Renewable Energy and Vehicular Technology Lab Topology Simplification Method based on Switch Multiplexing Technique to Deliver DC - DC - AC Converters for Microgrids Wen Cai , Shanxu Duan , Fan Yi & Babak Fahimi HUST & UTDallas September , 2015 Some pictures are from www.google.com
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Renewable Energy and Vehicular Technology Lab
Topology Simplification Method based on Switch Multiplexing Technique to Deliver DC-DC-AC Converters for Microgrids
Wen Cai, Shanxu Duan, Fan Yi & Babak Fahimi
HUST & UTDallas
September , 2015
Some pictures are from www.google.com
2015/11/12 2
Introduction
List of contents
Topology simplification with switch multiplexing
Conclusion
Experimental results
2015/11/12 3
1. Inclusion
In microgrid, various sources and loads with different electrical characteristics are connected together,
like solar panels, wind generators, batteries, fuel cells, utility grid and AC motors. Conventionally, several
converters are used with the common DC bus.
Background
Common DC bus
Fuel cell
Wind turbine
Battery
Solar panel
DC/DC
DC/DC
DC/DC
DC/DC
DC/AC
DC/AC
AC motor
Utility grid
For energy generating devices, like fuel cell and solar panel, unidirectional DC-DC converters are necessary;
For utility grid and AC motor, bi-directional DC-AC converters are required;
For energy storage devices, like battery and super-capacitor, one needs bi-directional DC-DCconverters.
……
2015/11/12 4
1. Inclusion
In order to integrate all the sources and loads and achieve high power conversion efficiency for microgrid
application, a compact multiport power converter with fewer components can be used to replace all the
converters with centralized control scheme which is easy to implement and protect.
Research objective
Common DC bus
Fuel cell
Wind turbine
Battery
Solar panel
DC/DC
DC/DC
DC/DC
DC/DC
DC/AC
DC/AC
AC motor
Utility grid
Fuel cell
Wind turbine
Battery
Solar panel
AC motor
Utility grid
Multiport
power
converter
Centralized contol
fewer components
2015/11/12 5
Introduction
List of contents
Topology simplification with switch multiplexing
Conclusion
Experimental results
2015/11/12 6
2. Topology simplification with switch multiplexing
Basic units for bi-directional power transfer
Basic unit for DC-DC power conversion
Basic unit for AC-DC power conversion
Fuel Cell
DC bus
Load DC bus
Solar panel
DC bus
Basic unit Buck Boost Bi-directional
DC busSource
DC busAC load DC bus
Grid
Basic unit Rectifier Inverter Bi-directional
In order to analyze multiport converter, two-port converter are investigated firstly. Then it is desired to
derive from two-port system to multi-port system. Here, non-isolated topologies are considered mainly.
2015/11/12 7
2. Topology simplification with switch multiplexing
Topology derivation based on switch multiplexing
AC-DC-ACDC-AC-DC
DC-DC-DC DC-DC-AC
1V 3V2V DC
DC
DC
DC
1V 3V2V DC
AC
DC
DC
1V 3V2V DC
AC
AC
DC
1V 3V2V AC
DC
AC
DC
Basic idea: constitute three-port converter by combining two basic units.
There are four cases as follows:
DC-DC Basic unit AC-DC Basic unit
AC-DC-ACDC-AC-DC
DC-DC-AC
2015/11/12 8
2. Topology simplification with switch multiplexing
Case 1: DC-DC-AC topologies
DC-DC Unit
DC/AC Unit
oL1V
2V
3V
1V 3V2V DC
AC
DC
DC
DC-DC-AC
oL
1L
1V 2V3V
Published
2V
1V
1 2<VV
1 2V Amp V
Note:The Voltage drop of
L is ignored
1 2 1 3,V V V Amp V 2 1 3V V Amp V
2015/11/12 9
2. Topology simplification with switch multiplexing
Case 1: DC-DC-AC topologies
DC-DC Unit DC-AC Unit
1V 3V2V DC
AC
DC
DC
DC-DC-AC
3V
2V
1V
Equivalent mode
1L
2L
1L 2L
1L
2L
1L 2L
1L
2L
2L1LG1
G2
T
G1
G2
G3
TExamples
L L
2 3V Amp V
2015/11/12 10
2. Topology simplification with switch multiplexing
Case 1: DC-DC-AC topologies
DC-DC Unit DC-AC Unit
1V 3V2V DC
AC
DC
DC
DC-DC-AC
Examples
1L
1V
2V
3V
Verified
Equivalent mode
1L
1L 2L
1Li2Li
2L
1L
1L 2L
1Li2Li
2L
1L
1L 2L
1Li2Li
2L
1L
2L
1 3V Amp V
2015/11/12 11
2. Topology simplification with switch multiplexing
Case 1: DC-DC-AC topologies
DC-DC Unit DC-AC Unit
2V
1V
3V1V 3V2V DC
AC
DC
DC
DC-DC-AC
DC-DC-AC three-port converter can be constituted with 4-6 switches.
Published
Equivalent mode
2L1L1L 2L
1Li2Li 1Li
2Li
2L1L1L 2L
1Li2Li 1Li
2Li
2015/11/12 12
2. Topology simplification with switch multiplexing
Case 2: DC-AC-AC topologies
DC-AC Unit
2)Switch multiplex
AC-DC-AC
1V 3V2V DC
AC
AC
DC
DC-AC Unit
1V
3V2V
1V
2V
3V
Examples
2015/11/12 13
2. Topology simplification with switch multiplexing
Case 2: DC-AC-AC topologies
DC-AC Unit
4) Bridge multiplex3) Dual switchmultiplex
AC-DC-AC
1V 3V2V DC
AC
AC
DC
DC-AC Unit
Examples
1V 2V
3V
1V 2V
3V
DC-AC-AC converter can beconstituted with 6-8 switches.
Published
2015/11/12 14
2. Topology simplification with switch multiplexing
Case 3: isolated topology derivation
Basic structure
Examples
1V 1L
2V 2L
3V3L
1V
2V
3V
DC
AC
DC
AC
DC
AC
Published
2015/11/12 15
2. Topology simplification with switch multiplexing
Previous topology
Multi-level units
Less harmonic
Low switch frequency
More switches
Resonant units
High efficiency
High power density
Frequency modulation
Multiport units
Flexible power flow
Low switch power loss
Complicated control
• NPC
• Flying cap
• MMC/CMC
• LLC-type
• LCC-type
Ls
Lm
C
Ls
C2
C1
C
1V
C1V
2V
outV
C
1V
2V
outV
• Isolated
• Non-isolated2V
1V
2015/11/12 16
2. Topology simplification with switch multiplexing
Extension
Combination of multi-level technique and switch multiplexing technique
Multi-level technique
Switch multiplexing
Less harmonic
Low switch frequency
More switches
Flexible power flow
Low switch frequency
Complicated control
Topology
Optimization
New topology
2V
1V
2V
1V
1L2L
3V
To be analyzed
2V
1V
3V
2015/11/12 17
2. Topology simplification with switch multiplexing
Extension
Combination of resonant technique and switch multiplexing technique
Switch multiplexing
High efficiency
High power density
Frequency modulation
Less switches
High efficiency
High voltage/current stress
New topology
2V
1V
1L2L
3V
Ls
Lm
C
sL1L
1C
2C
oC
inV
outV
sC
To be analyzed
Resonant technique
Topology
Optimization
2015/11/12 18
2. Topology simplification with switch multiplexing
Extension
Combination of multi-level unit and resonant unit with switch multiplexing technique
High efficiency
High power density
Frequency modulationNew topology
Resonant technique
Topology
OptimizationMulti-level technique
Less harmonic
Low switch frequency
More switches
Switch multiplexing
sL
1C
2C
oC
outV
sC
sL
1C
2C
oC
outV
sC
3V
1L
To be analyzed
2015/11/12 19
Introduction
List of contents
Topology simplification with switch multiplexing
Conclusion
Experimental results
2015/11/12 20
3. Experimental results
Prototype pictures
5-switch DC-DC-AC (1kW)
6-switch DC-AC-AC (5kW) 8-switch DC-AC-AC (2kW)
4-switch DC-DC-AC (500W)
2015/11/12 21
3. Experimental results
4-switch converter
Microgrid can achieve higher efficiency with modified topology;
2V
1V
1L2L
3V
6-switch converter 4-switch converter
C
1V
2L
3V1L
2 switches are omitted which leads to efficiency improvement and power integration;
Voltage rating of DC link capacitors is decreased with better reliability;
Power decoupling can be achieved with small capacitance;
Power flow control is more complicated;
PI
PWM
distribution
-+iL2_ref
vg
K
iL2
g1
g2
g3
g4
K
-+
ibat
ibat_refPI
d1-d3
++
d1
PIvcap_ref
-+vcap
PLL
Sin(Ө)
Control strategy
2015/11/12 22
3. Experimental results
4-switch converter
Experimental results demonstrate the feasibility of the 4-switch three-port DC-DC-AC converter
and 2.0% power efficiency improvement in comparison with conventional topology.