Maximum Power Point Tracking (MPPT)’s role in solar PV inverters
Author: Darvin Tocmo Date Posted:7 February 2017
Not many are aware of Maximum Power Point Tracking and its role in optimizing power output from solar PV inverters.
Most of our modern inverters today are already MPPT equipped. But a lot of people, solar owners in particular, still don’t know what an MPPT does. Maximum Power Point Tracking (MPPT) is a technology in solar PV inverters that maximizes power output.
MPPT in solar PV inverters
The MPPT is one of the most useful tools in solar PV inverters when sunlight is not at its best. It is designed to track the array maximum power point voltage (Vmp).
But there’s no need to make adjustments yourself. The system has a fully automatic algorithm that tracks the Vmp as it changes with weather conditions.
Simply put, you are sure to harvest the maximum power from the array with an MPT. Most solar PV inverters today have at least one MPPT input. So, if you’ve bought yours recently, chances are it already has an MPPT input working to render the most power for your system.
How does an MPPT work
To illustrate how MPPT works in a non-technical way, Bradley Detjen compared MPPT to a thumb placed over a garden hose. The solar sales engineer originally posted his explanation on Quora.com.
He said that if you put your thumb over the opening of the garden hose (adding resistance to the circuit), the pressure (voltage) goes up. The stream flies quicker. However, less water (current) goes through.
Nothing gets through if you cover it completely. Removing your thumb, on the other hand, lets the maximum flow rate go through. This would make the stream fall limply at your feet, though.
Basically, that’s how MPPT works. It adjusts resistance in the circuit to change current voltage.
Now think of solar panels as hundreds of pumps upstream of the hose. They are delivering water (or energy) to you. Some pumps even go offline (partial array shading). The force behind water delivery will, therefore, vary constantly.
If your task is to wash a car about 15 feet away, you need to constantly move your thumb. This will keep you from overshooting or undershooting.
The car in this instance is the Maximum Power Point – for any solar panel array. There is a configuration of current and voltage that aligns with maximum power generation (see image below).
According to Mr. Detjen, “the MPPT tracker varies resistance in order to keep hitting this point, using control logic to stay at the maximum just like a thermostat or cruise control.”