University of Pavia Department of Electrical Engineering...
Transcript of University of Pavia Department of Electrical Engineering...
P O W E R E L E C T R O N I C S L A B O R A T O R YProf. Enrico Dallago, Stefania Braga, Carlo Dallera, Daniele Finarelli,
Marco Marchesi, Diego Martinez, Giuseppe Venchi
Maximum Power Point Tracking (MPPT) development:
Capacitive Bridge Interface (CBI)
electric system modelling and simulation (matlab, Pspice)
circuit analysis and characterization
Inverter behaviour
mono-phase converter DC side rejection pulsating AC behavior
anti islanding technique
heat management
Collaboration with:
MC2 http://www.emmecidue.it/
Enertech http://www.enertech.bz/
Solar field data analysis and management
early failure detection
aging
safety
PV source characterization
mono crystalline, poly crystallinecells available for laboratory testing
PV panel available for outdoor testing and characterization
amorphous
PV panels available for outdoor testing and characterization
Active load test facility for cell/panel characterization
SVO method for modelling and parameter extraction
Microbial Fuel Cell (MFC)An MFC is an electro-chemical systems capable of generating electrical energy by oxidation of organic matter, using bacteria (and their metabolic enzymes) as catalysts. In this way, MFCs exploit biomass that is otherwise useless (e.g. the
biodegradable organic part of waste waters or the sediments on the ocean floor) to produce renewable electrical energy directly, without following a thermodynamic cycle or conventional electro-mechanic conversions.
As any Fuel cell, an MFC is composed of an anode (oxidation electrode) and
a cathode (reduction electrode). In anaerobic conditions, bacteria exchange
electrons to the anode in order to complete their metabolic reactions,
producing also an excess of hydrogen ions (cations). To “close the circuit”,
electrons have to flow from the anode, through an external electric load (RL),
to the cathode, where they can recombine (e.g. air-cathode MFC) with
oxygen and cations. The internal resistance (R) of the MFC represents all the
energy dissipations that occur inside an MFC in steady state working
conditions.
MFC systemsThe output power of an MFC system may be increased by using more cells connected together or scaling up the dimension. The optimum connection strategy (series or parallel configuration) depends on
the specific cell structure and application requirements. The series connection is appealing to increase the voltage but provides lower current and higher internal resistance. On the other hand, the parallel
connection gives a lower internal resistance, a lower voltage, and a higher current. In addition, it is more robust with respect to non-working cells (i.e., cells having a very high internal resistance). In
conclusion it is important to develop an interactive power management system, able to adapt the impedance of the external load and the connection topology between cells in order to extract the
maximum power from the MFC system in all the various operative conditions.
Energy Harvesting System Based on Mechanical Vibrations
Piezoelectric transducer
Teflon
tube
Coil
Levitating
magnets
Fixed
magnet
Direction of
magnetization
N
N
S
S
Start
MAX Detect
Zero Corss
S1
S2
Vin
V+
t
LC resonance
1st cycle2nd
3rd
RQ
S
Start
Zero
Corss
MAX
Detect
S1
RQ
S
Zero
Cross
S2
Cp
S1
S1
S2
S2
Cs
L
Max Detector,
Positive in Detector
Zero Corss
Vcp
Phase
Gen
S1
S2
VP
VM
When Vcp MAX Sw1&Sw2 OFF Sw3&Sw4 ON
When Vcp = 0 Sw1&Sw2 ON, Sw3&Sw4 OFF
D1 & D2 (or D3 & D4) ON
Vcs
D1
D2D4
D3
Sw1
Sw2
Sw3
Sw4
VinM1
M2
M3
M4
VCpp
VCpm
Voltage
Regulator
OUTP
OUTM
Transducer
Vdd
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 20
5
10
15
20
24
Time (s)
Cs v
olta
ge
(V
)
VCs
Voltage regulator output
Electromagnetic transducer All the magnets are magnetized in axial
direction (the red arrow in the picture).
The magnet material is NdFeB with Br
=1.3 T.
Fixed magnet of 10x1 mm (upper and
lower disc).
Moving magnets with diameter of 15 mm
and 8 mm high.
The magnets have been assembled in
magnetic repulsion configuration.
The coil (in red) has inner diameter of
18.2 mm and a transversal section of 2 x 6
mm.
The coil const of 500 turns realized with
a wire with diameter of 0.11 mm.The front-end is energetically
autonomous and able to collect
energy onto the storage capacitor
(Cs) during each voltage pulse
(negative and positive). The
experimental results are shown in
the figure . The efficiency of the ac-
dc converter is close to 40% with
an harvested power of about
1.5mW.
High-Frequency IGBT Soft Switching Buck Converter with Saturable Inductors
E
C
G
+
IGBTmain
E
C
G
IGBTaux
Load
A
T1
C1
C2
D1
D2Df
L3
C3
N1N2
V in L1
Io
iCa
iCm
IL3
iC1
Vout
iD1
iD2
iC2
This 800 W converter is intended for automotive
applications, and in particular to interface the rectified
output voltage of a permanent magnet alternator and the
DC bus in a racing car.
The basic Buck topology (bold) is enriched with an auxiliary
branch to obtain Zero Voltage Switching of the main IGBT. The
Aux IGBT also has zero current turn-on and zero voltage turn-
off for improved efficiency.
OFF
iD2
ON
V
GEmV
CEa
D1i
Cmi
GEa
CEmV
V
Cai
Q
rm
t
t
t
t
t
t
t
t
t
0 1 2 3 4 4' 5 6
fm
fa ra
I
t
L3i
IL3_min
IL3_min
IL3_maxIL3_min
a
TT
TT
t t t t t t t t
The circuit uses 900V / 28A IGBTs at a switching frequency of
80-100kHz.
90
91
92
93
94
95
0 200 400 600 800 1000
Output power [W]
Eff
icie
ncy
[%
]
DF
IGBTMain
IGBTAux
D1
D2
C1
C2
L1
T1
L3
C3
6 7 8 9 10 11 12-250
-200
-150
-100
-50
0
50
100
150
load current [A]
po
les r
ea
l p
art
a) input voltage (50 V/div)
b) output voltage (50 V/div)
c) Current in L3 (5 A/div)
The converter shows an oscillating behaviour when
used open loop.
It was explained by studying the small signal model, which
allows a controller to be designed.
stable stableunstable
Efficiency at 80 kHz is above 92% for
output power between 200 and 800 W.
A detailed analysis of the losses in the
switches demonstrated that the power
dissipated in the main and aux IGBT are
almost the same, confirming the well
balanced stress of the devices.
The prototype was designed
with the following
specifications:
Input voltage: 300 V
Output voltage: 80 V
Output current: up to 10 A
The magnetics use
commercially available cores
(P11x,7 E PLT22 and T184-
8/90 ).
University of Pavia Department of Electrical Engineering
This project is carried out in collaboration with CESI-RSE with the aim to use MFC technology to extract energy from wastewater treatment plants.
Photovoltaic Systems
http://www.unipv.it/electric/elpot/