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Five-Cell Multi-Level Converter

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This example shows a five-cell multi-level converter driving a static load.

Graham Dudgeon, Senior Consultant, The MathWorks, Inc.

Description

The system consists of a three-phase five-cell multi-level converter (MLC) constructed from cells containing diode rectifiers and IGBT H-bridge inverters. The MLC is supplied by an ideal 60Hz three-phase source and drives a static resistive/inductive load at 100Hz. The architecture of the converter is taken from [1]. The zig-zag input transformers for each cell are phase-shifted by 15 degrees relative to each other to ameliorate source harmonics below the 23rd harmonic. The H-bridge PWM carrier waves are phase shifted by 45 degrees relative to each other to produce the output voltage 'stacking' effect. The modular nature of a MLC is clearly seen by looking under the component mask.

Simulation

Start the simulation. Observe the voltage stacking effect from Scope block. Using the FFT Analysis tool in the powergui, confirm that the source current ISRC has no significant harmonics under the 23rd harmonic.

You can adjust the modulation waveforms to change output voltage amplitude and frequency.

References

[1] Wen, J. and Smedley, K.M., 'Synthesis of Multi-Level Converters Based on Single- and/or Three-Phase Converter Building Blocks', IEEE® Transactions on Power Electronics, Vol. 23, No. 3, May 2008.