A device for suppressing potential induced degradation, that is, connectable to an alternating current output terminal of a converter and a grid-connected power frequency transformer in a photovoltaic system, comprising: a rectification module; a non-isolated voltage conversion module; and at least one capacitor, wherein an input terminal of the non-isolated voltage conversion module is connectable to an output terminal of the converter, the non-isolated voltage conversion module is configured to perform voltage conversion on an alternating current output by the converter, the voltage conversion is boost conversion, the rectification module is configured to rectify an alternating current output by the non-isolated voltage conversion module into a direct current, the capacitor is connected in parallel with an output terminal of the direct current of the rectification module, and either a positive electrode or a negative electrode of the capacitor is grounded; the non-isolated voltage conversion module is a power frequency transformer, both a primary side and a secondary side of the power frequency transformer have Y-type structures, a neutral point of the primary side is connected with a neutral point of the secondary side, the primary side is connectable to a power grid, and the secondary side is connected to the input terminal of the rectification module; a boosting ratio of the power frequency transformer is adjusted to make a voltage to earth of the photovoltaic system negative, in a case that the positive electrode of the capacitor is grounded; and the boosting ratio of the power frequency transformer is adjusted to make the voltage to earth of the photovoltaic system positive, in a case that the negative electrode of the capacitor is grounded. a rectification module; a non-isolated voltage conversion module; and at least one capacitor, wherein an input terminal of the non-isolated voltage conversion module is connectable to an output terminal of the converter, the non-isolated voltage conversion module is configured to perform voltage conversion on an alternating current output by the converter, the voltage conversion is boost conversion, the rectification module is configured to rectify an alternating current output by the non-isolated voltage conversion module into a direct current, the capacitor is connected in parallel with an output terminal of the direct current of the rectification module, and either a positive electrode or a negative electrode of the capacitor is grounded; the non-isolated voltage conversion module is a power frequency transformer, both a primary side and a secondary side of the power frequency transformer have Y-type structures, a neutral point of the primary side is connected with a neutral point of the secondary side, the primary side is connectable to a power grid, and the secondary side is connected to the input terminal of the rectification module; a boosting ratio of the power frequency transformer is adjusted to make a voltage to earth of the photovoltaic system negative, in a case that the positive electrode of the capacitor is grounded; and the boosting ratio of the power frequency transformer is adjusted to make the voltage to earth of the photovoltaic system positive, in a case that the negative electrode of the capacitor is grounded.