Unstable grid with SMA TRIPOWER

[AdPower]

I am designing a PV system (30kW) to be coupled in a location where utility grid is highly unstable (fluctuation 190v to 230v), with up to 30v difference between two different phases.
I have chosen to use two Tripower 15000TL inverters from SMA.
I would like to know if I have to use a voltage stabilizer or maybe the inverters are able to withstand such variations without tripping-off. Can I program such wide range for tripping threshhold?

Mentionnend in the inverter's tech data:

Nominal AC voltage range 160 V - 280 V
AC power frequency / range 50 Hz, 60Hz / -6 Hz ... +5 Hz

Could you please advise?

 

[GoldDigger]

I am designing a PV system (30kW) to be coupled in a location where utility grid is highly unstable (fluctuation 190v to 230v), with up to 30v difference between two different phases.
I have chosen to use two Tripower 15000TL inverters from SMA.
I would like to know if I have to use a voltage stabilizer or maybe the inverters are able to withstand such variations without tripping-off. Can I program such wide range for tripping threshhold?

If the grid is that unstable, it may also present a high impedance. I would be concerned about whether the additional power supplied by the GT inverter could drive the grid connection voltage above the upper threshold of the GTI or adversely affect nearby users by causing them to see an overvoltage.
I would also worry about the phase voltage imbalance. If the inverter has a neutral connection, it should be sensing individual phase voltage as well as line to line.
If you look at line stabilizers, make sure they are designed/listed for backfeeding.

 

[jaggedben]

Given that the voltage fluctuations you say you are dealing with (190-230V) are well within the stated range of the inverter, I do not see a problem that needs to be solved. The inverter should not trip off if the voltage does in fact stay within that range.

I'm not familiar with this particular inverter model, and it may be that the spec sheet refers to an extended voltage range that needs to be programmed on the inverter. That is, it may be that the default settings of the inverter would cause it to trip off, but it can be programmed not to. SMA tech support should be able to walk you through that.

Golddigger may be right that if the grid is not very robust in the project area there may be other concerns. Hopefully the utility engineers are familiar enough with solar to be helpful. But on the particular question of whether the inverter will trip off due to fluctuating utility voltage you should be okay.

 

[AdPower]

Thank you for your answers

I had already contacted SMA tech and they said the same thing: they can get me to program large range thresholds for the AC Voltage. They also said that unbalanced phases is not an issue, it can be taken care of by inverter programming software.

As for the elevation of voltage nearby grid connection point, my understanding is that the voltage elevation is equal to the voltage drop in the line between inverter AC out and grid connection point, which can be minimized using a thicker copper cable. Am I right?

Regards, Ad

 

[GoldDigger]

As for the elevation of voltage nearby grid connection point, my understanding is that the voltage elevation is equal to the voltage drop in the line between inverter AC out and grid connection point, which can be minimized using a thicker copper cable. Am I right?

Regards, Ad

Elevation of the voltage at the GTI relative to the grid connection point can be controlled by using larger wire. But there is also a concern that the grid may be so weak down the distribution system that you would increase the grid voltage at your neighbor's connection as well as elevating the actual grid voltage at the point where you connect to the grid.

 

[SolarPro]

This article might be of some interest:

http://solarprofessional.com/article/?file=SP5_4_pg14_QA_1&search=

You'll be working with a more challenging grid, but the basic principals apply. John Berdner talks a little about grid impedance. If the facility has a reasonable service capacity, you'll probably be fine. It might be worth logging the grid for a few days or weeks at the site in advance to get an idea of whether and how you might need to tweak inverter setpoints.