For example, if I need to step-up a DC voltage would it be preferable to use a boost converter instead of a flyback converter because of its non-pulsating input current? If yes, why?
Normally the input of these converters is a DC voltage coming from the grid. Hence, to cope with grid regulations in terms of harmonics...etc, it is not allowed to let the converter input current (which came from the grid) discontious, instead it must be contious current.
In real world, it a common practice to add a input filter no matter what kind of converter used to fulfill the EMI requirement. Also, if you are using a independent DC power supply as a input of your converter, the input current can be any waveform.
Dear Wang,
Three oints here need to be clarified.:
1. The input filter size is a function of the current shape, and will add to system cost and control. Hence it is preferable to have a continuous less ripple current in the input.
2. What real world did you mean? And what independent dc source do we have in real world. Unfortunately, any dc supply will be fed from the grid by any means. Except batteries, which has some limitations and issues.
3. I strongly disagree with your last sentence, No we cannot let the input current of any shape, it should cope with grid regulations, which happened to be more stiff.
Dear Abner,
What I am really trying to say is there is no thumb rule for this. I think that is also why you asking this question. The selection of the converter type can only be driven by the design requirements.
Say you are designing a converter which got the requirement on input current ripple. And you also found that the input current ripple requirement can be fulfilled easily by implement a boost converter. Then it would be a good choice to select boost converter.
On the other hand, if you just want to build up a DCDC converter which will be used to supply 50V 1A power to some electronics test. There is no requirement on input current ripple. I think, in this case, you are free to choose any type of converter.
Dear Elgenedy,
Hope the answer above also clarifies your questions.
Actually the input current waveform is really important for low voltage renewable energy sources like fuel cell (FC) and photo-voltaic (PV) modules. It has been proven that both efficiency and life time of those sources are affected by the current drawn from them.
Particularly in a FC, the fuel consumption increases by employing high ripple input current converters and hence cause a decrease in their efficiency. on the other side, converters with continuous input current are also desirable in PV systems, because they allow the maximum power point (MPP) to be tracked accurately. Hence, continuous input current helps PV system to operate more efficiently.
Therefore in these kind of low voltage sources in order to suppress the stress and increase the lifetime, it is better to use converters with a continuous input current instead of a pulsating input current.
I can refer you to these papers for the aforementioned issues.
[1] S. K. Mazumder, R. K. Burra, and K. Acharya, "A ripple-mitigating and energy-efficient fuel cell power-conditioning system," Power Electronics, IEEE Transactions on, vol. 22, pp. 1437-1452, 2007.
[2] A. E. Khateb, N. A. Rahim, J. Selvaraj, and B. W. Williams, "The effect of input current ripple on the photovoltaic panel efficiency," in Clean Energy and Technology (CEAT), 2013 IEEE Conference on, 2013, pp. 478-481.
Regards,
Mojtaba
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