[RE-wrenches] RE-wrenches Digest, Vol 6, Issue 221

[Scott McCalmont]

Some of the Power-One inverters use an extended scan on a periodic basis to
make sure they are not tracking a local maximum. In essence, they collect
an entire I-V curve, and this can take place as often as every 15 minutes.
The reason why this can cause problems with Tigo optimizers is that is can
bring the string voltage down to a level where it appears that the system
is shut down. Turning off the "multiple MPP scanning function" does not
disable the MPPT of the inverter, just the scan, and allows the two systems
to coexist.

Don, regarding your second point, Tigo does not recommend installing on
partial arrays. There are two parts to optimization: balancing within a
string, and balancing between strings. If optimizers were installed on only
two of three parallel strings, the Tigo system could in fact become
confused because it would be unable to balance the strings.

Regards,
Scott
...

Scott McCalmont (scott.mccalmont at tigoenergy.com)
Director of Solar Technology
Tigo Energy, Inc.



On Thu, Jun 6, 2013 at 10:18 AM, <don at energysolarnow.com> wrote:

> Robin's description of the problem matches that given by the Tigo and
> PowerOne techs when we recently had the same issue. In fact, PowerOne now
> has a pdf on their website to the effect that you must disable the
> inverter's MPPT scan when using Tigos with them. But they will not admit to
> any product shortcomings. Each accused the other's tracking algorithm of
> being "too aggressive," leading me to suspect they don't really quite know
> what is going on.
> The crux is the Tigo Maximizers have the solar modules in series strings,
> with multiple strings in parallel. They do their own MPPT tracking at the
> module level, and attempt to adjust module and string voltages to match
> each other in the presence of shading. This can drive inverters nuts, as
> they are trying to do this also. It does not bode well for the new "smart"
> solar modules with Tigo Maximizers built in. They have to learn to play
> nice.
>
> Tigos drive themselves nuts if, for example, two out of three series
> strings have Tigos but the third string does not. They worked OK for the
> two strings with mixed modules, but their algorithm could not figure out
> why it was unable to control net string voltage, and shut down some modules
> until it arrived at some reduced power level it can control. This caused me
> to remove them from the array.
>
> Solar Edge is different-- their module units are DC-DC converters that
> boost module voltage to a fixed 375 VDC. All modules can be in parallel (up
> to amperage limitations) like with microinverters-- no series strings. This
> is potentially more compatible with other inverters, hence their
> announcement to that effect.
> Don Barch
> Energy Solar
>
> From: Ryan <ryan at kb1uas.com>
> To: re-wrenches at lists.re-wrenches.org
> Subject: Re: [RE-wrenches] Tigo and SMA AFCI -
>
> From Robin
>
> It has been pointed out that the Tigo modules can and do blow up some
> charge controllers and inverters. When a charge controller or inverter
> has fairly fast tracking, the two units fight each other. We have found
> Classics using the fast tracking mode will blow up with Tigo's in the
> system. We also found that putting the Classic in the slower tracking
> mode, Legacy, solves the issue. We are aware that at least one major
> inverter model must defeat the tracking in order not to blow up. We have
> not yet tested our arc fault detectors with Tigo modules, but plan on
> doing this in the near future. It might be possible that the Tigo
> modules present a signature that looks like an arc. That must be what is
> happening with the SMA inverter.
>
> Robin
>
>
> On 6/5/2013 3:33 PM, SunHarvest wrote:
> > Just an FYI for anyone wanting to use Tigo optimizers with SMA
> > inverters incorporating AFCI -
> > According to SMA the Tigo optimizers will not operate with the SMA
> > inverters. They didn't go into detail. They just said the AFCI feature
> > of the Sunny Boy is not compatible with Tigo. After further discussion
> > they acknowledged that disabling the AFCI feature in the Sunny Boy
> > would allow compatibility with the Tigo optimizer. Awesome.
> > After talking this over with Tigo they came to the same conclusion but
> > neither company seemed too happy or confident in the marriage. Awesome.
> > Eric Stikes
> > SunHarvest
>
>
> From: Richard L Ratico
> Sent: Wednesday, June 5, 2013 6:44 PM
> To: re-wrenches at lists.re-wrenches.org
> Reply To: RE-wrenches
> Subject: Re: [RE-wrenches] SolarEdge Optimizer - Was: Tigo and SMA AFCI -
> Was: AC coupled, grid-tied Sunny Island - contactor & bypass
>
>
> SolarEdge makes an optimizer / inverter system. We just installed one. Our
> clients are happy. So are we.
>
> Don't know if you can AC couple the inverter. Their website says they are
> about
> to release a version of the optimizer that will work with other
> manufacturer's
> inverters.
>
> Dick Ratico
> Solarwind Electric
>
>
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