Bidirectional DC-DC Converter For Electric Vehicle Application

Using FLC Controller

Taskeen M Challigid

, Manish Rathi

Department of Electrical & Electronics Engineering,PDA college of Engineering & Technology, Gulbarga, India

Keywords: Three level unidirectional MLI, AC_DC_AC conversion, Bidirectional Power flow capability, Reduced

components, T-type inverter.

Abstract: In this, A design of bidirectional DC-DC converter is proposed which is suitable for electric and hybrid

vehicles applications. The main advantages of the proposed structure are that it can utilize different energy

sources with different voltage-current characteristics. Moreover, the proposed structure is bidirectional, and

battery could be charged in braking mode too. These features along with high voltage gain make this converter

an excellent alternative for DC-DC converters in electric vehicles. A speed control structure is added to this

in order to control the speed of the motor using Fuzzy Logic Control (FLC) and the performance of the

proposed controller with conventional Proportional Integral (PI) controller under steady state and transient

conditions are compared in terms of peak overshoot, settling time, torque ripples, etc. the simulation is carried

out in MATLAB/Simulink software.

1 INTRODUCTION

Due to significant challenges including

contaminants in the air, global warming, and

increasing demand for fossil fuels, the electric vehicle

(EV) sector is expanding quickly nowadays. The

primary components of EVs are power converters and

drive systems, and several research initiatives are

carried out to increase the density and efficiency of

these converters. There are several different varieties

of EVs, including fuel cell-electric vehicles (FCEVs),

hybrid electric vehicles (HEVs), and pure electric

vehicles (PEVs). Each of these cars has an electric

motor that operates using batteries that are wired

through voltage source converters (VSCs) to the

motor. On the contrary, a large DC voltage is

necessary at the motor side with regard to the direct

link among the power supply of the electrical drive

and its voltage. As a result, a DC-DC converter

should be used to transform the weak voltage from

the battery side into a high voltage DC-link. Indeed,

the battery's output voltage drops as the level of

charge, or SOC, of the battery increases. The DC-DC

converters used in electric vehicles (EVs) should be

https://orcid.org/0009-0007-9645-6502

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able to function in a bidirectional mode. The

converter can send power from the battery side to the

motor side and the other way around thanks to this

characteristic. As a result, the battery is able to be

charged while the vehicle is in braking mode. High

efficiency, compact size, little battery current ripples,

and light weight are some of the most crucial factors

that should be taken into account while designing

these converters. The two types of bidirectional DC-

DC converters are isolated and non-isolated

architectures. A lightweight, highly reliable 3kW

standalone DC-DC converter with bidirectional

operation is presented for electric cars (Ansari, P.

Cheng et al,2016). With this converter, there are fewer

switching components needed for power transfer in

both directions. Contrary to other isolated converters,

this converter is less efficient. For fuel cell cars, a

clamp separated, bidirectional DC-DC converter is

shown that does not employ a snubber circuit.

Zero switching is employed on the converter's

primary side and secondary side, respectively.

Regarding bipolar DC micro grids, a brand-new

reversible step-up DC/DC converter with high

voltage gain and bipolar DC outputs is described.

M Challigid, T. and Rathi, M.

Bidirectional DC-DC Converter For Electric Vehicle Application Using FLC Controller.

DOI: 10.5220/0012504700003808

Paper published under CC license (CC BY-NC-ND 4.0)

In Proceedings of the 1st International Conference on Intelligent and Sustainable Power and Energy Systems (ISPES 2023), pages 24-31

ISBN: 978-989-758-689-7

However, the lack of an isolating transformer places

restrictions on this converter's voltage conversion

factor. A boost-powered converter with multiple

inputs and outputs that offers both gentle switching

and a high voltage gain is offered. This converter is a

good contender for fuel-cell systems because to these

properties.

This paper proposes a bidirectional converter

capable of handling multiple inputs and multiple

outputs for electric vehicle applications. Various

types of sources is used in the proposed converter

with different VI characteristics. Due to the switched

capacitor cell, the proposed converter is capable of

high voltage conversion ratio. And also due to the

bidirectional property, the regenerative braking can

be applied and increase the running time of the

vehicle. A speed control loop controls the speed of the

pmdc motor of the electric vehicle using Fuzzy Logic

Control (FLC).

2.SYSTEM DESCRIPTION

The block diagram of the proposed inverter is given

below in Fig 1.

Fig 1.

Here DC supply is given in order to charge the

battery, as switch S1 is ON and switch S2 is OFF. In

this battery acts as a load. When the supply is not

sufficient, the battery starts to discharge, as switch S1

is OFF and switch S2 is ON. In this battery acts as

source. The speed of the motor and dc voltage is

provided to the speed control loop which control the

bidirectional converter output voltage so that the

measured speed follows the reference speed. We are

using PI & FLC in the speed control loop. The

proposed dc-dc converter operates in three

operational modes of power supply with battery to

load, Power supply to battery mode, and regenerative

braking mode.

Fig 2

A. Power supply with battery discharging to

load

In this state, the converter's linked load is

powered concurrently by the battery and other input

sources, as well as by the connected loads itself.

Switch ST (the transfer switch), Power electronic

switch S3 and Sb (the braking switch), and the

remaining switches are all ON in this mode. In this

mode, the switches regulate the output voltage (VO).

The switching pulses of the proposed converter for

this mode is provided below:

Fig 3

1) Time interval 0<t<D1T:

In this mode, the battery is utilised along

with energy sources are used to power the load

attached to the converter. Switch ST continues to be

ON, power electronic switch S3 & Sb was

continuously OFF, and the remaining switches are all

ON in this and the battery is providing supply to the

load. The equivalent circuit of the proposed converter

for this mode is provided below:

Bidirectional DC-DC Converter For Electric Vehicle Application Using FLC Controller

Fig 4

2) Time interval D1T <tVin1).

S0 is operating, S1 is turned OFF, and the

remaining circuit elements are equivalent to those in

the preceding mode in this mode. The inductor is

charged by the primary energy source, such a fuel

cell. The inductor voltage is equal to the voltage that

is generated of the main source, and the current

through the inductor rises proportionally with a less

steep slope. (Vbat>Vin1). The equivalent circuit of

the proposed converter for this mode is provided

below:

Fig 5

3) Time interval D2T <t<D3T:

So is operating in this mode and the power

electronic switches S1 & S2 are turned OFF. D2 is in

forward bias and the inductor current starts to flow

and is maintained constant:

LP12

where I

LP12

is the inductor current of from previous

interval D2T <t. The equivalent circuit of the

proposed converter for this mode is provided below:

Fig.6

4) Time interval D3T <t

In this, S1, S2 and S0 are OFF and D2 is in

forward bias.

VL1=-VC

VL1=Vi

VL1=Vi-VC

From the above relations the average input

voltage is provided below

= V

in l

× D

+ ∑

i=2

in l

– D

i-1

) + V

bat

n+1

–

)

By simplifying, we get the voltage gain of the

converter for one switching cycle is provided below:

= 1/1-D

The equivalent circuit of the proposed converter

for this mode is provided below:

Fig 7

B. Battery charging mode by input sources

The battery is recharged in this mode by the input

sources. While load is not connected and the battery

has to be charged, this mode is active. Switches S1,

ST, and Sb remain ON, whereas switch S2, ST, and

ISPES 2023 - International Conference on Intelligent and Sustainable Power and Energy Systems

Sb remain continuously OFF. All other switches are

ON. Each of the three stages for the converter , as

illustrated below:

Fig 8

1) time interval 0 <t

S1 and S0 are both turned ON in this switching

condition. As a result, the S3 and D3 are reverse

biassed and have zero currents. The supply source

(Vin1) charges the inductor L, increasing its current

linearly. The equivalent circuit of the proposed

converter for this mode is provided below:

Fig 9

2) time interval D1T <t<D2T:

In this mode, the switch S0 starts operating, the

S1 is OFF, the D2 is forward biased, and the inductor

voltage is zero. The equivalent circuit of the proposed

converter for this mode is provided below:

Fig 10

3) time interval D3T <t

So is turned OFF and the inductor starts

discharging via S3 and charges the battery. The

voltage across the inductor is given as

VT+(1-D

)(V

-V

bat

)T=0

by simplifying the equation

bat

=1/1-D

C. Regenerative Braking Operation

The vehicle itself can function as a power source

and retain its energy in its batteries when it is braking

or travelling downward. The transducer's

effectiveness is increased by this mode of operation.

So, to achieve this situation, a switch is placed on the

rear route to provide a flickering mode for

conversion, an elevated voltage for the voltage of the

batteries, and battery energy conservation. The

switches S1, ST and S0 remain perpetually OFF, S3

is perpetually ON, and the remaining switches are in

operation. Sb regulates the battery's output voltage

(Vbat.) in this mode. The converter functions as a

straightforward buck converter while in the braking

condition.

Time interval 0 <t<D1T:

Sb is activated in this mode. The voltage

difference between Vo and Vbat equals the voltage

level of the inductor.

Bidirectional DC-DC Converter For Electric Vehicle Application Using FLC Controller

Fig 11

1) Time interval D1T <t<D2T:

In this state, Sb is off and the inductor's voltage is

set to Vbat. The inductive energy is lost in the battery

due to the opposing direction of the inductance and

battery voltages, and the current flowing through the

inductor decreases linearly as a result. The voltage

across the inductance is:

=-V

bat

The average voltage of the inductor in a period

must be zero, so:

-V

bat

)T+(1-D

)(-V

bat

)T=0

bat

Fig 12

3.PROPOSED CONTROL

STRATEGY

The DC reference voltage (𝑉

∗

𝑑𝑐

) is provided

below is calculated with the help of reference speed.

dc =

The reference voltage (𝑉

∗

𝑑𝑐

) is compared with the

actual load voltage (𝑉

𝑑𝑐

) and the error voltage (𝑉

𝐸

) is

provided below as

= V

- V

The generated error is given to proportional–

integral (PI) control, which provides the reference

voltage 𝑉

𝐶

as follows

(k) = V

(k - 1) + K

(k) – V

(k – 1)} + K

(k)

The pulses generated for the boost converter is as

follows

{If 𝑀

𝐶

< 𝑉

𝐶

gating pulse is HIGH}

{If 𝑀

𝐶

≥ 𝑉

𝐶

gating pulse is LOW}

Fuzzy Logic Controller

An approach to thinking that mirrors human

reasoning is fuzzy logic. The strategy mimics how

humans make decisions, which require considering

all middle options between the digital signals YES

and NO. Despite the fact that fuzzy logic (FL) may

not produce accurate thinking, it is beneficial

nonetheless. The FL's architecture is broken down by

modules that convert system inputs into fuzzy sets.

Another module that contains rules supplied by the

user's IF-THEN statements. a fuzzy inference engine

that uses IF-THEN rules and fuzzy interpretation on

the inputs to emulate human reasoning.

Defuzzification is a different module that converts the

fuzzy set acquired by the interfering engine into a

crisp value. The membership function operates on

sets of variables that are ambiguous. A fuzzy set can

be graphically represented and linguistic terms can be

quantified using membership functions. Simple

model parameters can be utilised because complex

functions do not increase output precision.

Table I. Knowledge based rules

Output

NVL

Zero

PVL

When the error, is negative, the measured voltage

is higher than reference voltage, then the fuzzy

controller will provide Low as output and when the

error is positive, the measured voltage is lower than

the reference voltage, then the fuzzy controller

increases the duty ratio (D).

ISPES 2023 - International Conference on Intelligent and Sustainable Power and Energy Systems

4.SIMULATION SETUP &

RESULTS

The simulation parameters for the proposed

inverter are provided below in Table II:

TABLE II Simulation Parameters

Input

Voltage

150 V

Input

power

6KW

Switching

Frequency

KHZ

Inductor

10µH

Coupling

Capacitor

50µF

Output

Capacitor

30µF

Battery

voltage

180V

Battery

capacity

100Ah

Motor

parameters

600V,

6KW,

1500 rpm

The simulation circuit of the bidirectional converter

with PI controller is provided below:

Fig 13 Simulation circuit of 3 leg 5 level inverter

The battery is discharging and provides supply to

the motor load (mode 1) from t=0 to 0.2s. The dc

voltage source is connected at t=0.2s and provides

supply to both motor and battery (mode2).

Regenerative braking is applied to the motor at t=0.4s

and energy stored in motor windings is fed back to

battery (mode 3). The battery voltage and %SOC is

provided below:

Fig 14

In this, battery is discharging in mode1 and the

%SOC is reducing until t=0.2s and in mode 2, the

battery is getting charged from dc voltage source and

hence %SOC starts to increase and at t=0.4s, the

regenerative braking is applied and the %SOC

continues to increase. The load voltage and current is

provided below:

Fig 15

During modes 1 and 2, the current flow is positive

i.e. in forward direction and in mode 3, the current

flow is reversed due to regenerative braking. The

motor speed and torque is provided below:

Fig 16

Bidirectional DC-DC Converter For Electric Vehicle Application Using FLC Controller

The speed is settled at t=0.2s in the set speed or

reference speed with PI controller. The PI controller

is replaced with fuzzy control and the speed and

torque is as provided below:

Fig 17

In this, the speed is settled at t=0.05s which is 4

times less than that of with PI controller.

A hardware prototype model of proposed

converter with input voltage of 24V, 50 Hz is

developed with 12V as battery voltage and output

voltage of 64V with load resistance of 1KΩ. The

hardware parameters is provided below in the

following Table III.

TABLE III Hardware Parameters

IRF 250N

MOSFET

200V,30A

U1560-DIODE

200-400-

600V,15A

CAPACITOR

1000 µF,

25V

TRANSFORMER

12V,1A

TLP 250- DRIVER

12V,1.5A

CD 4050 BUFFER

18V,0.32mA

12V

REGULATOR 7812

12V,1A

IN 4007 DIODE

700V,1A

ARDINO UNO

CONTROLLER

12V,20mA

Arduino uno control is used for generating the

pulses for the proposed converter and it is provided to

driver circuit (TLP 250) in order to drive the mosfets

IRF 250. The source voltage from the rectifier is

provided in the following waveforms:

Fig 18

In this the source1 voltage is around 22V and the

battery voltage is provided below:

Fig 19

In this, the battery will be charging when source1 is

available and when source1 is not available, the

battery starts discharging and provides energy to the

load. The load voltage is provided below:

ISPES 2023 - International Conference on Intelligent and Sustainable Power and Energy Systems

Fig 20

The load voltage of the proposed converter is around

64V.

5. CONCLUSION

In this, a bidirectional converter is designed with

multiple input multiple output and the modes of

operation of the proposed converter was analysed. A

control structure is formulated to reduce the voltage

distortions caused by varying loading conditions. A

switched capacitor cell is used to increase the voltage

conversion ratio. In my work we are compared

Proportional Integral (PI) controller and Fuzzy Logic

controller (FLC) in terms of speed of electric vehicle,

peak overshoot, settling time and torque ripples. After

comparing we come to know that Fuzzy Logic

controller is better than Proportional Integral

Controller, as the speed is 4 times increased than PI

controller. The regenerative braking is applied and

the energy from motor load is fed back to battery and

charges the battery. A hardware prototype model was

developed and the operation of the proposed

converter is verified with the results.

REFERENCES

S. Mohammadsalehian, F. Sedaghati, R. Eskandari and E.

Shokati Asl, "A Modified Double Input Z_source

DC_DC converter for Standalone PV/Battery System

Application," in Proc. 11th International Power

Electronics, Drive Systems and Technologies

Conference (PEDSTC), Tehran, Iran, 2020, pp. 1-7.

T. sharifi, A. Haji Biglo, M. Mirsalim, S. Farzamkia and J.

S. Moghani, "An asymmetrical cascaded single-phase

quasi Z source multilevel inverter with reduced number

of switches and lower THD," in Proc. 11th International

Power Electronics, Drive Systems and Technologies

Conference (PEDSTC), Tehran, Iran, 2020, pp. 1-5.

F. Sedaghati, S. Mohammadsalehian, H. Shayeghi, and E.

S. Asl, " A configuration for double input Z-source DC-

DC converters," 9th Annual Power Electronics, Drives

Systems and Technologies Conference (PEDSTC),

Tehran, Iran, 2018, pp. 449-455.

Haji Biglo, S. Farzamkia, S. Farhangi and H. Iman Eini,

"Utilization of Soft-Switched Boost Converter

for MPPT Application in Photovoltaic Single-

Phase Grid-Connected Inverter," in Proc. 11th

International Power Electronics, Drive Systems

and Technologies Conference (PEDSTC),

Tehran, Iran, 2020, pp. 1-6.

S. H. Hosseini, R. Ghazi, S. Farzamkia and M. Bahari, "A

Novel High Gain Extendable DC-DC Bidirectional

Boost-Buck Converter," in Proc. 11th International

Power Electronics, Drive Systems and Technologies

Conference (PEDSTC), Tehran, Iran, 2020, pp. 1-6.

Ansari, P. Cheng, and H.-J. Kim, "A 3 kW Bidirectional

DC-DC Converter for Electric Vehicles", Journal of

Electrical Engineering Technology, vol. 11, no. 4,

pp. 860-868, 2016.

S. Rezayi, H. Iman-Eini, M. Hamzeh, S. Bacha, S.

Farzamkia, ”Dualoutput DC/DC boost converter

for bipolar DC microgrids”, IET Renewable Power

Generation,vol.13, pp.1402-1410, 2019.

B. V. Kumar, R. K. Singh, and R. Mahanty, "A modified

non-isolated bidirectional DC-DC converter for

EV/HEV's traction drive systems," in 2016 IEEE

International Conference on Power Electronics,

Drives and Energy Systems (PEDES), 2016, pp. 1-

E.Babaei, O.Abbasi, “Structure for multi-input multi-

output dc–dc boost f converter”, IET Power

Electron., vol.12, pp. 1-11,2015.

F. Sedaghati, S. Mohammadsalehian, H. Shayeghi, and E.

S. Asl, " A configuration of double input Z-source

DC-DC converter for standalone PV/battery system

application," Journal of Energy Management and

Technology, 2(3), pp.60-69.

Bidirectional DC-DC Converter For Electric Vehicle Application Using FLC Controller