advanced mechanical design december 2008 shaghayegh kazemlou advisor: dr. shahab mehraeen louisiana...
TRANSCRIPT
Discrete Time Modeling And Control Of DC/DC Switching Converter For
Solar Energy Systems
Advanced Mechanical DesignDecember 2008
Shaghayegh Kazemlou
Advisor: Dr. Shahab Mehraeen
Louisiana State University
Part I: Grid-connected Renewable System
Part II: Converter Discrete-Time Model
Part III: Converter Discrete-time Control Design
Part IV: Simulation Results
Part V: Summary and Future Works
Outline
2
Grid-connected Renewable System
Advanced Mechanical DesignDecember 2008
Part I
Solar System Model
4
Solar power generation system Solar panels
DC-DC buck converter
Grid-tie inverter (GTI)
Objective stabilizing the inverter DC-link capacitor
Omitting solar power oscillations
Grid-Tie Inverter
5
Solar power generation system
Synchronous Generator (SG)
outv controller
dynamics es
outoutout PP
dt
dvvC
6
SG dynamical equations
fdd
ddq
d
d
dq
em
EVx
xxE
x
x
TE
PPM
)cos(1
1
0
fdERE
fd
d
dqd
d
q
qd
EKVT
E
Vx
xxE
x
x
TE
1
)sin(1
0
)(1
esout
PPC
fdrdr
drdrqr
dr
dr
rdqr EV
x
xxE
x
x
TE )cos(
)(1
0
)sin(
)(1
0V
x
xxE
x
x
TE
dr
drqrdr
dr
qr
rqdr
fdrErRrEr
fdr EKVT
E 1
Inverter dynamical equations
Inverter gain ( ) and ac voltage angle ( ) are the control inputsink
Grid-Tie Inverter Model/Observer
2)( 22outoout vv ( )
Converter Discrete-Time Model
Advanced Mechanical DesignDecember 2008
Part II
DC-DC Buck Converter
8
dc-dc buck converter control system
Objective: Maintaining the solar power constant by adjusting duty cycle d
Converter Discrete-Time Model
9
Photovoltaic array output current is a nonlinear function of
][]][][[])1[( kTvkTidkTiC
TTkv inLin
inin
][]][][[])1[( kTikTvkTvdL
TTki LoutinL
Converter discrete-time equations
][kTiin ][kTvin
)1(][ ][ Tsin VnkTvopspin eInInkTi
Converter Discrete-time Control DesignAdvanced Mechanical Design
December 2008
Part III
State Feedback Controller
11
kukTxgkTxfTkx ])[(])[(])1[(1
TLin
T ivxxx ][][ 21 duk Input:
Tracking error : ][][][ 11 kTxkTxkTz d
stable 10 K
][kTzKuu d
])1[(])[(])[( 11 TkxkTxfkTxgu dd
][])1[( kTzKTkz
][]][][[])1[( kTvkTidkTiC
TTkv inLin
inin
Neural Network function approximation
12
: activation function
Weight estimation error :
: positive design constant
]))1[(,(])1[(])[(])[( 111 TkxxWTkxkTxfkTxgu d
Tdd
WWW~ˆ
])1[(][ˆ])1[(ˆ 1 TkzckTWcTkW
NN weight update law :
1c
Simulation Results
Advanced Mechanical DesignDecember 2008
Part IV
Simulation Results
14
AVR+PSS mechanism for inverter
operational frequency of the converter : 10 kHz
three-phase resistive load with on each phase
Disturbance : load change from to at
solar module maximum power :
solar module maximum power point voltage :
System parameters
6R
WP mpps 1146,
Vv mppin 121,
6R 3.5R st 4.1
Simulation Results
15
Solar Voltage Less than MPP Voltage: Vv setin 116,
1 1.2 1.4 1.6 1.8 2 2.2 2.41060
1080
1100
1120
1140
time [s]
Ps
[W]
With Controller
Without Controller
1 1.2 1.4 1.6 1.8 2 2.2 2.4105
110
115
120
time [s]
Vin
[V
]
With Controller
Without Controller
Converter input power Converter input voltage
Disturbance between t=1.4s to t=1.6s
Simulation Results
16
Solar Voltage Less than MPP Voltage: Vv setin 116,
Converter output voltage Converter inductance current
1.2 1.4 1.6 1.8 2 2.2 2.495
100
105
time [s]
Vou
t [V
]
With Controller
Without Controller
1 1.2 1.4 1.6 1.8 2 2.2 2.410
10.5
11
11.5
12
time [s]
IL [
A]
With Controller
Without Controller
1 1.2 1.4 1.6 1.8 2 2.2 2.49.6
9.7
9.8
9.9
time [s]
Iin [
A]
With Controller
Without Controller
Converter input current
Simulation Results
17
Solar Voltage higher than MPP Voltage: Vv setin 131,
Converter input power Converter input voltage
1 1.2 1.4 1.6 1.8 2 2.2 2.4
1000
1050
1100
time [s]
Ps
[W]
With Controller
Without Controller
1 1.2 1.4 1.6 1.8 2 2.2 2.4127
128
129
130
131
132
time [s]
Vin
[V
]
With Controller
Without Controller
1 1.2 1.4 1.6 1.8 2 2.2 2.4
92
94
96
98
100
time [s]
Vou
t [V
]
With Controller
Without Controller
Converter output voltage
Simulation Results
18
Input Voltage Adjustment to Load Change:
Converter input power Converter input voltage
tforRstforR
stforRstforR
2.23.5;2.28.16
8.14.16.4;4.103.5
1 1.5 2 2.5 31050
1100
1150
time [s]
Pin
[W
]
With Controller
Without Controller
1 1.5 2 2.5 3105
110
115
120
time [s]
Vin
[V
]
With Controller
Without Controller
1 1.5 2 2.5 390
95
100
105
110
time [s]
Vou
t [V
]
With Controller
Without Controller Converter output voltage
Summary
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The inverter is controlled by a novel stabilizer similar to power system stabilizer (PSS).
The interaction of the solar array dc-dc converter with the GTI is addressed. A nonlinear discrete-time model of a photovoltaic-connected buck converter was
presented. Adaptive neural network (NN) controller is employed to enhance stability of dc-dc
converter connected to grid-tie inverter (GTI) in the presence of power system disturbances.
Simulation results of the controller imply that the converter input voltage and power as well as the inductor current are stabilized which verifies the accuracy of the converter discrete-time model and the effectiveness of the proposed discrete-time controller.
Recommendations for Future Works
20
Improve the efficiency and effectiveness of discrete-time adaptive neural network in the power system stability and control
The system model can be developed to a more general distributed generation system where other renewable generators or synchronous generators all are interconnected. In this case each system is influenced by other subsystem’s states and a more general control method is necessary.
The solar system connected dc-dc converter can be modeled in a dc distribution system with interconnected subsystems working in high penetration of renewable generation.
Thank You for Your Attention
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