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Boost topologies have been suggest previously in this thread. I understand that your bias towards separate single-phase PFC units is related to predesigned solutions from TI. Industry standard solutions are three phase PFC converters like Vienna rectifier or bidirectional active front end.What do you think about the boost topology?
Boost topologies have been suggest previously in this thread. I understand that your bias towards separate single-phase PFC units is related to predesigned solutions from TI. Industry standard solutions are three phase PFC converters like Vienna rectifier or bidirectional active front end.
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I don't agree that "synchronise with the AC-line" is the key point for different topologies. It's more generally the ability to sink a sinusoidal current independently in each phase. It's e.g. not possible if the mains current is routed through a three-phase bridge.
You are right, it's impossible to achieve sinusoidal input current through B6 bridge. But you can achieve 120° conduction angle with arbitrary waveform, similar to a buck PFC with 2:1 voltage ratio.Interestingly , on TI forum there are developers claiming to use one stage TI controllers after the 3 phase B6 rectifier bridge. I am confused because even if the IC develops a sinus form input current, it is really another story how the phase currents look like at each phase before the rectifier.
You really need a buck-boost input topology for good power factor from rectified two phase or single phase mains, else the buck is ineffective when Vin(instantaneous) < Vout.
A buck boost can be a buck converter followed by a boost, or you can add the extra bits around the buck choke to make it boost as well.
There are control chips avail for this.
Also Cuk converter - if you are experienced at the 1700W module level ...
good luck
If you draw it out - a buck boost only has one inductor, and one active switching power semi in ckt at any one time - hence not two converters in series, the boost stage always has the o/p diode in series and and the buck part will have the series pass element fully on when boosting - it is the most elegant solution for a number of reasons - most especially because you can set the Vo lower than for the peak Vin.
Sure you can boost to 385VDC or similar for single phase - but if you read the thread - OP was seeking two phase input for 3 modules, 400 phase - phase - this is ~ 600V peak so you would have to boost to 650 VDC at least ...
Just remember you can't join the 0v lines if you take each pair of phases and then run them through 3 bridge rectifiers ....
the peak currents in each of the 1700W flybacks would be problematic, and what about the turn off volts on the pri switch ...? also the cores would be quite large ...
It should be possible run each PFC as a flyback converter by adding a secondary winding to the PFC inductors. This can be designed for 10 VDC output, which means that the high-voltage DC bus is eliminated completely.
Each converter has it's own synchronous rectifier, but they can share the 10V DC bus (= the output voltage). The 10 V DC should have the 3-phase advantage of no ripple.
The threefold single phase solution has been already discussed at the begin of this thread. It's feasible but has some disadvantages. E.g. the energy storage of the single phase converters has to be designed for 100 Hz ripple. Three phase PFC has virtually no output ripple (not even 300 Hz), three phase sinusoidal current corresponds to continuous energy flow.
This would also mean that energy storage capacitors are better utilised. (Or can be a lower value just as in 3 phase rectifier).
No. Without energy storage, each single phase converter has output current swinging between 0 and 2*Iavg. You can either implement energy storage sufficient for 100 Hz ripple in front of each DC/DC converter, or need to design the DC/DC for 2*Iavg peak current, as discussed before.
Even a simple resistive load after the bridge has neither a good PF nor a good crest factor.
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