Grid Connect Inverters

String Inverters (Conventional DC Systems)

All the solar PV panels are series connected in a number of 400-600v DC strings.

The DC power is then converted  into AC power.

Advantages

  • The initial capital cost to install this type of system is lower.
  • String inverters are quicker to install.
  • It is easy to replace a single string inverter located at a central point.

 Disadvantages

  • The high DC voltages in an array string, makes protection less effective. There is more of a fire risk.
  • Shading of one panel in an array string or failure of one panel will affect the whole string – much more sensitive to shading.
  • Monitoring of system performance can only be realistically performed by monitoring the system as a whole.
  • Single point of failure (the string inverter).
  • Expanding the system is difficult (not impossible).

For more information on String Inverters, Click Here.

Micro Inverters (AC Systems)

 Micro inverters are attached between panel pairs and this effectively means each panel has its own inverter and is independent of all other panels.

Advantages of Micro Inverters

  • High DC voltages are avoided. As such AC protection can be used which is more effective (less fire risk).
  • As each panel is independent of the others shading or failure does not affect the other panels.
  • The overall system performance is greater when compared to string inverters.
  • Micro inverters genarally have a longer manufactures warranty.
  •  Micro inverters are more efficient when compared to string inverters (when directly compared about 8% more output).
  • Each micro inverter & panel performance can be remotely monitored more easily. Remote technical support is alerted and can notify faults faster than compared to string inverters.
  •  The PV system can be expanded easily. More panels can be added anywhere on a site and connected to the LV reticulation.
  • Higher reliability.
  • Flexibility, regarding size, orientation shading, tilt and most importantly if one micro inverter were to fail only that would have to be replaced. This is much cheaper than replacing a large string inverter.
  •  Micro arrays can be placed at any suitable locations on a site. They do not have to be clustered together.
  • Expanding a system you do not have to use panels with similar technical spec. You can take advantage of panel developments.
  • The system is built up of single phase ac circuits.
  • Three phase installations are very easy to implement.

Disadvantages of Micro Inverters

  • The initial capital cost of a micro inverter system is higher than string inverter systems.
  • There is more complex equipment comprising the system.

For more information on Micro Inverters, Click Here.

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