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Converter
Performance - Robustness

The performances of a photovoltaic installation rely partly but significantly upon the possibilities and reliability of the converter. A converter can be summarized as a static and electronic equipment whose task is to transform the Direct Current ( DC ) produced from the solar cells into an Alternative Current ( AC ) with the required frequency, tension and amps available on the local electricity transport network.

Performance :
The performance of the converter is defined through its capability to restitute on the electrical network, the output, as much as possible energy compared with the electrical feed got from the cells themselves on its input.

Within a photovoltaic system, the losses caused by the converter are linked with 4 factors:

  1. the internal yield of the converter itself ;
  2. the nominal power compared with the power supplied by the photovoltaic installation ;
  3. the adequacy with the tension delivered by the modules ;
  4. the operating temperature.
     
1. Internal yield of the converter

Currently, the usual performances met within industrial converters are varying from 92 up to 96% (converters + transformers). However, these catalog data can change sensitively with the tension fed, and decreases if the converter is operating with temperature conditions more important than the standard criteria of 25 °C. If a galvanic insulation is not required, some points of yield can be gained by using converters without transformers.

2. Selection of the converter power

A converter maximizes its efficiency while the load during the operations is close to the maximum accepted value. Moreover, its cost and weight are reduced if its power is minimized. The target of the design for a converter is accordingly to select an interesting compromise between the power delivered by the solar panels and the possibilities of the converter while on the other side, shutdowns for overpower need to be minimized. Generally, the power supplied by the solar installation rarely overpass 80 % of the peak power: for this reason, the design of the converter is sized between 80 and 100% of this potential peak power supply.

GT Series Grid Tie Inverter GT500E



Source : Xantrex

  Source : Alpha Technologiques

3. Range of inlet tension

Converters present limited possibilities for the variation of their feeding tension: this tension needs to be in agreement with the tension in serial of the modules, whatever is the outside temperature, the number of modules in series, and the technology.

By cold weather and if the number of modules is too important, the corresponding tension delivered can be more important than the accepted value of the converter. On the contrary, for too hot conditions or a too weak number of modules in series, a low tension can lead to shutdowns for low tension reasons.

To avoid any damages, the tensions available on a solar farm need to be included within the range of variation established by construction within the possibilities of the converter. This needs to be true on the whole range of the possible outside temperatures (from -10 up to + 70 °C). Moreover, for an optimized yield of the converter, this tensions variations need to be focused near the optimum yield of the equipment.

4. Operating temperature

The converter needs to operate in a fresh, temperature controlled and dry air conditions. An easy access is also required for maintenance operations. While the local temperature conditions are leading to non standard temperatures (> 25 °C), losses within the conversion chain are also increasing.

The appropriate performances of the converter are regularly controlled with the web transmitted indications of the converter instruments.

 SUNNY BOY 3300 / 3800

Source : SMA Solar Technology

SUNNY CENTRAL 800MV / 1000MV / 1250MV

 

Source : SMA Solar Technology



Robustness :
The new generation of this high tech equipment is very reliable. According to manufacturers, the converters can operate 10 years on average before the first failure (no sufficient feed-back currently anyway for valid statistical analysis).

The standard guarantee is build on a 5 years period, extensible to 10 years as an option possible depending on the manufacturer willingness.


 

M3P Solar - 115 Impasse des Iris - 26240 Beausemblant | Creation: e-partenaire | Email: | Partner: Q.CELLS