Power transmission system of hybrid electric vehicle

A power transmission system of a hybrid electric vehicle comprising:

• an input shaft receiving torque of an engine;
• a first planetary gear set including a first sun gear fixed to a transmission housing, a first planet carrier directly connected to the input shaft, and a first ring gear directly connected to a first motor/generator;
• a second planetary gear set including a second sun gear selectively connected to the transmission housing, a second planet carrier directly connected to the first planet carrier, and a second ring gear directly connected to a second motor/generator;
• a clutch selectively direct-coupling the second planetary gear set;
• and
• an output gear directly connected to the second ring gear and the second motor/generator.

A power transmission system of a hybrid electric vehicle comprising:

• an input shaft receiving torque of an engine;
• a first planetary gear set including a first ring gear fixed to a transmission housing, a first planet carrier directly connected to the input shaft, and a first sun gear directly connected to a first motor/generator;
• a second planetary gear set including a second sun gear selectively connected to the transmission housing, a second planet carrier directly connected to the first planet carrier, and a second ring gear directly connected to a second motor/generator;
• a clutch selectively direct-coupling the second planetary gear set;
• and
• an output gear directly connected to the second ring gear and the second motor/generator.