Lena Max

Power Electronics Design Laboratory Exercise for Final-Year M.Sc. Students

This paper presents experiences and results from a project task in power electronics for students at Chalmers University of Technology, Goteborg, Sweden, based on a flyback test board. The board is used in the course Power Electronic Devices and Applications. In the project task, the students design snubber circuits, improve the control of the output voltage, improve the gate drive of the main MOSFET transistor and study the influence of stray inductance. The project goals (the circuit improvements) are given, but the procedure for solving the problems and obtaining the results is not specified. Instead the students have to make their own specification in order to reach the goals. ldquoToolsrdquo that are given to the students are the hardware, measurement equipment, an example of the circuit in the circuit simulation software PSpice, and lastly lectures covering the material needed in order to attain the project goals. The project design builds on the ideas from the CDIO (Conceive, Design, Implement, Operate) initiative, where students are encouraged to consider the complete process structure. The result found was a substantial engagement by the students, who had both positive and negative reactions. The negative reactions were mainly that the project specification was too vague, in other words in the (C=Conceive)-phase of the CDIO structure. Further, the teachers observed increased learning, which also was noticeable for the students performing their M.Sc. thesis within the power electronics design area. Finally, it was found that a final written exam is definitely still needed to assess students adequately in the course.

Control method and snubber selection for a 5 MW wind turbine single active bridge DC/DC converter

In this paper the design and control aspects of the single active bridge DC/DC converter are investigated for the application to be used in a 5 MW wind turbine. The control of the converter is discussed as well as different design considerations as turn-off snubber circuits and leakage inductance of the transformer. It is found that the variable frequency control with a turn-off snubber capacitor gives the lowest losses for the application in a wind turbine. The losses for the single active bridge converter using variable frequency control is 3.2 - 3.8 % of the input power, depending on the position in the wind farm, compared to 3.8 - 4.1 % for the converter with constant frequency control.