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/