Getting Started

This is the page where I will archive articles on technology concepts in the design, manufacturing, or testing of inverters.

What is DMPPT?
DMPPT stands for Distributed Maximum Power Point Tracking.  The basic idea is to increase the resolution of power harvesting by tracking the MPP at each panel or each module, rather than at the string level.  This enables the user to extract maximum power from the overall system by overcoming degradation from shadowing, aging, soiling, or panel mismatch.  DMPPT is distinguished from centralized power point tracking methods that are used in higher power systems with string inverters or central inverters.

Who is using DMPPT?
There are several competing technologies that use the DMPPT concept to optimize power harvesting.  The two most common are microinverters and DC Power Optimizers.  Note that most people in the industry right now use DMPPT and DC Power Optimizers synonymously.  I like to consider microinverters and power optimizers both as DMPPT technologies, since both methods track the power point at a specific panel or module level, rather than at a system or string level.

Microinverters

Microinverters convert the DC energy from each solar panel to AC electricity, then route the AC directly to where it is being used.  Currently, microinverters are used mostly in small to medium sized residential installations, but the technology can be scaled up for commercial installations as well.  The main advantage of the microinverter is that you no longer need to provide a string inverter between the solar panels and the home or business.

Power Optimizers

Power optimizers are semiconductor devices that optimize overall system efficiency by controlling the operating point of each solar panel.  The main difference from microinverters is that the power is routed as DC, rather than converted to AC on a panel by panel basis.  This means that you still need a centralized inverter to convert the DC to AC.  Power Optimizers work very well for retrofit applications where there may be uneven aging or soiling between the panels.

For a great introduction to all the major players in both technologies, check out this article:  http://www.solarserver.com/solar-magazine/solar-report/solar-report/microinverters-and-power-optimizers-perspectives-of-distributed-pv-system-architecture-in-the-residential-market.html

How do you test DMPPT devices?
Microinverters and Power Optimizers take the output of a solar panel or module, measure it, then do something useful with it.  The best way to verify the performance of the MPP tracking algorithm is to simulate the solar panel output using an electronic device, like a Solar Array Simulator, or SAS. 

(click on the image to enlarge)





References