A ZVS Bidirectional dc-dc Converter Phase Shifted ...

IEEE - International Conference On Advances In Engineering, Science And Management (ICAESM -2012) March 30, 31, 2012

700

A ZVS Bidirectional dc-dc Converter Phase Shifted SPWM control for Hybrid Electric and Fuel cell Automotive Application T.Kokilavani

Dr.G.Selvakumar

Dr.C.Christober Asir Rajan

Research Scholar

Principal

Associate Professor

AEC

Department of EEE

Salem

Pondicherry Engineering College

India

Puducherry - 605 014

ngselva [email protected]

asir [email protected]

Anna University Coimbatore India [email protected]

Abstract-The

current-voltage-fed

bidirectional

dc-de

presented

control

scheme

automatically

determines

and

converter, which refers to a current-fed inverter at low voltage

compensates for the circuit delay. Also, it achieves ZVS

side and a voltage-fed inverter at high voltage side, can realize

without

zero voltage switching (ZVS) for the switches with the use of phase-shift (PS) technology for future hybrid electric vehicle and fuel cell automotive applications will be presented in this paper. However, the current-fed switches suffer from high voltage spike and high circulating conduction loss. In order to solve these problems,

a

novel

phase-shift

plus

sinusoidal

pulse

width

any

additional

external

components

or

timing

calculation circuits SHE technique is extended to apply in three-phase four-leg inverters [3]. The control signals of the fourth leg's switching components are calculated based on the idea of Fourier decomposition. The selective triplen harmonics are set to some specified values, which are equal to the triplen

modulation (SPSM) control ZVS bidirectional dc-de converter is

harmonics produced by other legs. The proposed control

proposed in this paper. By adopting active clamping branch and

scheme provides a low-impedance-current loop for unbalanced

PSP technology, the converter can realize ZVS for all switches in

current in essence. A family of high-efficiency bucktype dc

a wide range of load variation while input or output voltage

dc converters that is well suited for high-voltage applications

varies. In addition, a novel control strategy with one port voltage regulation and another port current regulation is proposed to make

energy

bidirectional

conversion

freely.

The

operation

principle is analyzed by a 27V/270V conversion.

Phase-Shift Plus Pulse Width Modulation (PSP), Pulse Width Modulation (PWM), Zero Voltage Switching (ZVS).

I

achieved using a three-level commutation cell, with decreased switching losses obtained from a ZVS technique. A PWM

Keywords-Active Clamping, Bidirectional dc-de Converter,

I.

[4]. The proposed converters combine the advantages of a reduction of the voltages across the switches, which was

resonant single switch isolated converter has been proposed [5],

which utilizes the transformer leakage inductor and

secondary capacitor as a resonant tank to derive the power, instead of a large filter inductor. The sinusoidal-shaped current reduces the switch turn-OFF loss and primary snubber loss.

Introduction

Moreover, the voltage stress on secondary diodes is clamped

N recent years, the development of high power isolated

to

bidirectional

Therefore, it features a simple structure, low cost, and high

important topic vehicle,

dc-dc

converters

because

uninterruptible

of

(BDC)

has

become

the requirements of

power

supply

(UPS),

an

electric

distributed

the

output

voltage

without

any

dissipative

snubber.

efficiency, promising for small-power high output voltage applications.

generation, energy storage, and aviation power system[I]-[9].

A novel repetitive controller that can be directly combined

Recent developments in hybrid automobile industry have

with an SPWM inverter is proposed [6]. The proposed

created a massive requirement for various power electronic

controller design method enables robust stability by restricting

converters. The present trend is to use more and more

the

electronic appliances in automobiles. An increasing demand

while heavily attenuating the high-frequency gains .A modular

exists for the dc appliances in future automobiles, and the

cancellation

within

medium-and-low-frequency

range

fuel cell stack and dc-dc converter concept has been presented

standard 14 V bus will not be suitable to supply the power

[7] it has been shown that the standard fuel cell stack can be

requirements for those dc loads.

reconfigured into several sections with smaller cell count, each

A bidirectional PWM converter by adopting multipulse

supplying an isolated power module in the dc-dc converter,

converter's topology, [I] which is suitable for high-power

resulting in a high-performance system. The proposed system

applications with the merits of low switching frequency,

has been shown to be fault tolerant and can continue to operate

perfect harmonic performance,

and little reactance filter.

Integrated ZVS control technique has been presented for PWM buck converters under DCM/CCM boundary [2]. The

at a reduced power level under fuel cell or power module faults. The concepts presented in [8] clearly have the potential to improve the power density of high-power converters with

ISBN: 978-81-909042-2-3 ©2012 IEEE

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IEEE - International Conference On Advances In Engineering, Science And Management (ICAESM -2012) March 30, 31, 2012 galvanic isolation.

701

The converter prototype, have the high

efficiency and high power density can be obtained at the same time. A new architecture of the delay-line-based window ADC is proposed to meet wide output voltage range. Dual-mode error control achieves fast dynamic response for a voltage mode digitally controlled synchronous buck converter [9]. In a typical UPS system, the battery is charged when the main power source is normal and discharges to supply power in case of the failure of lose of the main power source. In the aircraft high voltage direct current (HVDC) power supply system, when the 250V HVDC generators is in gear, it charges the 25 V battery and supplies the 25 V key load by the BDC, and when the generator is in failure,

the 25 V battery

discharges to supply 250 V key load by the BDC. The high low voltage conversion and electrical isolation are necessary in the above-mentioned conditions. The current-voltage-fed BDC is suitable for such system due to its high voltage conversion ratio and low current ripple in the current-fed port. A dual active full bridge dc-dc converter was proposed for the

Figure I.

Typical topological arrangement of a hybrid fuel cell vehicle drive train

high power BDC, which employs two voltage-fed inverters to drive each side of a transformer. Its symmetric structure enables the bidirectional power flow and ZVS for all switches. A dual active half bridge current-voltage-fed soft-switching bidirectional dc-dc converter was proposed with reduced power components. However, the current stresses in switches and are asymmetric. When the voltage amplitude of two sides

The circulating conduction loss is reduced, however, it results the asymmetric stresses in the main switches and a bias of the magnetizing current which decreases the utilization of the

transformer.

So,

it

is

not

suitable

for

high

power

bidirectional conversion.

of the transformer is not matched, the current stress and circulating conduction loss become higher. In addition, these

1,

converters cannot achieve ZVS in a wide range of load variation

while

input

or

output

voltage

varies.

These

disadvantages make them not suitable for large variation of

v.

input or output voltage condition. An asymmetric bidirectional dc-dc converter with PWM plus Phase shift (PPS) control was proposed. Bi-directional power management is an important attribute of a dc-dc converter used in several applications. In a hybrid automobile, there

are

many

electrical

loads grouped

into

two main Figure 2.

categories depending on the voltages they use. Fig. 1 shows the typical arrangement of the power electronic modules in fuel cell vehicle. The main traction motor is powered from the high voltage bus (around 500 V). There are also low voltage loads that need to be powered from a voltage source in the range of 40-50 V. The low voltage source could be a battery or a stepped down voltage from the high voltage battery pack or any source. When the high voltage source is a cell, the low voltage source is normally a battery pack. During the start up time of the vehicle, the low voltage battery pack delivers power to the fuel cell system and to the main motor, and the low voltage loads. in the vehicle, the dc-dc converter works in the up conversion mode. Once the fuel cell is ready, it provides power to the main motor and low voltage loads. The

It is proposed that a current-voltage-fed PSP ZVS BDC based on a current-fed half bridge and a voltage-fed half bridge guaranteeing volt-second balance of the transformer by its capacitors Ca and

avoid the voltage spike, achieve ZVS of Sl and S2, and also restrain the start-inrush current .By PWM control of and , the amplitude of Vab and Vcd well matched while input or output voltage varies, which can reduce circulating conduction loss, and realizes ZVS in a wide range of load variation. The control strategy of Phase-shift (PS) SPWM is realized by two individual controllers.

low voltage battery is also charged from the fuel cell if

system must have the capability to deliver power in both directions depending on the state of the fuel cell or the battery voltage.

Cb in this paper, as shown in Fig.2The

converter utilizes an active clamping branch Sal Sa2 and Cc to

II.

required. During this time, the dc-dc converter works in the down conversion mode. Thus, a dc-dc converter used in the

Main circuit of PSP ZVS BDC

Operation Principle

The BDC has two operation modes. It is defined as Boost mode

when

energy

flowing

from

side

to

side

and

the

counterpart is defmed as Buck mode. Before analysis, the following assumptions are given: 1) All the active power

ISBN: 978-81-909042-2-3 ©2012 IEEE



702

devices are idea switches with parallel body diodes ( and ) and parasitic capacitors , The inductance and are large enough to be treated as two current sources with value of 0.5 II ; 3) The transformer is an ideal one with series leakage inductor . III.

Control Strategy

The control strategy of PSP is realized with two individual controllers, as shown in Fig. 3. The BDC is difficult to control stably because of the different small signal characteristics in different operation mode. In this paper,

a novel control

strategy with one port voltage regulation and another port current regulation is proposed. By sampling one port voltage and another port current, the controller can realize the voltage regulation

and

transmission

current

direction,

regulation respectively.

in The

different

energy

control

strategy

unifies the control system, simplifies the control circuit, and makes energy bidirectional conversion free. The block diagram of phase-shift angle controller is shown

Figure 4.

Sinusoidal Pulse Width Modulation Control Technique For Forward Control

in Fig. 3, which is used to control the magnitude and direction of the transmitted power. When the voltage value on side is higher than the reference, the converter operates in buck mode and is controlled by single current closed-loop. The constant current setting for the low voltage side is decided by the current limiter, which can be regulated according to the charge condition of the battery. When the voltage value on side is lower than the reference, the converter will operate in boost mode, and be controlled by current and voltage dual closed loops. The maximum discharge current of the battery is limited by the current limiter. By selecting appropriate control parameters, this variable structure controller can improve the steady and dynamic performance of the system. Fig. 4 shows the Sinusoidal Pulse Width Modulation Control Technique for Forward Control. Fig. 5 shows the Sinusoidal Pulse Width Modulation Control Technique for Reverse Control. Figure 5.

Sinusoidal Pulse Width Modulation Control Technique For

Duty cycle regulation

Reverse Control

Simulation Results

IV.

Inpu.t voltage

. _ .. _ ...

.

... �

-

,.

..

, :, : .

�

... . . .

r'-";

..

; " - - ..

..... . .

... ...:. .. ...

.

•

_.

-

;-. ......�

. . ...

-

, .. - ... �-. -.�

"! ..

- ...

Cll!"rentlimiter Figure 3.

Control scheme

Figure 6.

Input Voltage vs time

ISBN: 978-81-909042-2-3 ©2012 IEEE


...: . . . . ,,-,.

. .

. .


Output voltage ' .. ... - :' . ... ... �- .. ,

i.o ... 1

.•

,•

•

, ! ... . .

.

. .. .. � ......

.... ... �... i

...

--=... !

...

,�

�' -

v.

/

Analysis Of Simulation Results

In SPWM control the input of 27V has been applied. This

..

. - ... ! ...... ..

... . -

.. .. ..

.

has been boost into 270V at the time period of 2.5 msec, This technique will find a useful application in air craft, For example 270V DC supply is needed for the operation of

/

certain equipment in aircraft, instead of using a number of batteries to provide 270V DC, by using this technique; we can

.

, ,

use a 27V DC supply which can boost it up to 270VDC.

,

.' J' ,

,

.. �.�

703

..

.

. ..

II.

-..

'" _ '"� � •

'"

I

.. .

I

. " .. . .. ..

VI.

" .. "

"

Conclusion

A novel ZVS bidirectional dc-dc converter with PS

i

SPWM control is proposed in this paper, which has the following advantages. •

Figure 7.

•

V oltage across p11mru:y

\i'....

All switches realize ZVS in a wide range of load variation while input or output voltage varies.

Output vs time

The

PS

SPWM

control

reduces

the

circulating

current.

inding

•

The converter avoids the voltage spike of and with the use of an active clamping branch

•

J �

,. II

i" !:

If

[,

,I

� I'I :l

'I

II]

/,

t:I �,

I

�

control

strategy

which

has

realizes high

energy

steady

conversion

and

dynamic

performance,

,- ,

These merits are verified by a 27 V/270 V,

:,1

concluded; this kind of converter is extremely suitable for

References

VII. [I]

1\

�l

l

I

It can be

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Figure 8.

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ISBN: 978-81-909042-2-3 ©2012 IEEE
