A power supply system, comprising: a photovoltaic panel string, an inverter, and a transformer, wherein an input end of the inverter is connected to an output end of the photovoltaic panel string, an output end of the inverter is connected to an input end of the transformer, and an output end of the transformer is configured to output a supply voltage, the power supply system further comprising a voltage controller, wherein the voltage controller comprises: a first sampling unit, a control unit connected to the first sampling unit, and an inverter unit connected to both the first sampling unit and the control unit; and the voltage controller further comprises: a first terminal, a second terminal, and a third terminal, wherein an end of the first terminal is connected to a first output end of the inverter unit, the other end of the first terminal is connected to a first output end of the inverter, an end of the second terminal is connected to a second output end of the inverter unit, the other end of the second terminal is connected to a second output end of the inverter, an end of the third terminal is connected to a third output end of the inverter unit, and the other end of the third terminal is connected to a third output end of the inverter; the inverter unit comprises: an energy storage circuit, a primary circuit connected to the energy storage circuit, and a filter circuit connected to the primary circuit; the first sampling unit is configured to sample an initial voltage of a neutral point of the energy storage circuit in the inverter unit; the control unit is configured to determine, according to a difference between the initial voltage and a first voltage, a duty cycle of a pulse width modulation, PWM signal outputted by the control unit, and drive on/off of switching transistors of the primary circuit in the inverter unit according to the PWM signal, so as to control the inverter unit to output a first alternating current voltage through the filter circuit, wherein the first voltage is a voltage to ground of the photovoltaic panel string connected to the input end of the inverter; and the inverter unit is configured to output the first alternating current voltage under control of the control unit; and if a peak amplitude of the first alternating current voltage is greater than a peak amplitude of a second alternating current voltage outputted by the inverter, the control unit controls the energy storage circuit to discharge, to lower a voltage of a neutral point of an alternating current side of the inverter; or if the peak amplitude of the first alternating current voltage is less than the peak amplitude of the second alternating current voltage, the control unit controls the energy storage circuit to be charged, to increase the voltage of the neutral point of the alternating current side of the inverter, wherein the alternating current side of the inverter is a side of the inverter for outputting an alternating current voltage. the voltage controller comprises: a first sampling unit, a control unit connected to the first sampling unit, and an inverter unit connected to both the first sampling unit and the control unit; and the voltage controller further comprises: a first terminal, a second terminal, and a third terminal, wherein an end of the first terminal is connected to a first output end of the inverter unit, the other end of the first terminal is connected to a first output end of the inverter, an end of the second terminal is connected to a second output end of the inverter unit, the other end of the second terminal is connected to a second output end of the inverter, an end of the third terminal is connected to a third output end of the inverter unit, and the other end of the third terminal is connected to a third output end of the inverter; the inverter unit comprises: an energy storage circuit, a primary circuit connected to the energy storage circuit, and a filter circuit connected to the primary circuit; the first sampling unit is configured to sample an initial voltage of a neutral point of the energy storage circuit in the inverter unit; the control unit is configured to determine, according to a difference between the initial voltage and a first voltage, a duty cycle of a pulse width modulation, PWM signal outputted by the control unit, and drive on/off of switching transistors of the primary circuit in the inverter unit according to the PWM signal, so as to control the inverter unit to output a first alternating current voltage through the filter circuit, wherein the first voltage is a voltage to ground of the photovoltaic panel string connected to the input end of the inverter; and the inverter unit is configured to output the first alternating current voltage under control of the control unit; and if a peak amplitude of the first alternating current voltage is greater than a peak amplitude of a second alternating current voltage outputted by the inverter, the control unit controls the energy storage circuit to discharge, to lower a voltage of a neutral point of an alternating current side of the inverter; or if the peak amplitude of the first alternating current voltage is less than the peak amplitude of the second alternating current voltage, the control unit controls the energy storage circuit to be charged, to increase the voltage of the neutral point of the alternating current side of the inverter, wherein the alternating current side of the inverter is a side of the inverter for outputting an alternating current voltage.