How does XW works with Genset in Genset support mode?

murali · June 2015

We are testing our setup in three phase and the sources are connected in parallel. XW (3*6048 ), Genset (15kVA), Conext TL (8kVA, PV) & all loads are connected to the same bus. We are operating XW in shunt configuration but not in a typical pass through mode. As we all know, XW has 3 terminals, say AC1 , AC2 & AC out.
1. I assume that during off-grid operation (with genset), XW connects to the bus and effectively to the genset through the AC2 terminal. Is this right?
2. In case of excess power on the bus, is it possible to utilize the same AC2 terminal to charge the XW batteries?
3. If the total load current is at 18 A and genset support amperes are set at 10 A, will the XW supply the remaining 8 A and through the AC2 terminal again?

BB. · June 2015

Welcome to the forum Murali!

If I understand your questions correctly... Yes to all of them.

However, just to be clear, the AC2 is an "Input" to the XW and the AC Out is an "output" (direction of power flow).

So, if you have an 18 Amp AC Out load, 10 amps will come from the AC2, and 8 amps will come from the XW "Inverter+Battery Bank".

And for three phase operation--Power wise, each of the three XW's will act "independently" of each other. One XW may output 18 amps in Phase A, a second may output 12 amps into Phase B loads, and the third 2 amps into Phase C loads.

Of course the three will synchronize in frequency and phase to each other and the same 3 phase genset.

-Bill

mike95490 · June 2015

AC1 & AC2 are inputs. AC1 is preset to be the GRID with tight frequency and voltage specs. AC2 is presumed to be the genset. and has looser Fq & volt specs. AC1 & AC2 should never BOTH be powered at the same time, I don't know what the XW will try to do.
AC out is the output, and can be straight through from the AC input if active, from the batteries, or battery assisted generator power. (Generator Support Mode)

If the grid is down, the XW can pass generator power through it, and charge batteries at the same time, according to the limits set by AC2 breaker, Batt size, GenSupport mode, % of battery size charge rate. A quick sample of my settings for a modestly derated 3Kw genset and 1,000ah battery bank ( I call it 1,000 ah because it makes the charge % math real easy)
---
Battery Bank Capacity 1000 A (1,000A makes for easy, direct conversion to charging amps,
mistakes are limited to AC2 & Generator Support amps limits)
Maximum Charge Rate 5-35 A (I adjust as my diesel warms up)

AC2 Breaker Size 19.5 A (each breaker is only @ 120V so both will add, this setting = a limit of 4680w, derated to 3744w)

Generator Support Enable : Enabled
Generator Support amps 13.1 A (each breaker is only @ 120V so both will add, this setting = a limit derated to 2515w)
Generator Support PLUS Enabled
---

As AC loads vary, the brains in the inverter will reduce charging amps so as to not overload the generator.. If the XW senses generator overload, it stops charging and switches to INVERT to assist the generator, as soon as loads ease, the XW resumes charging

Here is a video of the XW gen support
https://www.youtube.com/watch?v=3nWOQNGl3MU&list=LL3rM6w61Ib56r_-9wW70Q-w&index=2

new2PV · June 2015

Mike your posts are always very informative....Wow...:cool:

SkiDoo55 · June 2015

If you have power available on AC1 and AC2 it will depend on which one has priority set. Normal is set as AC1 but if you had an alternate source on AC2 hydro etc you could set priority to AC2 and use the grid on AC1 as the backup source.

mike95490 · June 2015

new2PV wrote: »

Mike your posts are always very informative....Wow...:cool:

I gleaned a lot from Chris Olson's posts about the XW and generators.
(link to his posts here -
http://forum.solar-electric.com/search?searchJSON={"authorid":["9634"],"channel":"2","exclude_type":["vBForum_PrivateMessage"] )

Chris is no longer on this board, or active on any other board, but his posts remain. (He is OK, just busy busy)
http://www.solarpaneltalk.com/search...archid=1539119.

murali · June 2015

Attachment not found.

Hi BB., mike95490 and SkiDoo55,

Thanks for the reply!!

I understood that Genset power has to pass through AC2 and AC out.
To get clarified i have attached Drawing -1 and Drawing-2.

Drawing-1:
1.As suggested by Forum members Genset power is given as input to AC2 where it charge the battery and supplies the remaining power to the loads through AC2.
2. If my Genset support is set to 10A and the Genset generating capacity is 15A , will the XW has the capacity to restrict the input current through AC2 terminal to 10A and supply the remaining say 8A from the batteries via AC out terminal along with the 10A from the genset?

Drawing-2:
When the genset support current is set (10A) where, genset also connected to the same bus as shown in diagram-2 thus, supplying 10A from the genset and the remaining current of 8A is supplied only through AC2 of XW ?

It would be great if the esteemed forum members can confirm the right configuration viz. Drawing-1 or Drawing-2. Thanks in advance!!

mike95490 · June 2015

Dwg 1 is correct. Dwg 2 provides no way for the XW to sense any load current, Where the heck did Dwg 2 come from ? IT IS WRONG.

murali · June 2015

Thanks for the reply, Mike!!

We have only assumed Dwg 2 since we have not come across any info about connection of Genset with XW in XW installation guide or manual.
Can you please answer to question 2?
If my Genset support is set to 10A and the Genset generating capacity is 15A , will the XW has the capacity to restrict the input current through AC2 terminal to 10A and supply the remaining say 8A from the batteries via AC out terminal along with the 10A from the genset?

During On-grid operation when XW is connected to the Grid, can XW operate in sell mode only through AC1 when both Grid and XW are on the same Bus?

BB. · June 2015

murali wrote: »

If my Genset support is set to 10A and the Genset generating capacity is 15A , will the XW has the capacity to restrict the input current through AC2 terminal to 10A and supply the remaining say 8A from the batteries via AC out terminal along with the 10A from the genset?

The XW does not directly limit the AC2 to 10 amps directly... It does it indirectly by measuring AC2 current and deciding to "inject" 10 amps from the XW's inverter block (really in GT mode, I think) onto (in this case) the common AC "bus" such that the sum of both currents limits AC2 input to 10 amps.

And remember that in US/North America, you may find some "deratings". If the AC2 breaker is defined as 10 amps in the XW software menu, it (probably
/should/does?) limit the AC2 current to 8 amps... NEC says that a 10 amp breaker * 0.80 NEC derating = 8 amps maximum sustained current.

murali wrote: »

During On-grid operation when XW is connected to the Grid, can XW operate in sell mode only through AC1 when both Grid and XW are on the same Bus?

From a hardware point of view AC1 and AC2 are probably nearly (or even exactly) mirrors of each other (identical in hardware design).

However, from a software point of view, AC1 is assumed to be Grid Power and AC2 is generator power. It is assumed that no standard AC generator should be back fed power from the XW inverter as this will either damage the genset and/or trip voltage/frequency limits in the XW.

I believe that is how they implemented the XW software (just guesswork from me).

Could you reprogram the XW to allow GT on AC1 or GT operation on AC2--possibly. But remember that the utilities/UL/NRTLs have limits on frequency and voltage to prevent installer/network harm from GT operation. Most GT inverters (if they support field reprogramming of Utility voltage/frequency limits) do this with additional passwords to prevent the users from "playing" with safety/regulatory settings.

-Bill

SkiDoo55 · June 2015

AC1 is the only connection that will allow Grid tried (bi-directional) power flow. If selling it will match the freq and voltage of the grid source within specification before selling.
AC2 does not have the capability to back feed to protect the generator or alternate source of power. The restricted (set limit) from generator will be controlled by the XW adding power from batteries to support the loads on AC out up to the inverter/battery capacity, as previously mentioned.
If your generator has a Continous 15 amp rating you can set it at what ever load on it you need. If loads are less than that setting the XW will you excess gen power for battery charging up to the set gen limit. Charger section voltage/amps setting need to be set for your battery bank so as not to over charge or not charge completely. Need to set bank amp-hour capacity etc.

murali · June 2015

Thanks for the reply!!

If current from genset=15A

Case1 (Load current<Genset). If Load=7A, Genset support =10A, will the remaning current of 3A is used charge batteries? What happens if the charger is disabled in this case?
Case2(Load current =Genset current). If Load=8A, Genset support =8A ,will the inverter/charger be idle in this case?
Case3 (Load current>Genset). If Load=18A, Genset support =10A, will the remaning current of 8A is supplied from the batteries of XW? Does the inverter has to be enabled or XW will take care of itself?

BB. · June 2015

murali wrote: »

If current from genset=15A

Case1 (Load current<Genset). If Load=7A, Genset support =10A, will the remaning current of 3A is used charge batteries? What happens if the charger is disabled in this case?

Yes, remaining 3 amps is used to recharge the battery bank

If charger is disabled, then only 7 amps is supplied by the generator and sent to the loads (XW would use some Watts just to run its electronics and internal transformer losses).

Case2(Load current =Genset current). If Load=8A, Genset support =8A ,will the inverter/charger be idle in this case?

More or less, plus whatever the XW tare losses are (don't remember but something like 20-60 Watts or so).

Case3 (Load current>Genset). If Load=18A, Genset support =10A, will the remaning current of 8A is supplied from the batteries of XW? Does the inverter has to be enabled or XW will take care of itself?

You are getting close to the maximum working current of the XW (depending on size of inverter). They can surge ~2x their rated current for a short period of time (starting a well pump as an example). What will happen in generator support mode if the inverter + geneset exceeds ratings--I do not know.

There are a fair number of configuration settings in the XW--I don't know what happens if one or more are miss-configured, but if done wrong the unit will not automatically fix itself.

-Bill

mike95490 · June 2015

murali wrote: »

Thanks for the reply!!

If current from genset=15A

Case1 (Load current<Genset). If Load=7A, Genset support =10A, will the remaning current of 3A is used charge batteries? What happens if the charger is disabled in this case?
The charger stops and genset only sees 7a load
Case2(Load current =Genset current). If Load=8A, Genset support =8A ,will the inverter/charger be idle in this case?
yes, charger will not activate
Case3 (Load current>Genset). If Load=18A, Genset support =10A, will the remaning current of 8A is supplied from the batteries of XW? Does the inverter has to be enabled or XW will take care of itself?
Charger must be enabled in a menu somewhere, AND all the parameters that control it (Battery size, max amps....) should be set

This all assumes that the many settings that interrelate are set right. Wait till you see what has to be tweaked to get Grid-tie to work properly with the batteries !!

BB. · June 2015

I will add something else too...

You are asking a lot of detailed questions about AC current and generator support. One thing to remember/understand about AC current is that:

Volts * Current = VA
Volts * Current * Cosine (phase angle between voltage and current) = Watts
Volts * Current * Power Factor (0.0 to 1.0) = Watts

What comes from the battery bank is:

Watts = Batt Volts * Batt Current * 1/Inverter Efficiency

If you have a purely resistive load (electric heater for example), then Watts = VA (cosine of 0 degrees = 1.0 = PF)

If you have an induction well pump, the power factor / Cosine of the phase angle can be as low as 0.67 (more or less, depends on motor design, operating conditions, etc.). For example if you measure 10 amps with a current meter:

VA = 10 amps * 240 volts = 2,400 VA load
10 amps * 240 volts * 0.67 PF = 1,608 Watts from battery bank
1,608 Watts AC load / 0.85 inverter eff = 1,892 Watts from battery bank
1,892 Watts DC / 52 volts battery bank = 36.4 amps from battery bank

When Cosine/Power factor is less than 1.0 (Cosine of zero degrees), current (Amperes) is used "less efficiently" to make power. The batteries do not "see" VA, they only see the Watts of the load.

However, your AC wiring, transformers, inverter, AC generator, circuit breakers, fuses, etc. all "see" VA (or actual current) flow. And must be rated to manage this.

If you are asking this level of detail about the XW inverters/generator support, you probably need to understand this about AC power too. From school, if you remember adding "vectors", this is what AC power is (there are other ways that VA does not equal Watts--And that is if the AC loads are not sine waves but other wave forms--Many electronic supplies take current in a non-sinusoidal manner).

The details in AC math are amazingly complex.

-Bill

murali · June 2015

Thanks for the detailed reply Bill & mike95490 !! Now i am more clear about the operation of XW in genset mode.We are using purely resistive load. I understood that battery supplies only active power, when genset rated current is 15A , genset support =10A, Load=18A, then inverter of XW supplies remaining 8A. I completely agree with the analysis presented for the AC loads. It is important to understand that the battery sees only the active part of load current and cables, transformer, breakers etc. will always see the total effective current due to the effective "VA". Still, I have slight doubt about enabling/disabling of inverter/charger in few scenarios. I think we will have to confirm by operating XW actually under these scenarios.

tampasolar · October 2017

Is GFS Enabled ? (under Active Power Control)
What is Generator Plus actually doing is Enabled ?
Can you link me any documentation on these concepts on the XW ? ComBox ?

How does XW works with Genset in Genset support mode?

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