Power conversion system, photovoltaic optimizer and power tracking method thereof

A method of power tracking applied to a photovoltaic power generation system having an inverter and a plurality of photovoltaic optimizers coupled in series between input terminals of the inverter, for each of the plurality of photovoltaic optimizers, the method comprising:

• a) adjusting an input voltage reference signal corresponding to an input voltage of the photovoltaic optimizer, in accordance with changes of the input voltage, an output voltage, and/or an output current of the photovoltaic optimizer, in order to track a maximum power point of a photovoltaic panel coupled to the photovoltaic optimizer;
• b) adjusting the input voltage reference signal in accordance with the change of an input voltage of the inverter that is equal to the output voltage of the photovoltaic optimizer in a first mode, thereby tracking a maximum power point of the photovoltaic panel, wherein a duty cycle of the photovoltaic optimizer is 1 during the first mode;
• and
• c) adjusting the input voltage reference signal in accordance with the change of the input voltage of the photovoltaic optimizer in a second mode, thereby tracking the maximum power point of the photovoltaic panel, wherein the duty cycle of the photovoltaic optimizer is adjusted and less than 1 during the second mode.