2. Chapter 3
The performance of PV power system interconnected with EU can be
improved through an application of advanced control method. This
chapter introduces an application of an artificial neural network on the
operation control of the PV/EU to improve system efficiency and
reliability. There are two modes of PV system operation. As is said
before.
This chapter focus on the operation control of a hybrid system consists
of PV system accompanied with or without battery storage
interconnected with EU taking into account the variation of solar
radiation and load demand during the day. Different feed forward neural
network architectures are trained and tested with data containing a
variety of operation patterns. A simulation is carried out over one year
using the hourly data of the load demand, insolation and temperature at
Zafarâna site, Egypt as a case study.
2
3. Chapter 3
It introduces also a complete computer simulation program of PV
system interconnected with EU. The proposed computer simulation uses
hysteresis current control and instantaneous p-q (real- imaginary) power
theory. A computer simulation program has been designed to simulate
phase voltage of the inverter leg, phase-to-phase voltage of the inverter
leg, current in each IGBT's, DC input current to the inverter, AC output
current of the inverter that injected to the load/grid, load current, grid
current, power output of the inverter and finally power factor of the
inverter.
The following Figure represents the proposed configuration of PV
system which can feed a part of the load demand of 500kW.
3
4. Chapter 3
In v e rte r
D C /A C
B o o s t C o n v e rte r
D C /D C
L
F ilte r
b
V
500 kW
P V s u b s y s te m
V
C
IG B T
b
V
L
in v a
0 .4 /2 2 k V
500 kV A
f
in v b
in v c
b
D C
L in k
C
f
S te p -U p
T ra n sfo rm e r
1 3 2 /2 2 k V
500 kV A
~
EU
S1
S3
S2
S te p -D o w n
T ran sfo rm er
2 2 /0 .4 k V
500 kV A
S te p -D o w n
T ra n sfo rm e r
Fig. 3-1 PV/Load/EU System Block Diagram.
L oad
380 V ,
50 H z
4
5. Chapter 3
3-2 METHODOLOGY OF CONTROL STRATEGY
R
ad
i
at
io
n
3-2-1 Control strategy Issue of PV System Connected to EU without
BS.
D C /D C
V
D C /A C
F ilt e r
dcpv
S 3
S 2
Output
Input
E U
t
S 1
L oad
Fig. 3-2 Single-Line Diagram for the Control Strategy of the PV/EU
System
5
6. Chapter 3
.Power flows in Fig. 3-2 must satisfy the following equations
Ppv (t) ± Pg (t) = P (t)
L
Ppv (t) = ON pv * Ppv, out (t)
Where;
Ppv(t)
: The power from PV system, kW.
Pg(t)
: The power to or from EU, kW.
PL(t)
: The Load demand, kW.
t
: The hourly time over one year.
ONpv
: Optimum number of PV system.
Ppv,out(t)
: The output power from one PV module (see chapter 2).
Pg(t) is positive when the PV power is less than the load demand and
negative when PV power greater than the load demand.
6
7. Chapter 3
3-2-2
Control Strategy Issue of PV/BS
System Connected to EU
The design and installation of this system are more
complicated and expensive, but it is more reliable
than the PV/EU without BS. In this type of intertie
system, the load demand has both PV system, EU
and BS as shown in Fig. 3-3.
7
8. Ra
di
a ti
on
Chapter 3
D C /A C
C o n tro lle r
D C /D C
S4
F ilte r
0
1
B a tte ry
S 3
S2
Output
E U
Input
S 1
L oad
Fig. 3-3 Single-line Diagram for the control strategy of the PV/EU/BS
System
8
9. Chapter 3
3-3-2 Modeling of a DC/AC Inverter
There are two power inverters topology for utility
interface:T h re e -P h a se
E le c tric U tility
1- Line Commutated Inverter, LCI.
P
2. Voltage Source Inverter, VSI
+
P
dc
G
V
dc
G
1
C
V
V
G
3
V
G
in v
L
5
in v a
f
in v b
in v c
4
G
6
G
2
C
D C
L in k
f
C o n s ta n t F re q u e n c y
P W M In v e rte r
Fig. 3-5 Circuit Diagram of the Three-Phase Voltage Source Inverter
9
10. Chapter 3
3-4 APPLICATION AND RESULTS
3-4-1 Operation control strategy of PV System
Connected to EU.
Figure 3-11 shows the structure of the proposed three layers
NN. X1, X2 and t are the three-input training matrix which
represent electrical power generated from PV, load demand,
and time respectively.
10
11. Chapter 3
Iutputs
W
(1)
W
X1
(2)
Outputs
Signal to S1 ( 1 or 0)
Signal to S2 (1 or 0)
X2
Signal to S3 (1 or 0)
Time
bais
Fig. 3-11 Structure of the Proposed Three Layers NN
used for Control Strategy of PV/EU.
11
14. Chapter 3
Figures 3-16 displays the output of the proposed
NN of 3+6+3 for month of January using test data.
Fig. 3-17 Outputs of Neural Network for Month of July.
14
15. Chapter 3
3-4-2 Operation control strategy of PV/BS
System Connected to EU
In This Item we insert BS to feed critical load . The
Critical load equal to 18% of a maximum load demand.
A new subroutine computer program has been proposed
and written using Matlab software to simulate the PV/BS
system. The flowchart of this program is shown in Fig. 318. The output of this program has been used to be the
input of NN. The outputs of NN are four trip signals that
send to switches S1, S2, S3 and S4 as shown in Fig. 3-3.
15
16. Chapter 3
F o r i= 1 :1 :1 2 m o n th
F o r tim e = 1 :1 :2 4 h r
B a tte rie s a r e c h a r g e d
i.e . S 4 = 1 a n d th e lo a d
fe d fro m g rid
yes
If
0 .1 < R a d < 0 .2 o r
In v e rte r fa ilu r e
N o
F e e d th e lo a d S 1 = O N
yes
P
pv
yes
N o
(t) > P L (t)
P p v ( t)= P L ( t)
N o
If S O C (t) >
0 .8 * s iz e o f b a tte r y
N o
If S O C (t) >
0 .2 * s iz e o f b a tte r y
N o
S u rp lu s p o w e r s e n d to
B a tte ry S 4 = 1 , S 1 = O N
yes
yes
S u r p lu s p o w e r s e n d to
E U S3= O N , S2=O FF
L o a d fe e d fro m E U ;
S1=O FF, S2=O N
L o a d fe e d fr o m b a tte ry
S1= O N , S4= 0
E nd
Fig. 3-18 Flowchart of the Proposed
Computer Program for PV/EU
Accompanied with BS.
F ro m E n d o f P ro g r a m F ig . 2 -5
16
17. Chapter 3
Figure 3-19 shows the structure of the proposed
three layers NN. X1, X2, X3, X4 and t are the five-input
training matrix and represent state of charge, electrical power
generated from PV, electrical power for EU, load demand and
time respectively.
W
W
(1)
(2)
Iutputs
Outputs
X1
Signal to S1( 1 or 0)
X2
Signal to S2(1 or 0)
X3
Signal to S3 (1 or 0)
X4
Signal to S4 (1 or 0)
Time
Fig. 3-19 Structure of the Proposed Three Layers NN used
for Control Strategy of PV/EU Accompanied with BS.
bais
17
18. Chapter 3
Fig. 3-11 Operation control Strategy of PV/EU accompanied
with BS using NN
18
19. Chapter 3
3-5 SIMULATION RESULTS OF PV/EU
The circuit of Fig. 3-1 is simulated using Matlab/simulink
version 6 as shown in the following Figure.
The output power from PV solar cells array as shown in Fig.
3-27 have been applied to the inverter to feed the load with the
EU. The total power load level is 300 kW with load current
455.8 Ampere for duration 0.3 Sec. After 0.3 Sec., the load
has changed from 300 kW to 100 kW with load current 151.93
Ampere for duration from 0.3 Sec. to 0.5 Sec. as shown in Fig.
3-27.
19
20. f the PV System Connected with EU.
Chapter 3
20
21. Chapter 3
Fig. 3-27 Simulated of Generated Power from PV, Load Demand
and EU Power from/to EU.
21
22. Chapter 3
The following Figures show simulation results of the
proposed control strategy.
Figure 3-28 Simulated phase voltage of the inverter leg.
22
