Masters Thesis: Design of a highly efficient charger for Nickel-Iron batteries

122 Pages·2015·4.99 MB·English

by  Anil Kumar Ananda

Design of a
highly efficient charger
for Nickel-Iron batteries
Anil Kumar Ananda
s
i
s
e
h
T
e
c
n
e
i
c
S
f
o
r
e
t
s
a
M
DC Systems, Energy Conversion and Storage

Design of a
highly efficient charger
for Nickel-Iron batteries
Master of Science Thesis
For the degree of Master of Science in Electrical Power Engineering at
Delft University of Technology
Anil Kumar Ananda
August 24, 2015
Faculty of Electrical Engineering, Mathematics and Computer Science (EEMCS) · Delft
University of Technology
The work in this thesis was supported by E-stone Batteries Incorporated. Their cooperation
is hereby gratefully acknowledged.
Copyright (cid:13)c Electrical Engineering
All rights reserved.
i
DESIGN OF A HIGHLY EFFICIENT CHARGER
FOR
NICKEL-IRON BATTERIES
by
AnilKumarAnanda
inpartialfulfillmentoftherequirementsforthedegreeof
MasterofScience
inElectricalEngineering
attheDelftUniversityofTechnology,
tobedefendedpubliclyon28thAugust,2015.
Studentnumber: 4306368
Supervisor: Prof.Dr.Ir.JelenaPopovic-Gerber
DailySupervisor: Ir.FransPansier
Thesiscommittee:
Prof.Dr.Ir.PavolBauer,TUDelft
Prof.Dr.Ir.ReneVanSwaaij,TUDelft
Anelectronicversionofthisthesisisavailableathttp://repository.tudelft.nl/.
Master of Science Thesis Anil Kumar Ananda
ii
Anil Kumar Ananda Master of Science Thesis
Abstract
Obtaining good performance from stand-alone PV systems requires successful integration of
batteries that are reliable, effective, long lasting, environmental-friendly and affordable as it
is crucial to deal with variable solar illumination throughout the year. Nickel Iron battery
technology (Ni-Fe) is a perfect fit for the solar-powered households as it is satisfies all the
requirements. Charge controllers need to be efficiently designed for Ni-Fe batteries for pro-
tection from overcharge/discharge.
This thesis concentrates on selecting the best topology from B2R converters from the patent
550 of ESA to be applied for designing the charge controller for Ni-Fe batteries. An analysis
is carried out to determine the advantage of B2R converters in the patent over conventional
buck-boost topologies like SEPIC or Cuk and evaluate their utility for charge control applica-
tions. The focal point of topological selection will be the evaluation of topologies on the basis
ofefficiencyandcomplexityforrealisticadaptationintoachargecontroller. Afterdefiningthe
load power parameters, the operation of the topologies in two different modes of conduction
(BCM & CCM) is investigated and an analytical model is developed for losses. Significant
factors that play a role in determining the efficiency for varying source parameters (input
voltage) are scrutinized. The relative merits of using BCM/CCM for design are inspected
by carrying out simulations for loss calculations using the analytical model with data-sheet
parameters from realistic components for their suitability for the application. Component
selection is done by keeping in mind the prevalent technologies in the market that are cost-
effective and the procedure followed in the design of magnetics for the topologies in different
modes of conduction and its impact on efficiency is discussed and an assessment is carried out
on the performance of the components with variations in input voltage for the same power
level.
TheproposedanalyticalmodelsforswitchinglossesinMOSFETsandoveralllossestopologies
are validated by carrying out experiments on the prototypes of two best topologies in both
conduction modes. The results critique the accuracy of the analytical model in determin-
ing the actual efficiency of the topologies, the margin of deviation by means of comparison
with the experimental results and concludes with suggestions for selecting the most efficient
topology and recommends a mode of conduction for best results.
Master of Science Thesis Anil Kumar Ananda
iv
Anil Kumar Ananda Master of Science Thesis
Table of Contents
1 Introduction 1
1-1 Objectives of the thesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1-1-1 Research questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1-1-2 Methodology and thesis layout . . . . . . . . . . . . . . . . . . . . . . . 2
2 State of Art 3
2-1 Changing world order - PV proliferation . . . . . . . . . . . . . . . . . . . . . . 3
2-2 Nickel Iron batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2-3 Battery charge control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2-4 Role of power converters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2-5 Topological evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2-6 Modes of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2-7 Efficiency calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2-8 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3 Topologies 13
3-1 B2R DC-DC converter topologies . . . . . . . . . . . . . . . . . . . . . . . . . 13
3-2 Topologies overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3-2-1 Topology B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3-2-2 Topology A and C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3-2-3 Topology D and E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3-3 Necessity of switches S1-A and S1-B . . . . . . . . . . . . . . . . . . . . . . . . 17
3-4 Selecting the topology for design . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3-5 Comparison of the topologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3-5-1 Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3-5-2 Complexity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Master of Science Thesis Anil Kumar Ananda
vi Table of Contents
3-6 Modes of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3-6-1 When can BCM become advantageous over CCM? . . . . . . . . . . . . 20
3-6-2 Condition for BCM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3-6-3 Frequency effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3-6-4 Change in magnetics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3-7 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4 Losses and component selection 25
4-1 Losses overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4-1-1 Ripple current and its effect on the device selection . . . . . . . . . . . . 27
4-2 Capacitor losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
4-3 Diode losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4-3-1 Modelling forward characteristics . . . . . . . . . . . . . . . . . . . . . . 30
4-3-2 Modelling recovery characteristics . . . . . . . . . . . . . . . . . . . . . 30
4-4 MOSFET losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
4-4-1 Models for analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
4-4-2 Switching transitions in CCM . . . . . . . . . . . . . . . . . . . . . . . . 33
4-4-3 Switching loss calculations in CCM . . . . . . . . . . . . . . . . . . . . . 34
4-4-4 Switching loss calculations in BCM . . . . . . . . . . . . . . . . . . . . . 36
4-5 Inductor losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
4-5-1 Core loss calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
4-5-2 Winding loss calculation for CCM . . . . . . . . . . . . . . . . . . . . . 38
4-6 Component selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4-7 Inductor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4-7-1 Core selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4-7-2 Design of the inductor . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4-7-3 Optimising the design . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4-7-4 Windings - Litz wires . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
4-7-5 Conduction mode based design . . . . . . . . . . . . . . . . . . . . . . . 45
4-8 Capacitor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
4-8-1 Significance of selecting transfer capacitance. . . . . . . . . . . . . . . . 46
4-8-2 Ripple ratings of capacitors . . . . . . . . . . . . . . . . . . . . . . . . . 47
4-9 Selection of active devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
4-9-1 Initial parameters for diode and switch selection . . . . . . . . . . . . . . 48
4-10 Diode selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
4-10-1 Selection of diode technology . . . . . . . . . . . . . . . . . . . . . . . . 48
4-11 MOSFET selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
4-11-1 MOSFET selection parameters . . . . . . . . . . . . . . . . . . . . . . . 49
4-12 MOSFET drivers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
4-12-1 High side and Low side drivers . . . . . . . . . . . . . . . . . . . . . . . 51
4-13 Simulation results of analytical models . . . . . . . . . . . . . . . . . . . . . . . 53
4-13-1 Inductor losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
4-13-2 Switching losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
4-13-3 Overall efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
4-14 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Anil Kumar Ananda Master of Science Thesis