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2010
Conference Paper
Titel
Improvement of power quality by PV inverters
Abstract
The increasing usage of non-linear electrical loads in the low voltage grid, leads to new challenges to the electrical network. These loads, such as electronic rectifiers or converters will strain the grid by introducing current harmonics. They create a voltage drop over the grid impedance, with respective spectra, that leads to a non-sinusoidal grid voltage. PV inverters that feed the grid decentrally and can support the grid with reactive power are generally capable of not only supplying the grid with a sinusoidal active current, but also specific non-sinusoidal reactive currents depending on the quick response of the current control. A compensating current can be determined with the measured grid voltage and respectively the complex and frequency dependent grid impedance, which ideally eliminates the voltage harmonics. For that, the grid voltage signal needs to be analysed by a group of digital filters tuned to different harmonics. Thus, from the filter results and the knowledge of the grid impedance angle or adequate control algorithms, the compensating current can be determined and adjusted.