Abstract: With the increasing penetration rate of distributed photovoltaics in the distribution network, the issue of voltage exceeding limits in the distribution network is receiving increasing attention. An online overvoltage prevention and control strategy based on the Thevenin equivalent to address the issue of overvoltage caused by the uncoordinated operation of loads between the power grid and photovoltaic systems is proposed. Under normal operating conditions, the photovoltaic system tracks its output at maximum power. When the voltage at the grid connection point is higher than the preset voltage value, the upper limit of photovoltaic output power is predicted in real-time through the Thevenin parameter and the preset voltage value. The adaptive droop curve is dynamically adjusted to keep the grid connection point voltage within the specified range. This method avoids frequent start-up and shutdown of the inverter, keeps the photovoltaic system always online in the distribution network, and maximizes photovoltaic power generation. The effectiveness of this control strategy is verified through simulation of an IEEE 34-node system.