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High Efficiency Modified Pulse-Width Modulation Bidirectional Converter for Medium Power Drives

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International Journal of Application or Innovation in Engineering & Management (IJAIEM),Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com

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									International Journal of Application or Innovation in Engineering & Management (IJAIEM)
       Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 1, Issue 2, October 2012                                         ISSN 2319 - 4847




             High Efficiency Modified Pulse-Width
             Modulation Bidirectional Converter for
                    Medium Power Drives
                                  A.Amalin Rishma1, P.Rajarajeswari 2, M.Sasikumar 3
                         1
                         PG Scholar, Jeppiaar Engineering College, Chennai, Tamil Nadu, India – 600 119
                     2
                      Asst.Professor, Jeppiaar Engineering College, Chennai, Tamil Nadu, India – 600 119
                         3
                             Professor, Jeppiaar Engineering College, Chennai, Tamil Nadu, India – 600 119




                                                            ABSTRACT
In this paper, a high efficiency PWM bidirectional ZVT converter with coupled inductor is introduced. Soft switching condition
is achieved with the help of two auxiliary switches and coupled inductor. Moreover, the presence of coupled inductor provides
significant reduction in converter volume. Since all the converters are implemented on a single core. The proposed converter
employs a coupled inductor with same winding turns in the primary and secondary sides. In step-up mode, the primary and
secondary windings of the coupled inductor are operated in parallel-charge and series-discharge to achieve high step-up voltage
gain. In step-down mode, the primary and secondary windings of the coupled inductor are operated in series-charge and
parallel-discharge to achieve high step-down voltage gain and thus high efficiency is achieved for full line voltage range. The
proposed bidirectional converter is fully analyzed for both step-up and step-down modes. Finally, a 50-100 -V prototype circuit
is implemented to verify the performance for the efficient drive system.
Keywords: Bidirectional dc-dc converter (BDC), Zero Voltage Transition (ZVT), Pulse Width Modulation (PWM),
Metal Oxide Semiconductor Field Effect Transistor (MOSFET).

    1. INTRODUCTION
Nowadays the development of bidirectional dc-dc converter (BDC) has become an important topic in power
electronics. Bidirectional ZVT converters are used to transfer the power between two DC sources in either direction.
These converters are widely used in industrial applications, such as hybrid electric vehicle energy systems
uninterrupted power supplies, Efficiency drive system, fuel-cell hybrid power systems, PV Hybrid power systems,
Battery chargers and Satellite. In those application bidirectional converter control the power flow between the dc bus
and the low-voltage sources and back up batteries, fuel cells, and super capacitor are act as the energy storage element
[4]. BDC are capable of reversing the direction of current flow between two dc sources thereby, maintaining the
voltage polarity between the dc sources. Various Bidirectional converters (BDC) can be classified into non isolated
and isolated converters. In isolated type is used for grounding the supply system. Transformer is needed for isolated
type converter which increases the cost, volume and losses. In case of non isolated type of converter does not require
any isolation and high voltage ratio. Forward and fly back converters are the isolated type of converters and non
isolated BDC converters are such as BUCK, BOOST, BUCK-BOOST, CUK, SEPIC and Zeta. In order to reduce the
reactive component size and cost high frequency operation of BDC is desirable. Soft switching techniques are used to
reduce the switching losses, switching stress and reduce the Electro Magnetic Interference [5]. Soft switching
techniques are used for overcoming the hard switching problem. Zero voltage transition and Zero current transition
are two techniques which incorporate a soft switching function. Moreover ZVT techniques can eliminate the turn on
capacitive losses and thus MOSFETs are preferred.

    2. PROPOSEDBIDIRECTIONAL CONVERTER DESCRIPTION
In the proposed converters the idea of coupled inductors are used for create soft switching .Full duty cycle can be
achieved based on the power flow direction [1]. No extra voltage and current stress on the main switches and the ease
of control are the other properties of proposed converter.


Volume 1, Issue 2, October 2012                                                                                     Page 94
International Journal of Application or Innovation in Engineering & Management (IJAIEM)
       Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 1, Issue 2, October 2012                                         ISSN 2319 - 4847




          Figure 2.1 Circuit diagram of proposed converter for (a) step down converter (b) step up converter

The proposed converter is composed of two main switches S1 and S2, two auxiliary unidirectional switches Sa1 and
Sa2, a snubber capacitor Cs, and two coupled inductors L1 and L2 with a turn ratio of n2/n1(L2 = (n2/n1)2L1). The
coupled inductors can be modeled as a combination of a magnetizing inductance (LM), an ideal transformer with
corresponding turn ratio (n2/n1), and a leakage Inductance (Llk). The magnetizing inductance LM is employed as the
converter filter inductor. In proposed converter method bilateral filter is used for reducing the ripple voltages. The
proposed converter has two modes of operations. Such as step up mode and step down mode, the following assumptions
are made.
1) All elements are ideal, and the converter is operating at steady-state condition.
2) Magnetizing inductor LM is large enough to assume that it’s current (ILM) is constant in a switching cycle.
3) The input and output voltages are constant and modeled by two voltage sources V1 and V2, respectively.
4) The turn ratio of coupled inductors is n (n2/n1 = n).

   2.1 Step Up Mode of Operation:
When the power transferred from battery to high voltage side it behaves as a step up converter. To avoid the inrush
current, the output voltage is always higher than the input supply voltage. In step up mode of operation voltage
increases and current decreases slowly. S1 and sa1 are the main and auxiliary switches .Before starting conduction, all
the switches are off and the magnetizing inductor current (ILM) is transferred to the output voltage through the body
diode of S2. Therefore there is no current flow in the windings of the ideal transformer in the model and the CS voltage
is output voltage (V2).

   2.2 Step Down Mode Of Operation:
When the power flows from high-voltage side to battery it behave like step down converter .To avoid the inrush current
input supply voltage higher than the output voltage. In step down mode energy storage placed on low voltage side so
voltage get reduces and current get increases. Here S2and Sa2are the main and auxiliary switches. Before starting
conduction, all the switches are off and (ILM) is transferred to the v1 through the body diode of S1.Therefoe no current
flows through the ideal transformer winding and the Constant supply voltage is input voltage (v1)

    3. CONTROL STATEGY
The PWM control strategy is used for bidirectional ZVT converter. Normally single pulse and multiple pulse width
PWM schemes are used for this type of converter [2]. In the ZVT PWM converter, a coupled inductor serving as the
resonant inductor is used to transfer the resonant energy back to input source. PWM techniques are particularly
attractive high voltage conversion ratio applications [1]. Figure shows the block diagram of the proposed converter
control circuit.




Volume 1, Issue 2, October 2012                                                                                Page 95
International Journal of Application or Innovation in Engineering & Management (IJAIEM)
       Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 1, Issue 2, October 2012                                         ISSN 2319 - 4847




                                     Figure 3.1 Block diagram of Control strategy

The converter operation mode is determined by the enable signal V Enable. When Venable is low, the BDC operates in
step up mode, and when V Enable is high, the BDC operates in step down mode. The overall control block diagram
consists of two main control blocks, namely, the PWM controller block and the adapting block. The PWM controller
block includes a PWM controller which is applied to BDCs. This control block consists of two feedback loops, such as
outer voltage loop and inner current loop. Since the converter input current is not almost constant, a low-pass filter is
applied to the inductor current to estimate the average current. The adapting block plays the role of adapting the output
pulse of PWM controller to the proposed converters. In step up mode of operation, channel 0 of the multiplexers is
chosen. Thus X2 and X3 are sent to S1 and Sa1, respectively. Similarly, in step down mode of operation, channel 1 of
multiplexers is chosen. Thus, X2 andX3 are sent to S2 and Sa2, respectively.

    4. SIMULATION RESULT AND PRACTICAL IMPLEMENTATION
The simulation model for step up and step down modes of non isolated bidirectional ZVT dc-dc converter and their
voltage and current waveform are obtained. A battery module working at the low-voltage side is employed as an
energy-storage element, whose voltage rating is 50 V. The high-voltage side is 100 V for boost operation. These
simulation results for step up and step down modes of non isolated bidirectional ZVT dc-dc converter with a are
obtained by using the simulink in MATLAB and their voltage and current waveform are obtained by using VLV=50V,
VHV=100V, Lm=360 µH, Clv=5µF, Chv=450µF. The two MOSFET switches and two auxiliary switch acts as diodes are
used in the ZVT bidirectional converter design. The circuit model of non isolated step up D-C to D-C. converter is
shown in Fig 4.1.DC input voltage is 50V as shown in fig.4.2.The circuit model of non isolated step up converter
output voltage is 100v as shown in fig.4.3. Current waveform ids is shown in the fig.4.4The square Pulse width is
applied with constant frequency and driving pulses for MOSFETS M1 and M2 is shown in the fig 4.5..The coupled
inductor act as the transformer. The transformer is used to stepped up the voltage and the resultant voltage is given to
the auxiliary switch thus used for achieve the soft switching condition thereby voltage stress and current stress get
reduced .The two parallel connected capacitor act as the bilateral filter is used to reduce the voltage ripple and is
connected across the R-load. The simulation model for D.C to D.C converter operating in step down mode is shown in
Fig 4.6.The driving pulses for MOSFETS M1 – M2 are shown in fig.4.7. Simulink model of the proposed dc-dc
converter with a motor load is shown in the fig.4.11 and the waveform for speed measured is shown in the fig.4.12.




  Figure 4.1. Simulink model of the proposed non isolated bidirectional ZVT PWM dc-dc converter for step up mode




Volume 1, Issue 2, October 2012                                                                                Page 96
International Journal of Application or Innovation in Engineering & Management (IJAIEM)
       Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 1, Issue 2, October 2012                                         ISSN 2319 - 4847




                                  Figure 4.2 Input voltage of step up converter




                                 Figure 4.3.Output voltage of step up converter




                                 Figure 4.4 Output current of step up converter




                            Figure 4.5 Switching pulse and voltage across MOSFET




Figure 4.6.Simulink model of the proposed non isolated bidirectional ZVT PWM dc-dc converter for step down mode



Volume 1, Issue 2, October 2012                                                                       Page 97
International Journal of Application or Innovation in Engineering & Management (IJAIEM)
       Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 1, Issue 2, October 2012                                         ISSN 2319 - 4847




                             Figure 4.7 Input voltage of step down converter




                            Figure 4.8 Output voltage of step down converter




                        Figure 4.9 Switching pulse and voltage across MOSFET




                           Figure 4.10 Output current of step down converter




                  Figure 4.11 Simulation model of step up zvt converter with motor load.




Volume 1, Issue 2, October 2012                                                            Page 98
International Journal of Application or Innovation in Engineering & Management (IJAIEM)
       Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 1, Issue 2, October 2012                                         ISSN 2319 - 4847




                                       Figure 4.12 Motor speed for step upmode




                             Figure 4.13 motor torque for step up and step dowm mode




                                     Figure 4.14 Motor speed for step down mode

    5. CONCLUSION
This paper has presented a non isolated bidirectional ZVT PWM converter is used for low to medium power
applications. In these converters soft switching condition for all semiconductor elements is achieved only by adding two
auxiliary switches and coupled inductors for full duty cycle range. A battery module working at the low-voltage side is
employed as an energy-storage element, whose voltage rating is 50 V. The high-voltage side is 100 V. Soft switching of
power switches reduces the switching loss and improves the efficiency. It can be observed that the conversion efficiency
of the proposed converter is around 89%–92%.Moreover, it provides the ripple free current characteristics in low
voltage side regardless of load condition. This characteristic can enlarge the lifetime of the low voltage source.

REFERENCES
[1] Sasikumar M. and Chenthur Pandian S. (2012), ‘Modified Bi-directional AC/DC Power Converter with Power
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[2] F. Shang and Y. Yan, “Novel forward-flyback hybrid bidirectional DC-DC converter,” IEEE Trans. Ind.
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[3] T.-F. Wu,Y.-C. Chen, J.-G. Yang and C.-L. Kuo, “Isolated bidirectional full-bridge DC-DC converter with a
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[4] R.-J.Wai, C.-Y. Lin, andY.-R. Chang, “High step-up bidirectional isolated converter with two input power
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[5] S. Dwari and L. Parsa, “An efficient high-step-up interleaved DC-DC converter with a common active clamp,”
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[6] C.Benin and Dr.M.Sasikumar “Simulation and Analysis of Soft-Switching CCM Boost Converter With High
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[7] J. Zhang, J.-S. Lai, R.-Y Kim, and W. Yu, “High-power density design of a soft-switching high-power
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[8] T.Umaranjani and Dr.M.Sasikumar “ A New Soft Switching Scheme for an Isolated Bidirectional Full-Bridge Dc-
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Volume 1, Issue 2, October 2012                                                                               Page 99
International Journal of Application or Innovation in Engineering & Management (IJAIEM)
       Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 1, Issue 2, October 2012                                         ISSN 2319 - 4847

[10] K. T. Chau, T. W. Ching, and C. C. Chan, “Bidirectional soft-switching converter-fed DC motor drives,” in Proc.
     IEEE Power Electron. Spec.Conf., 1998, pp. 416–422.

AUTHOR

            A.AMALIN RISHMA is currently pursuing the M.E Degree from Jeppiaar Engineering College, Anna University,
            Chennai, India. She received her B.E degree in Electrical and Electronics Engineering in ST.Xavier’s Catholic College
            of Engineering, Anna University, Chennai India in 2011. Her current research interests include Induction Motor
            Drives, DC-DC Converters, and Inverters.

            P.RAJA RAJESWARI has received the Bachelor degree in Electrical and Electronics Engineering from Mepco schlenk
            engineering college, Madurai Kamaraj University, India in 2004, and the M.E degree in power electronics from
            Sathyabhama University, in 2006. Her current research interests include Induction Motor Drives, DC-DC Converters,
            and z source Inverters.
              Dr.M.Sasikumar has received the Bachelor degree in Electrical and Electronics Engineering from K.S.Rangasamy
              College of Technology, Madras University, India in 1999, and the M.Tech degree in power electronics from VIT
              University, in 2006. He has obtained his Ph.d. degree from Sathyabama University, Chennai. Currently he is working as
              a Professor and Head in Jeppiaar Engineering College, Chennai Tamilnadu, India. He has published papers in National,
              International conferences and journals in the field of power electronics and wind energy conversion systems. His area of
interest includes in the fields of wind energy systems and power converter with soft switching PWM schemes. He is a life member
of ISTE.




Volume 1, Issue 2, October 2012                                                                                          Page 100

								
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