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MPPT and CCCV Battery charging algorithm
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Siddhat:
Hey everyone! Hope everyone's doing fine.
I've successfully designed and simulated a Maximum Power Point Tracking (MPPT) algorithm using a buck-boost converter. Now, I need to charge a 12V lead-acid battery with the converter. For charging the lead-acid battery, an algorithm that consists of 3-stage CCCV charging method is needed. But I am not clear in the concept that how can both MPPT and the battery charging algorithm be combined and implemented using a single stage DC-DC converter? What is the circuitry needed?
Siwastaja:
By very definition, MPPT and CC/CV can't coexist at the same time. They can be in the same system, though.

MPPT gets the maximum power out of the panels.

CC and CV both limit the power that can go in the battery.

When the maximum power out of the panels is more than the battery can handle, you can't fully utilize the panels. Hence, it's not MPPT anymore.

Basically you have three modes:
MPPT, CC, CV

By default you are in MPPT, but if the output voltage exceeds the CV setpoint, you fall out of MPPT and go to CV.
Similarly, if the measured current exceeds the CC setpoint, you fall out of MPPT and go to CC.
uer166:
How do you switch from one mode to the other without discontinuities or state oscillation between say CC and MPPT modes? I can understand how a current mode buck converter switches seamlessly between the modes since the inner control loop is current, outer control loop is voltage. But for MPPT, how would the control system look like, considering the input variables are coming from different places.
Siwastaja:
Batteries being relatively slow devices, I don't see mode oscillations as a problem, and you can always add hysteresis bands to prevent oscillations between modes, if you want.

This being said, what does it matter even if the modes oscillate? Even at a high frequency?
2N3055:
One type of MPPT make regulation slow and let it oscillate between two loops. It's called perturbation mode, oscillating slightly around MPPT point.
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