Upgrading Victron Setup: Hub-4 vs Parallel Inverters

[NickNou]

Hi there all,

 

First post on the forum - Been a member for some time, but Ive mostly been lurking around benefitting from the wealth of info available here. This is a great place if you need some guidance or info, and has been incredibly useful for my projects.

I embarked on going off-grid with the bulk of my household around 18 months ago. Things drew to a close in February, but as you'll know - there is always room for improvement on these projects.

In short my setup consists of the following: backbone is a 5kVA Victron Quattro being fed from a 660AH 48v traction/forklift battery bank. Solar input is provided by an AC-coupled SMA with 3.8kWp installed in two arrays (East and West bias).

I hope to give some info to discuss how I went about settling on the above figures - perhaps a post in the members installations area is in order.

The setup is currently setup to run with hub 2V3 configuration, with the idea of maximizing self consumption of my PV yield. Export of my surplus is unfortunately not possible, as I'm metered, like most of us, on prepaid. My PV integration is, as per the forum's norms, slightly "unconventional". I have gathered most of the installations are either pure grid-tie where export is possible, or make use of charge controllers.

The idea when opting for AC over DC coupling was to push the PV straight into the inverter "AC bus or Microgrid" which powers the loads, requiring the Victron to only supply the shortfall, or to absorb any surplus. This effectively places less load in the Victron when PV generation is available, meaning you can increase loads during the day (very well suited to my domestic load profile). Modulation of the PV generation is done by means of frequency shift on the Victron output when in invert mode. I find this to be an extremely simple, yet elegant PV output modulation method.

The project also spurred me to reduce my domestic base load. I run my entire household off the "microgrid" I generate (bar electric oven and hot water heat pump) connecting to mains only for overloads or battery maintenance charging.

I do however have the following issues:

1. At Night, when there is no PV incoming, the inverter output is very susceptible to changes in load or impulsive loads. This seems to occur with the onset of a sudden moderate load (500-600W). I have alot of issues with flickering LED's when we have some appliances running at night.
2. Being technically inclined, I am sympathetic to my kit. I don't like imparting high surge loads on my inverter. Even with options like grid-assist (where the unit reconnects to grid under heavy load) you have the inverter abnormally loaded for a short period of time. 
3. I want to push surplus solar to my heat pump, which is excluded from the Hub2 setup, as Im trying to keep the base load down.

Now, I have two options to resolve my the above:

Option A: 

Install a second Victron in parallel with the first. This should allow the system to:

1. Better absorb peaks or changes in load.
2. Reduce load by sharing the demand over the two inverters
3. Better operation of inverters (less load
4. Redundancy in event of having a unit fail
5. More off-grid peak capacity for a higher base-load
6. System stays with existing architecture - proven that it works.

Option B:

Revise the setup to run on a Hub 4 configuration - so many advantages to this system.

This uses the grid to absorb peak loads and provide some stability, as the main unit runs in Parallel with the grid. HUB4 will allow me to push surplus or stored PV to loads with are normally grid connected. I have however realized the following:

1. We have terrible power quality in our area, and get outages every week. This will require me to connect the bulk of my loads to AC1 (no break). This is not a problem, and my system will maintain UPS functionality as I already have with Hub2V3.
2. Assuming a standard Hub 4 setup and control algorithm, the Victron unit is always in bypass (I.e connecting Grid to the Inverter output) this means that everything is running at grid frequency (50Hz). This completely throws the concept of frequency shift out the window. If you are using a GTI, you must be able to export the excess PV or pull in a dump load. Please note this is not a problem if you running with MPPT's and running Hub 4 (see Plonkster's recent posts on HUB4). If you are going the route of a GTI on hub-4 and can't export, you need to opt for a Fronius unit, which has comprehensive integration and control possibilities with the Victron CCGX.
3. Anti-islanding protection? To my understanding off-the-shelf Victron units have Anti-islanding protection, but they do not conform to local NRS requirements. I found a topic by Plonkster from two years back regarding this. It still seems to be a bit of a dark horse?

Also, I do not have any monitoring as yet, but will be looking at a CCGX/Venus/VRM in the near future, especially if Hub-4 is already on the cards.

I would appreciate input from you guys. Thanks retrospectively for the indirect guidance many of you have provided in the past!

Nick

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Nick,

There are so many cool things coming in version 2.0 of Venus (the firmware for the CCGX). The hub assistants are all going away to be combined into one assistant. So soon you may not have to choose between Hub2 and Hub4, you will have one assistant installed in the inverter and it will all be controlled by the CCGX.

I would go for Hub-4. I'm running a very small hub-4 system at the moment with a 1600VA Multiplus Compact. When a large load on the inverter output starts up, it still makes that little buzzing sound (I'm sure you know it), but of course no such problem with loads on the input side.

As to being sympathetic: I've pulled my Multiplus into shutdown -- well not me exactly, visiting family with their hair dryer -- and if you think that little buzzy sound it makes when a load starts sounds bad, you should hear the terrible ruckus it makes when overloaded to 200% (which it can handle for about a second or so) before it shuts down.

A CCGX is around 8k, a second Quatro is over 40k. I think venturing into the other hub systems will be a lot more cost-effective.

Anti-islanding is a problem still. You will have to get the Ziehl UFR-1001E. That makes it NRS-097-2-1 compliant. The 2017 Multiplus will have it built-in.

I also have a Conlog BEC23 meter which is known to trip if you feed back. I don't know if my meter was kindly or mistakenly configured to allow feedback, if I'm lucky, or perhaps my inverter is just too small, but even at full barrel (1600VA) suddenly turning off a load does cause a large spike to be fed back, but so far no tripping.

Also, if you want to avoid the load on the inverter, you will have to use a second current sensor. The hub-4 system supports the Carlo Gavazzi meter out of the box. That's a rather expensive unit though. Still, the combination of a CCGX, current meter and Anti-islanding will cost less than a second multiplus.

You can also look at using a Beaglebone unit instead of the CCGX. Victron sells them now, in a nice enclosure with the vebus port built in. No LCD screen, but fully supported.

There is also a Raspberry Pi version in the works. It lacks testing because not many people use it and the guy working on it (me) only has a few hours a week to spend on it, but it's coming along nicely.

[NickNou]

Hi Plonkster,

Thanks for the quick and comprehensive feedback.

I really like the approach that Victron has taken opening up the Venus Firmware on the CCGX. I have been following the updates on the Google Venus development group, an am keen on getting Venus running on a BBB. It sounds like really exciting stuff – even if it’s slightly out of my scope of expertise for now.

Yes, Hub 4 would be the best route in my case. Up until recently, the older hub 2v3 configuration was the only option to get decent self-consumption. With this in mind, and given the issues above, I purchased a second Victron Unit a while ago, for a very good price, with the idea of installing it this summer.

Regardless, Hub 4 just seems like a better configuration all round.

Hairdryers and Vacuum cleaners - My wife has on occasion pushed the limits of my kit – I’m quite aware how loud a Victron can buzz and complain under load!

I would like to stick to a GTI AC-coupled to the output of the inverter, instead of going for MPPT’s. Currently in a bit of a pickle with the SMA – which can’t be controlled by the CCGX in any method other than Frequency shift. I’ve tried to think of a number of ways to still integrate the SMA into a Hub-4 while limiting grid export. One of the options would have been to install an SMA sunny manager + sensor to prevent export (Horrifically expensive – even by Victron standards) but even this could be unstable if implemented with Hub-4, according to the feedback from Victron.

For hub 4, I’m contemplating swapping the SMA SB out for a Fronius Primo/Galvo to give me reasonably hassle free integration with the CCGX.

As for metering. My house is still fed from an old Ecolec 570 unit. I’m hoping that the unit lacks the required “resolution” to pick up any short term export peaks. In addition to this there is a second Landis municipal meter – will need to be a process of trial and error to see if this guy trips out into tamper mode.

On CCGX / Venus Hardware:

I’ve gathered that the bulk of the Venus development has been on BBB. I know that they were working on a complete BBB based blue-box product with the required cape - think it’s called the Beaglebone Controller? Can’t seem to find any information on this being marketed yet? If I have it correctly, if I use a standard BBB without any cape, running Venus, I will require the following:

• Mk2/Mk3-Usb to Comm with Multiplus/Quattro
• 485 to USB adaptor to Comm with the Gavazzi EM24
• VEdirect to USB adaptor to Comm to my BMV (not entirely necessary in my case)

From this I should already be able to setup Venus to upload my systems data to the VRM?

Anti-islanding:

I really can’t find an alternative to the UFR 1001E other than the UFE ENS26. I don’t think the latter has compliance to local NRS requirements. And then I wonder how many installations are actually installed with proper anti-islanding in place...seeing at these units are almost impossible to get hold of?

Nick,

 

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3 minutes ago, NickNou said:

opening up the Venus Firmware

Some of it was open to begin with. It's based on a Linux distribution known as OpenEmbedded. I first ran into OpenEmbedded around 2007, on a satellite receiver known as the DreamBox. I do love the fact that they opened up so much of their other stuff too. The ultra-sensitive stuff remains closed source of course.

9 minutes ago, NickNou said:

GTI AC-coupled to the output of the inverter,

This remains the best option for direct consumption.

9 minutes ago, NickNou said:

SMA – which can’t be controlled by the CCGX in any method other than Frequency shift.

Yeah the problem comes in when you're making more than you're consuming and you have to throttle back. Only way to do that is to disconnect from the grid and run your own little island. This apparently causes problems in some installations, the switching back and forth and altering frequency are not ingredients to creating a stable system, Victron themselves see "prevent feedback" as somewhat of a thorn in the side becaise of this. The CCGX can control the Fronius directly to avoid this, which is why the Fronius is preferred. However... I know they use Modbus RTU and the sunspec protocol on the Fronius, and I also read that SMA also supports sunspec, so there is a possibility that it can be made to work... although this is pure speculation based on reading a few specification sheets.

15 minutes ago, NickNou said:

bulk of the Venus development has been on BBB

Not really, the bulk was on their own hardware known as the CCGX, which is itself based on a Texas Instruments development board (Technexion TAM-3517, Sitara AM3517 based SoC). But that's ARM Cortex A-8, which is the same as the chip on the beaglebone. The Raspberry Pi-2 runs an Arm7 chip, so that is also close enough that it ports with very little effort. It is true however that there has been way more work on the BBB than on the Rpi!

19 minutes ago, NickNou said:

complete BBB based blue-box product with the required cape

I believe this is in stock now. Though you'll have to order from HQ, I don't believe local stockists keep it.

20 minutes ago, NickNou said:

if I use a standard BBB without any cape, running Venus, I will require the following:

• Mk2/Mk3-Usb to Comm with Multiplus/Quattro
• 485 to USB adaptor to Comm with the Gavazzi EM24
• VEdirect to USB adaptor to Comm to my BMV (not entirely necessary in my case)

From this I should already be able to setup Venus to upload my systems data to the VRM?

You want the new mk3-usb. It looks much nicer and firmware upgrades are much easier with the mk3. The mk2 is not really supported, you can make it work, but the only place it will be officially supported is in the CCGX itself. In the CCGX there is a built-in mk2 with a hardware line that power-cycles it to force a reset. This means the CCGX has control which you don't have with the mk2-USB, and this is precisely the problem and the reason you want the mk3.

Cost is the same, so there really is no reason to buy an mk2 now.

You'll need to modify at least one configuration file to make the external unit work, but it's no problem, it works as expected with that one small change.

Other than that, completely correct.

23 minutes ago, NickNou said:

seeing at these units are almost impossible to get hold of?

ABB has a unit that you might be able to get hold of locally, but it costs MORE than the Ziehl or the ENS26. I ended up ordering my kit directly from Victron HQ and having them courier it down. Courier costs are only 35 Euro, but of course the rest isn't cheap... but it isn't cheap locally either because of our poor exchange rate.

[NickNou]

Plonkster,

21 hours ago, plonkster said:

However... I know they use Modbus RTU and the sunspec protocol on the Fronius, and I also read that SMA also supports sunspec

I had a look at the SMA modbus parameters this afternoon. As you said, SMA is standardized as per Sunspec. There seems to be quite alot of information available on implementing Modbus comm's on the SMA. They have some very good documentation explaining the various addresses for parameters. What makes this even more interesting, is that out of the box, SMA's inverters are supplied with a Webconnect module (TL-21's). This module can, according to their product literature, be configured for Modbus TCP. A Modbus RTU module can be bought for around R1300.

If there is a governing standard (Sunspec) and you can easily duplicate comms, zero-export Hub-4 with an SMA and CCGX seems to be do-able

I'm not sure if the Fronius-CCGX is RTU or TCP based - Off hand, I think the Fronius' data manager supports both.

20 hours ago, plonkster said:

It is true however that there has been way more work on the BBB than on the Rpi!

Sorry - this is what I meant. There seems have been alot more focus on the BBB  as packages came available in the past few months. 

20 hours ago, plonkster said:

You want the new mk3-usb. It looks much nicer and firmware upgrades are much easier with the mk3. The mk2 is not really supported, you can make it work, but the only place it will be officially supported is in the CCGX itself

Noted. Unfortunately I already have a Mk2-USB. I'll order myself a BBB this week so that I can tinker with it over the festive season. 

21 hours ago, plonkster said:

ABB has a unit that you might be able to get hold of locally

I've had a look at the ABB, the ENS26 and the 1001E. The 1001E seems to be the default option for anti-islanding.

However, The ENS26 is lot simpler to integrate, as all switching is done inside the module itself. It does not seem to need any external relays or contractors, but is limited to 5-point-something kw and single phase. You only have a set of feed and mains terminals (each L-N) to connect up.

I think the purpose of an anti-islanding unit is two-fold. The first is that you properly/safely isolate yourself from the grid in the event of a blackout. The second benefit is that you protect your inverter from abnormal grid conditions (brown outs, abnormally high voltages..etc).

Nick

 

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34 minutes ago, NickNou said:

I'm not sure if the Fronius-CCGX is RTU or TCP based - Off hand, I think the Fronius' data manager supports both.

Stole this screenshot from a draft blog post (the one that is being worked on for Venus 2.0) :-)

 

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37 minutes ago, NickNou said:

There seems have been alot more focus on the BBB  as packages came available in the past few months.

The BBB port and the Rpi port both have one guy behind it (mostly), I think the difference is that the Rpi porter has a day job and started a LOT later :-P

Right now there's actually just a few more items, the most pressing one is remote updates (swupdate), and figuring out how to deal with the mk3 (probably some udev magic).

41 minutes ago, NickNou said:

Unfortunately I already have a Mk2-USB.

I have both now. I'm going to keep the mk2 for use with veconfigure while the mk3 will do duty with the Rpi. Perhaps, in time, I will butcher it and see if I can hook into the rx/tx lines. I know there is a FTDI chip and a PIC Microcontroller inside, so it can definitely be done. Then the idea is to build something using either an arduino or a STM32 board that talks directly to the mk2. It's just an idea for now :-)

43 minutes ago, NickNou said:

The 1001E seems to be the default option for anti-islanding.

I think the Ziehl is the best one to go for because it complies with NRS-097-2-1 already and it's also on the Cape Town approved list. I mean, the others might comply too, but imagine the cost and effort of convincing the authorities. It needs an external contactor but this is not a contactor that works very hard. In my case, since the transfer switch is only capable of 16A, I got away really cheaply (25A 3-phase unit at R350). With the big units (50A and up) you're looking at a 63A double-pole relay, which can get costly.

49 minutes ago, NickNou said:

protect your inverter from abnormal grid conditions

Yup, that too. It makes one sleep a little easier knowing you have that extra protection.