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Journal for Studies in Management and Planning

Available at http://edupediapublications.org/journals/index.php/JSMaP/

e-I SSN: 2395-0463

Vol ume 02 I s s ue 12

Dec ember 2016

Available online: http://edupediapublications.org/journals/index.php/JSMaP/ P a g e | 102

Hybrid Cascade of Various Levels of Power Management Battery Applied To

Electric Vehicles Adapter

1. T. JHANSI,2. B. SHANKAR

1PG Scholar, Department Of EEE, Sri Sai Educational Society's Group of Institutions, Kodad.

2Assistant Professor, , Department Of EEE, Sri Sai Educational Society's Group of Institutions, Kodad.

Abs tract: Now a day the electrical energy utilization is

increasing day by day like in industries, home appliances,

and in electric vehicles. In electric vehicles the electrical

energy is required to drive the motor drives. The electrical

energy is given to electric drives through batteries like

lead-acid, lithium, etc. Batteries are connected in series to

provide energy cause circuit damage, voltage imbalance

and less utilization of energy. This is because of different

chemical characteristics and state of charge (SOC) of

batteries. To avoid these disadvantages we are using

Hybrid Cascaded multilevel converter. In this converter

we have a half bridge arm and a H-Bridge. Half bridge

arms are including the batteries into the circuit or bypass

the batteries from the circuit. Half bridges are produce

stair case dc output voltages from batteries and H- Bridge

is used to convert dc voltages to AC output voltages. The

output voltage is multilevel voltage which has less

harmonics and lower dv/dt. To smoothen the output

voltages and currents the pulse width modulation

technique used is space vector pulse width modulation

technique. And the current control technique is fuzzy

logic control technique both provide lesser total harmonic

distortions. By these techniques the utilization of battery

energy is increased, voltage balance and fault-tolerance

also improved. The simulation is done in MATLAB

and experimental results are observed to know the

performance of the converter.

Keywords: Fault Tolerance, MATLAB, State of

Charge, Total Harmonic Distortion, Voltage

Balance.

INTRODUCTION

In electric vehicle the batteries plays a crucial role to

provide the energy for the running of motor drives. These

batteries are like lead-acid and lithium batteries. Normally

these batteries are connected in series to provide the energy.

But in the case of series connection if one battery is damaged

or disconnected the whole system does not work. The

batteries are having the different chemical characteristics and

they have the different state of charge (SOC) and different

terminal voltages. In the series connected circuit the charging

and discharging of the batteries are done by the same current.

Due to different chemical characteristics and state of charge

the batteries are charged the any one battery is reached to its

cut off voltage the whole circuit is unable to provide charging

and the battery stack is not work in a proper manner. So to

avoid this problemthere are two types of equalization circuits

for battery charging and discharging. Generally there are two

types of equalization circuits for batteries overcharging and

over discharging. Due to different terminal voltages the

equalization should done to avoid terminal voltage

imbalance.

In the two equalization circuits one consumes the redundant

energy on parallel resistance to keep the terminal voltages of

all cells equal. For example in charging course, if one cell

arrives at its cut-off voltage, the available energy in other cell

must be consumed in their parallel connected resistance. By

using this equalization circuit the energy utilization is very

low. So another kind of circuit to realize the energy

equalization which consists of number of inductances or

transformers and converters. In this the higher voltage

batteries the energy can transfer to the lower voltage batteries

to improve the energy utilization ratio [1]-[5]. But the

disadvantage is need of inductances or isolated transformers

and converters. The cost and size of the circuit is increases.

The losses are also increasing so some zero current and zero

voltage switching techniques are also used to reduce the loss

of the equalization circuit [6].

Fig1. Exis ting Circuit.

Multilevel converters are widely used in medium and high

voltage motor drives. In these multilevel converters the

isolated capacitors and dc sources are replaced with the

batteries. The batteries are combined in cascaded in series

combining with the converters instead of connecting series

directly. In multilevel converters cascaded multilevel

converter is used to realize the terminal voltage balance and

to connect the batteries in cascaded manner. The H-bridge

converter output voltage is a multilevel which is suitable to

run the motor drive [7]. In the cascaded multilevel converter

the cascaded topology has the Better fault tolerant ability by

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Journal for Studies in Management and Planning

Available at http://edupediapublications.org/journals/index.php/JSMaP/

e-I SSN: 2395-0463

Vol ume 02 I s s ue 12

Dec ember 2016

Available online: http://edupediapublications.org/journals/index.php/JSMaP/ P a g e | 103

its special design. In this converter there is no limitation on

the number of cascaded cells the output voltage is very high

voltage which is useful to drive the high voltage motor drive

by using less voltage battery cells. By comparing the H- bridge converter with the traditional circuit the voltage

equalization and terminal voltage balance is easy and is very

suitable.

Hybrid cascaded converters are designed to realize terminal

voltage equalization more than the H-bridge converter. In

multilevel converters some ultra capacitors are used instead

of the batteries which can have high voltage. A hybrid

cascaded multilevel converter is designed in this paper to

realize the voltage equalization and terminal voltage balance.

This hybrid cascaded multilevel converter can also realize the

charge and discharge control by the same current. A required

output is multilevel output voltage is obtained at H-bridge

output side to connect to the motor drive or to the power grid.

As the output of the H-bridge is multilevel ac voltage there

are no other requirements like inverters or chargers. The

output of the hybrid cascaded multilevel converter is

proportional to the number of batteries connected in

cascaded. So to get the fewer harmonic i.e for pure sinusoidal

output voltage the number of batteries is connected should be

increase. In this paper simulation and experimental results of

hybrid cascaded multilevel converter are obtained to verify

the performance.

I . PROPOSED CIRCUIT TOPOLOGY

In figure1 the existing circuit shown for voltage balance by

using energy transfer circuit and inductance is connected in

between every two nearby battery cells. The number of

switching devices in this existing circuit are 2*n-2 and the

Fig2. Hybrid cascaded multilevel converter.

inductances are n-1.in this existing circuit for voltage balance

and terminal voltage equalization we should have an inverter

to give ac output voltage to the motor drive and a charger to

recharge batteries. Fig shows hybrid cascaded multilevel

converter consists of mainly two parts; they are half bridges

and H-bridge. Left part shows the half bridge and the right

part shows the H-bridge. All the batteries are connected in

cascaded by using the half bridges and the H-bridge is

connected to convert the dc voltage waveforms to ac output

voltage waveforms. The controls of batteries are done by half

bridges i.e to include the batteries into circuit or bypass

depends upon the dc bus voltage change.

The power electronics switches used in proposed circuit

are of two types. In half bridges the switches are MOSFETS

and in H-bridge the switches are GTOs or IGCTs. MOSFET

operates at higher frequencies and at lower voltages as they

are lower voltage devices. The IGCTs are operates at base

frequency and at higher voltages as they are higher voltage

devices.

Fig3. Three phas e cas caded multilevel converter.

The three phase converter topology shown in figure3. In

each phase the number of batteries are n and the number of

switching devices are 2*n and the half bridges are connected

for every single battery cell.

I I. CONTROL TECHNIQUE OF HYBRID

CASCADED CONVERTER

In the hybrid cascaded multilevel converter the switching

states of switches in half bridges are given by

Sx = 1 upper switch is on and lower switch is off

= 0 lower switch is on and upper switch is off

When Sx=1 the upper switch is conducted means the

battery is connected into the circuit and is in discharging

mode, when Sx=0 the lower switch is conducted then the

battery is neither in charging mode nor in discharging mode.

When upper switch is conducted the instantaneous discharge

power from the battery is given by

P  Sx Ux i

Here Ux is the battery cell voltage, i is the charging current

in the circuit. In the circuit the charging and discharging of

the batteries are realized by the current direction. The

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Available at http://edupediapublications.org/journals/index.php/JSMaP/

e-I SSN: 2395-0463

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Dec ember 2016

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switches are controlled by the Space Vector pulse width

technique in half bridges.

A different approach to SVPWM is based on the space

vector representation of voltages in the d, q plane. The d, q

components are found by Park transform, where the total

power, as well as the impedance, remains unchanged. Fig4:

space vector shows 8 space vectors in according to 8

switching positions of inverter, V* is the phase-to-center

voltage which is obtained by proper selection of adjacent

vectors V1 and V2.

Fig4. Inverter output voltage space vector.

Fig5. Determination of Switching times.

The reference space vector V* is given by Equation (1),

where T1, T2 are the intervals of application of vector V1

and V2 respectively, and zero vectors V0 and V7 are selected

for T0.

VTz  V1T1V 2T2 V 0(T /2)V 7(T /2)

In H-bridge converter the pulse width modulation

technique used is hysteresis pulse width modulation

technique.

I II. FUZZY LOGIC CONTROL TECHNIQUE

Fuzzy logic control is a multi-valued logic which

Fig6. Fuzzy input and output.

Fig7. Current control scheme for battery charging.

Ibrahim mamdani proposed three steps procedure to create

fuzzy controller

1. Fuzzification

2. Rule evolution

3. Defuzzification

Fuzzification means converting of crisp values to fuzzy

sets by using membership functions then rule evolution is

application of the fuzzy rules for the inputs and

defuzzification is the converting of the fuzzy sets to crisp

values. The current control is done by a closed loop control

technique in charging and discharging process of the

batteries. The charging and discharging of the batteries is

done by current directions.

I V. LOSS EVOLUTION

In existing circuit and in proposed circuit there are two

types of energy losses. Switching losses and conduction

losses, the switching losses are depends on the current and

voltage stress applied on the switch with the switching time

period. Conduction losses are depends on the current flowing

through the switch and the on resistance of the switch. The

switching and conduction losses are quite different in the

existing circuit and in proposed circuit. The following

equations give the loss calculations. In hybrid cascaded

multilevel converter the energy losses are given by equation

resembles the human thinking. The fuzzy logic application is Jloss

 Js

B  Js H  Jc B  Jc H (2)

suitable when there is any ambiguity in deciding the output

results. In fuzzy technique the output can get with nearly as

equal to the decision making of the human. Fuzzy control

technique is fast growing technique as compared with P, PI,

Where Js_B, Js_H are switching losses of half bridges and H- bridge. Jc_B, Jc_H are the conduction losses of the half

bridges and H-bridge. In existing circuit the energy losses are

given by

PID controllers. Fuzzy logic is not like computers software Jloss

 Js

T  Js I Jc T  Jc I (3)

which understands only binary values or concrete values like

1.5, 2.8 etc. it is like human thinking and gives decisions like

human resemblances’.

Where Js_T, Js_I are switching losses of energy transfer circuit

and inverter while Jc_T, Jc_I are the conduction losses.

Fuzz