-
8/11/2019 btech-vssut
1/4
2 1 2
FPGA
I m p l e m e n t a t i o n of
MPPT
Using
Variable
S t e p - S i z e
P OAlgorithm
for
PV
Applications
N o p p a d o l
K h a e h i n t u n g 1
T h e e r a y o d
W i a n g t o n g 2 P h a o p h a k
S i r i s u k 3
D e p a r t m e n t o f
C o n t r o l
a n d
I n s t r u m e n t a t i o n
E n g i n e e r i n g
2 D e p a r t m e n t o f
E l e c t r o n i c s E n g i n e e r i n g
3
D e p a r t m e n t
o f C o m p u t e r E n g i n e e r i n g
F a c u l t y o f E n g i n e e r i n g , M a h a n a k o r
n
U n i v e r s i t y
o f
T e c h n o l o g y
5 1
C h e u m - S a m p a n R d . , N o n g c h o k , B a n g k o k
,
T h a i l a n d , 1 0 5 3 0
E m a i l :
n o p p a d o l g m u t . a c . t h , t h e e r a y o g m u t .
a c . t h
a n d
p h a o p h a k g m u t . a c . t h
A b s t r a c t - T h i s
p a p e r
d e s c r i b e s FPGA
i m p l e m e n t a t i o n o f
a
Maximum
Power P o i n t T r a c k i n g (MPPT) f o r
P h o t o v o l t a i c
( P V )
a p p l i c a t i o n s .
By s l i g h t l y m o d i f y i n g t h e
o r i g i n a l a l g o r i t h m ,
a n
i m p r o v e d v a r i a b l e s t e p - s i z e P&O a l g
o r i t h m i s r e a l i z e d
a n d
e f f i c i e n t l y i m p l e m e n t e d u s i n g a
h a r d - w a r e
d e s c r i p t i o n l a n g u a g e
( V H D L ) . S u b s e q u e n t l y ,
t h e new MPPT
a l g o r i t h m
i n t e g r a t e d
w i t h
a
s o l a r - p o w e r e d
b a t t e r y
c h a r g i n g
s y s t e m
i s
i m p l e m e n t e d
o n
t h e
XC2C384 FPGA
w i t h o u t e x t e r n a l
s e n s o r
u n i t
r e q u i r e m e n t .
E x p e r i m e n t a l r e s u l t s w i t h a
c o m m e r c i a l
PV
a r r a y s h o w
t h a t
t h e
p r o p o s e d a l g o r i t h m o u t p e r f o r m s t h e c
o n v e n t i o n a l c o n t r o l l e r
i n
t e r m s
o f
t r a c k i n g s p e e d
a n d
m i t i g a t i o n
o f
f l u c t u a t i o n
o u t p u t
power
i n
s t e a d y
s t a t e o p e r t i o n T h e o v e r a l l s y s t e m e f f
i c i e n c y
i s
w e l l a b o v e 96%.
I .
I N T R O D U C T I O N
A t p r e s e n t , p h o t o v o l t a i c ( P V ) h a s
r e c e i v e d
m u c h
i n t e r e s t
a s
a
s e c o n d a r y e n e r g y
s o u r c e . T h i s i s b e c a u s e t h e
p r o b l e m
o f
f o s s i l
e n e r g y
d e p l e t i o n
b e c o m e s m o r e s e v e r e . T h e t e r n PV
r e f e r s t o
t h e
p h e n o m e n o n
i n v o l v i n g
t h e c o n v e r s i o n
o f
s u n l i g h t
i n t o
e l e c t r i c a l
e n e r g y
v i a
a s o l a r
c e l l
[ 1 ] .
P e r f or ma nc e o f
a
P V - b a s e d s y s t e m
s t r o n g l y
d e p e n d s u p o n
t h e
c a p a b i l i t y t o
d e t e r n i n e
a n
o p t i m a l o p e r a t i n g p o i n t
o f
t h e PV a r r a y a t w h i c h
t h e
maximum
p o w e r
c a n b e
d r a w n f o r
a n y g i v e n
l o a d . U n d e r
c e r t a i n
t e m p e r a t u r e
a n d
l i g h t i n t e n s i t y ,
t h e r e i s
o n l y
s i n g l e
m a x i m u m - p o w e r
p o i n t
( M P P )
i n
a n o r m a l
c e l l .
T h e r e f o r e ,
maximum
p o w e r
p o i n t t r a c k i n g
( M P P T )
o f t h e
PV
c e l l
i s
e s s e n t i a l a s
f a r
a s t h e
s y s t e m e f f i c i e n c y
i s
c o n c e r n e d .
D u r i n g
t h e l a s t
d e c a d e s ,
s e v e r a l
o f MPPT
t e c h n i q u e s
h a v e
b e e n
p r o p o s e d . Many
o f t h e m
w e r e
i m p l e m e n t e d
o n
d i g i t a l
p r o c e s s o r ,
e s p e c i a l l y ,
w i t h a s o l a r - p o w e r e d
b a t t e r y c h a r g i n g
( S P B C ) a p p l i c a t i o n .
T h e y r a n g e
f r o m
c o n v e n t i o n a l
m e t h o d s ,
s u c h a s t h e P e r t u r b a t i o n a n d O b s e r v a t
i o n M e t h o d
( P O )
[ 2 ]
i m p l e m e n t e d
o n
D i g i t a l
S i g n a l
P r o c e s s o r
( D S P )
a n d
t h e
RISC
m i c r o c o n t r o l l e r w i t h
H i l l - C l i m b i n g
M e t h o d
[ 3 ] ,
t o m u c h
m o r e
s o p h i s t i c a t e d
a r t i f i c i a l
i n t e l l i g e n t
m e t h o d s b u i l t i n
RISC
m i c r o c o n t r o l l e r ,
s u c h a s
F u z z y L o g i c
C o n t r o l
( F L C ) [ 4 ] ,
n e u r a l n e t w o r k
( A N N ) [ 5 ] .
C o m p a r a t i v e l y ,
c o n v e n t i o n a l
m e t h o d s
g i v e p o o r e r p e r f o r m a n c e s ,
b u t
t h e y
a r e e a s i e r
t o
i m p l e m e n t .
A r t i f i c i a l
I n t e l l i g e n t
m e t h o d s ,
o n t h e o t h e r
h a n d ,
p e r f o r n
b e t t e r ,
b u t
t h e i r s t r u c t u r e s a r e
g e n e r a l l y
m o r e
c o m p l i c a t e d
a n d
r e q u i r e r e l a t i v e l y
h i g h
p e r f o r m a n c e
p r o c e s s o r .
M o s t
i m p o r t a n t l y , t h e y
g e n e r a l l y l a c k t h e
a d a p t a b i l i t y
t o
d e a l
w it h t im e
v a r y i n g
e n v i r o n m e n t s .
R e c e n t l y ,
t h e i n c r e a s i n g
p e r f o r m a n c e a n d c o s t r e d u c t i o n o f
d i g i t a l
c i r c u i t s h a v e
m a d e p o s s i b l e
t h e i r
a p p l i c a t i o n s
f o r
p o w e r c o n v e r t e r
c o n t r o l
[ 6 ] .
C o m p a r i s o n w i t h o t h e r
d i g i t a l
s i g n a l
p r o c e s s o r s ,
F i e l d
P r o g r a m m a b l e
G a t e A r r a y ( F P G A )
b a s e d
s y s t e m s c o u l d
p r o v i d e
a n u m b e r
o f r u n - t i m e
a d v a n t a g e s
o v e r
t h e
s e q u e n t i a l
m a c h i n e s
s u c h
a s
a
m i c r o c o n t r o l l e r .
M o r e o v e r ,
w i t h c o n c u r r e n t
o p e r a t i o n ,
i t i s e x e c u t e d
c o n t i n u o u s l y
a n d
s i m u l t a n e o u s l y
w h i c h f a s t e r t h n D S P . T h u s
t h e
FPGA
h a s
b e e n
a p p l i e d
f o r
h i g h
s p e e d s w i t c h i n g
c i r c u i t
t o
r e d u c e e q u i p m e n t - s i z i n g [ 7 ] .
I n t h i s
p a p e r ,
w e
p r o p o s e
a n i m p l e m e n t a t i o n
o f
a d a p t i v e
MPPT
o n FPGA.
T h e a d j u s t a b l e a l g o r i t h m
i s b a s e d o n
t h e
i m p r o v e d
P&O m e t h o d .
An
XC2C384
FPGA
[ 8 ] i s e m p l o y e d
f o r t h e
a l g o r i t h m p r o c e s s i n g ,
a n d i t i s
i n t e g r a t e d
t o
a
DC/DC
b o o s t
c o n v e r t e r
t o
f o r m
S P B C .
T h e r e i s
n o
e x t e r n a l
s e n s o r y
u n i t
r e q u i r e d
t o b e a d d e d i n t o t h e
s y s t e m .
D e s p i t e
o f i t s c o s t -
e f f e c t i v e n e s s a n d
h i g h s p e e d p r o c e s s i n g ,
w e s h a l l
d e m o n s t r a t e
t h a t t h e
s y s t e m
p e r f o r n a n c e
i s
o u t s t a n d i n g .
T h e
r em ai nd er o f
t h e
p a p e r
i s
o r g a n i z e d
a s
f o l l o w s .
A
t y p i c a l
s o l a r
p o w e r s y s t e m
a n d a c o n v e n t i o n a l MPPT P&O
t e c h n i q u e
a r e
r e v i e w e d i n S e c t i o n
I I .
T h e
s y s t e m
c o n f i g u r a t i o n
o f t h e
p r o p o s e d
SPBC a n d
a d a p t i v e
MPPT
m e t h o d
a r e
a d d r e s s e d
i n
S e c t i o n I I I .
I n
S e c t i o n
I V ,
t h e
d e v e l o p m e n t
o f
a d a p t i v e
MPPT
o n
FPGA
f o r SPBC
( F P G A -
S P B C )
i s d i s c u s s e d .
T h e
e x p e r i m e n t a l
r e s u l t s a r e
s h o w n
i n
t h i s
s e c t i o n .
F i n a l l y ,
c o n c l u s i o n s
a r e d r a w n
i n S e c t i o n
V .
I I . THE MPPT
FOR
A PV ARRAY
A . C h a r a c t e r i s t i c
o f
a
P
V
a r r a y
T y p i c a l l y ,
a
PV
a r r a y
c o m p r i s e s
o f
a
n u m b e r
o f
s o l a r
c e l l s
c o n n e c t e d
i n
e i t h e r s e r i e s
o r
p a r a l l e l .
I t s m a t h e m a t i c a l
m o d e l
may
b e
g i v e n
a s
[ 5 ]
P
=
n P I p h 1 V -
n p I o e x p K K o
V(+
I T R s T
- 1 ) V
- ( V / n ,
+
I T R T ) V / R h T
I
( 1 )
w h e r e
P d e n o t e s
t h e
o u t p u t
p o w e r
( W ) ,
V
d e n o t e s
t h e
o u t p u t
v o l t a g e
o f t h e
PV
a r r a y
( V ) ,
I p h
d e n o t e s
t h e c u r r e n t
o f
t h e PV
0 - 7 8 0 3 - 9 7 4 0 - X / 0 6 / 2 0 . 0 0
e 2 0 0 6
IEEE
W3D-5
I S C I T 2 0 0 6
-
8/11/2019 btech-vssut
2/4
2 1 3
a r r a y
t h a t i s p r o p o r t i o n a l t o l i g h t
i n t e n s i t y
( A ) , I T
d e n o t e s
t h e
o u t p u t
c u r r e n t p r o p o r t i o n a l
t o
t e m p e r a t u r e ( A ) ,
I ,
d e n o t e s
t h e
a r r a y ' s
r e v e r s e
s a t u r a t i o n c u r r e n t
( A ) , R S T
a n d
R s h T
a r e
d e f i n e d
a s
t h e
e q u i v a l e n t s e r i e s a n d
p a r a l l e l
r e s i s t a n c e
( Q )
r e s p e c t i v e l y ,
n ,
i s
t h e n u m b e r
o f s e r i e s
s t r i n g
i n
t h e PV
a r r a y ,
n p
i s t h e
n u m b e r
o f
p a r a l l e l
s t r i n g
i n
t h e PV
a r r a y
a n d
K 0
i s a
c o n s t a n t .
G e n e r a l l y , t h e
c h a r a c t e r i s t i c o f
a
PV
a r r a y
c a n b e c o m -
p r e h e n s i v e l y d e s c r i b e d
b y
i t s
o p e r a t i n g
c u r v e
k n o w n
a s
I - V
c u r v e . T h i s
s p e c i f i c
c u r v e i s
u s u a l l y s u p p l i e d b y
t h e
m a n u f a c t u r e r s . I t s h o w s
t h e
r e l a t i o n s h i p
b e t w e e n
o u t p u t
v o l t a g e
a n d
c u r r e n t
o f
t h e
PV
a r r a y
a s
d e p i c t e d
i n
F i g .
1 .
I t
c a n b e
o b s e r v e d t h a t ,
u n d e r a c e r t a i n
l i g h t
i n t e n s i t y
a n d
t e m p e r a t u r e ,
t h e r e i s a
u n i q u e p o i n t
o n
t h e
I - V c u r v e a t w h i c h
t h e maximum p o w e r
c a n
b e
g e n e r a t e d
f r o m
t h e
PV
a r r a y .
T h u s , a m e c h a n i s m i s
r e q u i r e d
t o
t r a c k t h i s
s p e c i f i c
p o i n t ,
s o
t h a t t h e o p t i m a l
o p e r a t i o n
o f
t h e o v e r a l l
s y s t e m
c a n b e
a c h i e v e d . T a b l e
1
s h o w s t h e
s p e c i f i c a t i o n
o f a c o m m e r c i a l
PV a r r a y u s e d
i n
t h i s r e s e a r c h w o r k .
B .
V a r i a b l e
s t e p - s i z e
P&O
a l g o r i t h m
A s
t h e n a m e s u g g e s t s ,
t h e P&O
a l g o r i t h m
o p e r a t e s b y
p e r i o d i c a l l y p e r t u r b i n g
t h e
c o n t r o l
v a r i a b l e a n d
c o m p a r i n g
t h e
i n s t a n t a n e o u s
PV
o u t p u t
p o w e r
a f t e r
p e r t u r b a t i o n
w i t h t h a t
b e f o r e .
I n
a n
o r i g i n a l
MPPT
c o n t r o l l e r
u s i n g
P&O
m e t h o d t h e
a d j u s t m e n t
o f t h e
o p e r a t i n g
p o i n t
i s a c h i e v e d
b y
c h a n g i n g
t h e
r e f e r e n c e v o l t a g e
o f t h e c o n t r o l l e r
[ 2 ] .
H o w e v e r ,
t h e
a d j u s t m e n t
c a n
b e
m a d e
t h r o u g h
t h e
d u t y
r a t i o
D .
T h e
a l g o r i t h m
i s
s u m m a r i z e d
i n
T a b l e I I .
N o t e t h a t
V ( k )
a n d
P ( k )
a r e
o u t p u t v o l t a g e
a n d t h e
p o w e r
o f
PV w h i c h
i s
c a l c u l a t e d f r o m
V ( k ) x I ( k )
a t
t i m e
k , r e s p e c t i v e l y .
B e s i d e s ,
D
a n d
AD
r e s p e c t i v e l y
d e n o t e
d u t y
r a t i o a n d
c h a n g e
o f
d u t y
r a t i o . T o
a c h i e v e
f a s t e r
MPPT
r e s p o n s e
a n d m o r e
a c c u r a t e MPP u n d e r
d y n a m i c
e n v i r o n m e n t ,
v a r i a b l e
p e r t u r b a t i o n s t e p - s i z e ,
i . e .
AD c a n
b e
e m p l o y e d .
I n
f a c t ,
AD
c a n
b e s e l e c t e d a s
f u n c t i o n o f PV
p o w e r
a s :
AD
( k )
=
a o . 8 ( P ( k )
-
P ( k
-
1 ) )
,
( 2 )
w h e r e
a
i s t h e c o n s t a n t v a l u e t o
c o n t r o l
t h e movement
t o w a r d
t h e
MPP
a n d t h e
a c c u r a c y
o f
c o n v e r g e n c e
f o r
M P P T ,
4
i s
t h e
s i g n
o f
s t e p
d e p e n d e n t
o n
p e r t u r b a t i o n
d i r e c t i o n .
I I I .
THE
P R O P O S E D FPGA-SBC SYSTEM
A .
T h e
p r o p o s e d
c i r c u i t
c o n f i g u r a t i o n
I n
o u r
d e s i g n ,
t h e c o n t r o l l e r
p e r f o r m s
t w o
m a i n f u n c t i o n s .
F i r s t ,
i t
d e t e r m i n e s
d u t y
r a t i o D
f o r t h e
o p e r a t i o n
o f s w i t c h S
i n
s u c h
a
way
t h a t t h e
o p e r a t i n g
p o i n t
o f
t h e
PV
a r r a y
c a n b e
c o n t r o l l e d
t o w a r d
t h e maximum
p o w e r p o i n t .
T h e
c o n t r o l l e r
a l s o
h a s
t o
c o n s i s t e n t l y
d e t e c t
t h e
b a t t e r y v o l t a g e
t o a v o i d
b a t t e r y
o v e r c h a r g i n g .
When
t h e
b a t t e r y
i s
f u l l y c h a r g e d ,
t h e
c o n t r o l l e r w i l l
s w i t c h o f f t h e s w i t c h S .
T h e
c o n f i g u r a t i o n
o f
FPGA f o r SPBC
u s e d i n t h i s
r e s e a r c h
i s s h o w n
i n
F i g .
2 ,
a
k e y
o f
t h i s
p r o p o s e d s y s t e m
i s a n
a d a p -
t i v e MPPT
a l g o r i t h m
i m p l e m e n t e d
o n XC2C384 FPGA
[ 8 ]
o
u4
04
O 2
o
~ 1 1
D=1
F i g .
1 .
2 4
6 1
0
1 2
T h e
s o l a r
a r r a y g e n e r a t o r
v o l t a g e ( V ) D=O
D u t y r a t i o ( D )
I - V a n d
P o w e r c u r v e u n d e r l i g h t i n t e n s i t y
a n d
t e m p e r a t u r e .
T a b l e
I
PV a r r a y
s p e c i f i c a t i o n
( 2 5 C ,
I O O m W / c m 2 )
P a r a m e t e r s D e f i n i t i o n s
Maximum p o w e r ,
P m a x
V o l t a g e
a t
Maximum
power
p o i n t ,
V , ,
C u r r e n t
a t
Maximum
power
p o i n t ,
I , ,
T a b l e I I
MPPT
U s i n g M o d i f i e d P&O M e t h o d
i f ( ( P ( k )
-
P ( k -
1 ) ) > O )
i f ( ( V ( k )
-
V ( k - 1 ) ) > O
D = D - A D ;
e l s e
D=D+AD;
e n d
e l s e
i f ( ( V ( k )
-
V ( k - 1 ) ) > O
D=D+AD;
e l s e
D = D - A D ;
e n d
e n d
a)
bo
It 1
E v
l O . O W
l O . O V
l . O A
o p e r a t e d
a t
25MHz
c l o c k
s p e e d .
T h e b o o s t c o n v e r t e r c i r c u i t
u s e d i n
t h e
b a t t e r y c h a r g i n g
m e c h a n i s m
c o m p r i s e s
o f t w o
c a p a c i t o r s
( C l
=
1 0 0 , u F , C 2 = l O O , F ) ,
a n d
t w o
S c h o t t k y
d i o d e s
D 1
a n d D 2 .
A
p o w e r
MOSFET
B UZ 1 I
o p e r a t i n g
a t 9 7 . 6 5 k H z
i s u s e d
a s
a
s w i t c h i n g
d e v i c e
S ,
s o ,
o n e s m a l l i n d u c t o r
( L = l 5 O H )
c a n
b e
s a t i s f i e d
f o r
t h i s
r e s e a r c h w o r k .
A
c o m m e r c i a l - g r a d e b a t t e r y
b a n k w i t h r a t e d a t
1 2 V ,
5 A h r
i s
u s e d f o r t h e
p o w e r
s t o r a g e .
I n
F i g . 2 ,
t h e PV
i n p u t
v o l t a g e
a n d
c u r r e n t
a r e s e n s e d a n d
i n p u t
t o A/D c o n v e r t e r .
T h e
PWM
s i g n a l
w i t h
t h e c a l c u l a t e d
a n d
g e n e r a t e d
t h e
d u t y
r a t i o
D
s e n t
t o
t h e s w i t c h
S
t h r o u g h
a
g a t e
d r i v e r c i r c u i t .
N o t e t h a t V H D L
i m p l e m e n t a t i o n
o f t h e
p r o p o s e d
MPPT
i s
d e p i c t e d
i n
F i g .
3 .
I V .
E X P E R I M E N T A L
R E S U L T S
F o r
p e r f o r m a n c e e v a l u a t i o n ,
t h e
a d a p t i v e
MPPT s o f t w a r e
w a s
d e v e l o p e d u s i n g
V H D L
l a n g u a g e
f o r XC2C384
F P G A [ 8 ] .
U s i n g
t h e
PV
a r r a y
w h o s e
c h a r a c t e r i s t i c s d e s c r i b e d
a b o v e ,
t r a c k i n g p e r f o r m a n c e
o f
MPPT
o b t a i n e d f r o m
t h e
p r o p o s e d
MPPT a n d
t h e
c o n v e n t i o n a l P&O
a l g o r i t h m
[ 2 ]
w a s
e x a m i n e d .
I t s h o u l d b e n o t e d t h a t
a
s m p l i n g
t i m e f o r b o t h
a l g o r i t h m s
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214
T a b l e I I I
FPGA
R e s o u r c e s s u m m a r y
M a c r o c e l l s
P t e r m s R e g i s t e r s
P i n s
F u n c t i on B l o c k
U s e d U s e d U s e d
U s e d I n p u t s U s e d
1 0 6 / 3 8 4
1 9 6 / 1 3 4 4 9 6 / 3 8 4 7 4 / 1 1 8 1 9 7 / 9 6 0
( 2 8 0 % ) ( 1 5 0 % )
( 2 5 0 % )
( 6 3 0 % )
( 2 1 0 % )
M-I
1
F i g .
2 . T h e
p r o p o s e d ANN-SPBC s y s t e m .
C l o c k
2 5 N M z
Coute
8 b i t
C o m p a r a t o r _PWM
out
A r c h i e c t u r e
f o r
t h e
8 b i t _
p r o p o s e d
MPPT
D ( k )
F i g . 3 .
T h e V H DL f o r t h e
p r o p o s e d
MPPT
was s e l e c t e d t o b e I m s . T a b l e I I I d e p i c t
s
t h e FPGA
resources
summary
f o r ou r
p r o p o s e d
c o n t r o l l e r .
I n
t h e e x p e r i m e n t , t h e
l i g h t source
was t u r n e d on
a t
t
=
O s
u n d e r
l i g h t i n t e n s i t y
o f
8 5 m W / c m 2
a n d
t e m p e r a t u r e
o f
4 0 0 C .
T h e
maximum
power
p o i n t
a t
t h i s
e n v i r o n m e n t i s 8 . 0 W .
F i g .
4
( a )
a n d
( b )
s h o w
t h e
power
t r a c k i n g
r e s u l t s
o b t a i n e d
f r o m
t h e
P&O
m e t h o d
w i t h t h e f i x e d c h a n g e
i n d u t y
r a t i o ,
A D ,
o f
2 / 2 5 6
a n d 5 / 2 5 6 , r e s p e c t i v e l y . I t
can
b e
seen t h a t t h e s e t t l i n g
t i m e
( t 5 )
when
AD
=
2 / 2 5 6 i s 2 0 0 m s w h e r e a s
i t t a k e s o n l y
l O O m s when
AD
=
5 / 2 5 6 .
T h e l a r g e r
A D , h o w e v e r , g i v e s
l a r g e r
f l u c t u a t i o n s
i n o u t p u t power as s h o w
i n F i g . 4 ( b ) .
F i g .
5 s h o w s t h e r e s u l t s
o b t a i n e d f r o m t h e p r o p o s e d
v a r i a b l e
s t e p - s i z e
P&O
a l g o r i t h m .
W e
can
o b v i o u s l y see
t h a t
t h e
s e t t l i n g
t i m e
i s s u b s t a n t i a l l y r e d u c e d ,
o n l y
8 5 m s ,
a n d t h e
power
f l u c t u a t i o n s are
very
s m a l l
t h r o u g h o u t
t h e course.
T h e s e
s y s t e m p e r f o r m a n c e s
h a v e b e en
t e s t e d u n d e r more
p r a c t i c a l
s c e n a r i o s .
T h e l i g h t
i n t e n s i t y
i s s e t t o b e
v a r y i n g
w i t h
t h e v a l u e s
o f
8 5 ,
4 5
a n d
75mW/cm2 a t
0
t o
2 s , 2 t o 4 s ,
a n d
4 s
o n w a r d ,
r e s p e c t i v e l y .
T h i s
e n v i r o n m e n t
r e s u l t s i n
t h r e e
maximum
power p o i n t s o f
a b o u t
8 . 0 , 4 . 0
a n d 6 . 4 W ,
r e s p e c t i v e l y .
T h e r e s u l t s o b t a i n e d f r o m
f i x e d AD
=
2 / 2 5 6 ,
5 / 2 5 6 a n d
ou r
p r o p o s e d
s y s t e m
are
c o m p a r e d as
d e p i c t e d
i n
F i g .
6
( a ) , ( b ) a n d ( c ) , r e c e p t i v e l y .
A g a i n , t h e maximum
power p o i n t
can b e
t r a c k e d
r e l a t i v e l y
f a s t a n d w i t h s m a l l
f l u c t u a t i o n s ,
even u n d er s u c h
d y n a m i c
e n v i r o n m e n t .
T h e D C - l i n k
c u r r e n t
f l o w i n g t h r o u g h t h e
b a t t e r y
a t
s t e a d y
s t a t e i s
s h o w n
i n
F i g .
7 i n
o r d e r t o v e r i f y t h e
e f f i c i e n c y
o f t h e
o v e r a l l
s y s t e m .
T h e
s t e a d y s t a t e
power r e c e i v e d b y t h e
b a t t e r y
h a s b e e n m e a s u r e d . I t i s o b s e r v e d t h a t
t h e
b a t t e r y v o l t a g e ,
U n ] l
5
am
Math 2 0
Math
2 0
V
P=4W
DI V
V=5V/
DI V
I=400mA/
DI V
) 1 l u u m s
Ch l
J
( a )
P=4W
DI V
V=5V/
DI V
I=400mA/
DI V
( b )
F i g .
4 . T r a c k e d po w er
f r o m
P&O m e t h o d
u n d e r a
l i g h t
i n t e n s i t y o f
8 5 m W / c m 2
a n d
t e m p e r a t u r e o f 4 0 C ( a ) f i x e d
AD
a t
2 / 2 5 6 a n d ( b )
f i x e d
AD
a t 5 / 2 5 6
Math
2
VV
F i g .
5 .
T r a c k e d
power
f r o m t h e p r o p o s e d
MPPT
u n d e r a l i g h t i n t e n s i t y
o f
8 5 m W / c m 2
a n d
t e m p e r a t u r e
o f
4 0 C
2001nc IW
W
;..
14.
X / X S
V
1
* - - i -
4 - - i - - - -- , - - 4 - -- - - 4
- - , - - H . - - i - - , - - - >
- - 4 - - - - - - ,
- - > - 4 - - i - - - - - , *- -
->
- - - 4 - - - , - - 4 - - i - - 4 - - i - - , - - - i - - -
->
- - - - , - - - - - 4 - - i - - 4 - - - - - - - > - - -
..
1
/_____LE
1
2
......
. /
J
. .
.. .
:: :: :: ::
::: ::
:: :::: :::
-
8/11/2019 btech-vssut
4/4
215
1 - 4 1
( a )
( b )
( c )
Fig.
6. Tracked
power
under
dynamic
environment
( a )
fixedAD
at
2 / 2 5 6
( b )
fixed
AD
at
5 / 2 5 6
and
( c )
the
proposed
MPPT
V b a t ,
measured
after the boost
converter
is
1 2 . 2 V ,
and the
battery
current is 0.63A.
Hence,
the
output power
fed
into
the
battery
becomes
7.7W.
This meansthe
overall
efficiency
of
the
proposed system
is morethan 960o
given
that the
output
power
PV
array
is 8.0W.
V.
CONCLUSIONS
In this
paper,
the
development
ofan
adaptive
for
a
variable
perturbation step
size
on field
programmable
gate array
for
I b = 2 5 O m A
/DIV
3 v
ME
200MV M~3I Cnl x r 3 . V
F
i g .
7.
Battery
current and controlled switch
signal
at 8.0W
power
from
PV
array
maximum
power p o i n t
tracking
fur
p h o t o v o l t a i c
systems
has
been
presented.
The
experimental
results
obviously
show that
the
proposed
algorithm
can
give
significantly
faster
tracking
speed
than the conventional P O
method.
Furthermore,
the
power
fluctuation
in
steady
state
condition
is
substantially
mitigated.
The
proposed algorithm
can
be
easily
implemented
on a
XC2C3
84 FPGA-based
system
to
form
a
high
performance
with
small-sizing component
solar-powered
battery charging system.
Without
any external-measuring
unit,
the maximum
power point
of
the PV cell
can be
efficiently
tracked
with
fast
and smooth reaction
to the
environment
changing,
The
efficiency
of
the
whole
system
is
well above 9600.
RE-FERENCES
[ 1 ]
T.
Markvart,
Solar
Electricity,
John
Wiley
ons,
1994.
[ 2 ]
H.
Chihchiang
and S .
Chihming, Study
of Maximum
Power
Tracking Techniques
and
Control of
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Proc. IEEE
PESCPower
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vo l .
1 ,
pp.
86-
9 3,
1998.
[ 3 ]
M.
G.
Simoes
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Franceschetti,
A RISC-
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1151
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2000.
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N.
Khaehintung,
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P.
Sirisuk,
Implementation
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Proc.
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2004
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W.
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N.
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P.
Sirisuk
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Kiranon,
A
Solar-powered Battery Charger
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Neural
Network
Maximum
Power
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ona Low-Cost
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2 0 0 5 ,
pp.
507-5
10 ,
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Prodic,
D.
Maksimovic,
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R.W.
Erickson,
Design
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implementation
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a
d i g i t a l
PWM
controller for a
high-frequency switching
dc-dc
power
converter,
Proc.
IEEE
I n d
Electron. Soc.
Conf
,
vol.
2,
pp.
893-898,
200
1 .
[ 7 ]
A.
de
Castro,
P.
Zumel,
0.
Garcia,
T.
Riesgo
and J .
Uceda,
Concurrent and
simple
d i g i t a l
controller of an
AC/DC
converter with
power
factor correction based on
an
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pp.
334-343,
Jan. 2003.
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h t t p : / / w w w . x i l i n x . c o m /
f 9 7 . 6 5 H P W
I
.
1 .
1 . 2 ; .
, P i - . .. I . 1 I II 11
