Page 134 - Renewable Energy Devices and System with Simulations in MATLAB and ANSYS

Overview of PV Maximum Power Point Tracking Techniques 121

Ideal PV array voltage PV array series resistance
Discrete, v + +
Ts= 0.1 s. – +
Controlled current
Powergui Open-circuit voltage (V) – source (ideal PV array)
57 Vd s
Voc
6 + + + + Isc + i – PV array output current
Ns Id
Short-circuit current (A) Tc PV
n
1st step change of the short-circuit current (A) Ideal PV array
model
+ Controlled voltage source
2nd step change of the short-circuit current (A) DC/DC converter Buck converter model (Buck converter
+ output voltage (V) V o s – with output voltage V )
o
90 v Vpv
– 12 DC Converter
Number of solar cells in series PV array
45 output
Solar cell temperature (°C) voltage × Scope
1 1 V o PV array output power
Ipv
Ideality factor of solar cells Delays Vpv DC calculation
Tapped Delay 1 delta MPPT
V oc
1 P&O MPPT
Delays algorithm
Tapped Delay 2
0.001
Perturbation step (0-1)
FIGURE 5.21 A MATLAB /Simulink model of the P&O MPPT process applied to a buck-type DC/DC
®
®
converter with a constant output voltage.
plots of the variations in the PV array output current, voltage, and power, as well as the DC/DC
converter duty cycle, which arise when the P&O MPPT process is executed and step changes of the
PV array short-circuit current also occur.
An example of the PV array output current, voltage, and power, as well as the DC/DC converter
duty cycle, during the operation of the P&O MPPT process, is shown in Figure 5.22. Three
different levels of short-circuit current are applied at time instants t = 0, 15, and 25 s, respectively.
In each of these cases, the PV array output current, voltage, and power and the DC/DC converter

PV array output current (A)
10
7.5
5
2.5
0
0 5 10 15 20 25 30 35 40
PV array output voltage (V)
59
51
43
35
0 5 10 15 20 25 30 35 40
PV array output power (W)
400
300
200
100
0
0 5 10 15 20 25 30 35 40
DC/DC converter duty cycle (range: 0–1)
0.32
0.29
0.26
0.23
0.2
0 5 10 15 20 25 30 35 40
Time (s)
FIGURE 5.22 Simulation results of the PV system operation when applying the P&O MPPT process.