Piotr Grzejszczak

Bidirectional modular DC/DC converter for directcurrent microgrids

This work presents concept and implementation of a bidirectional coupling between direct-current circuits of significantly different voltage levels using galvanic isolation in the form of a high-frequency transformer. Standard 5-kW/100-kHz compact dual active bridge modules were used for construction of the coupling. Possibilities of modular construction of the system were presented, in which both parallel and series-parallel connections of developed modules were analyzed. The work takes into account simulation studies of the presented solution as well as studies of an experimental model equipped with an advanced control and measurement system based on DSP-type processors. Modular construction of the converter ensures simple configuring depending on the application, increased reliability and reduced design and maintenance costs.

Opis procesu wyłączania tranzystora MOSFET w przekształtnikach wysokiej częstotliwości

This paper contain a detailed study of high voltage Power MOSFET turn off process which occur in high frequencies applications. Presented description is based on simulation with very precious simulation model of Infineons CoolMOS transistor (IPW60R070C6). Experimental results of MOSFET turn off power losses measurement in H-bridge inverter works with 100kHz were also presented. This results confirmed correctness of analytical description presented by the author. (Study of high voltage MOSFET turn off process in high frequency converters).

Switching losses in a new high-voltage MOSFETs

The paper presents a description of switching energy losses in high-voltage MOSFET operating in a bridge topology. Energy losses in both hard and soft switching, as well as during switching on at light load current and in unloaded operation have been analyzed. The description has accounted for the effect of parasitic junction capacitances and the external capacitances of semiconductor elements, as well as the parasitic capacitance of the receiver. For deriving the relationships defining the MOSTET energy losses, the electric charge and energy conservation principle was used. The second part of the paper describes the results of simulation and experimental studies performed on the model of a dual active bridge with high-voltage MOSFETs. The obtained results are coincident with the theoretical calculation results, thereby confirming the correctness of the performed analysis.

Flyback-based high-side gate driver for a 10-kV SiC MOSFET

Aside from providing voltage and current of sufficient values, a gate driver of a SiC MOSFET must also be durable enough to keep operating properly in given place of a main circuit of a converter. A high-side SiC MOSFET constitutes a challenge to being driven properly, since a high-voltage potential becomes repetitively applied at an output of the gate driver. In order to limit a resulting flow of parasitic current Cdv/dt to ground of the driver, a low-capacitance isolation must be implemented. Presented in this paper is a flyback-based gate driver, which is dedicated for driving a high-side 10-kV SiC MOSFET. Required properties of the gate driver such as high dielectric strength and low input-to-output stray capacitance were evaluated through a series of measurements. Switching voltage values and switching speeds of the driver were examined in an 800-V double pulse test with a 1.2 kV SiC MOSFET and compared with two other devices potentially capable of operating with the 10-kV SiC MOSFET.