MATLAB SIMPOWERSYSTEMS 5 Manual de usuario descargar pdf (Pagina 16)

Palestine Polytechnic University

Workshop Matlab/Simulink in Drives and Power electronics – Lecture 418-21 May 2009

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Tunning the snubbers

– If firing pulses to forced-commutated devices are blocked, only antiparallel

diodes operate, and the bridge operates as a diode rectifier. In this condition

appropriate values of Rs and Cs must also be used.

– When the system is discretized, use the following formulas to compute

approximate values of Rs and Cs,

where

– These Rs and Cs values are derived from the following two criteria:

• The snubber leakage current at fundamental frequency is less than 0.1% of nominal

current when power electronic devices are not conducting.

• The RC time constant of snubbers is higher than two times the sample time Ts.

– These Rs and Cs values that guarantee numerical stability of the discretized

bridge can be different from values of a physical circuit.

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MATLAB SIMPOWERSYSTEMS 5 Manual de usuario Pagina 16