voltage sense and current sense at solar microinverter input

A solar panel outputs a constant voltage, right? but current varies in the difference in light radiance and temperature. Is it really important to put a voltage sense across the input? or a current sense is enough?

With PV panels you have these extremes:

(a) high ohm load, high V, low A

(b) low ohm load, low V, high A.

Notice that both are inefficient, because they yield low power (low watts, or V * A).

You can expect maximum watts at medium load, medium V, medium A.

A PV Panel is a non-ideal current source that when lightly loaded rises to an Voc limit.
Typically maximal power is transferred when the source impedance matches the load.
A PV current source ( like a current source with a lossy zener for no load max voltage and maximum power is usually transferred between 75~80% of Voc.

Since the PV load can vary and the solar input can vary so will the output voltage.
Even if the output is a storage battery, the State of Charge must be monitored with charge and discharge current to protect both the battery and charger..

dann11 said:

A solar panel outputs a constant voltage, right? but current varies in the difference in light radiance and temperature. Is it really important to put a voltage sense across the input? or a current sense is enough?

Click to expand...

Yes and no !

As stated above the solar panel acts mostly as a current source, and the output voltage changes dramatically with different amounts of load applied.

If you very carefully adjust the load, there will be a point where maximum power is transferred from panel into the load.
But that optimum load point constantly changes as the solar input changes.

If you hook up a power meter, the optimum load at the point of maximum power transfer will occur over a fairly narrow range of voltage, regardless of solar input from twilight to full mid day summer sun.

But to keep it at that peak operating point, the amount of load needs to constantly change to match the amount of available solar input power.

To do this you need to monitor both the voltage and the current, and have a control strategy that constantly tracks to juggle the correct amount of loading on the solar panel to track the optimum peak power point.