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Advances in Natural and Applied Sciences, 8(21) Special 2014, Pages: 30-36
AENSI Journals
Advances in Natural and Applied Sciences
ISSN:1995-0772 EISSN: 1998-1090
Journal home page: www.aensiweb.com/ANAS
Design, Control and Implementation of High Gain Negative Output Relift DC-DC
Converter for Photovoltaic Applications
1
1
2
V. Chamundeeswari and 2Dr. R.Seyezhai
Associate Professor, Department of EEE, St.Joseph’s College of Engineering, Chennai-119, India
Associate Professor, Department of EEE, SSN College of Engineering, Chennai-603110, India
ARTICLE INFO
Article history:
Received 3 September 2014
Received in revised form 30 October
2014
Accepted 4 November 2014
Keywords:
DC-DC converter, Negative output
super lift Luo converter, relift
converter, PI controller.
ABSTRACT
Superlift converter is a type of DC-DC converter in which the output voltage increases
in geometric progression. This paper proposes the design and analysis of relift negative
output superlift luo converter (NOSLC) with the implementation of an analog PI
controller. The focus is on the negative output as the negative voltage finds its role in
telecom industries, automobile sectors, rig lines etc. Since the relift converter has a very
high output voltage compared to the basic self lift, a PI controller is implemented using
Ziegler-Nichol’s tuning for load regulation. Simulation results are presented to validate
the theoretical design. Hardware circuit of the proposed converter is developed to
validate the simulation results. The high gain obtained using the proposed converter is
suitable for photovoltaic applications.
© 2014 AENSI Publisher All rights reserved.
To Cite This Article: V. Chamundeeswari and Dr. R. Seyezhai, Design, Control and Implementation of High Gain Negative Output Relift
DC-DC Converter for Photovoltaic Applications. Adv. in Nat. Appl. Sci., 8(21): 30-36, 2014
INTRODUCTION
Voltage lift technique has been successfully employed in design of DC-DC converters. However, the output
voltage increases in arithmetic progression. Super lift technique is an advanced one which implements the
output voltage increasing in geometric progression. It effectively enhances the voltage transfer gain.
The first lift circuit is an elementary circuit which performs the voltage conversion from positive source
voltage to negative load voltage. It is the basic circuit of negative converter in which the output voltage
increases in geometric progression. The next lift circuit is relift wherein the output voltage increases in multiples
of input voltage. This paper investigates the potentials of relift converter with suitable control strategy for load
regulation.
Section II deals with the Relift circuit and its mode of operation followed by the simulation results of open
loop relift DC-DC converter. Section III depicts the design of a PI controller for relift circuit with its simulation
results and finally section IV portrays the hardware implementation of relift circuit followed by conclusion in
section V.
Opertation of negative output relift converter:
The NOSLC is a new series of DC-DC converters possessing high-voltage transfer gain, high power
Density, high efficiency, reduced ripple voltage and current (Fanglin luo 2003). The relift circuit performs
the voltage lift in a higher way compared to the self lift by the additional capacitors added (Y.Jiao, F.L.Luo,
M.Zhu 2011). The circuit diagram of Relift circuit is shown in the fig 1.The inductor L2 act as a linking inductor
and the capacitors C3 and C4 perform the characteristic function to lift the voltage by twice that of source
voltage. The currents through the capacitors are exponential functions.
Modes of operation:
During switch on ie.mode 1 as shown in the fig.2, the voltage across the capacitor C1 is charged to Vin.The
voltage across the capacitor C3 is charged to (V1+Vin).The current through the inductor L2 increases with slope
V1+Vin/L2 during switch on period kT and decreases with slope – (V0-2V1 – Vin)/L2 during switch off (1-k) T i.e.
mode2 as shown in the fig.3. The input current I in is equal to (iL1 +iC1 +iL2 +iC3) during switch on and zero
during switch off.
Corresponding Author: V. Chamundeeswari, Associate Professor, Department of EEE, St. Joseph’s College of
Engineering, Chennai-119 India.
E-mail: [email protected]
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V. Chamundeeswari and Dr. R. Seyezhai,2014
Advances in Natural and Applied Sciences, 8(21) Special 2014, Pages: 30-36
Fig. 1: Circuit diagram of Re-lift circuit.
Fig. 2: Mode 1 Circuit diagram of Re-lift circuit.
Fig. 3: Mode 2 Circuit diagram of Re-lift circuit.
The voltage across the capacitor C1 is given by,
V1= Vin/1-k (1)
The variation of current iL2 is given by,
iL2 = V0-2V1-Vin (1-kT)/L2 (2)
The output voltage is given by,
V0 = (2-k/1-k) 2 Vin
(3)
The voltage transfer gain is,
G = V0/Vin = (2-k/1-k) 2 (4)
Based on the above design equations, the DC-DC converter is designed and the simulation parameters are
shown in Table: 1.
Fig. 4: Current through the inductor L1 and L2
The following waveforms depict the simulation output of relift converter.Fig.4 shows the current through
the inductor L1 and L2. The current through the capacitor C1 and capacitor C2 is depicted in Fig.5 which shows a
charge to -20mA and discharge effectively.Fig.6 and 7 shows the current through the capacitor C 3 and C4
followed by the voltages across the inductor L1 and L2 depicted in the figure 11.
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V. Chamundeeswari and Dr. R. Seyezhai,2014
Advances in Natural and Applied Sciences, 8(21) Special 2014, Pages: 30-36
TABLE I: Simulation Parameters for Re-lift DC-DC Converter.
NAME OF THE PARAMETER
INPUT VOLTAGE
OUTPUT VOLTAGE
INDUCTORS
CAPACITORS
SWITCHING FREQUENCY
LOAD RESISTANCE
DUTY CYCLE
SYMBOL
Vin
Vout
L1, L2
C1,C2,C3,C4
fS
RL
K
VALUE
12V
-182V
10mH
2µF
100KHz
15KΩ
67%
Fig. 5: Current through the capacitor C1 andCapcitorC2
Fig. 6: Current through the capacitor C3 and C4.
Fig. 7: Voltage across the inductor L1 and L2.
Design of pi controller for relift circuit:
The relift converter produces an enhanced output voltage which shows the geometric progression rise. To
produce a steady state output for the load changes, a controller is designed which modify the error signal and
produce a proper control action. Here the analog PI controller is taken for implementation. The proportional
gain constant (Kp) and the integral constant (Ti) are tuned using Ziegler Nicholas tuning. (K.Ramash Kumar,
S.Jeevananthan 2010, Arulselvi et al.,2004, N.Dhanasekar,Dr.R.Kayalvizhi 2012, H.Mingzhi and X.Jianping,
2007)
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Advances in Natural and Applied Sciences, 8(21) Special 2014, Pages: 30-36
The circuit transfer function is calculated from the modes of operation which is given as,
G(s) = V0(s)/Vi(s)
G(s) = 50/2e-10s5 + 2e-7s4 +5e-4s3 + 0.4s2 + 250s +1, 50000
The step response is plotted using the above transfer function as shown in the fig.8.
-4
8
Ste p Re s pons e
x 10
7
6
Amplitude
5
4
3
2
1
0
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
Tim e (s e c)
Fig. 8: Step response of Relift circuit.
From the step response, Kp and Ti values are tuned using Ziegler-Nichols tuning which is shown below.
Table 2 depicts the values of Kp and Ti derived from the step response.
TABLE 2: Values of Kp and Ti using Ziegler Nichol's.
Kp
1.4362
Ti
0.00643
Fig. 9: Closed loop control of Relift converter Using PI controller.
Output Voltage(V)
-87.63
-87.64
-87.65
-87.66
-87.67
1
1
1
1
1
Time(s)
1
1
1
1
1
1
1
1
Time(s)
1
1
1
1
Input Voltage(V)
13
12.5
12
11.5
11
1
Fig. 10: Input voltage and Output voltage of Relift Dc-Dc converter (with Kp and Ti approximated (values)
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V. Chamundeeswari and Dr. R. Seyezhai,2014
Advances in Natural and Applied Sciences, 8(21) Special 2014, Pages: 30-36
Using Ziegler-Nichols tuning, Kp was found to be 1.4362 and Ti was calculated as 0.00643.where T is the
time constant and L is the delay time. (C.F.Hsu,I.F 2009, K.S.Tang,Kim fung man 2001, K.Ramash kumar,
Dr.S.Jeevanathan 2010, Mahdavi et al.,1997).
The fig 9 depicts the closed loop control of Relift converter using PI controller which brings a steady state
output for load changes. (Y. B.Shtessel et al.,2002, K. Ramash Kumar, S. Jeevananthan 2009, Pawan Gupta,
Amit patra 2003, J.Matas, et al., 2000). Fig 10 portrays the output voltage of Relift converter as -87V for an
input voltage of 12V with an approximated Kp and Ti values and and further increases to a high boosted output
of -186V with the real values of Kp and Ti as shown in fig.11.fig.12 shows the pulse produced from the PI
controller circuit which is given to the switch.
Fig. 11: Input voltage and Output voltage of Relift Dc-Dc converter (without approximating Kp and Ti (values)
Fig.12: Gate pulse to MOSFET.
Hardware implementation:
The Hardware implementation of re-lift DC-DC converter is depicted in fig 13 which shows the converter
circuit with the controller. The input voltage is provided using a rectified DC which is depicted as 8V.The
output voltage is highly boosted to -186.2V which is shown in the below figure14. To generate the pulse of 100
KHz for the MOSFET switch of relift converter, PIC 16F877A is used. The relift converter uses two inductors
of 10mH and four capacitors of 2 µF each.
Fig. 13: Overview of the Relift Dc-Dc converter circuit.
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V. Chamundeeswari and Dr. R. Seyezhai,2014
Advances in Natural and Applied Sciences, 8(21) Special 2014, Pages: 30-36
Fig. 14: Input and output voltage of Relift Dc-Dc converter.
From the simulation results of fig 11, it has been shown that the output voltage is boosted to a very high
value of -186V and the same has been depicted in the hardware implementation as -186.2V in fig 14. Thus the
progressive rise in multiples of input voltage is highly shown with the results.
Comparison of output voltage values of lift circuits:
Type of Lift circuit
Self lift
Relift
Input voltage(V)
12
12
Output voltage(V)
-36
-186V
The above table II depicts that the relift produces a high boost voltage compared to the primary self-lift
circuit. The self lift circuit produces an output of -36V for an input voltage of 12V whereas the output voltage
produced by relift circuit is -186V.
Conclusion:
Thus the paper depicts the design and analysis of Relift circuit and its topology thereby proving the value of
high gain rise. It also has portrayed the implementation of PI controller for the relift type which helps in
maintaining the steady state output for load changes. The proposed relift converter is a promising high gain
topology that is suited for photovoltaic applications.
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