Solar MPPT Solar MPPT TechniquesTechniques
Geno GargasGeno Gargas
ECE 548ECE 548Prof. KhalighProf. Khaligh
Purpose of PresentationPurpose of Presentation
I. Provide general description of solar MPPT techniques
II. Describe design of solar MPPT MATLAB model constructed
III. Present results of MATLAB simulation
IV. Give analysis of results with recommendation for future work
I – Basics of MPPTI – Basics of MPPT• Solar panel characteristic has non-linear relationship
with Temperature and Irradiance
• MPP also moves non-linearly
• MPPT can improve efficiency by 15-20%
Common MPPT methodsCommon MPPT methods
Cheap and Easy Implementation Fractional Open-Circuit Voltage
Fractional Short-Circuit Current
Intermediate Price and Implementation Perturb and Observe
Incremental Conductance
Expensive and Difficult Implementation Fuzzy Logic Control
Neural Networks
Incre
ase
d E
fficie
ncy
Incre
ase
d E
fficie
ncy
Ch
eap
er
an
d E
asi
er
Ch
eap
er
an
d E
asi
er
Basic Perturb and ObserveBasic Perturb and Observe Implemented through a DC/DC converter
Logic
1. Change duty cycle
2. Observe consequences on power output
3. Decide direction of next change in duty cycle
P & O Design ParametersP & O Design Parameters
Balance Δd between size of the oscillation across MPP, and inability to not get confused
Two degrees of freedom: Δd and Ta
Ta Constraints Δd
where
II – Creation of MATLAB modelII – Creation of MATLAB model Boost converter with a typical 12V, 64W solar
panel, using the P&O algorithm for MPPT
3 Subsystems
1. Solar Panel
2. Boost Converter
3. MPPT controller
1 - PV model design1 - PV model design
Vout -
2
Vout +
1
ih
Vpv
v+-
Rs
Rh
Photocurrent 1
s
-+
Photocurrent
s -+
Ipv control
Vpv
Ipv
Ih
Temp
Ipv s
Ipv
i+ -
Ih control
Temp
Suns
Ih s
Ih
i+ -
Diode
Suns
2
Temp
1
Important equations
Equivalent Circuit
MATLAB Model
I/P -> Sun and Temperature
O/P -> Panel voltage
Uses controlled current sources
PV model simulationPV model simulation
0 5 10 15 200
0.5
1
1.5
2
2.5
3
3.5
4
4.5
Panel Voltage (V)
Pan
el C
urre
nt (
A)
I-V characteristics for varying irradiance conditions
S = 300 W/m2
S = 500 W/m2
S = 800 W/m2
S = 1000 W/m2
0 5 10 15 200
10
20
30
40
50
60
Panel Voltage (V)
Pan
el P
ower
(W
)
P-V characteristics for varying irradiance conditions
S = 300 W/m2
S = 500 W/m2
S = 800 W/m2
S = 1000 W/m2
I-V and P-V characteristics of simulated PV model with various levels of irradiance
Very similar to characteristics of real solar panels
2 – Boost converter design2 – Boost converter design
Load
Cin
Vin -2
Vin +
1
triangle
RelationalOperator
<=
gm
12
Duty cycle
.2
ParametersL = 20 mH
Cout = 125 μF
Rload = 10Ω Cin = 1000 μF
Freq = 25 kHz
Large L to reduce size of current ripple
Simple PWM generator through use of ramp and comparator
Boost model simulationBoost model simulation
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.160
0.5
1
1.5
2
2.5
3
3.5
time (s)
PV
cur
rent
(A
)
Panel current at various Duty cycles in Boost converter
D = .1
D = .2
D = .3
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.1612
13
14
15
16
17
18
19
20
time (s)
PV
vol
tage
(V
)
Panel voltage at various Duty cycles in Boost converter
D = .1
D = .2
D = .3
Voltage and current of input vs. time for various duty cycles
Quick transient decay
Low ripple
Input source is model of solar panel
3 – MPPT controller3 – MPPT controller
Timing Sequence
1. Sample new values after transient decays
2. Sample for direction of new Δd
3. Sample values for use in next period
4. Make change in Δd
Logic1. Get Power and Duty values of
K and K+1 periods
2. Figure out direction of change in duty cycle
3. Change duty cycle
4. Repeat
Model of controllerModel of controller
Dire
2
Dout
1
direction
In S/H
1
delta D
.1
Memory
OR
ANDNOT
ANDNOT
NOT
NOT AND
OR
AND
D
-1
K
3
P comp
2
D comp
1
Given values from comparing Pk+1 and Pk and Dk+1 and Dk
Performs logic and outputs new duty cycle
III - SimulationIII - Simulation
Test the system during three types of irradiance
1. Fast Changing (50 W/m2s)
2. Slow Changing (15 W/m2s)
3. No Change (0 W/m2s)
Test with different Δd
1. Large Δd (Δd = .02)
2. Small Δd (Δd = .005)
0 0.2 0.4 0.6 0.8 1 1.20.89
0.9
0.91
0.92
0.93
0.94
0.95
0.96
time (s)
Irra
dian
ce (
W/m
2 )
Fast changing irradiance
0 0.2 0.4 0.6 0.8 1 1.20.89
0.9
0.91
0.92
0.93
0.94
0.95
time (s)
Irra
dian
ce (
W/m
2 )
Slow changing Irradiance
Fast Changing IrradianceFast Changing Irradiance
0 0.2 0.4 0.6 0.8 1 1.240
42
44
46
48
50
52
54
56
time (s)
Pow
er (
W)
Power with D=.02 and fast changing irradiance
0 0.2 0.4 0.6 0.8 1 1.20.3
0.31
0.32
0.33
0.34
0.35
0.36
0.37
0.38
0.39
time (s)
duty
cyc
le
Duty cycle with D=.02 and fast changing irradiance
(Δd = .02)
0 0.2 0.4 0.6 0.8 1 1.240
42
44
46
48
50
52
54
56
time (s)
Pow
er (
W)
Power with D=.005 and fast changing irradiance
0 0.2 0.4 0.6 0.8 1 1.20.31
0.315
0.32
0.325
0.33
0.335
0.34
0.345
0.35
0.355
0.36
time (s)
duty
cyc
le
Duty cycle with D=.005 and fast changing irradiance
(Δd = .005)
PV
pow
er
Du
ty C
ycl
e
Slow Changing IrradianceSlow Changing Irradiance
(Δd = .02) (Δd = .005)
PV
pow
er
Du
ty C
ycl
e
0 0.2 0.4 0.6 0.8 1 1.20.31
0.32
0.33
0.34
0.35
0.36
0.37
0.38
0.39
time (s)
duty
cyc
le
Duty cycle with D=.02 and slow changing irradiance
0 0.2 0.4 0.6 0.8 1 1.245
46
47
48
49
50
51
time (s)
Pow
er (
W)
Power with D=.005 and slow changing irradiance
0 0.2 0.4 0.6 0.8 1 1.20.31
0.315
0.32
0.325
0.33
0.335
0.34
0.345
0.35
0.355
0.36
time (s)
duty
cyc
le
Duty cycle with D=.005 and slow changing irradiance
0 0.2 0.4 0.6 0.8 1 1.245
46
47
48
49
50
51
time (s)
Pow
er
(W)
Power with D=.02 and slow changing irradiance
No Change in IrradianceNo Change in Irradiance
(Δd = .02) (Δd = .005)
PV
pow
er
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.545
46
47
48
49
50
51
52
53
time (s)
Pow
er (
W)
Power at constant irradiance and D=.02
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.545
46
47
48
49
50
51
52
53
time (s)
Pow
er (
W)
Power at constant irradiance and D=.005
IV - ResultsIV - Results
Δd Fast change in S Slow change in S No change in S
.02 48.68 W 47.95 W 47.2 W
.005 48.87 W 48.14 W 48.05 W
Average Power in each simulation
These results were found using the mean statistical data provided by MATLAB in each simulation
Average Maximum power available from solar panel
Fast change in S Slow change in S No change in S
Max Power 49.22 W 48.44 W 48.1 W
These results were found by simulating the panel at the average insolation for each form of change in irradiation, and finding the maximum point on the power curve.
AnalysisAnalysis
Δd Fast change P Slow change P No change P
.02 98.9 % 99 % 98.1%
.005 99.3 % 99.4 % 99.9%
Efficiency of MPPT algorithm for various parameters
Higher efficiency with small Δd, regardless of how the sun is changing
I observed that the smaller Δd takes much longer to get to the MPP from a step change in irradiance
The step change is a very rare occurrence, so this may not be an issue
Design the system for the smallest Δd possible for the best efficiency
Future WorkFuture Work
Design a controller that can vary the size of the perturbation with respect to how far from the MPP it is
Leave Δd at a small value and adjust the sampling time to see if that has any effect.
Simulate the MPPT controller for other converter types, possibly in line with a battery charge controller
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