question

Nicholas Herbst avatar image

ESS Inverter response too slow - tripping utility meter

Hello Community,

Our company is struggling with a number of installations in the Tshwane (Pretoria) region of South Africa. The municipality (utility provider) has rolled out the installation of Conlog meters. The majority of these meters are overly sensitive to reverse energy detection. One of the meter models is the Conlog BEC42X (Single Phase).

Many of our installations consist of an ESS setup like the following: MultiPlus II 5kVA, BlueSolar MPPT Charge Controller, Color Control GX, Carlo Gavazzi Energy Meter, BMV700 and a Lithium Battery.

Many of these installations, in the Tshwane area, are experiencing frequent tripping of the Conlog utility meter.

Some forums have indicated that these meters are tripping at a point as low as 20W over 15 seconds - or some 300 Joules of reverse (export) energy detected. This is incredibly sensitive and clearly the root problem. However, this is very difficult to resolve with the municipality (utility provider) and they are mostly unwilling to assist.

We have had to resort to setting the grid set point significantly higher than desired, sometimes around 300W and have had to limit inverter power, in some instances to as low as 750W. With these restrictions placed on the system, we are mostly unable to process (store and discharge) all of the solar energy available from the solar array resulting in compromised economic performance.

What can we do to improve the control of export power to the utility?

It is inevitable that some export energy will be supplied to the utility in a grid-connected ESS system, but one observation that we have made is that the MultiPlus & Quattro inverters appear to react quite slowly AFTER a large load is switched off - this observation comes from the Color Control display panel where we can see the grid import/export as reported by the Carlo Gavazzi Energy meter, as well as the amount of power being discharged by the battery, as reported by the BMV700.

Once a large load is dropped, can the inverter not reduce it's power faster to avoid overshoot and subsequent export energy being supplied to the utility?

From this link, we see that the response time of ESS has been limited to 400W per second as per ESS version 162... but now we need a work around?

This thread comments on a similar aspect: https://community.victronenergy.com/questions/51697/victron-ess-et112-slow-response.html


After reading the above thread, can we not adjust the refresh rate and baud rate for the energy meter (Carlo Gavazzi) to aid the situation in swiftly recognizing the change in the grid import/export condition?

Alternatively, is the 100A:50mA Current Transformer a temporary solution for MultiPlus II ESS installations?


If this cannot be achieved with the ESS assistant, is there a combination of assistants that will allow us to operate in a similar fashion to ESS while overcoming the issues presented by the hard-coded rate limiting?


Thanks in advance for your input and suggestions.


Multiplus-IIESSEnergy Meter
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I would really like to see Victron address this problem better. I think they could do a few things :

  • Allow the Baud rate of the Energy Meter to be adjusted. The Carlo Gavazzi supports multiple rates. This would probably affect distance so should be defaulted to a low rate but allow you to adjust it up. I'm not sure how much better this will make the response but it would be worthwhile testing.
  • Allow multiple grid point settings based on time or even battery level or both. This would mean you don't have to site with a high grid point indefinitely and can set it to a higher point at critical points.
  • Speed up the Inverter response to changes. This is probably more complex and may not be something they can do in a Firmware fix. In the linked post the person talks about better responses from the CT, which would result in less feedback to the grid, maybe you should give it a test.

I think combination of these would go a long way to give you better control of what gets fed back to the grid

Regards


3 Answers
Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @Nicholas Herbst @SolarHack

Even with improvements in speed we are working on, these meters trip too fast.

One solution that Alexandra also gave: do not use ESS but use the grid like you'd use a generator:

https://www.victronenergy.com/live/assistants:ignore_ac_input_using_the_generator_assistant

note that I'd now use the generator start/stop function of the GX device, connected to the inverters to ignore AC input.

The other solutions is to ask the utility company for an exception so the meter doesn't trip.

setting a higher baudrate for the energy meter doesn't help, because it only sends an update once every 750 ms

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Nicholas Herbst avatar image
Nicholas Herbst answered ·

We have tried to implement the Current Transformer as a replacement for the ET112 in installations involving the MultiPlus II.

The observed performance of the CT is far better than the ET112, and we essentially do not get any further tripping of the Utility meters.

Unfortunately, we discovered a "fatal" error that effects this configuration (Using the CT) where the inverter enters an Error 24 mode - System protection initiated. I am going to upload a video to YouTube and create a thread specifically related to this new problem.

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Alexandra avatar image
Alexandra answered ·

@Nicholas Herbst

AC ignore is the other option.

https://www.google.com/url?q=https://www.victronenergy.com/live/assistants:ignore_ac_input_using_the_generator_assistant&sa=U&ved=2ahUKEwjUtLa4qrTqAhXLiFwKHa4UDh4QFjABegQIChAB&usg=AOvVaw1ivo1FZZM85omVUt3mDZL0

Where you can set conditions and state of charge for it to reconnect to grid for use like a generator.

This should not be used with was however as it is intentional islanding.

My other thought was when is the feedback in these systems worse? Is it when batteries are full by any chance? We have in some cases found that not having full batteries helps as the excess pv and feedback from loads dropping off has somewhere to go.

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