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Transcript of 18 NEW ZV-ZCS FULL BRIDGE DC-DC CONVERTER WITH FUZZY ZV-ZCS...¢  NEW ZV/ZCS FULL BRIDGE...

  • Proceedings of the International Conference on Emerging Trends in Engineering and Management (ICETEM14)

    156-169, December, 2014, Ernakulam, India

    156

    NEW ZV/ZCS FULL BRIDGE DC-DC CONVERTER WITH

    FUZZY & PI CONTROL

    ASWATHY HARIDAS 1 ,

    SARITHA K.S 2 , AJITH K.A

    3

    1 P G Scholar, Electrical & Electronics department,

    Sree Narayana Gurukulam College of Engineering, Kolenchery, India

    2 Associate Professor, Electrical & Electronics Department,

    Sree Naryana Gurukulam College of Engineering, Kolenchery, India

    3 Assistant Professor, Electrical & Electronics Department,

    Sree Naryana Gurukulam College of Engineering, Kolenchery, India

    ABSTRACT

    DC-DC conversion technology has been developing very rapidly and DC-DC converters have been widely used

    in industrial applications. The main problem related to the conventional full bridge dc to dc converter is the large voltage

    spikes across the output diodes. Lose of ZVS will increase the losses and EMI. In order to avoid these, here a new

    ZVZCS full bridge converter is introduced. In this paper Conventional full bridge DC to DC converters and the proposed

    converters are compared and simulation analysis also included. Moreover, closed loop control using different control

    strategies is evaluated using the PI controller and fuzzy logic.

    Keywords: Zero Voltage Zero Current Switching, Fuzzy Logic Controllers, Pi Controllers, Electro Magnetic Interference

    1. INTRODUCTION

    DC-DC conversion technology has been developing very rapidly, and DC-DC converters have been widely used

    in industrial applications such as DC motor drives, computer systems and communication equipments. In this paper, a

    novel type of DC to DC full bridge converter which is having ZVZCS capability is presented. Conventional full bridge

    DC to DC converter is having the problem of large voltage spikes across the output diodes due to leakage inductance of

    the transformer. Since leakage inductor will act as a current source, it will lead to voltage spikes across the transformer

    secondary, output voltage and the voltage across the output diodes. For example, for a 300V output DC supply a 1000V

    voltage appears across the output diodes. As the switching frequency of the converter increases, the high frequency

    voltage spikes are getting intensified at the output[1]. In the meantime EMI noise may arise. Thus the output diodes have

    to withstand the voltage spikes and they get over rated. For high voltage high switching frequency applications,

    MOSFET’s are mostly used. MOSFET should be switched under zero voltage for the reliable and robust operation.

    Zero Voltage Switching (ZVS) topology, allows operation at a higher frequency and at higher input voltages

    without sacrificing efficiency. Lose of ZVS will increase the losses and EMI increases, efficiency decreases. In order to

    avoid these, here a new ZVZCS full bridge converter is introduced. The converter is operated under soft switching by

    using an auxiliary circuit and the voltage across the output diode bridge is clamped. In this paper, the performance of the

    INTERNATIONAL JOURNAL OF ELECTRICAL ENGINEERING &

    TECHNOLOGY (IJEET)

    ISSN 0976 – 6545(Print) ISSN 0976 – 6553(Online) Volume 5, Issue 12, December (2014), pp. 156-169

    © IAEME: www.iaeme.com/IJEET.asp Journal Impact Factor (2014): 6.8310 (Calculated by GISI) www.jifactor.com

    IJEET

    © I A E M E

  • Proceedings of the International Conference on Emerging Trends in Engineering and Management (ICETEM14)

    156-169, December, 2014, Ernakulam, India

    157

    conventional full bridge converter with the novel ZVZCS full bridge converter. The controller is used to improve the

    dynamic performance of DC-DC converter by achieving a robust output voltage against load disturbances. This paper

    presents the performance of PI , Fuzzy controllers. Fuzzy controllers are well suited to nonlinear time-variant systems

    and do not need an exact mathematical model for the system being controlled. The fuzzy logic controller determines the

    operating condition from the measured values and selects the appropriate control actions using the rule base created from

    the expert knowledge.

    2. OVERVIEW

    The ZVZCS full bridge DC to DC converter is implemented and operational principles are analyzed here. The

    proposed full bridge converter is compared with the conventional full bridge DC to DC converter under the conditions of

    identical supply DC voltage and frequency. Also different control strategies adopted for the closed loop control of the

    converter is also implemented and analysed. Simulations are presented to verify the validities of the proposed inverter.

    There are a number of simulation software available and the most efficient tool is the MATLAB. Hence, the Simulink

    part of the MATLAB is employed. Various control strategies like fuzzy and PI control are also adopted and obtained the

    simulation results.

    2.1. CONVENTIONAL FULLBRIDGE CONVERTER

    The full bridge inverter converts DC to AC and the output is a quasi-square wave voltage. Transformer step up

    the output voltage of the full bridge inverter. The output rectifier rectifies the output obtained in the secondary side of the

    transformer and we get a DC output.

    Fig.1. Conventional full-bridge converter

    The main problem related to the conventional full-bridge DC/DC converter is the voltage spikes across the

    output diodes due to the transformer leakage inductance. Basically, the leakage inductance of the transformer acts as a

    current source and this will leads to the voltage spikes across the output diodes. Theses spikes get intensified as the

    switching frequency of the converter is increased. Thus, the diodes should be designed overrated in order to withstand

    these voltage spikes. And also, these spikes significantly increase the EMI noise of the converter. This fact makes the

    topology not very practical for high frequency, high voltage applications. In battery charger applications, after the battery

    is fully charged, the load is zero. So, the converter might be operating at absolutely no-load for a long period of time and

    the converter should be able to safely operate under the zero load condition. In case of conventional full-bridge PWM

    converters, the ZVS is achieved by utilizing the energy stored in the leakage inductance and this is used to discharge the

    output capacitance of the MOSFETs. So, the range of the ZVS operation will highly depend on the load and the

    transformer leakage inductance. Thus, the conventional converter is not able to operate under ZVS condition for a wide

    range of load variations. The loss of zero voltage switching will lead to extremely high switching losses at high switching

    frequencies and very high EMI due to the high di/dt and can also cause a very noisy control circuit, which leads to shoot-

    through and loss of the semiconductor switches. The ZVS range can be extended by increasing the series inductance, but

  • Proceedings of the International Conference on Emerging Trends in Engineering and Management (ICETEM14)

    156-169, December, 2014, Ernakulam, India

    158

    having a large series inductance will limit the power transfer capability of the converter and it will reduce the effective

    duty ratio of the converter.

    2.2. PROPOSED ZV/ZCS FULLBRIDGE DC/DC CONVERTER

    The proposed converter rectifies the voltage stress problems related to the conventional full-bridge DC/DC

    converter. The proposed ZVZCS full bridge DC to DC converter topology provides zero current switching (ZCS) for the

    output rectifiers, and zero voltage switching (ZVS) for the full bridge inverter.

    Fig.2. Proposed ZVZCS full-bridge converter

    Output diode rectifiers are turned on when the current zero in the transformer leakage inductance. In the

    proposed ZVZCS converter, an auxiliary circuit is used to produce the reactive current for the full bridge switches and

    this ensures the ZVS. This auxiliary circuit will be working independently of the system operating conditions and is able

    to guarantee ZVS at all operating conditions. The role of the auxiliary circuit is to provide reactive current for the full-

    bridge semiconductor switches, which guarantees zero voltage switching for the semiconductor switches.

    3. MODES OF OPERATION

  • Proceedings of the International Conference on Emerging Trends in Engineering and Management (ICETEM14)

    156-169, December, 2014, Ernakulam, India

    159

  • Proceedings of the International Conference on Emerging Trends in Engineering and Management (ICETEM14)

    156-169, December, 2014, Ernakulam, India

    160

    Fig.3. Modes of operation (i) Mode 1 (ii) Mode 2 (iii) Mode 3 (iv) Mode 4(v) Mode 5

    (vi) Mode 6 (vii) Mode 7

    3.1 Mode 1: (t0≤ t ≤ t1) In mode1, S1 is discharging and S2 is charging in this mode.VAB is nearly zero. is is not sufficient to forward

    bias the secondary diodes. (i) shows the active components during this mode of operation .