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. <EOS>