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martin-krahn avatar image
martin-krahn asked

Feature request / development idea about diversion load regulation

Hi,

In my off-grid home (working since 29 years, in between mostly managed with victron products) I am used to put excess energy (from 7kWp solar and 3 kWp wind energy) into hot water tanks (for central heating and hot water).
In the beginning, when I only had 800 W solar and 1kW wind max power I used a LMW 24v power regulator that put the excess power into a 1.2 kW/24V heating element in my hot water tank, and this regulator managed it to burn exactly only that power that was excessive when the batteries were full: It powered up the element stepless when the system voltage was increasing (I think using MOSFETs) above f.e. 28.2V. So the batteries were protected from bigger loads as it would be if the excess "burning" was switched by a relay: only excessive power would be burnt.
Now I put the excessive power (when the batteries are full and the voltage exceeds 27.6V) into water, and I am using the 3 relays in my Quattro for switching 3 heaters of each 1.4 kW in steps of + 0.3V. But these steps are rather raw, and on a day with many clouds or changing winds the relays are switching and switching. I could delay their reactions, but that would stress the batteries more.

So I asked Johannes Boonstra from victron if he is interested in developing such a device that regulates excessive power stepless (in the wallbox a similar solution should be implemented). but he answered that they won't build such a device.
Who helps me to design and build a DC-voltage-controlled unit for a stepless powering of a 230V-heater, f.e. up to 6 kW for using all the maximum excess power of my solar panels and the power of the Quattro? I have some ideas, but I cannot design electronic circuits - I can solder and build near everything, but developing or programming.....that is not mine!

I think first I need a voltage devider that gives me the excessive voltage out to feed an OpAmp or a microcontroller that gives out PWM signals to drive a thyristor-power-regulator array / phase conrtrolled modulator.

I am sure that out there are many home mechanics who would welcome such a circuit.

Anybody out there who likes to design it for us and (if needed) programs a sketch for a controller?

Thanks in before,

Martin Krahn


victron community
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12 Answers
johanndo avatar image
johanndo answered ·

I don't understand your point. You say you have a working solution with the LMW - whatever that is. Why don't you use this? Add some more MOSFETS in parallel to the output for higher current switching and thicker wires / connections. You can use the output of your LMW (whatever that is) to control a analog regulator and the power, or you can add more LMW in parallel, one per heater.

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martin-krahn avatar image
martin-krahn answered ·

Hi Johann,

the difference is: The old unit regulated 24V up to 1000 W. The new one should handle about 5-6 kW at 230V (as the current would not be easy to handle when I stay at 24V). And: the old circuit has burnt long time ago...

Martin

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Mike Dorsett avatar image
Mike Dorsett answered ·

use a variable speed drive to power the heater. This will convert the excess AC power to dc, then back to AC using variable amplitude and frequency. Pick a model with external or remote speed control. Your heater will not mind the frequency, and the voltage should be controllable from about 80V or so to 240.

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martin-krahn avatar image
martin-krahn answered ·

Hi Mike,

yes, such a kind of regulator might work, too. But how should it be automatically regulated by the voltage of the battary? And isn't it more expensive than my idea with a microcontroller and some thrysistors?

Martin


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johanndo avatar image
johanndo answered ·

Not if you have to pay someone to do it for you, I guess.

Have you explored the options of the assistants on your Quattro?

You can program the outputs to do crazy things based on data, you can also control AC output 2 and use it to control your heaters.

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martin-krahn avatar image
martin-krahn answered ·

Johann,

as I did not want to pay someone for doing it for me/for us/also for himself, I asked my question here in the forum... ;)

I'll have a look at the capabilities of my Quattro - until now I did not remember that it is capable of giving a PWM or other kind of regulated signal. But I will check it, thanks!

Anybody else who feels addressed or curious?
Martin

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martin-krahn avatar image
martin-krahn answered ·

Johann,

I digged through the manuals of the Quattro and VE Configure, studied the virtual switches and the assistants, but I did not discover any possibility to drive a voltage-sensitive PWM- or only simple analog output. But I could not find anything about programming the analog or digital in- or outputs, perhaps here is a possible way?
Does anybody know?
Thanks,

Martin

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johanndo avatar image
johanndo answered ·

https://m.youtube.com/watch?v=tJGP3G0P7no

There is a video on how to divert dump loads ...

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martin-krahn avatar image
martin-krahn answered ·

Yes, Johann,

this video shows using a relay that diverts energy to a dump load when -for example- the batteries are full enough.

That is what I do already since years, even with three relays in three steps. But, as I explained, even three steps are kind of rough: If I do not want the relays to switch off and on at each small cloud, I can use some delays, but then the batteriy is stressed by the dump load for some time though just moments later the sun is back again and loads the batteries again. So I have a continuous up an down that is not useful. If a regulated dump load would be loaded with only that power that is excessive, my batteries would be treated with more care and live longer.

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johanndo avatar image
johanndo answered ·

There is no excess energy in the circuit you can divert, if a charge source can provide more than a load or the battery can accept, it just provides what is needed and relaxes.


The only way you can force it to work is to increase the load. What you can do, is measure the charge current and increase the load to keep the charge current at zero or as low as it gets when you divert the power, can be done by a PIC like an ESP32 with a AD converter at the shunt or by reading the charge current from a BMV or Cerbo (then delayed, and would make ripple)

You can then either use PWM or a DAC to control and regulate your load via a TRIACs or MOSFETs.

You can stop the charging this way at any point (based on SOC preferably during BULK, so the charge controller doesnt go to sleep in float) and dump all available energy into your dump load.

Hope that helps you..

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martin-krahn avatar image
martin-krahn answered ·

Yes, Johann, you are right again:

In my very first text up here I wrote: "I think first I need a voltage devider that gives me the excessive voltage out to feed an OpAmp or a microcontroller that gives out PWM signals to drive a thyristor-power-regulator array / phase conrtrolled modulator."

I already have an idea what should be done, but I asked here for help for the precise layout....

Martin

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martin-krahn avatar image
martin-krahn answered ·

Hello,

I pick up my own thread here after some struggle with my problem...

Some of you might have heard about the AC-Thor, which is an power diverter/dumpload regulator that can turn up to 9 kW electric power into heat.

It is very good, versatile, but not cheap.

And, theoretically, it shall work together with the Victron inverters that have the capability to rise the net frequency when the batteries are full.

So far, so good.

I bought a AC-Thor 9s and regulated it with the AC-inverter-frequency-regulation assistant of my Quattro. But unfortunately this frequency regulating assistant is entirely useless for this controlling as it rises the frequency but sometimes does not decrease it in time, so that it may happen that the AC-Thor powers the batteries empty, because the Quattro says him to do so.

And unfortunately too, Victron does not care about this problem at all. Since a longer time.

I solved the problem by regulating the AC-Thor directly via a Voltage-to-PWM-Module built myself with a ESP32.

So after nearly two years I found a solution that is not simple but feasable. And I had to face some frustration with the lack of service of Victron.

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