Hi. I have a Deye SUN-8K-SG01LP1 EU.   It is working as it should. However, I have noticed something strange. When the inverter is on, even if PV is disconnected, there is a voltage detected at the PV IN terminals (equal voltage of about 130v AC on all PV input terminals (both - and + PV input). The voltage causes a test screw driver to light up (showing there is significant AC voltage present) and by a multimeter I measured 130V AC between the PV IN terminals and ground. Is this normal?   If so, wouldn't this be bad for the solar panels? I mean there is an AC voltage being applied to the panels. Also isn't this a safety concern? Doesn't this cause a risk of an AC current back flowing from the inverter to the panels and into ground?

I would appreciate if you could explain to me why I am observing this. 

Note:  I also asked some others with installed inverters (both Deye and Growatt) and they tested their inverters and had the same behavior!  A friend told me he actually got a nasty electric shock when he touched the PV IN terminal (with no PV connected, so the electricity was coming from the inverter).

I would really appreciate any ideas as to why inverters do that.

Thank you.

I think this actually happens in all inverters of 450_500V   . , but not on 145v inverters !! 

Yes. It's a "feature" of all transformerless inverters with high PV voltage. It's because the Solar Charge Controller is a boost converter that feeds the DC bus, so it's referenced to the DC bus negative end. Neutral (which is or should be at earth potential) is connected to either the negative or positive end of the DC bus, depending on whether the generated AC waveform is positive or negative respectively.

So PV- typically has a square wave at 50 Hz at near zero and about -380 V. When PV is connected, the PV+ will obviously be hundreds of volts positive with respect to that. So with PV at 190 V, PV+ would be roughly symmetrical (± 190 V) with respect to earth. When the PV voltage is higher than the bus voltage would otherwise be, it pushes the bus voltage even higher, making the square wave at PV- have even higher amplitude.

This square wave is slightly filtered, but still this can cause significant Radio Frequency Interference from the PV wiring. Also, any leakage to earth due to rain and/or dust can cause problems, sometimes pushing up the bus voltage and even causing faults codes to be thrown.

The 145 V max PV models use a buck converter connected directly to the battery. The battery is isolated from the AC input and output, so these models don't have this problem.

Thank you very much for your answers. Finally someone know what they are talking  about and gives me a scientific explanation. Since after asking around, it seemed like this is an issue not unique to me, but still I was very curious to understand why it happens.  On other forums, the only answers I got were:  oh, no that is not normal.   Or: oh, this is the first time anyone has described such behavior from an inverter.  Or:  pls send me the serial number of your inverter so we can contact the manufacturer and report this defective inverter.     Even the manufacturer, who I emailed, asked me to send the serial number of my inverter and a video showing my multimeter readings and they will look into it.   To tell you the truth, it is really annoying that so many people reply to posts on forums, yet they really don't know anything. I mean, some of the above mentioned replies were from users who had hundreds of posts on forums dedicated to discussing solar installations and inverters..etc...   

Anyways, thank you very much.

11 hours ago, Coulomb said:

Yes. It's a "feature" of all transformerless inverters with high PV voltage. It's because the Solar Charge Controller is a boost converter that feeds the DC bus, so it's referenced to the DC bus negative end. Neutral (which is or should be at earth potential) is connected to either the negative or positive end of the DC bus, depending on whether the generated AC waveform is positive or negative respectively.

So PV- typically has a square wave at 50 Hz at near zero and about -380 V. When PV is connected, the PV+ will obviously be hundreds of volts positive with respect to that. So with PV at 190 V, PV+ would be roughly symmetrical (± 190 V) with respect to earth. When the PV voltage is higher than the bus voltage would otherwise be, it pushes the bus voltage even higher, making the square wave at PV- have even higher amplitude.

This square wave is slightly filtered, but still this can cause significant Radio Frequency Interference from the PV wiring. Also, any leakage to earth due to rain and/or dust can cause problems, sometimes pushing up the bus voltage and even causing faults codes to be thrown.

The 145 V max PV models use a buck converter connected directly to the battery. The battery is isolated from the AC input and output, so these models don't have this problem.

Thank you Coulomb for your explanation , some one advised me to install an mc4 diode in series with pv cables  out of inverter to (block) this voltage  coming out of inverter , would that solution be effective ? 

8 hours ago, Riyad179 said:

some one advised me to install an mc4 diode in series with pv cables  out of inverter to (block) this voltage  coming out of inverter , would that solution be effective ?

Huh, I never thought of that. One diode in the negative PV lead (cathode and bar on the PV side) should work. It should prevent shocks on the roof, and presumably also avoid the fault code 08 ("bus voltage too high") that can happen with panels that have leakage to earth. it might also reduce Radio Frequency Interference and buzz in audio systems.

On 2022/11/14 at 4:28 AM, Coulomb said:

Huh, I never thought of that. One diode in the negative PV lead (cathode and bar on the PV side) should work. It should prevent shocks on the roof, and presumably also avoid the fault code 08 ("bus voltage too high") that can happen with panels that have leakage to earth. it might also reduce Radio Frequency Interference and buzz in audio systems.

Well , then it would be nice to try this solution .

Thank you Guys i have a different view as well now i was experiencing the same problem with my SRNE 5kVA High voltage Inveter.