Commercial rooftop installation project with direct grid-connected photovoltaic inverters

A low-pressure end of the entrance of the facility has a connection point of a megawatt commercial rooftop systems require 1-4 grid-connected photovoltaic inverters. When using the conventional inverter, each one must be associated with a separate isolation transformer or custom matched - regardless of whether the inverter transformer and integrated, always the case. Therefore, the power supply is immediately reduced, because the efficiency of the isolation transformer is usually only 98% to 99%, which allows a maximum of 2% performance degradation.

As bulky and heavy, traditional inverter will limit the PV inverter system design. Using two inverters 500 kilowatts system design requires installing the inverter on the ground, because the inverter / transformer with a large size and weight. Even though the inverter isolation transformer can be separated from each other, due to the lower voltage and higher current which causes high installation costs of the wire, each of the required inverter gridtiepowerinverteronline output voltage and a lower limit multi-winding will the distance separating each other.

Integrated inverter stability issues also need attention. Conventional inverter design usually undamped large triangle filter when many devices placed in parallel or inverter is set in long transmission line, these filters may cause the system to run unstable. Moreover, if the inverter is placed in parallel in the same box, each 500 kilowatts

Inverter consists of four smaller 125 kilowatts unit drive, then this system is susceptible to electrical interference, but also for the entire PV system brings multiple points of failure.

In contrast, the true transformerless grid tie power inverter is directly fixed on the entrance of a building, or is fixed at a sufficiently large size distribution on the mounting plate. Since there is no isolation transformer, the power from the PV modules to obtain additional 1% to 2% of the energy efficiency directly into the load, the power of 500 kW, it implies that the minimum free additional output of 5 kW. In addition, directly into the available voltage instead of the lower pole AC voltage inverter, and the alternating current is reduced more than half, thereby reducing the cost of the AC end of the wire.