Post on 22-Jun-2018
Renewable Energy Applications: Photovoltaic and Wind Energy Conversion Systems (WECS)Page 1
Socrates – Erasmus Visit
Renewable Energy Applications: Photovoltaic and Wind Energy Conversion Systems (WECS)
Josep PouAntoni Arias
Renewable Energy Applications: Photovoltaic and Wind Energy Conversion Systems (WECS)Page 2
Socrates – Erasmus Visit
Outline
1. Renewable Energy Perspectives2. Solar Photovoltaic (PV)3. Wind Generation4. Power Electronics
Renewable Energy Applications: Photovoltaic and Wind Energy Conversion Systems (WECS)Page 3
Socrates – Erasmus Visit
Outline
1. Renewable Energy Perspectives2. Solar Photovoltaic (PV)3. Wind Generation4. Power Electronics
Renewable Energy Applications: Photovoltaic and Wind Energy Conversion Systems (WECS)Page 4
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1. Renewable Energy Perspectives
Primary Energy Use
Estimation of primary energySource: German Advisory Council on Global Change 2003, WBGU
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There will be a decrease in the use of power sources based on fossil fuels (especially coal and oil) and also nuclear.On the other hand, it is expected an increase in the use of the renewable energy, mainly photovoltaic, wind and waves.In the long term, the photovoltaic generation will be the key to cover power demand. Great changes in the photovoltaic cell technology are expected that will increase the ratio efficiency/cost.
Energy Sources
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Outline
1. Renewable Energy Perspectives2. Solar Photovoltaic (PV)3. Wind Generation4. Power Electronics
Renewable Energy Applications: Photovoltaic and Wind Energy Conversion Systems (WECS)Page 7
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2. Solar Photovoltaic (PV)
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1000 W/m2
Power (W)
Maximum Power Point Tracking (MPPT)
Renewable Energy Applications: Photovoltaic and Wind Energy Conversion Systems (WECS)Page 9
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Single-Phase PV System
Solar Radiation
AC Voltage
Lga
vdc
b
ELECTRICAL GRID
PV
C
Single-Phase Inverter (DC-AC)
LLC FILTER
Low Power Systems (up to 5kW – 10kW)
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Three-Phase PV System
Solar Radiation
AC Voltagesvdc
ELECTRICAL GRID
PV
C
Three-Phase Inverter (DC-AC)
LLC FILTER
vT
vS
vRLg a
Lg b
Lgc
High Power Systems (above 10kW)
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Socrates – Erasmus Visit
vdc Regulator Inverter (DC-AC)
Batteries
a
b
Solar Radiation
PV
DC-DC Converter(Boost)
Autonomous PV System
Renewable Energy Applications: Photovoltaic and Wind Energy Conversion Systems (WECS)Page 12
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Science Museum
Example in Terrassa
Renewable Energy Applications: Photovoltaic and Wind Energy Conversion Systems (WECS)Page 13
Socrates – Erasmus Visit
Example in Barcelona
Forum Area
Renewable Energy Applications: Photovoltaic and Wind Energy Conversion Systems (WECS)Page 14
Socrates – Erasmus Visit
Outline
1. Renewable Energy Perspectives2. Solar Photovoltaic (PV)3. Wind Generation4. Power Electronics
Renewable Energy Applications: Photovoltaic and Wind Energy Conversion Systems (WECS)Page 15
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3. Wind Generation
Main classification:- Fixed-speed wind turbines.- Variable-speed wind turbines.
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The electrical generator is connected directly to the grid.- An induction generator is normally used.- Since the grid frequency is fixed, the speed of the wind turbine is settled by the ratio of the gearbox and by the number of poles in the generator.
Fixed-Speed Wind Turbines
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Induction generator operating at fixed speedAdvantages:- Robust design.- No need for maintenance.- Well enclosed.- Produced in large series.- Low price.- Can withstand overloads.
Disadvantages:- Uncontrollable reactive power consumption.- Fixed speed means more mechanical stress.
Fixed-Speed Wind Turbines
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- Capacitors banks compensate for reactive power from the induction generator.
- Maxim use of the electrical grid is done operating at unity power factor.
Capacitor Banks
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Example of reactive power as a function of the active power(The reactive power is compensated by capacitors at no-load)
Reactive Power Compensation
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This device allows for a continuous compensation using switched capacitor banks and some inductors. They are connected to the grid by
thyristors (SCR: Silicon Controlled Rectifier).
Static VAr Compensator (SVC)
InductionGenerator
…
x3 x3 x3 x3
Δ Δ Δ Δ
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Why a gearbox is needed?-The gearbox is used to increase the speed of the electrical generator. - Without a gearbox, for a wind turbine rotational speed of 30 rpm, a generator of 100 pair of poles (!!!!) would be needed (assuming 50-Hz grid frequency).- Furthermore, the mass of the rotor has to be roughly proportional to the torque.T=P/ω; if ω↓ then T↑ for a constant P.T: Torque, P: Power, ω: Rotational speed
Gearbox
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- If you connected (or disconnected) a large wind turbine generator to the grid with a normal switch, you would be quite likely to damage both the generator and the gearbox. Also large currents in the neighborhood grid would be produced.- To prevent this situation, wind turbines connect and disconnect gradually to the grid using thyristors.- To avoid thyristor losses under normal operation mode, a bypass switch is activated (main contactor).
Soft-Starter
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Variable speedThe frequency of the generator voltages can be different from the electrical grid (50-60 Hz) and therefore the turbine speed can change.
Advantages:- More energy production.- Less mechanical stress.- Reduce power fluctuation.- Capacity of noise reduction.- May have more control on the grid currents.
Drawbacks:- The system requires power electronic converters. - More expensive.
Variable-Speed Wind Turbines
Renewable Energy Applications: Photovoltaic and Wind Energy Conversion Systems (WECS)Page 24
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- The slip of the rotor can change within a wide range (and therefore the wind-turbine speed as well).- It is the most common topology produced by large manufacturers nowadays.
ALSTOM-ECOTECNIA
Doubly-Fed Induction Generator (DFIG)
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-Multipole synchronous generators may not need a gearbox (these generators have a large diameter).- The rotational speed can change within a wide range.- This is expected to be the most common wind turbine configuration in the future.
?
ENERCON E-126 (7 MW)
Multipole Synchronous Generators (MPSG)
Renewable Energy Applications: Photovoltaic and Wind Energy Conversion Systems (WECS)Page 26
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1. Renewable Energy Perspectives2. Solar Photovoltaic (PV)3. Wind Generation4. Power Electronics
Outline
Renewable Energy Applications: Photovoltaic and Wind Energy Conversion Systems (WECS)Page 27
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4. Power Electronics
Power electronics is the engineering study of converting electrical power from one form to another.At a world-wide average rate of 12 billion kilowatts every hour of every day of every year, more than 40% of the power generated is being reprocessed or recycled through some form of power electronic systems. By 2010, it is expected this will increase up to 80%.
Source: North Carolina State University, Department of Electrical and Computer Engineering (http://www.ece.ncsu.edu/research/pes)
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v
iN
NON
OFF
Diode
v
i
N
ON
OFFOFF
Thyristor or SCR (Silicon Controlled
Rectifier)
F
OFF
Triac
v
i
F
ON
OFF
ON
F
N
N
Power Electronic Semiconductors
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v
i
FF
ON
OFF
Transistor(BJT, MOSFET, IGBT,...)
v
i
N
ON
OFFOFF
GTO (Gate Turn-Off) Thyristor,IGCT (Integrated Gate Commutated
Thyristor)
FF
Power Electronic Semiconductors
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Source: L.M. Tolbert, “High Power Electronics for a Sustainable 21st Century,” NSF Workshop for Sustainable Energy Systems, The University of Tennessee, Dec. 2000, Atlanta, Georgia.
Power Electronic Semiconductors
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Application of Power Semiconductors
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DC AC
AC DC
V1 V2 , f2
V1 , f1 V2
Inverter
DC/DC Converter
Rectifier
FROM: TO:
Classification of Power Electronic Converters
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Inverter
V1 , f1
DC AC
AC AC
V2 , f2
V2 , f2= f1
Static AC Switches
FROM: TO:
• Cycloconverter (f2<f1)• Matrix ConverterRectifier
Classification
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π 2π α
0ψ =
2T1T3T
3T '1T '
3T
2T ' 1T '
Rv
CP
CN
Lv
+
−
π 2π α
1D2D 3D
2T1T3T
0ψ =
Three-phase half-controlled rectifier
Three-phase fully-controlled rectifier
Rv
CP
CN
Lv
+
−
Rectifier Examples (from AC to DC)
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DC-DC Converter Examples
E U
T
D
L
iT
iD
iL
i
+
-
++ -
Lv
Current Source
Voltage Source
DC motor
Mechanical load
E UT
DLLv
E U
T D
L
ONT
mLI
Tα T
Tα T
0
0
OND E UL−
UL−
1
1
1
2
2
2
IΔ
iTiD
LiBuck
Boost Buck-Boost
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Inverter Example (from DC to AC)
2dcv
)0(dcv
C2
C2
as bs cs
as bs cs
+
−2dcv
)(a)(b
)(c
0av0bv0cv
0 0.01 0.02 0.03 0.04 0.05 0.06-30
-20
-10
0
10
20
30
Time (s)
va0/10 ia, ib, ic
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Cycloconverter (from AC to AC)
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Bi-directional switch
SAc
T2
D2
T1
D1
Matrix Converter (from AC to AC)
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Back-to-back-connected three-level converters. These converter topologies can provide three voltage a the outputs. Example of application to wind turbines.
AC-DC-AC System Example
(NP)
CvC2
vC1C
rVd
st
a
b
c
Wind-Turbine NPC Converter Grid-Connected NPC Converter
vr
vs
vt
3*Lgiwt ig
Multipole Synchronous Wind Turbine
ElectricalGrid