Why micro inverters are the future?

The micro inverters are an excellent solution for small photovoltaic systems up to ~3kWp. Above this power-class an string-inverter will be probably cheaper, today and in the future.

Why micro inverters are the future?

Short and briefly

• the microinverter allows to install small solar systems, solar electricity already from single solar panel
• different solar panel orientation can be used, extrem flexible in system design
• allows simultaneously usage of different solar panels technology (Poly/Mono/a-Si…)
• best system performance under partial shading (affects single  panel)
• best system performance under long cable distances (low DC losses)
• easy and quick system expansion, possibly at any time

Because the micro inverters and in general the regulating technology ist the most important component in the whole solar panel system, we offer only proven, solid and high quality products. Exclusively as official and authorized distributor (eg. Power-One, AEconversion).

We offer micro inverters in 230V/50Hz and 110V/60Hz typology. Ask us in case of individual requirements.

Technical aspects of the Microinverters

While designing a solar panel system based on micro inverters, you have to consider two important aspects:

• the system safety (grid and inverter)
• the system efficiency

Safety (local grid) 

System safety means mainly automatic disconnection of inverter, when missing the local grid (50Hz synchronization). The inverter will try within short period to gain the 50Hz frequency in the local  grid, and if this will be not possible (due technical work, failures etc.) the inverter automatically disconnects itself from the local grid, as protection against creation of dangerous power-islands. This type of protection is also called an anti-island protection in the local LV grid. If the grid synchronisations 50Hz comes back, the inverter begins to transmit 230V/50Hz electricity into home/office/factory or directly into the local grid, depending on system design.

This kind of protection is generally regulated by national LV grid operator and its regulations and requirements (parameters). The most common requirement is the two-stage disconnecting structure within the micro inverters:

1. internal disconnector (often based on internal software)
2. integrated MSD (Monitoring Switching Device) physically galvanic disconnector.

Safety (microinverter)

Example: if the inverters max. DC input voltage is 45V. The proper max connectable voltage (from PV generator or single solar panel) should be reduced by 10-15% of the given Voc in the panels datasheet. The reduction depends on PV panel temperature coefficient and increases under low temeprature (then e.g. instead of defined in the datasheet 37Voc may appear 41Voc and more).
So for an inverter with 45Vdc max input voltage, an panel with 37Voc would be an excellent solution.
Several combinations in different cable wiring (in series or parallel) allows to create different PV generators (single or dual panels based). But the DC input voltage, can never exceed, the allowed inverters parameters (Vdc max).

Efficiency of the microinverter

Efficiency come from the miroinverter parameters and its technology, an important aspect here is the inverters MPPT-starting voltage range. A solar module should be choosen this way, that inverters input MPPT-starting voltage range, will be reached by the PV panel so quick as possible.

That can be problematic if you choose eg an 180Wp solar module to a 250Wdc micro inverter. That would be an mismatching in the system efficiency and it will work, but the micro inverter will reach probably very seldom his max efficiency. And in case of 60-80Wp PV panel the required starting input voltage will be never reached.

In turn an slight over-sizing the microinverter, eg. 260Wp PV panel connected to an 250Wdc micro-inverter is an quite smart solution, if not exceeding the allowed voltage and current, within the inverter. Optimal for each inverter is to bring him at its maximum power, where his efficiency is the best and highest.

Against slight exceeding the power (Wdc) and current (Idc) PV inverters are able to protect them self (goes into the derating), but against exceeding the max allowed voltage (Vdc) not.

Micro inverters advantages

Small PV systems

The Micro-Inverter is ideal for the use in small PV-systems, since it starts converting solar energy from just a single module.

In contrast, the string-inverter typically requires 200V input voltage, which has the consequence, that at least 8 modules are required to build up an classical PV-string.

Different PV panels orientation

With micro inverters, a PV-system is an efficient system even with different module orientations. Because of the individual connection of each micro inverters with the PV-modules, the highest possible performance (individual MPPT) can be achieved. The modules operate independently from one another.

Thus, the total return is much higher compared to systems using string-inverters because there, the module performing the worst power, limits the performance of other modules and the whole PV-string.

Different PV panel types and technology

At different modules, which have different benefits from each module, the maximum possible power is taken (individual MPP tracking). With a micro-inverter modules which operate independently and the total yield is therefore significantly greater than that of a string system.

System expansion

With little effort, each system can be transformed and expanded with additional modules depending on needs and available capital.

It does not matter whether the PV-system consists solely of micro inverters or the new PV-module is added to a string-based system. With the micro inverter, you have all the freedom to expand your system at any time.

Partial shading

The micro inverter will increase the energy harvested, by eliminating sources causing high energy losses. In case of a shadow, snow, dirt, leaves or other obstructions on a PV-module in a system using central- or string inverters, the energy harvest of the entire string drops dramatically. Due to the individual connection in micro inverter based systems, a shadow on one module does not affect others modules or the whole string and therefore has only a minimal effect on the systems energy yield. In addition, in systems using micro inverters, the PV-modules are not affected by the tolerances of other modules, letting each operate at its maximum. In conventional systems, the central- or string-inverter perform MPPT for the whole PV generator, leaving some modules working below their Maximum Power Point. Micro inverters vary the electrical operating point of each module individually, maximizing the available power from each module.

Long distances (small losses)

For string systems, large distances between the modules lead to high losses in the PV lines. In systems with micro inverters, the voltage is transmitted with lower losses.

The high DC current in an PV system must first go through a long path through the system until it is converted in the string inverter into AC current. Due to the long distance and the high current, a lot of the performance is lost.

The DC current from PV module is converted directly at the module and transmitted as AC current. Due to the high voltage, hardly any AC power is lost.

Enphase Energy is a NASDAQ-listed energy technology company headquartered in Petaluma, California. Enphase designs and manufactures software-driven home energy solutions that span solar generation, energy storage and web-based monitoring and control. The company has shipped about ten million micro solar inverters, known as “microinverters”, sold primarily into the residential and commercial markets in North America, Europe and Australia. Buy the best solar micro inverters from NASDAQ and Bloomberg listed solar panel microinverter manufacturers at best price; suitable for all weather conditions. 

Related links to the Enphase Microinverter :

• Do you have any questions regarding this product?  or call +44 (0) 333 772 0526 or + 1 786 600 1814.
• All products by Enphase Energy
• How to install an Enphase Microinverter and Enphase Envoy
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• You need a PV Inverter? Read more about solar pv inverter range we sell – selected TOP Brands

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