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Spikes in DC link voltage connected in between 3-diode rectifier and 1-phase SPWM Unipolar Inverter

0 votes


asked Jan 2, 2021 by Silpa (18 points)
Did you post the correct model?  The measurement in the model you shared differs from the scope trace in the attached figure and seems reasonable.  This is based on the "Vdc_ou" measurement in your model.



1 Answer

0 votes
This is not an error in PLECS but simply the response of your circuit.  This forum is generally intended for PLECS questions and not general power electronics design issues, but an explanation is below.

With the LC filter at the output, the harmonics in the DC voltage are due to the combined effect of the rectifier input and inverter output harmonics.

With only a resistive load the behavior arises from the controller and modulator.  The controller is attempting to regulate the output voltage which toggles between +/-Vdc every switching event since there is no output filtering. This, along with the feedforward in your circuit results in the modulation index toggling between very high and very low values every switching cycle.  For some portions of the cycle this results in an effective 0.5 duty cycle. Your controller isn't properly handling this condition, although please consider if a purley resistive load without any line inductance is reasonable.
answered Jan 5, 2021 by Bryan Lieblick (1,995 points)


Thank you Bryan for your answer.