In power factor correction converter, when I am sensing the rectified voltage before LC filter to create sinusoidal template, power factor correction is not achieved. while when i m sensing rectified voltage after LC filter, power factor correction is achieved WHY ?. Filter is mandatory to use.
If you uses a grid connected converter. You must sense the voltage of the grid after the LC filter because the voltage before the LC filter is the output voltage from the converter. This voltage is not sinusodial waveform. Therefore, the voltage oriented control will not work probably in this case.
Dear Ankit,
According to te model of the power factor correction circuit given in the paper at the link:http://www.vicorpower.com/documents/application_notes/an1_active-pfc.pdf,
It is so that after full wave rectifying the ac voltage, it is boosted using boost dc to dc converter. The input current of the boost converter is forced to take the same shape of the full wave rectified voltage waveform by controlling the DC TO dc CONVERTER.
It is so that the dc to dc converter must drop a voltage which is the difference between the the output DC bus voltage and the the full wave rectified input. In this way the current will be also sinusoidal and the the input of the converter seems as a constant resistance load, which means unity power factor.
So, one has to control the DCto DC converter by the difference of the bus voltage and the the direct output of the full wave rectifier other wise the current waveform will be deviated from that of the full wave rectified one.
You can map your case on this model.
wish you success
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