Five-Level Single-Phase Grid-Connected Converter for Renewable Distributed Systems

8/16/2019 Five-Level Single-Phase Grid-Connected Converter for Renewable Distributed Systems

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Five-Level Single-Phase Grid-Connected

Converter for Renewable Distributed Systems

Presented by B MALLIKARJUNA REDDY

Roll No!!"#$""%

Under the esteemed

guidance of Dr.N.VISWANATHAN

Professor & '(D in !!! De)t*

N+,

1


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./S,R.C,

Recently, converter topologies employing a high frequency transformer in order toreduce size &weight .

The trade-off between high efficiency &low cost is a hard task for these architectures

because they require several power stages .

n low power applications - International standards recommends the use of grid

connected power converters without any galvanic isolation.

Transformer less architectures in low power distributed systems are recommended

The proposed work is a novel five level converter topologies that are used in!" #$%% based single phase grid connected converters.

imulation of these topologies are carried out by using '(T%()*imulink.

2


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3

(/0!C,+1!S

#omparison of + and + topologies in terms of T+,

leakage current and parasitic capacitor voltage.

To balance the voltages across the # link capacitors by closed

loop operation.


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PRESENTATION

OUTLINE/.

0TR12#T10

3. '1$ 14 1!$R(T10 14 '% T1!1%15$

6. 5R #100$#T$ '% T1!1%15$

7. !"-5R #100$#T$ '% T1!1%15$

. #%1$ %11! 1!$R(T10 14 + T1!1%158

. '2%(T10 R$2%T (0 #210

9. #10#%210 4


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5

+N,R(D2C,+(N


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PV SYSTEMPOWER

CONVERTER

TRANSFORMER POWER GRID

Single phase converter with Transformer :

/enefits : afety , leakage current reduction, no dc current in:ected in to the grid.

Single phase multi level converter without

Transformer:

P Vsystem

MLIP!e"#"$%

rawbacks : %arge size, heavy weight , e;pensive and overall conversion efficiency

&

INTRODUCTION cont<


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'

Single Phase (H-Bridge )Cascaded Multilevel Inverter

The main advantages of cascade inverter are as follows=

/. #ompared with the diode clamped and flying capacitor inverters, it requires

the least number of components to achieve the same number of voltage

levels.

3. oft switching techniques can be used to reduce switching losses and devicestresses

isadvantage of single phase cascaded '% is the usage of large number of

switches, this can be over come by hybrid topologies + and + .

)ecause of above statements, this work proposes + and + '% topologies

1utput voltage waveform

INTRODUCTION cont<


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(

H 5 T O P O L O G Y

H 6 T O P O L O G Y

INTRODUCTION cont<


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)

3odes of ()eration of Pro)osed

,o)ologies


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1*

1(L,.G!L!1!L S

% S$ S4 S5 S6

1dc % " " % "

1dc7$ " " " % %

" " " % % "

-1dc7$ " % " " %

-1dc " % % " "

3odes of o)eration (f '6 to)ology

witching states of + topology


3odes of o)eration cont8**

S%

S4 S5

S$

S6

+m


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11

P3 Pulses of '6 to)ology generated by SP3



12/4012

voltage

level

S% S$ S4 S5 S6 S9

1dc 1 " " % % 1

1dc7$ % " " % " 1

" " " % % " *

-1dc7$ " % % " % >

-1dc " % % " % 1

3odes of o)eration of '9 to)ology


witching states of + topology


S%

S$

S4 S5

S6

S9

+m


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13

P3 Pulses of '9 to)ology generated by SP3


3 d f ti t


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.t f s :%6;'"1= R:%"""?=

3:"*>@

O,t-,t+t/#e

0 5

t-#y

O,t-,t+t/#e

0 &

t-#y

14

3odes of o)eration cont8

3 d f ti t


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'A/R+D! C.S!C.D!D 32L,+L!1!L +N1!R,!RS B'6&'9 +,' R -L(.D

.t f s :%6;'"1=R:%"""?=3:"*>@E

15

The voltage stresses are low in + topology

The switching losses are low in + topology ?T+ is low in + topology

+owever the total number of switches consisting in the + topology is low compare with + topology.

3odes of o)eration cont8


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1&

GR+D C(NN!C,!D

3L+ ,(P(L(G+!S

GR+D C t d 3L+ tGR+D C t d 3L+ t


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1'

GR+D Connected 3L+ cont8**

5eneral hybrid multi level inverter connects to the single phase grid=

(.# voltage source act as a grid with required nominal voltage of 36>" and > +z frequency.

The filter must be designed precisely.

• To reduce the voltage distortions when delivers to the load

• To stabilize the energy output

• To achieve sinusoidal shape and precise value.


GR+D Connected 3L+ cont


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1(

UTPUT FILTER DESIGN:


+@:AB

+@:AB@R*%A where B3CpiCfDBdamping factor=

)y substituting 3B@R*%ADD @3AB@/*R#A are in the above equation then,

+@:AB/-:@/*3A

E +@:AEB

Fhen the increase then magnitude E +@:AE decreases .f phase angle increase while damping decrease.

n time domain f G/ that causes under damping

f H/that causes over damping and

f B/ that causes critical damping .

)ut when B@/*AB>.9>9 ,then the filter circuit act as low pass filter .


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2*

$ffectiveness of the filter in + topology

converter output

voltage waveform

T+ before filter

is 66.I?

converter output

voltage waveform

T+ after filter

is >.J?




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2121

$ffectiveness of the filter in + topology

converter output

voltage waveform

T+ before filter

is 67.9>?

converter output

voltage waveformT+ after filter

$s 1.1*




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/efore filter

B1o

.fter filter

B1g

Fundamental ,'D Fundamental ,'D

445*$1 4$*>9 4$@*$1 "*#6

/efore filter

B1o

.fter filter

B1gFundamental ,'D Fundamental ,'D

44%*>1 45*@" 4$>*>1 %*%"

!ffectiveness of the filter in '9 to)ology

!ffectiveness of the filter in '6 to)ology

n compression of both topologies with grid connection the followingobservations are made

+ and + topologies gives better performance with less variations

4urther research continues for the both topologies with source of !"-#ell

instead of a dc source



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23

P1-GR+D C(NN!C,!D

3L+ ,(P(L(G+!S

P1-GR+D Connected 3L+ cont8**


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24

F$#: PV #"$% & t-#y s$m,$ %$/#"/m

P1 GR+D Connected 3L+ cont8**

56T-#y " &6Topology



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25

718

728

738

" pvB-R sC pv@7A

F$# : E9,$+/et C$",$t 0 /PV e

P1 GR+D Connected 3L+ cont8**



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2&

I-+$s /% ,""et

Is $s -;t ,""et " s;"t $",$t ,""et

I%$s %$%e ,""et

Is$s "e+e"se s/t,"/t$ ,""et 0 t;e %$%e

9 $s t;e ;/"#e 0 eet""1 to the proposed circuit during operation

!"-panel takes short circuit current as 6.I>9( and open circuit voltage is />>>" and

series resistance is assumed to be >.//79 K.



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Topology nverter 1utput "oltageL"oM

5rid "oltageL"gM

!arasitic capacitor

voltage

L" pM

%eakage current

Li%M

4undamental ?T+ 4undamental ?T+

+ 666./" 63.JJ 63I.7" /.>> >I.9" /.//>>(

+ 63J.J" 66.J 63I." >.JI 667.3" >.77J(

1utput results of !" grid proposed topologies@+ and +A

@(t f sB/N+zD"dcB6I>"D'B>.I9A

2'

The main aim of this !ro"ect is to address the !ro#$ems%iL and

v)H ,'D& associated 'ith the transformer $ess s(stems• Nte : At,/y 1A e//#e ,""et /,ses ;/"m0, eHet t;e

system< -/"/s$t$ /-/$t" +t/#e m,st ?e e9,/ t t;e m$%-$t +t/#e

Vm (s per the leakage current and voltage balancing point of view the + had outstanding

features, but it not enough.

o that we are go to the closed loop operation for + topology.


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)LOSED LOOP )ONTROL O P*+GRID ,- TOPOLOG.

2(

Closed loo) cont8**


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2)2)

/locI scheme of the balancing control of the mid)oint voltage

)

Closed loo) cont8**


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3*

and configurations providing the same voltage V '! to the full bridge rails. n

@aA, the + capacitor is discharging, and in @bA, the % capacitor is discharging.

Closed loo) cont8**


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C HS = C LS = C

C d(V dc−V MP ) = I dc − I D5 dt

C dV MP = I dc − I D5− IMP

dt

dV MP = − IMP

dt 2C

31

# capacitor circuit employed for the analytical

analysis of the "oltage )alancing

In asymmetrical conditions ,V '! OV dc / 3 .

Closed loo) cont8**


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MVC !"$# $ /se 0 / -s$t$+e FB

grid ! FB " #$S% provides & MP

grid ' FB " #(S% provides & MP)

32

/locI diagram )resentation of closed loo) o)erationClosed loo) cont8**


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33

/locI diagram )resentation of closed loo) o)eration


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34

SI/ULATION RESULTS

(2,P2, R!S2L,S D2! ,( CL(S!D L((P C(NF+G2R.,+(NResults cont8**


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35

(2,P2, R!S2L,S D2! ,( CL(S!D L((P C(NF+G2R.,+(N(F '9 ,(P(L(GA

)on0erter out!ut0o$tage %*o&

T,D 123425

Grid 0o$tage %*g& T,D 164375

Results cont8**


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3&

!arasitic ca!acitor0o$tage %*!&1-%9"*61

ha$f of the su!!$(0o$tage %*dc8&1%9"*61

Results cont8**


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3'

$ea9age current iL1"*"59>$.

57-e -8 &7-e -8 &7se% -8*

*.2

*.4

*.&

*.(

1

1.2

1.11

*.44

*.*4

e//#e ,""et

Results cont8**


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3(

+nverter

(ut)ut 1oltage

B1o

Grid 1oltage

B1g

Parasitic

ca)acitor

voltage

B1)

LeaIage

current

BiL

3id-)oint

voltage

B1m)Fundamental ,'D Fundamental ,'D

4$>*>1 %@*#% 4$>1 "*@6 -%9"*61 "*"59>$. %9"*61

Closed Loo) Control (f P1-GR+D '9 ,o)ology


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3)

C(NCL2S+(NS

4rom the table it can be concluded that parasitic capacitance is

greatly reduced which can reduce the voltage stress on the

switching devices.

t is also concluded that the leakage current is also greatly

reduce from /.//( to >.>7I3(.

)ecause of reduction in the leakage current grid performance is

improve to the >.9? of T+.

4rom above conclusion it can be stated that + topology is

recamended for the transformer-less !" P5R system.


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TAN> YOJ

Documents

Five-Level Single-Phase Grid-Connected Converter for Renewable Distributed Systems