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

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

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. ……

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)

Background and motivation Power loss reduction

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;

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

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

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

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

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

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

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.

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

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

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

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

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

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