Siemens' Sinvert transformerless solar inverters achieve 98% efficiency

Transformerless inverters supplement the Sinvert series of solar inverters from the Siemens Industry Automation Division. The three-phase photovoltaic inverters achieve 98% efficiency — 2% higher than proceeding units with transformers. This performance enables the plant operator to make a higher profit during infeed into the medium-voltage system. In addition, system costs can be reduced with the option of an increased voltage window from 900 to 1000 volts. The inverter series includes units with graduated ratings of 500 kilowatts, 1000 kilowatts, 1500 kilowatts and two megawatts. The Sinvert inverters are suitable for applications in medium- and large-scale PV power plants.

The central inverter units satisfy medium-voltage regulations and can be used in combination or as stand-alone solutions. The master-slave principle with “rotating master ” is an advantage in the event of changing intensities of solar radiation in the course of the day or in case of cloudiness. Depending on the degree of radiation, the necessary inverters are energized or de-energized. This increases the efficiency of the PV plant, especially in partial-load operation. Only the required number of inverters are operated subject to light intensity. The connection of as many as four inverters in the form of a master-slave system enables the plant to start at low levels of solar radiation and to achieve high efficiencies even in the low output range. The rotating master contributes to the long useful life of the system. The inverter unit with the lowest operating hours is always controlled as master, and the operating time is distributed uniformly among the inverters.

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