TIDA-010042: Simulating a battery with an electronic load

Hi Diego,

Simulating a battery with a CC mode electronic load is incorrect - there will be interaction with the CC set by he load and the MPPT loop, and hence the MPPT circuit will never be able to stabilize. Battery simulation can be done using electronic load in CV mode and a small capacity PSU (or battery) as shown in the diagram below:

Since the CV level (in this example 13V) is set higher than the PSU output voltage (here 12V), it will never get loaded by the electronic load. This PSU is only required if the program needs an initial voltage at the battery terminal to start operation of the MPPT circuit (I think this is the case with this design - I may be wrong). We can switch off/disconnect the PSU after the circuit starts. The diode prevents the MPPT circuit pumping power into the PSU.

When the circuit starts, the voltage at the battery terminal quickly builds up to 13V, and the CV load now acts as an infinite current sink. In this condition, only the output voltage is set by the electronic load, and the MPPT circuit has the freedom to set output current according to the power available from the panel.

Regards,

Salil

Hello Salil,

Thanks for your fast reply.

I have implemented the configuration you have proposed for the battery simulation (except for the diode) but it is still not working.

When I power up the power supply (CH1 =18V@3A for the Solar panel simulation and 12V@1A for the Battery) the display of the electronic load (configured in CV mode 13V) shows 12 V. When I disconnect the battery from the electronic load the voltage in spite of going to 13V falls to 5V and make stable.

Do you have any idea of what is happening?

Best regards and thanks

    Diego

Hi Diego,

These are the few things to check:

See if the electronic load is able to take all the power available.

Try reducing the difference between the PSU voltage (12V) and CV setting on the electronic load. Sudden jumps in output voltage may be sensed as fault by some MPPT algorithms.

Check if the circuit is able to work with CR setting on electronic load. If yes, the program has to be re-tuned to accept CV load.

Regards,

Salil

Hi Salil,

With respect to the Load power, the model that I’m using is 400W, and this no problem expect with this.

I have also reduced the voltage difference between PSU and electronic load. I have try several values (e.g.: PSU 12.3 and CV setting 12.7) with the same results than previously explained. When I disconnect the battery the regulations falls to 5V.

Finally with the CR, the voltage starts from 0 and go up until the famous 5V and make stable.

Note, I have assembled the HW variant 001 (equal than 002), and thus some electronic components are not assembles. Please confirm that this is ok.

Thanks for your help.

Best regards.

Hi Diego,

I am not sure what is happening on the board. Are you using the latest code? I think there was a code refresh about 3 - 4 months back to solve similar kind of problem. Also, please refer to the design guide and check if all sections of hardware are working properly.

Regards,

Salil

Hi Salil,

I'm using the latest code from the web (updated 9-jan-2020). In fact I have downloaded it just now for a double check with the same results.

I only have changed one parameter on the software before build and load, that is define SYS. I have commented the SYS 48 and uncommented the SYS12.

Do you have any Idea? Maybe you may send me directly a generated .out file for a 12V battery system to check if this solves the problem.

I will also make test with a real battery today. I will come back to you.

Best regards and thanks

    Diego

Hi Diego,

I was not involved in the software design. So let me connect you to someone who has worked on it. To my knowledge, software issues related to faulty operation during low load conditions were solved with the latest release of the code.

Regards,

Salil