Control Strategy for Photovoltaic Grid-connected Inverter with Harmonic Suppression

A photovoltaic inverter control strategy based on the virtual impedance method is proposed, which makes the inverter compensate the harmonic of power grid to achieve the purpose of harmonic suppression while the inverter transmit the active power to the grid. An algorithm of finding the best virtual impedance is designed. The search range of the virtual impedance is determined by estimating the equivalent impedance according to the Norton equivalence theorem. Using the harmonic value of the grid voltage by detecting and the initial virtual impedance value to calculate the harmonic current signal that is added to the inner current loop. Finding the best virtual impedance through adjusting the virtual impedance value and analyzing the voltage harmonic distortion. The harmonic consumption power is maximal and the total harmonic distortion of voltage is minimal when reached the point. A prototype is built to validate the effectiveness of the proposed control strategy.