TIDA-00120: MPPT stopped charging after panel voltage is lower than 17V

Hi Anwej,

Please measure the input and output voltages to see which parameter causes a shutdown of the system. Are you able to operate the circuit with higher voltages?

Regards,

Salil

Hi Salil,

Thanks for your response.

Do you mean V and I for both Input and Output?

Regards,

Anwej Alam

Hi Salil,

Please find below the table for measurements done for input and output. Yes, It works on Higher Voltages

Hope you will be able to find the issue and abnormality in the functionality of MPPT.

Regards,

Anwej Alam

Hi Anwej,

What is clear from the measurements is that there is no shutdown happening at any point, but MPPT is not happening. There is a gradual reduction in power transfer to the battery as the input voltage is reduced. there could be multiple reasons for this happening:

1. The input power source characteristics do not have a clear MPP. A solar emulator will give a clear MPP. We can approximate the performance of a solar emulator even with a power supply which can be set for CV/CC operation.

2. The MCU is not able to measure parameters required for MPP tracking - the input voltage and input current for this design. Please check the values read by the MCU to see if it can detect the variation of these parameters accurately. There could be hardware issues or excessive noise pick-up that could affect this.

3. The power stage could be faulty. The circuit efficiency drastically reduces below 17V input. That could be an indication that all is not well with the power stage.

Regards,

Salil

Hi Salil,

Thanks for your observations and suggestions

1. The input power source characteristics do not have a clear MPP. A solar emulator will give a clear MPP. We can approximate the performance of a solar emulator even with a power supply which can be set for CV/CC operation.

ANWEJ: We are using a Power Supply in CV/CC Mode, Parameter set as 50W PV, Voc and Isc. I think the power supply is not the issue.

2. The MCU is not able to measure parameters required for MPP tracking - the input voltage and input current for this design. Please check the values read by the MCU to see if it can detect the variation of these parameters accurately. There could be hardware issues or excessive noise pick-up that could affect this.

ANWEJ: We are able to debug the MCU during debug operation, It always reset the MCU by WDT interrupt, Do you recommend any firmware version and any application that can monitor the measured parameter over UART?

3. The power stage could be faulty. The circuit efficiency drastically reduces below 17V input. That could be an indication that all is not well with the power stage.

ANWEJ: if the Power stage is faulty, it means this circuit never performs as MPPT even on higher voltage also.

Please advise the corrective action to be taken to resolve the issue

Regards,

Anwej Alam

Hi Anwej,

I am not an expert on the software and MCU debug. But from my experience, it is possible to observe the variables in the code in real time debug mode with CCS. So it should be possible to observe the measured parameters. The doubt about measurement noise is because the design is for higher power and you are testing below 10% of the designed load of the circuit. So the effect of noise will be more pronounced at the power at which you are testing.

The efficiency of lower than 40% at input voltages below 17V is an indication of abnormal operation of the power stage. Please see if all the bias voltages (including the bootstrapped supply voltages for the high side switches) are within normal operating range.

Also, please take a look at an improved version of this design (TIDA-010042) to see the changes done for improved performance.

Regards,

Salil

Dear Salil,

Yes, This is operating at a very lower Power, it should also work fine, I don't understand MPPT functionality is not working in my design and efficiency is very poor.

Could you please advise the step to check the noise and power stages circuit?

Regards,

Anwej Alam

Dear Salil,

Please advice

Regards,

Anwej

Hi Anwej,

The noise in current measurement can be seen by the fluctuation of the read value at any fixed operating point.

The bias voltages can be measured using a DMM.

Regards,

Salil

Dear Salil,

I want to share the schematic with you if you can check the power stage of our schematic. The problem is not solved yet.

Regards,

Anwej 

Dear Salil,

Please share your email id.

Regards,

Anwej