Photovoltaic-inverters as active filters to improve power quality in the grid. What can state-of-the-art equipment achieve?

Modern grid connected inverters offer a wide range of possibilities beyond the sole injection of active power into the grid. The behavior of inverters at various voltage quality conditions is analyzed by laboratory tests and a characterization according to their emission of current harmonics is provided. In addition, the contribution of PV inverters to an improvement of power quality is discussed. The characteristics of the injected current of inverters depends in many cases on the actual phase angle of the injected harmonic current related to the voltage harmonic present on the grid. The test results show that state-of-the-art inverters could already be capable to operate as active filters and thus improve the voltage quality in the network.