Simulate CT (current transformer) output?

Hi guys. I want to install a battery storage for my house. It needs 2x CT clamps to measure PV generation + consumption to limit charge/discharge rate. Unfortunately I can't route CT clamps - so looking if I can cheat the system and pretend to have a CT clamp installed.

Here is a CT clamp I need to simulate: OPCT10AL

It outputs CURRENT (3000x less than on input) - is there a way to simulate this with arduino? How the circuit would look like? I don't think the output has to be phase synchronized with the input (but that would be a bonus).

Thanks in advance! Irek

irekz: I want to install a battery storage for my house. It needs 2x CT clamps to measure PV generation + consumption

CT (current transformer) is for AC. The "50Hz~200KHz" rating is a hint. PV panels generate DC. Batteries are DC. Try a hall sensor or shunt resistor. Leo..

Wawa: CT (current transformer) is for AC. The "50Hz~200KHz" rating is a hint. PV panels generate DC. Batteries are DC. Try a hall sensor or shunt resistor. Leo..

Sorry for not making it clear in the first place: I want to install batteries on AC side (so can charge it from AC when electricity is cheap at night and from solar PV). This requires use of CT clamps as on this image: |500x196

As clamps output current (not voltage) I suspect I might need an inverter circuit to convert DC to AC: http://www.theorycircuit.com/arduino-inverter-circuit/ - would this work? is this the simplest solution?

Simulate with what.

A CT can be measured this way.
Leo…

Wawa:
Simulate with what.

With arduino + wifi shield. I have a real-time PV production and consumption data available on WiFi.
Would like to connect arduino instead of CT clamps to the battery storage system.

Hi,

Why can't you route your CT clamps?

If you simulate the CT outputs, how will your system controller know what is going on?

Can you please tell us your electronics, programming, Arduino, hardware experience?

I think you need to realize your system with batteries and grid tied unit and charging system is a complex balance of power, and an accurate measurement of REAL current is a critical part of that.

This where you need professionals to do your installation, not just for safety, but approval by your utility and insurance company.

Tom... :)

1 Like

TomGeorge: Hi,

Why can't you route your CT clamps?

If you simulate the CT outputs, how will your system controller know what is going on?

Can you please tell us your electronics, programming, Arduino, hardware experience?

I think you need to realize your system with batteries and grid tied unit and charging system is a complex balance of power, and an accurate measurement of REAL current is a critical part of that.

This where you need professionals to do your installation, not just for safety, but approval by your utility and insurance company.

Tom... :)

Hi Tom. Routing CT clamps would require a lot of drilling, and even then would not be perfect as I have two separate solar arrays with two inverters in separate locations. I'm software engineer by trade - so programming arduino or esp8266 is an easy part for me. I already have a home automation system that collects data in real-time from both solar pv inverters and consumption data from "Network OWL" device - all is pushed via UDP broadcasts into rapberry pi.

What I want to achieve is to be able to control battery storage with my own code (charge when surplus PV is available, or at night when electricity is cheap, most likely take into account weather forecast). Software part is easy - but I'm having problems finding a decent hardware that I can control.

Essentially all battery storage systems use CT clamps - so I'm hopping for relatively easy way to "hack" the system and replace CT input with my hardware+software. One system that is of good price is this one This system is using CT clamps that output current (voltage would be much easier!) - so I'm exploring if it's possible to "simulate" such CT clamp, and when connected to the battery charger/inverter to tell it that either there is spare PV, or that it should start discharge. It would be much better to have like RS232 interface to be able to control it (no it does not, already asked the vendor).

My own research point to DC to AC circuit needed: http://www.theorycircuit.com/arduino-inverter-circuit/. I wonder if you guys have comments/ideas/show stoppers here (I'm not electrical engineer so better to ask first :)). If this is not feasible - I will wait until some battery storage with proper API will be available on the market.

Cheer, Irek

Did you figure this out? I need to do exactly the same thing.

irekz: With arduino + wifi shield. I have a real-time PV production and consumption data available on WiFi. Would like to connect arduino instead of CT clamps to the battery storage system.

Just use a function to return the current current consumption, write one version that uses the WiFi data, and when the CTs come on line write a different version that uses the CT readings. You might also need a function to call regularly from loop() that drives the measurements/data collection regularly.

You could even wrap these functions in a library, then you'd substitute libraries when CT's are available, just have both libraries implement the same set of functions.

I found this on a search looking for the same solution. Looks like most respondents didn’t even understand the question.

Which question?

Hi,
I think we did, he wants to make a simulation of the two CT in this diagram.

@irekz hasn’t addressed is if he/she gets the arduinos to simulate each of the CTs, how will he/she know what magnitude current to simulate.
@irekz wants to control the operation of his system, and using CTs measuring real time currents is the only way to do it.
The basic problem is access to the wiring from what I can gather.

Tom… :grinning: :+1: :coffee: :australia:

Did you do the ct simulator?

I was also looking for this solution, i have a different usecase however. I have a 3 phase grid connection with a shelly em3 monitoring my usage. On one phase i have a solar inverter with battery that only checks one phase to see if the inverter needs to discharge the battery or not. I would like to use the sum of the 3 phases that i get from the shelly to fake the CT clamp to the inverter.
The grid meter just adds up the sum of the 3 phases, so it doesnt matter if i return power on phase1 and use power on phase 2.