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Boost converter in cascade with SEPIC converter

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timothyarora

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I want to use non-isolated boost converter for mppt control in cascade with non-isolated SEPIC converter for voltage regulation. I've made the simulation but whenever I connect them in cascade (i.e. SEPIC converter acting as a nonlinear load for boost converter), simulation is not upto mark.
Is it possible? Please tell me the problems associated with cascading of non-isolated converters.
 

Hi,

I can't see the idea behind this setup.
Why not using a single SEPIC?

I see some issues:
* MPPT is an input referred regulation system. Therefore the output (voltage, current) depends on the input.
* in case you get it working ... efficiency will drop with two systems in series.

Isolated or not ... makes no difference.

Klaus
 

Dear,
If the mppt output voltage (Vmp) is different from the dc grid (or load voltage), I want to regulate the dc grid voltage and extract the maximum power from the solar panel too at the same time, can I achieve both things at the same time?
Here is my system.
My System.jpg
 
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I would expect that the bidirectional DC-DC converter is keeping the DC grid voltage constant. The MPPT converter can feed this constant voltage terminals, no useful purpose of a second DC-DC. If the PVT converter can overload the battery converter, it must be cut down however.
 

Hi,

I don't think so.
Either your regulation is input referred (MPPT) with varying output conditions (voltage, current)
Or your regulation is output referred (usually V, sometimes I) but with varying input conditions.

Imagine:
If your load is a light bulb, an audio amplifier, a PC, a refrigerator....all need a fixed voltage...and the current is unknown somehow.
(refrigerator ON/OFF, audio amp volume..). Solar cells with MPPT isn't useful...either there is enough sun energy to power the load or the system will fail.
If the load needs 100W, but there is only 90W available, this will cause a problem.
If the load needs 100W, but there is 150W available...then you don't need MPPT to use the full 150W.

But if you have to charge a battery, then it is completely different.

Klaus
 

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