Alleviating power quality issues when integrating PV into built areas: Design and control of DC microgrids

Increasing penetration of PV sources in LV grids is introducing new challenges to the quality of voltage. Variability of solar radiation can cause power ramps of up to the nominal power of the plant in one second, which directly induces voltage fluctuations on distribution feeders. To mitigate this impact on power quality, we investigate the introduction of dc micro-grids interfaced to the ac grid through four-quadrant inverter. The introduced control strategy is able to manage the entire system without any communication layer and to ensure at the same time: i) ramp-rate control of the power exchanged with the ac grid; ii) voltage stability on both dc and ac grids; iii) maintaining the state of charge of storage devices connected to the dc grid. In the paper the effectiveness of the proposed strategy is shown with numerical simulations considering real profiles of solar irradiation and load power.