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Microinverter and MPPT technologies – Designing Solar Applications with the Right Converters



Solar installers and project developers are constantly looking for ways to squeeze more efficiency and power from solar cells. Two newly developed technologies for improving solar performance are microinverters and maximum power-point tracking (MPPT).

Microinverters convert DC from a single solar module (panel) to AC for grid consumption. They contrast with conventional string-inverters that support a large number of solar panels connected to a single inverter. MPPT devices are high-efficiency DC/DC converters that present an optimal electrical load to a solar panel or array at a voltage suitable for the load. These devices help increase power harvested in some solar applications, but they’re not standard solutions that can be applied to all applications. MMPT devices may be a perfect fit for some applications but could actually lead to low efficiency and even higher costs in others. So how can solar installers and project developers determine the best fit?

First, they need to understand the technology. Some industry leaders claim MPPT offers the best solution for the majority of solar projects. But while MPPT is a valuable technology, its appropriateness for the system depends on the specific size and application of the solar installation. A primary consideration is the levelized cost of electricity (LCOE).

The LCOE calculation provides a common way to compare the cost of energy across technologies. It takes into account the installed system price and associated costs such as financing, land, insurance, transmission, operation and maintenance, and depreciation, among other expenses. Carbon emission costs and solar panel efficiency can also be taken into account. This calculation gives an apples-to-apples comparison between solar and other types of power generation. These comparisons can be applied to different inverter and power optimization configurations for residential, commercial and utility uses.

Recent findings, including a report entitled, “Shorting out the Myths of Solar Power Electronics: What Fits and What Fails,” help solar installers and project developers navigate the expanding landscape of power electronics options available,

To help determine which technologies provide the best performance and lowest cost in residential, commercial, and utility markets, keep these facts in mind:
  • Smaller solar systems favor increased distribution architecture, giving microinverters an edge. That trend reverses, however, toward the utility-scale side of the spectrum where the sum of losses creates a more favorable market for centralized inversion.
  • Cost-of-electricity analysis shows a market awaits every power architecture. LCOE is a metric used to indicate the cost-per-kilowatt-hour of generating power from a given solar system, accounting for the net present value of the up-front cost of the system, installation and continuous maintenance. Looking at the LCOE for each power electronics option across applications, microinverters appear to be best suited for the residential market, string inverters for the commercial segment, and central inverters for the utility segment.
  • Installers and project developers emphasize reliability and lifetime. When all other factors are equal, installers and project developers consider reliability the single most important factor in new and old inverter technologies. Inverter efficiency and system performance, however, are close behind. Looking to the future, cost and ease of maintenance are prominent areas for improvement.
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