The best Active Harmonic Filter in The World 1

[Guilhermebr]

Hello

In your experience and opinion, What is the best active harmonic filter in the world?

GS

 

[davidbeach]

An M-G set.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[edison123]

LOL. True, David. All pure sine.

Muthu

http://www.edison.co.in

 

[Guilhermebr]

Off grid

GS

 

[Marke]

Hello Guilhermebr

If you are looking to use an active filter for an "off grid" application, then you need to be careful about what, how and why.
Active filters operate in much the same manner as a reverse connected VFD in that they usually have a three phase active bridge using PWM waveforms with special harmonic software to create an output waveform that cancels any harmonics that the load generates. The output of the active filter usually comprises an LCL filter to provide an attenuation to the high frequency switching waveform so that only the low frequency currents are passed through to the supply.
The problem is, that if the impedance of the supply is quite high at the higher frequencies, then the small switching currents that pass through the LCL filter can equate to a significant high frequency voltage that can cause interference with the operation of other equipment on the supply.
I have seen significant voltages in the order of 6 - 10KHz caused by active filters on rural (high Z) networks.
I believe that it is also possible for instability of the control algorithms to occur if the inductive reactance is too high. I have not experienced this my self, but there have been reported cases from the field.

Mark Empson
Advanced Motor Control Ltd

 

[Guilhermebr]

Hello Marke. My initial question, was about the best supplier active harmonic filter in the world in your opinion and experience. I used passive harmonic filter with diesel generator (off grid) suppling vdf 300kw 6 pulses, and worked very well. I had problmes too with HF and Active harmonic filter ( see attached)

GS

 

[davidbeach]

The original question was extremely vague. But, even so, if your "off-grid" source powers the "M" and the noisy load is connected to the "G" the rest of the system on the "M" side will not see any harmonics from the "G" side. It would be nice if folks asked the complete question up front with all of the relevant details (this OP is far from unique in that regard). Maybe frame some boundaries around the question. As asked, my M-G set is clearly the "best". Maybe not the most practical. Maybe not the most economical. Maybe overkill for the application. But clearly the "best".

Perhaps some realistic bounds could be established and the full scope established. Maybe?

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[Marke]

Exactly as I expected!!

Somehow, you need to either reduce the high frequency impedance of the supply, or reduce the common mode current fed back into the supply.
The LCL filter works well on the condition that the supply fault current is high and the high frequency supply impedance is low.
I did improve one installation by connecting an RC network across the supply, but we were talking KW power dissipated tin the R to make it work!!

My choice of Active filter is the Comsys and it could be worth while asking them the question, but as a rule, I will not use an active filter where the fault current is low.

Mark Empson
Advanced Motor Control Ltd

 

[Marke]

A couple of questions.
1. What was the actual supply source?
2. How were the measurements made?
3. What problems are being experienced as a result of the switching waveforms?

Mark Empson
Advanced Motor Control Ltd