1. Topology Derivation and Performance Optimization of Multiport Power Electronics Interfaces
Wen Cai
Supervisor: Dr. Babak Fahimi
December 04, 2015
Renewable Energy and Vehicular Technology Lab

2. List of contents Introduction
Topology derivation with switch multiplexing
Multi-objective model predictive control
Case 1: Single-stage single-phase battery charger
Case 2: LED drive without electrolytic capacitor
Case 3: Advanced switched reluctance motor drive
Conclusions

3. Background and motivation
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.
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-DC converters. ……

4. Background and motivation
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.
fewer components
(low cost, high density)

5. Background and motivation
Power loss reduction

6. Background and motivation
With multiple sources, loads and compact power converter, the power flow can’t be decoupled by dc link capacitors. The power flow control is worth further investigating and studying.
Power control
Power control
Power control
Multiple variables control
Hard to achieve
Model accuracy affects performance
Objectives:
To propose a generalised method to derive multiport topology with extra benefits;
To find generalised power flow control methods for derived topologies based on various requirements;

7. List of contents Introduction
Topology derivation with switch multiplexing
Multi-objective model predictive control
Case 1: Single-stage single-phase battery charger
Case 2: LED drive without electrolytic capacitor
Case 3: Advanced switched reluctance motor drive
Conclusions

8. Topology derivation with switch multiplexing
Basic units for bi-directional power transfer
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.
Basic unit for DC-DC power conversion
Basic unit for AC-DC power conversion
Basic unit
Basic unit
Basic idea: constitute three-port converter by combining two basic units.
DC-DC Basic unit
AC-DC Basic unit

9. Topology derivation with switch multiplexing
Topology derivation based on switch multiplexing
There are four cases as follows:
DC-DC-DC
DC-DC-AC
DC-DC-AC
DC-AC-DC
DC-AC-DC
AC-DC-AC
AC-DC-AC

10. Topology derivation with switch multiplexing
Case 1: DC-DC-AC topologies
DC-DC-AC
DC/AC Unit
1)Combine
Published
Note：
The Voltage drop of L is ignored
DC-DC Unit

11. Topology derivation with switch multiplexing
Case 1: DC-DC-AC topologies
DC-DC-AC
2)Switch multiplex
DC-DC Unit
DC-AC Unit
Examples
Equivalent mode

12. Topology derivation with switch multiplexing
Case 1: DC-DC-AC topologies
DC-DC-AC
3)Switch multiplex
Verified
DC-DC Unit
DC-AC Unit
Examples
Equivalent mode

13. Topology derivation with switch multiplexing
Case 1: DC-DC-AC topologies
Published
DC-DC-AC
4)Bridge multiplex
DC-DC Unit
DC-AC Unit
Equivalent mode
DC-DC-AC three-port converter can be constituted with 4-6 switches.

14. Topology derivation with switch multiplexing
Case 2: DC-AC-AC topologies
1)Combine
AC-DC-AC
2)Switch multiplex
DC-AC Unit
DC-AC Unit
Examples

15. Topology derivation with switch multiplexing
Case 2: DC-AC-AC topologies
Examples
AC-DC-AC
DC-AC Unit
DC-AC Unit
3) Dual switch multiplex
4) Bridge multiplex
DC-AC-AC converter can be constituted with 6-8 switches.
Published

16. Topology derivation with switch multiplexing
Case 3: isolated topology derivation
Basic structure
Examples
Published

17. Topology derivation with switch multiplexing
Efficiency comparison
Fewer switches = lower power loss?
The power loss is separated to two kinds:
Switching loss
It is calculated as:
Conduction loss
It is calculated as: vs

18. Topology derivation with switch multiplexing
Advanced basic units
Multi-level units
Multiport units
Resonant units
Less harmonic
Low switch frequency
More switches
Flexible power flow
Low switch power loss
Complicated control
High efficiency
High power density
Frequency modulation
Isolated
Non-isolated
LLC-type
LCC-type
NPC
Flying cap
MMC/CMC

19. Topology derivation with switch multiplexing
Case 3: isolated topology derivation
Basic structure
Examples
Published