Optitrac global peak - What is a MPPT solar regulator?

Optitrac global peak - What is a MPPT solar regulator? Is a mechanism in the inverter that ensures that the electrical converter does not optimally load the solar panel. Therefore obtains the maximum power from the solar charge controller. Before we explain how that works, we first make a small trip to the internal combustion engine.

We do this to show that it is quite normal for a device to not perform at its maximum if you load it heavily. A combustion engine in the car does not give the most tracktion and torque at the highest possible speed of the engine.

At low speed, the PK's and torque are also not maximum. Somewhere between these two extremes, a combustion engine delivers the maximum. If you want to get the best out of your car as a preparer, you will have to drive around this optimal speed point. That is then the point of maximum power (or torque).

Optitrac global peak - What is a MPPT regulator?

voltage, current and power of a photovoltaic panel measured at different irradiation levels

A MPPT regulator is these days in every solar inverter. When the inverter loads the photovoltaic module heavily or lightly, it does not take the maximum power out. The inverter connected to the solar panel has to charge in such a way that it gets the maximum power out to get the most out off the PV system.

The electronics are capable of determining for themselves how much current flows from the solar panel to the DC converter. The inverter thus influences the output voltage (see solid lines in the graph). Therefore it determines how heavily it loads the array, comparable to the variation of the speed at the combustion engine.

When the inverter supplies the solar panel with the maximum achievable current. See at the far left of the graph, the output voltage has dropped to 0 Volt. This is the point at the far left in the graph at the upper solid line.

The current is then 8.3 Amps and the voltage is 0 Volts. The output is then 0 Volt x 8.3 Ampere = 0 Watt. You have nothing to do with that.

What is maximum power point in photovoltaic cell?

The other extreme is if the inverter does not supply the solar panel with power. We are then on the right side of the graph. The current is then 0 Ampere but the input voltage is then maximum, here about 37 Volts. Even then, the delivery is 37 Volt x 0 Ampere = 0 Watt.

That is not smart either. Somewhere between these two extremes is a point where it will transfer the most power to the inverter.

This point of maximum delivery is not a fixed point. This point varies with the irradiation, the temperature and any partial shadow. That is why the best point must always be sought. Hence the word "tracker" in the term Maximum Power Point Tracker.

In the graph the interrupted three lines show a curve at three different irradiation levels (on the right y-axis the corresponding electricity is in watts). At the bottom dashed line (low irradiation level) the maximum is achieved at a voltage of approximately 27 Volts and 4.6 Ampere.

First find the top at the dashed line and then go down perpendicular and find the corresponding point on the solid line where you can derive the voltage and current. The maximum and is about 126 watts. At the top dashed line (full sun) this point is at about 29.5 Volt and 7.6 Ampere. It then gives an output of approximately 225 watts.

What does an MPPT controller do?

Conclusion you can draw here is that when the sun is not shining so strongly, the inverter will get the most out of the panel with a solar voltage of 27 volts. But at full sun that voltage is 29.5 volts. The MPPT tracking will always, at different irradiation levels, adjust the current, including the voltage. So that this maximum power point tracking is looked up in the graph.

The graph shows these differences at a cell temperature of 25 degrees Celsius. At lower and higher temperatures the curves of this graph change. Then the point of maximum power delivery will also shift. The MPP tracker will constantly try to find the best point for all these variables and thus get the most wattage from the solar panels.

Optitrac global peak - What is a MPPT regulator?


Partial shade at solar panel strings

What is the best MPPT charge controller?

When a solar panel is already in the shade a little, even though only one of the 60 or 72 cells is partially shaded, the power graph as shown above will change shape. The current that the partly shaded cell can supply collapses. Because the cells are in series, it affects the performance of the entire string.

In fact, the matter is even more complex because the modern panels use by-pass diodes. In partial shade, think of the shadow of a chimney of branches of a tree. The MPPT mechanism will try to get the best out it, without less voltage drop.

With SMA inverters, the Sma sunny boy and tripower series, this scanning technique is called "OptiTrac Global Peak" and can be switched on and off. More about SMA and mppt optitrac.

What is MPPT in PV inverters?

With most PV panel installations they are in series, also known as a string or solar array. If you suffer from partial shading on one or more PV boards in such an installation, the MPPT mechanism may not get the maximum wattage. In such a situation, an inverter that can make this scan is a wise choice.

At regular intervals, for example every 15 minutes, the inverter will vary the current from maximum to zero and then measure what this produces. In fact, the inverter will follow the curve in the graph from the beginning to the end and determine where the maximum operating points are and then choose the best power point.

This scanning takes a few seconds and at that moment the wattage delivery will not be optimal. This reduces the yield for a short time. That temporary decrease in revenue is more than offset by the fact that with this scanning technique you always get the maximum.

However, if you have solar panels that never lie in the sun for most of the day, the power loss during scanning will not work to your advantage. In that case it is wise to turn off or leave this scanning technique.

What is MPPT technique?

Realize that not all string inverters have an MPPT scan. If they have it, you have to see if you can turn this scan on and off. With SMA inverters, this scanning technique is called "OptiTrac Global Peak" and can be turned on and off. Other manufacturers have invented other beautiful names and sometimes this is standard (which is not always wise).

If the description of the inverter does not mention anything about this MPPT scanning technique then it is almost certain that the electrical converter does not have this scanning technique and, in the case of solar panel installations that suffer from (a little) shadow, will generate much less energy losses.