A downhole power generation system, comprising: a turbine generator system comprising: a turbine driven by flow of a downhole fluid to rotate; and a generator coupled with the turbine and having an AC-DC rectifier, wherein the generator is configured for converting rotational energy from the turbine to electrical energy and outputting a direct current voltage; and an optimized power control unit via which the turbine generator system is coupled to a load, wherein the optimized power control unit is configured for controlling to regulate an output voltage of the generator and providing a regulated output voltage to the load so that the turbine generator system has an optimized power output, characterised in that the optimized power control unit is configured for regularly disconnecting the generator from the load and measuring an output voltage of the generator after disconnection, and reconnecting the generator with the load and regulating the output voltage of the generator equal to the measured output voltage of the generator multiplied by an optimized voltage ratio predefined for optimized power control, wherein the optimized voltage ratio is equal to a ratio of an optimized power control voltage of the generator to an open circuit voltage of the generator in any one flow rate of the downhole fluid, the optimized power control voltage of the generator being defined as a voltage in which the turbine generator system has the optimized power output, and the open circuit voltage of the generator being defined as a constant no load voltage of the generator. a turbine generator system comprising: a turbine driven by flow of a downhole fluid to rotate; and a generator coupled with the turbine and having an AC-DC rectifier, wherein the generator is configured for converting rotational energy from the turbine to electrical energy and outputting a direct current voltage; and a turbine driven by flow of a downhole fluid to rotate; and a generator coupled with the turbine and having an AC-DC rectifier, wherein the generator is configured for converting rotational energy from the turbine to electrical energy and outputting a direct current voltage; and an optimized power control unit via which the turbine generator system is coupled to a load, wherein the optimized power control unit is configured for controlling to regulate an output voltage of the generator and providing a regulated output voltage to the load so that the turbine generator system has an optimized power output, characterised in that the optimized power control unit is configured for regularly disconnecting the generator from the load and measuring an output voltage of the generator after disconnection, and reconnecting the generator with the load and regulating the output voltage of the generator equal to the measured output voltage of the generator multiplied by an optimized voltage ratio predefined for optimized power control, wherein the optimized voltage ratio is equal to a ratio of an optimized power control voltage of the generator to an open circuit voltage of the generator in any one flow rate of the downhole fluid, the optimized power control voltage of the generator being defined as a voltage in which the turbine generator system has the optimized power output, and the open circuit voltage of the generator being defined as a constant no load voltage of the generator.