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Introduction to static conversion

by Agnès Gaunie Picart - published on , updated on


Static converters are electrical circuits using power semiconductor which switch voltage and current in order to efficiently modify electrical energy and to provide the following features:

  • Transformation: generating an alternating voltage from a direct current source and vice versa.
  • Control: constant load supply from a variable power source.
  • Adaptation: feeding a low voltage load from a high voltage source and vice versa.

Goals of power electronics

Our research activities cover the key issues of the electrical energy conversion and are based on a combination of theoretical and experimental approaches around the concept of switching cell.

The group is specialized in the study of new structures of multicell converters for medium and high power (kW of MW) application, involving original arrangements of imbricated switching cells in series-connection, parallel superposed and global or partial parallelization through innovative magnetically coupled devices. These arrangements, considered alone or mixed, are used to produce multilevel waveforms having high apparent frequency which reduces filtering costs on a wide range of needs:

  • for applications requiring very low supply voltage (from 10V to 50V): commutation cell parallelization,
  • for applications requiring very high supply voltage (>kV) and/or high current (>500A): imbrication and superposition of commutation cells.

This is done by integrating on the design stage, specific constraints to these areas.

The validation of these new conversion structures requires the development of specific fast analog and digital controls for observation and management of all internal state variables. It is always associated to an experimental realization in a significant power level, which involves dealing with problems such as connections, thermal, three-dimensional assembly and integration of the control (ASIC, FPGA). Simulation, co-simulation and optimization tools are used, adapted and coupled in order to globally determine the best compromise in the design stage and control (PWM). This methodology is particularly implemented on the design of compact converters at the 3DPHI French national program. These studies are complemented by work on the robustness of power components and their failure modes related to the circuit topology resulting in new safe structures and with fault tolerant properties.