Impact Suppression Method for PV Power Generation Grid-reconnection Based on DC Voltage Control

Photovoltaic(PV) power system plays an important role in emergency control as well as fault restoration of power systems by its fast power control capability. Nevertheless, despite a lot of methods for low-voltage ride-through(LVRT) of PV power system, the disconnection of PV under certain degrees of failure and duration cannot be avoided due to the limitation of impact resistance of power electronic devices. In order to avoid the deterioration of the operating status of power grid and give full play to the control ability of PV, PV should be quickly reconnected to the grid after the grid impact is eliminated. Since there is a certain delay in restoring the power output after the shutdown of PV, the shutdown should be avoided after PV is grid-disconnected. Whereas, the operating status of the disconnected and non-stop PV changes continuously with the output of the PV panels, the control of the inverter, and the duration of grid disconnection. Its output may fluctuate greatly after reconnecting to the grid, causing an impact on the power grid. At present, the impact of PV reconnection and the measures to address it have not received much attention. Therefore, the disconnection and reconnection process of PV power system is theoretically analyzed in this paper. The mechanism and influencing factors of current impact caused by PV reconnection are studied. An impact suppression method for PV reconnection based on DC voltage control is proposed. The simulation results are used to verify the effectiveness of the proposed method. The proposed method realizes the stable restoration of power after PV reconnection by suppressing the DC voltage of PV during disconnection, and effectively avoids the current impact of PV reconnection.