European Conference on Nanoelectronics and Embedded Systems for Electric Mobility. ecocity emotion

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1 European Conference on Nanoelectronics and Embedded Systems for Electric Mobility ecocity emotion DC/DC converter for bi-directional battery charger using SiC power switches th September 2014, Erlangen, Germany Inverters for Electric Vehicle Chargers Dr. Ashot Melkonyan, Dr. Kai Kriegel Siemens AG, CT RTC PET POE-DE, Munich

2 Overview 1. The role of bi-directional charger in energy management system 2. Architecture of the battery charger and grid inverter 3. Short topology description of the DC/DC converter and the power switches demands 4. Improvements of the commutation processes by using SiC devices 5. The prototype power board and summary

3 1. The role of bi-directional charger in energy management system Increase of localised electric power generation through renewable technologies demands a grid stabilization and its robust regulation. Vehicle-to-Grid (V2G) integration enables an Electric Vehicle owner to transfer energy from the EV traction battery back to the grid at times of peak-loading, in exchange for some cost-benefit incentive. Bi-directional power flow For smart grid interfacing an isolated bi-directional converter is required!

4 380 V The Smart Grid and Electric Vehicles integration concept Mass-produced electric vehicles or PHEV (plug-in hybrid) can be used as a mobile intermediate electrical energy buffer Battery charging, power flow control and galvanic isolation Grid interfacing and power factor correction Renewable energy source ~ M 3 ~ Battery 3 ~ M 3-phase motor inverter

5 2. Architecture of the battery charger and grid inverter General AC-DC / DC-AC converter architectures with Grid Interfacing Power Factor Correction Switch mode AC/DC Rectifier / Battery charger Isolated Non-Isolated Bidirectional Unidirectional Bidirectional Unidirectional Two stage Two stage Single stage Single stage Two stage Single stage Two stage Single switch, multi-swicth, resonant, bridge / H-bridge, reconfigurable, two level, multilevel, voltage source, current source etc. topologies

6 3. Bi-directional isolated AC/DC rectifier DC/DC converter ~ Filter Bi-directional isolated two-stage converter with PFC Active Front-End rectifier (non-isolated PFC) Bidirectional DC/DC converter (isolated, full bridge) I stage II stage PFC is realized at Stage I Easy reconfigurable for single and 3-phase systems Inverter control is realized by means of FOC Galvanic Isolation is realized at Stage II DC/DC buck conversion using transformer Accurate output current and voltage control EMI reduction due to soft switching and isolation transformer Energy Storage (Battery)

7 Battery 380V 700V DC Bus DC Bus Topology of the integrated battery charger / inverter HF Bidirectional DC/DC converter - inverter Battery 700V DC ~ Grid 380 V Stage I 350V - 400V 600V - 700V Bi-directional battery charging Stage II Vdc 380Vac Bi-directional grid inverter DC/DC converter 150kHz (B) 17 khz DC/AC grid inverter (C) SiC

8 3. Topology description hard and soft switching operation modes During commutation the current flow direction is: from the switch to the diode Soft switching Current flow direction during commutation is: from the diode to the switch D3 Hard switching D4

9 4. Improvements of the commutation processes by using SiC Switching with MOSFET and ultrafast soft recovery diode (600V) Switching with SiC JFET and LV mosfet cascode (1200V) +

10 5. Power Board of the 3 Phase Bi-Di Charger / Inverter 3phase bi-di Charger / Inverter AC Filter Inductors DCDC Trafo DCAC Gate Drivers HV DC Bus AC Grid Relais SiC Gate Driver Low Voltage Gate Driver Low Voltage DC Bus uc Connector DC Input

11 First results of the bidirectional DC-DC converter (DAB) Boost mode operation discharging battery and recuperating energy into AC Grid Buck mode operation : Charging battery from AC Grid

12 Summary Decentralised electric power generation through renewable technologies requires a strong and stable utility grid with robust and smart regulation Bi-directional power converters are the enabling technology to interact the Electric Vehicles with Smart Grids. Implementing a bi-directional vehicle-to-grid communication and controlled battery charging, this technology enables an effective integration of the electric vehicles and their charging infrastructure into energy management system. (e.g. in Building Energy Manager) Using bi-directional converters, the mass-produced electric vehicles or PHEV (plug-in can be turned into mobile intermediate electrical energy buffers. hybrid) Progress beyond the state of the art has been made by bi-directional on-board chargers scalable through modularity, efficient, compact and light-weight. A 6kW soft switching converter system has been designed, constructed and validated, which weights ~9kg incl. forced air-cooling and achieved over >96% efficiency. With new SiC transistors very high current slew rates can be handled. This results in excellent dynamic behavior and lower EMI under hart-switching operation modes.

13 Thank for your attention!