Multiplus II: What is the tolerance of the input frequency range set to 50Hz ?

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bbo asked Dec 14, '23

Multiplus II: What is the tolerance of the input frequency range set to 50Hz ?

Hello,

I have a ESS with a Multiplus II 48/5000/70-50 230Vac inverter, the grid frequency is 50Hz.

In the manual I see 3 options for the input frequency range: : 50, 60 or 45 – 65 Hz.

My grid operator requires using of a Frequency Monitoring Relay (together with Voltage Monitoring Relay, Overcurrent Monitoring) that should disconnect the invertor from the grid in case the frequency becomes lower than 48Hz (for 10sec) or higher than 50.3Hz (for 1 sec)

I wonder what will be the behaviour of the Multiplus II if I set it to frequency 50Hz (the first option), what will be the frequency tolerance accepted by the inverter and at what deviation it will be disconnected from the grid? Also, what willl be the reaction time?

Can the Multiplus II be configured to replace the required external Frequency Monitoring Relay?

Multiplus-II frequency

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Answer 1 · 2023-12-15T05:24:21Z

Alexandra answered · Dec 15, 2023 at 05:24 AM

@bbo@abv.bg

Depends on the grid code used?

If no grid code, I have seen the inverters be comfortable 0.5 Hz up and down.

They do not like sudden changes and will disconnect then.

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bbo commented · Dec 15, 2023 at 06:03 AM

Hi Alexandra,

Thanks for the reply! Is there any specification on this behaviour?

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Alexandra ♦ bbo commented · Dec 17, 2023 at 12:31 PM

No documentation.

In ve config on demo mode you can look at the grid codes and how they are set.

The rejection is just something I have seen and experienced in installations.

Our grid is unstable. So we see the frequency fluctuate quite a bit.

From generators if the generator is unstable (many thread on the forum about it) it rejects it.

You can set a wider frequency range for acceptance for use with generators but if there are sudden changes there will still be rejection as the inverters try to match the incoming.

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