The present disclosure provides a switch unit and a power generation system thereof. The switch unit includes a contact switch having a main contact and a control terminal, where the control terminal receives a first drive signal to turn on the contact switch; and a bi-directional controllable switch structure, which is connected in parallel to two ends of the main contact of the contact switch and receives one or more second drive signals to turn on the switch structure. When the switch unit performs a turn-off operation, the bi-directional controllable switch structure provides a commutation bypass for the contact switch, so as to protect the contact switch.