To realize a very high gain DC power supply for a single PV panel application what topology is advantageous : among current fed topology and voltage fed topology? The role of the converter will be tracking Maximum power point and convert to very high DC voltage say 30 volt to 400 volt.
Current fed or Voltage fed Push pull converter is the advantageous topology in PV applications with a very high DC gain.
Dear Zarzisur,
In order to increase the voltage of the PV source and at the same time adjust the operating point of the the PV source you have to use boost DC/DC converter with pulse width adjustment for the voltage step up ratio for matching of the switching transistor. In this application the PV source is can be considered as a voltage source with series resistance or a current source with shunting resistance.
But from the point of view of charging the inductor of the converter i think it isbtter charged from a voltage source rather than a current source.
Since, vL= L di/dt, L is the inductor of the boost converter..
and so i= Integral v dt /L, if v =consatnt, then
i= v t/L, so the charging final current in the inductor will be proportional to t the charging time.
Where constant current I will generate large voltage at the switching and afterwards the transient voltage goes to zeros dI/dt= 0 and the current in the coil will be always =I. So the control ability of the voltage source is much better than the current source. The solar cells works as a voltage source with an internal resistance.
Best wishes
Seriously "drawing" energy from a PV source requires a more or less constant current. (Usually some constant current with a ripple current overlaid.)
As your "very high voltage" is DC, I assume your setup is the input stage for some solar inverter.
What I*d suggest is to follow the current control approach. As Prof. Zekry stated, voltage and current of the PV source are not independent, so it seems not to matter whether you go for voltage control or current control. But when it comes to the practical implementation, you have to decide on the current switching points of the boost converter. The boost converter's output voltage ("rail voltage") is a function of rail capacitance and the difference between power provided (by the PV yource) and power drawn (by the output side).
And MPPT can only be achieved as long as the output side is capable to accept the power created on the PV side. (Applying current control, the MPPT is implemented by varying the current drawn, resulting in input voltage fluctuations.)
Dear all respected sir,
Thank you for your insightful answer. Surely if voltage source is used then input voltage ripple will be low. But in my application I can not use boost converter as it can not provide me sufficient gain to make necessary high voltage. Most probably i will use an isolated converter. In the literature i have found that Voltage fed DC-DC converter has high input current ripple. This high current ripple is tackled by very high capacitance electrolytic capacitor which is costly and decrease the lifetime of the system. Isolated voltage fed DC-DC converter is typically buck derived so high turn ratio is needed in high frequency transformer which add high leakage inductance and reduce efficiency. In a voltage fed converter flux imbalance can poses serious problem and destroy switches. Whereas, in a current fed converter, series inductor is used in input side which inherently boost the voltage .Current fed DC-DC converter is best suited for tracking MPPT because it offers small current ripple which causes small deviation from maximum power point.
So most probably i will go for current fed push pull or isolated two inductor boost converter.
Nevertheless, current fed topologies have disadvantage of high voltage surge across switch during turning off due to leakage inductance of the transformer .
Best wishes
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