Power supply system, power supply method, and power supply apparatus

A power supply method, comprising:

• detecting whether power of an electrical signal provided by a mains system is greater than total power of at least one load;
• sending, in response to determining that the power of the electrical signal provided by the mains system is not greater than the total power of the at least one load, a first control instruction to a maximum power point tracking unit, wherein the first control instruction enables the maximum power point tracking unit to detect maximum power of an electrical signal generated by a renewable energy conversion unit, and to provide an electrical signal of specified power for the at least one load;
• detecting whether total power of the electrical signal provided by the mains system and the electrical signal provided by the maximum power point tracking unit is greater than the total power of the at least one load;
• and
• sending, in response to determining that the total power of the electrical signal provided by the mains system and the electrical signal provided by the maximum power point tracking unit is not greater than the total power of the at least one load, a second control instruction to a fossil energy conversion unit, wherein the second control instruction enables the fossil energy conversion unit to provide an electrical signal of the specified power for the at least one load.