A photovoltaic system, wherein the photovoltaic system comprises at least one photovoltaic module group, at least one photovoltaic inverter, a grounded metal frame, and a sampling control unit, the photovoltaic module group is mounted on the grounded metal frame, an output end of the photovoltaic module group is connected to an input end of the photovoltaic inverter, and an output end of the photovoltaic inverter is connectable to a power grid; and the sampling control unit is coupled to both the photovoltaic module group and the photovoltaic inverter, and is configured to: detect a current value of a leakage current formed by a common-mode voltage of the photovoltaic inverter on a parasitic capacitor, wherein the parasitic capacitor exists between the photovoltaic module group and the grounded metal frame; and adjust an injection amount of the common-mode voltage in a pulse width modulated signal of the photovoltaic inverter based on the detected current value of the leakage current, to reduce the leakage current; wherein the sampling control unit is configured to: when detecting that the current value of the leakage current is greater than a current threshold, reduce a common-mode injection coefficient of the pulse width modulated signal of the photovoltaic inverter to reduce the injection amount of the common-mode voltage in the pulse width modulated signal; wherein the sampling control unit is configured to: when a modulation ratio of the photovoltaic inverter is greater than 1, reduce the common-mode injection coefficient of the pulse width modulated signal of the photovoltaic inverter to reduce the injection amount of the common-mode voltage in the pulse width modulated signal, until the common-mode injection coefficient is 0 and/or the detected current value of the leakage current is less than or equal to the current threshold; characterized in that the sampling control unit is further configured to: when a modulation ratio of the photovoltaic inverter is greater than 1, if after reducing the common-mode injection coefficient to 0, it is detected that the current value of the leakage current is still greater than the current threshold, adjust the modulation ratio for the pulse width modulation of the photovoltaic inverter to be less than or equal to 1. the sampling control unit is coupled to both the photovoltaic module group and the photovoltaic inverter, and is configured to: detect a current value of a leakage current formed by a common-mode voltage of the photovoltaic inverter on a parasitic capacitor, wherein the parasitic capacitor exists between the photovoltaic module group and the grounded metal frame; and adjust an injection amount of the common-mode voltage in a pulse width modulated signal of the photovoltaic inverter based on the detected current value of the leakage current, to reduce the leakage current; wherein the sampling control unit is configured to: when detecting that the current value of the leakage current is greater than a current threshold, reduce a common-mode injection coefficient of the pulse width modulated signal of the photovoltaic inverter to reduce the injection amount of the common-mode voltage in the pulse width modulated signal; wherein the sampling control unit is configured to: when a modulation ratio of the photovoltaic inverter is greater than 1, reduce the common-mode injection coefficient of the pulse width modulated signal of the photovoltaic inverter to reduce the injection amount of the common-mode voltage in the pulse width modulated signal, until the common-mode injection coefficient is 0 and/or the detected current value of the leakage current is less than or equal to the current threshold; characterized in that the sampling control unit is further configured to: when a modulation ratio of the photovoltaic inverter is greater than 1, if after reducing the common-mode injection coefficient to 0, it is detected that the current value of the leakage current is still greater than the current threshold, adjust the modulation ratio for the pulse width modulation of the photovoltaic inverter to be less than or equal to 1.