My flickering LED problem is finally solved

[fmeili1]

I had bad flickering LED's on one of the two phases.

After a couple of days/weeks searching the cause of the problem, I finally found it.

Environment: 6x EG4-6500 in split phase, batteries only (no solar so far)

I've checked/tried everything like

• checking for N-G-bonding problems
• parallel communication and current sharing wiring problems
• firmware updates
• program 42 settings
• bonding screws first out now back in (and program 42 set to enabled)
• try to use just one inverter on the problematic phase instead of all 3 in parallel
• ...

none of this helped!

The problem was just one specific load in the house which causes interference with the inverters PWM control electronic - it is an 20 year old slot machine which causes the problem and is usually always on and runs on a small UPS (slots should not be switched on/off too often - they are designed for 24/7 runtime). Now I will try to find one of these "Dirty Electricity Filter" plugs to be able to use the slot without interfering with the inverter.

Thanks to @Adam De Lay's hint in one of his videos about his Apple notebook power supply which causes his flickering problems!

Here is a SolarAssistant picture which shows my AC-out voltage with the slot running and at about 18:42 I pulled the plug from the UPS so the slot was not longer connected to power (only driven by the small UPS) and the problem was not longer existing. The output voltage is now much more stable (now on both phases).



My guess is that many (for sure not all) of the reported LED flickering problems have the same cause!

I've isolated the problem by watching one of these flickering LED's and switching off one by one breakers in the house main breaker panel to identify the room which causes the problem. If the problematic load is isolated to a room it's pretty simple to find the load which causes the problem.

 

[Plum Crazy Rob]

@RCinFLA was right, it's the "Tacoma Narrows bridge" of electronics..

Post in thread 'Solark inverter - flickering lights' https://diysolarforum.com/threads/solark-inverter-flickering-lights.62252/post-800351

 

[webbbn]

If I'm understanding correctly, you had a slot machine plugged into a UPS, which was then plugged into the output of your inverters?

If so, I would suspect the UPS rather than the slot machine. It would be interesting to see if you see the problem with something else powered off of the same UPS that uses a similar amount of current.

It sounds to me like the flickering is due to a harmonic generated from the interaction of the PWM frequency of the inverter and the (in this case) UPS, kind of like an out of tune instrument.

It would also be interesting if it would change/decrease if you added something else, like another UPS, or a switching power supply. Adding another PWM frequency should at least change the harmonic frequency.

 

[LydMekk]

In Adams case it was also the UPS...some of the cheap ones are poorly made.

 

[Adam De Lay]

In Adams case it was also the UPS...some of the cheap ones are poorly made.

It wasn’t the UPS which caused the flickering in my case. I still had the flickering when I removed it.

 

[LydMekk]

Ok, off the video you posted I thought you said it was the office UPS which aggravated the issue. In the video you mentioned it clicked on/off a lot when running on your old EG4 inverters.
I remember it came down to the inverters, yes?
Hope your Victrons are treating you better atm. ^^

 

[Adam De Lay]

Ok, off the video you posted I thought you said it was the office UPS which aggravated the issue. In the video you mentioned it clicked on/off a lot when running on your old EG4 inverters.
I remember it came down to the inverters, yes?
Hope your Victrons are treating you better atm. ^^

Yeah the UPS clicking was a different issue. It was either dirty power or the UPSs being too sensitive. You be the judge… ?

Victrons are just working. You almost could forget they’re there.

 

[Quattrohead]

@RCinFLA was right, it's the "Tacoma Narrows bridge" of electronics..

Post in thread 'Solark inverter - flickering lights' https://diysolarforum.com/threads/solark-inverter-flickering-lights.62252/post-800351

Yep and I agreed with his diagnosis.
And as I have previously said, an inverter is just a bloody great big amplifier/transmitter and you have to treat their output load with the same caution you would an audio amplifier or radio transmitter. A bad load can cause mayhem.

 

[fmeili1]

If I'm understanding correctly, you had a slot machine plugged into a UPS, which was then plugged into the output of your inverters?

yes

If so, I would suspect the UPS rather than the slot machine. It would be interesting to see if you see the problem with something else powered off of the same UPS that uses a similar amount of current.

No, it's not the UPS itself it's the slot machine. When the receptacle where the UPS input side is plugged in has power, the UPS is working in bypass mode like it would not be there (I've double checked that by removing the UPS completely).

I only mentioned the UPS in this context because it's the reason why the slot was never switched off so my flickering was always there. If I would have used the slot like a usual device and had switched it on and off from time to time than I would have been able to notice that it correlates with the LED flickering..

It sounds to me like the flickering is due to a harmonic generated from the interaction of the PWM frequency of the inverter and the (in this case) UPS, kind of like an out of tune instrument.

Interaction between the inverter and the slot's power supply electronic (but not the UPS). The link of @Plum Crazy Rob's post describes the problem very detailed.

It would also be interesting if it would change/decrease if you added something else, like another UPS, or a switching power supply. Adding another PWM frequency should at least change the harmonic frequency.

Until now, I found no other load in my house which also causes constant flickering.

 

[Zwy]

Yeah the UPS clicking was a different issue. It was either dirty power or the UPSs being too sensitive. You be the judge… ?

Victrons are just working. You almost could forget they’re there.

I fixed the flicker problem too, with a pair of LV6548's.

 

[SparkyJJO]

Yep and I agreed with his diagnosis.
And as I have previously said, an inverter is just a bloody great big amplifier/transmitter and you have to treat their output load with the same caution you would an audio amplifier or radio transmitter. A bad load can cause mayhem.

And I think HF inverters are inherently more sensitive to stuff like this. The big transformer in LF inverters I suspect absorbs all that noise a heck of a lot better.

 

[Crowz]

yes

No, it's not the UPS itself it's the slot machine. When the receptacle where the UPS input side is plugged in has power, the UPS is working in bypass mode like it would not be there (I've double checked that by removing the UPS completely).

I only mentioned the UPS in this context because it's the reason why the slot was never switched off so my flickering was always there. If I would have used the slot like a usual device and had switched it on and off from time to time than I would have been able to notice that it correlates with the LED flickering..

Interaction between the inverter and the slot's power supply electronic (but not the UPS). The link of @Plum Crazy Rob's post describes the problem very detailed.

Until now, I found no other load in my house which also causes constant flickering.

Most people have no idea that all of the fancy claims a normal off the shelf walmart/bestbuy ups are lies.

Normal consumer ups's don't filter anything actively. They just bypass till an under or over voltage condition occurs or a dead short so any funky effects being back fed thru them or fed thru them is not effected by the ups at all.

You have to get into a much higher priced ups to have active filtering of effects.

 

[fmeili1]

Most people have no idea that all of the fancy claims a normal off the shelf walmart/bestbuy ups are lies.

Normal consumer ups's don't filter anything actively. They just bypass till an under or over voltage condition occurs or a dead short so any funky effects being back fed thru them or fed thru them is not effected by the ups at all.

You have to get into a much higher priced ups to have active filtering of effects.

You're right! See my post about building an online UPS by myself because of the high costs...

 

[fmeili1]

Follow up.

I haven't used my 3D printer for a while and now I've recognized that this machine (Anycubic Vyper) produces even worse LED light flickering (I think it's the heating element control electronic for the bed and/or the nozzle)! Even on the grid, I can see the LED lights flickering not as bad as with running by the inverters but definitely visible!

After doing a lot of research it looks like that HF inverters are in general more sensitive with phase control loads (triac) and PWM loads if these loads do not have well designed EMI AC-filters, compared to LF inverters. I found comments for these problems with all kind of different HF inverters from different vendors. It's more a principle problem with "dirty" loads (as some others already mentioned and explained in this forum). The effect of the LED flickering may be more or less visible depending on the inverter vendors implementation, the quality of the electronic components, firmware, etc/ but none of them will be able to completely solve this problem, because it seems to be inherent in the HF design itself.

It looks like this will be a real challenge to get rid of this problem. As a next step, I will try different types of EMI AC-inline filter to find out if this is more a common mode or a differential mode EMI problem - or maybe both. I've already tried a simple ferrite core in the AC wire of the 3D printer, but no success. Also I've tired a simple $30 EMI filter but it also didn't help (but this filter reduced the LED flickering problem with my old slot machine). If nothing helps, I may try to mod the 3D printer itself (but I don't really want to do this).

I wonder why no out of the box solutions exists for this problem. A Google search with "3D printer LED flickering" brings a ton of problem descriptions - even without inverter usage, just with the grid! So this problem seems to be widely known and I guess there should be some sort of an "external filter solution" already available - but I couldn't find one.

 

[RCinFLA]

Slot machine probably has electro-mechanical solenoids that have high peak surge currents when activated. Sudden load current changes sets the inverter PWM filter ringing causing instability in inverter AC output voltage regulation.

Other possibility is simple AC to DC rectifier-filter capacitor power supply that has high peak current crest factor to recharge the filter capacitors at only the AC sinewave voltage peaks.

If you apply more real (resistive) load on inverter it will dilute the effects of the short load current pulses.

 

[fmeili1]

Just for curiosity - maybe someone could answer this.

I know 3 different types how to control the power of AC loads with a constant voltage source.

• phase angle control (triac)
• PWM
• integral cycle (aka "burst firing")

I wonder which type of power control does a HF inverter design stresses at most and which at least, or doesn't it matter? My guess is PWM load will stress at most because the HF inverters also uses PWM to drive it's H-bridge circuit. If I'm right, it wouldn't be a real EMI problem but maybe there are interferences between both PWM signals which results in this problem.
With my understanding, "burst firing" would be the cleanest way to regulate a load with the least EMI - but if this would reduce the HF inverter problems? I don't know!
However, in the AC-output graph it's visible that the HF inverters control loop is not able to fully stabilize the output voltage (see my first post) which causes the LED flickering.

 

[SunDave]

I wonder why no out of the box solutions exists for this problem. A Google search with "3D printer LED flickering" brings a ton of problem descriptions - even without inverter usage, just with the grid! So this problem seems to be widely known and I guess there should be some sort of an "external filter solution" already available - but I couldn't find one.

I have what you may consider a strange idea, but I'll throw it out there anyways. Instead of fighting the problem as "I need an inverter to work with this certain type of bulb" you could change out your LED bulb to CFL or something else that may not flicker. There is not as big of a difference between LED and CFL in lumens per watt as the old filament bulbs. Maybe you would still have the same problem, but it would only take one bulb to test the theory.

More of a workaround than a fix. Just a thought.

There are even many types of LED bulbs, some with way better drivers.

 

[fmeili1]

Slot machine probably has electro-mechanical solenoids that have high peak surge currents when activated. Sudden load current changes sets the inverter PWM filter ringing causing instability in inverter AC output voltage regulation.

Other possibility is simple AC to DC rectifier-filter capacitor power supply that has high peak current crest factor to recharge the filter capacitors at only the AC sinewave voltage peaks.

If you apply more real (resistive) load on inverter it will dilute the effects of the short load current pulses.

Yes! As soon as e.g. my water heater starts, the LED flickering is nearly gone! But even with a high inductive load with my central heat pump (with MicroAir soft start), the flickering is nearly invisible.

 

[fmeili1]

I have what you may consider a strange idea, but I'll throw it out there anyways. Instead of fighting the problem as "I need an inverter to work with this certain type of bulb" you could change out your LED bulb to CFL or something else that may not flicker. There is not as big of a difference between LED and CFL in lumens per watt as the old filament bulbs. Maybe you would still have the same problem, but it would only take one bulb to test the theory.

More of a workaround than a fix. Just a thought.

Yes, that's a possibility, but I feel uncomfortable because of the high voltage fluctuations which would still be there - even if not longer visible. I don'k now if I would like this and I don't know if sensitive electronic may like it also. I fear that the voltage range fluctuations may be worse sometimes for some moments. Until now I see voltages between 117V and 122V which is not really bad (more like grid), but compared with the output voltage without the 3D printer running, all inverters have exact and stable 120V output.

I don't know, if by coincident the PWM filter ringing or the high peak current crest factor (as @RCinFLA noted) may cause very huge instabilities - which could cause the voltage to drop below e.g. 105V or over e.g. 135V - I don't know if this may be possible.

There are even many types of LED bulbs, some with way better drivers.

 

[SunDave]

Hi. I totally understand trying to figure out the root of the problem.

It is also interesting that everyone came to the conclusion that sometimes adding loads helps. I heard years ago that sometimes running a fan or some type of motor can smooth out poor power.