current Wave Shaping Techniques
Lijin K L
M.Tech Research Scholar Electrical and Electronics Engineering
Govt. Engineering College, Idukki Idukki, India
Mr. Sunil Kumar P R
Asst. Professor
Electrical and Electronics Engineering Govt. Engineering College, Idukki
Idukki, India
AbstractFor low harmonic distortion and high input power factor leads to active current wave shaping techniques. Such circuits consists of input boost converter operated in discontinuous current conduction mode and output dcdc converter such that flyback converter derived from buckboost converter such class of power supplies known as single stage single switch power factor correction regulator. Here expression for boost inductance, critical inductance of flyback converter, energy storage capacitance, output capacitance derived .based on that a 50W, 230V, 50 Hz AC/50V DC single stage single switch power factor correction regulator was designed and simulated using orcad 16.5 software package in open loop control and closed loop control, the problem of dc voltage dependency was found eliminated almost.
I.INTRODUCTION
An AC to DC Converter is an integral part of any power supply unit used in all electronic equipments. Usually Power converters use a diode rectifier followed by a bulk capacitor to convert AC voltage to DC voltage. Since these power converters draw pulsed current from the utility line the power factor becomes poor due to high harmonic distortion of the current waveform. Therefore, a power factor correction stage has to be inserted to the existing equipment to achieve a good power factor. Several standard and review articles in the literature have addressed power quality related issues in AC to DC converters. New configurations of power factor corrections are being developed to mitigate the harmonic effects on the input line current and improve the power factor The input power factor correction stage and the output DC to DC converter stage. Continuous efforts to further make these power converters compact and cost effective to learn to the development of new class of power supplies known as Single Stage Single Switch power factor correction regulator, which is the integration of PFC stage and the DC to DC converter stage. It uses only one switch and controller to shape the input current and regulate the output voltage. The energy storage device in between is necessary to absorb and supply the difference between the pulsating instantaneous input power and constant output power A major problem associated with Single Stage Single Switch power factor correction regulator is strong dependency of DC BUS voltage stress across the capacitor with the output load Power unbalance between PFC stage
and DCDC stage is the inherent reason for causing high DC bus voltage stress. Frequency control is other solution proposed to overcome high DC voltage stress But this call for complex control circuit. The concept of series charging, parallel discharging capacitor scheme is another solution. But this call for more component count in the power circuit In this paper a design solution is proposed to avoid the problem of energy unbalance between energy stored during ON period of switch and energy dissipated in the load by optimally sizing the boost inductor. Maximum energy stored in the inductor shall be limited to such a value that this energy matches with maximum output power required. The instant at which maximum power delivered shall be matched with the instant when the input ac voltage is at the peak. Also consider the fact that maximum power is delivered at a duty ratio which is slightly less than the limiting duty ratio (0.5) for DCM operation[1]. Equal Area Criterion is applied between theoretically calculated fundamental component of input ac current and the peak inductor current when TON is maximum. Using this approach the design was carried out, and simulated testing as well as experimental observation showed only a very small rise in DC bus voltage at light load condition, even under open loop [2]. After introducing closed loop control with output voltage as controlled variable and duty ratio as manipulated variable the DC bus voltage dependency was found almost insignificant.
Classical line commutated rectifiers suffer from the following disadvantages:

They produce a lagging displacement factor w.r.t the voltage of the utility.

They generate a considerable amount of input current harmonics. These aspects negatively influence both power factor and power quality. The massive use of singlephase power converters has increased the problems of power quality in electrical systems.
Power factor is the relationship between working (active) power and total power consumed (apparent power). Essentially, power factor is a measurement of how effectively electrical power is being used.[3] The higher the power
factor, the more effectively electrical power is being used and vice versa. A distribution systems operating power is composed of two parts: 1) Active (working) power and 2) Reactive (nonworking) magnetising power. The ACTIVE power performs the useful work. The REACTIVE power does not as its only function is to develop magnetic fields required by inductive devices. Generally, power factor decreases (Ã˜ increases) with increased motor loads.[4] Therefore, when more inductive reactive power is needed, more apparent power is also needed. An active approach is the most effective way to correct power factor of electronic supplies. Here, we place a boost converter between the bridge rectifier and the main input capacitors. The converter tries to maintain a constant DC output bus voltage and draws a current that is in phase with and at the same frequency as the line voltage [5].
The paper is organized in the following way. Section II provides Open loop control of S4 PFC regulator. Section III presents closed loop control of S4 PFC regulator. Section IV represents design of S4 PFC regulator and Section V gives Design of a 50W, 230V, 50 Hz, 50 VDC S4 PFC regulators. Simulations are shown in Section VI.

OPEN LOOP CONTROL OF S4 PFC REGULATOR
Basic configuration of single stage single switch power factor correction regulator with input boost converter and output flyback converter as shown in the fig .1. When switch s is ON current in inductor Li increases linearly depends on input line voltage, when switch s is OFF the stored energy in inductor to bulk capacitor and to the load. If there is any
Fig .1: open loop control of S4 PFC regulator
Fig .2:closed loop control of S4 PFC regulator
Mode II
In this mode, when switch s is turned OFF so current in boost inductor decreases linearly with proportional to the voltage difference between input instantaneous voltage and sum of capacitor voltage and output voltage in transformer primary
change in the load will leads to the unbalanced power between input and output,due to this unbalanced power increases output voltage,this can be avoided by closed loop control in
L di V
1 dt m
sin t Vdc nV2
(3)
which on period of switch is reduces automatically when output voltage increases[6]
i Vm L1
sin tdt
Vdc nV2 dt
L1
(4)

CLOSED LOOP CONTROL OF S4 PFC REGULATOR
Closed loop control configuration of single stage single switch power factor correction regulator with input boost converter and output flyback converter as shown in the fig .2 To explain the working of ircuit,the operation is divided into three modes.
Mode I
In this mode of operation, switch s is ON so current in boost converter inductor increases linearly, which is
Mode III
When current in boost inductor reaches zero mode III starts and the Diode D3 conducts, which leads to the transfer the energy from inductor to the output capacitor and then to the load

DESIGN OF S4 PFC REGULATOR
For design purpose consider a reference current Im sin t and magnitude of this current is chosen such a way that
depends proportionally to the instantaneous values of input voltage
Pout Vrms Irms
A. Design of boost inductor
(5)
V sin t L di
m 1 dt
i Vm sin tdt
(1)
(2)
From the circuit diagram current in boost inductor during
ON time is
L1
V
L1
ir I1 m
cos cos t
Where < t < ton (6)
Current in boost inductor during OFF time is
V V nV
Value for the 500 W is obtained as
2
ir I2 m cos ton cos ton t dc 2 t
R= = 88.09 = 90 and
L1
L1
(7)
Lc = 1.2 mH
Considering that I1 =0 and maximum current occurs when = 900
C. Calculation of energy storage capacitor
Substituting this in equation (1) we get boost inductance as
I peak
DTEm
L
(13)
1
L Vm DT
(8) 1
I 2 peak
.45 50106 230
1.57 103
2 4.66Amp
B. Design of fly back converter
For Volt Second transformer Balance
Energy stored in the boost inductor is transferred to the energy storage capacitor during second mode of operation
V V
D nV
V 1 D
(9)
C V 2 L I 2
(14)
1 sat 2 f 1 1
and
i2avg
nI p 1 D
2
V 2
R
(10)
We get C1 =22.6Âµf
D. Design of output filter
Vbase = 230V = 1 pu Pbase = 50W = 1 pu
Assuming zero switching losses Pin = Pout = 1 pu
From above equation we obtain the equation of critical inductance of flyback converter as
This yields
I
base
Pbase
V
50
230
0.2174 A
V V R1 D2 n2
base
c
L 2 f
(11)
Z Vbase
230
1058
2V2 fs
base
Ibase
0.2174

DESIGN OF A 50W, 230V,50 HZ,50 VDC S4 PFC
REGULATOR
Vout
pu
50
230
.2174

Calculation of boost inductor
Switching instant is considered as =900 for maximum rising and falling
Switching frequency ,fs = 20 KHz
Duty ratio D = 0.3(for DCM mode operation D should be
Bulk output capacitor may be determined by settling the output ripple constraint by allowing a 5% output ripple and considering the ripple frequency to be twice the line frequency ,we get
Vripple .05Vout pu .05 0.2174 0.0108
less than 0.5)
Vripple
0.01087 230 2.5V
Pout Vrms I rms
C I2
I 50 0.2174 A
nV
(14)
rms
230
I2 is twice the line frequency current equating instantaneous
I m 0.3074 A
input power to out put dc power
Ipeak
for a duty cycle for duty cycle is obtained as
I 230 0.2174 .999 A
2 50
Ipeak = 1.36 A
C
0.999
2 2 50 2.5
6.36104
=636 Âµf
L1
DTEm
I peak
.3 50 106 230 2
1.36
E. Design of magnetic components Maximum energy stored in boost inductor

Calculation3.5o8fmHcritical inductance of flyback converter
For D =.3
= 1 2 = 0.5Ã—3.58Ã—103Ã—1.362
2
= 3.36Ã—103 Joules
KwAw a
Secondary voltage
= Ã—
(12)
K A NI/J
2 1 2
w w
Substituting the values in above equation we get
2= 66.37 V
Kc = Im/Irms = 2
Let Bmax = 0.2, Ac = 0.4, J = 3Ã—106 A/m2
Aw Ac
= 2E
Kw Kc JB max
(15)
output voltage as shown in the fig. 4, but there is no change in the input current
Area product(Ap) = KwAw
From equation (15) we get Ap=1.98Ã—104 mm4 So core E 42/21/9 is a proper choice
Then
Aw = 2.56Ã—100 mm2 Ac = 1.07Ã—100 mm2
So Number of turns, N =LIm/AcBm
=3.58Ã—103 Ã—1.36
107 Ã—106 Ã—0.2
=228 turns
F. Design of transformer for the flyback converter
The transformer used in flyback converter also acts as inductors so it is different from other transformer configurations
B swing Bn =0.5 and = 0.84
In = 0.75 and n =N2/N1=1/3=0.333 V0 = nV1(D/1D) (16) When D= 0.3,V0 = 66.7V
Dmax = 0.37 for 100V
Dmin = D max/(Dmax+(1Dmax))Ã—(Vcc max/Vcc min)
= 0.328
Fig 3: input current waveforms
I /I + = 1 I =10.75 =0.25
1 1 n
1
I ++I1 = 2I1 av /Dmin =2nI2 av/Dmin
I + = (2nI /D )/ 1.25
1 0 min
= 3.24 A
Fig 4: variation in output voltage with load
I1 = 2.43 A
I2 = I1/n = 7.31 A
Bm = B/Bm ,Bm = 0.2 So B = 0.1 T
Now power in obtained by
Po2 = (V0+ VD)I0((1Dmin) /Dmin)
=102.5 watts Now area product ,
1 4D 41 D
Po2
n 3 3
(Ap) =
K w JBf s
(17)
Substituting values in equation (17),we get Ap = 11.4Ã—104 mm4
Choose a suitable area which has an Ap greater than calculated value E 65/32/13 is a proper choice
The equation for calculating number of turns in primary is
Fig 5: input current waveform
N1=
(18)
We get N1 = 297 turns and N2 = 99 turns


SIMULATION RESULTS
Simulation of S4 PFC regulator with circuit parameter having designed values was done in ORCAD software package. Simulation results were satisfies the design intends

open loop control
when duty ratio is varied output voltage is varied linearly with change in duty ratio and input voltage is sinusoidal which achieve high input power factor fig. 3 shows the sinusoidal input current in open loop control. But any change in the output voltage will leads to the variation in
Fig .6 harmonics spectrum of input current,
Fig 7. Output voltage
From Fig.4, it is cleared that during light load output voltage will increases. From Fig. 6 the fundamental frequency is dominant and other higher frequencies can be neglected. Fig 7 shows that, the output voltage which is a constant value so it gets the name regulator.

Closed loop control
Closed loop simulation is done by varying the reference voltage, output vary linearly with the reference voltage and input current is almost sinusoidal and in phase with the input voltage which leads to high power factor. Fig 5 shows the input current which is almost sinusoidal


EXPERIMENTAL RESULTS
50W, 230V, 50 Hz AC/50V DC single stage single switch power factor correction regulator is built and using IRFPF 50 as switch by taking following circuit parameters
Parameter 
values 
L1 
3.58 mH 
C1 
22.6uF 
n 
0.333 
L2 
636 uF 
Fs 
20 KHz 
D 
0.3 
Load 
90 
D1N 1190 is used in rectifier section, TL 082 opamp is used in control section as differential amplifier and comparator and ICL 8038 as triangular wave generator
Fig .8 hardware configuration of S4 PFC regulator
Fig .9 Input current waveform
Fig .10 input voltage waveform
From figure 9 and 10 input current and voltage is sinusoidaland are in phase so it achieve high power factor and is satisfy all the conditions
VII. CONCLUSION
S4PFC Regulator design by applying EAC to determine value of boost inductance and by using closed loop control is presented. The dc bus voltage stress at light load is found completely eliminated under closed loop operations. Output voltage regulation using duty ratio variations and fixed switching period is the most simple method of control. For normal performance of the converter the duty ratio needs to be limited up to 0.5. Experimental results demonstrate that it is possible for the proposed converter to have fast response and low line current harmonic content.
A DCM boost converter is chosen here which draws energy at line frequency. It has inherently low line current harmonics. A fly back converter is used to eliminate the disadvantages of boost rectifier. Thus the voltage stress in the capacitor is reduced and the output voltage is tightly regulated. EAC is used for design of boost inductance. Output voltage regulation using duty ratio variations and fixed switching period is the simplest method of control.
Simulation results demonstrate that it is possible for the proposed converter to have fast response and low line current harmonic content. The proposed converter is expected to maintain a good source power factor and tight output voltage regulation without compromising with high DC bus voltage. Moreover, the efficiency of overall power conversion is expected to be high.
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