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cydrox avatar image
cydrox asked

using MPPT solar inverter DC input with an AC generator

Hello,

I have a question regarding the possibility of using an AC generator with an MPPT solar inverter.

So basically I have a wind power turbine, the generator is a 3 phases permanent magnet synchrone generator.

In order to have a DC voltage, I will use a diode bridge with a DC/DC converter to meet the requirement of DC input of the inverter.

Lets say I will use the Victron EasySolar-II GX (who handle a DC input between 38V - 66V) without battery, and I'm able with the diode bridge and the DC/DC converter to convert the voltage of the AC generator to a DC voltage that oscillate between 38V - 66V. Will the inverter be able to generate power and behave normally ?

I want to know too how the MPPT will work under those circumstances. Feel free to correct me if I'm mistaken, from what I understood, the MPPT algorithme changes the value of the voltage on the DC input in order to find and drag maximum power. In the system that I explained above, the source imposes the voltage I believe, how the MPPT algorithm will be able to find the maximum power point?

Feel free to ask more questions if I misexplain something.

Thanks in advance

Regards



MPPT ControllersPhoenix Invertersolardc systemac
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solarbone avatar image solarbone commented ·
As i have seen commented in another respect, the MPPT is not designed to work without battery.
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cydrox avatar image cydrox solarbone commented ·
@solarbone

Thank you for your comment, I dont think so, as I've found on the net some wind turbine inverters that have the MPPT option, but dont have a DC input ( only AC for wind turbine generator). So basicaly you cannot put batery with such inverters and they have the MPPT option.

You can correct me if I have mis understood something

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2 Answers
marekp avatar image
marekp answered ·

@cydrox

If you connect your wind gen to MPPT input of MP inverter, you will get DC-ripple error and that will be the end of the experiment.

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cydrox avatar image cydrox commented ·

@MarekP Thank you for your answers.


I thaught that there is only input voltage that matter, and if my input voltage is in the inverter's input voltage range it should works. Thank you for clarifying things.


Although, I cannot find the DC ripple limit on the datasheet. I imagine there is a limit that we should not exceed. Do you have any idea, documents datasheets of the DC ripple limit for the inverter in question (Victron EasySolar-II GX ) or any other MPPT solar inverter ?


I imagine that knowing the DC ripple limit, we can calculate the proper value of a capacitor to put after the diode bridge, in order to have a stable DC voltage.

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marekp avatar image marekp cydrox commented ·

@cydrox

screen-shot-2022-10-28-at-25052-pm.png

Can you clarify to what input you want to connect your wind gen?

The 38-66V range is for battery input but you keep asking about MPPT.

MPPT, inside ES-II, is for PV panels and here voltage can be between "battery volts + 5V" as a minimum and "250V" (hard limit) at maximum.

Neither of those inputs can be used for wind gen output.

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screen-shot-2022-10-28-at-25052-pm.png (60.5 KiB)
cydrox avatar image cydrox marekp commented ·

@MarekP Thank you for your answer.


Perhaps I have not explain well.

Basicaly, I have a wind generator ( who is a 3 phases synchronous generator). I am well aware that you cannot use it with a solar inverter since the solar inverter has 2 DC inputs : one for the solar pannels and one for the battery.

What do I want to know is that if I take the solar inverter, and in the DC solar input, instead of putting solar pannels, I will take the 3 phases of the generator, connect them with a diode bridge to convert the 3 phases AC into a DC, add a capacitor to reduce the voltage ripple, as shown bellow:

1666962940651.png

For sake of argument, lets say that the generator has a rotation speed that is generating a voltage that, after rectifying it and filter it with the capacitor, is in the input range of the "solar DC input" and has a good voltage ripple. Will the inverter be capable of generate power from that power source ? and how the MPPT algorithme will behave since its a DC voltage comming from a source other than solar pannel ?


In your first answer, you talked about a ripple voltage error, were you talking about a ripple coming from battery DC voltage or solar DC voltage ?



in the data sheet :

1666963383384.png

the input voltage highlighted in yellow, is it the DC battery input voltage or the DC solar voltage input ?


If there is still something badly explained, please dont hesitate to ask me again.


Thank you for your time

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1666963383384.png (139.1 KiB)
marekp avatar image marekp cydrox commented ·

@cydrox

DC ripple is measured on the battery terminals.

Input voltage range is for battery.

Solar panel DC input:

screen-shot-2022-10-28-at-35045-pm.png

You cannot use the SmartSolar Charge Controller for Wind Turbine generator because it those not have a brake function. Even after you make its output a DC.

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screen-shot-2022-10-28-at-35045-pm.png (22.1 KiB)
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bje avatar image
bje answered ·

Can the Inverter be configured to disable MPPT input regulation and replace it with Constant Voltage input regulation ? .

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