A power supply system, comprising: at least one photovoltaic cell panel string, at least one inverter, a transformer, and a voltage controller, wherein an input end of the at least one inverter is connected to an output end of the at least one photovoltaic cell panel string, an output end of the at least one inverter is connected to an input end of the transformer, and an output end of the transformer is configured to output a power supply voltage; the voltage controller comprises: a communication unit configured to obtain a voltage to earth of the at least one photovoltaic cell panel string, a first sampling unit, a control unit connected to the first sampling unit, and an inverter unit connected to the first sampling unit, wherein the first sampling unit is configured to sample a voltage and a current of the inverter unit; and the output end of the at least one inverter is further connected to an output end of the inverter unit; characterized in that the voltage controller further comprises: a DC converter connected between earth and a midpoint of the input of the inverter unit, configured to output a DC converted voltage; and a second sampling unit, connected to the control unit, and configured to sample a voltage and a current of the DC converter, wherein the control unit is further configured to adjust a bus voltage of the inverter unit and an input and/or output voltage of the DC converter, wherein the bus voltage of the inverter unit is the voltage across the input terminals, so that a voltage to earth output by the voltage controller is continuously adjusted starting from 0. at least one photovoltaic cell panel string, at least one inverter, a transformer, and a voltage controller, wherein an input end of the at least one inverter is connected to an output end of the at least one photovoltaic cell panel string, an output end of the at least one inverter is connected to an input end of the transformer, and an output end of the transformer is configured to output a power supply voltage; the voltage controller comprises: a communication unit configured to obtain a voltage to earth of the at least one photovoltaic cell panel string, a first sampling unit, a control unit connected to the first sampling unit, and an inverter unit connected to the first sampling unit, wherein the first sampling unit is configured to sample a voltage and a current of the inverter unit; and the output end of the at least one inverter is further connected to an output end of the inverter unit; characterized in that the voltage controller further comprises: a DC converter connected between earth and a midpoint of the input of the inverter unit, configured to output a DC converted voltage; and a second sampling unit, connected to the control unit, and configured to sample a voltage and a current of the DC converter, wherein the control unit is further configured to adjust a bus voltage of the inverter unit and an input and/or output voltage of the DC converter, wherein the bus voltage of the inverter unit is the voltage across the input terminals, so that a voltage to earth output by the voltage controller is continuously adjusted starting from 0. a DC converter connected between earth and a midpoint of the input of the inverter unit, configured to output a DC converted voltage; and a second sampling unit, connected to the control unit, and configured to sample a voltage and a current of the DC converter, wherein the control unit is further configured to adjust a bus voltage of the inverter unit and an input and/or output voltage of the DC converter, wherein the bus voltage of the inverter unit is the voltage across the input terminals, so that a voltage to earth output by the voltage controller is continuously adjusted starting from 0.