Heat pump system for a vehicle

A heat pump system for a vehicle, comprising:

• a compressor configured to compress a refrigerant;
• a heating, ventilation, and air-conditioning (HVAC) module including an internal condenser and an evaporator;
• a heat-exchanger connected to the compressor via a refrigerant line;
• a first expansion valve provided on the refrigerant line between the heat-exchanger and the evaporator;
• a gas injection device connected to the internal condenser or the heat-exchanger, and configured to selectively expand and flow the refrigerant supplied from the internal condenser, or the refrigerant supplied from the heat-exchanger, to selectively supply a partial refrigerant among the supplied refrigerant to the compressor, and increase a flow amount of the refrigerant circulating the refrigerant line;
• a first valve provided on the refrigerant line between the compressor and the heat-exchanger;
• a first connection line having a first end connected to the first valve and a second end connected to the internal condenser;
• and
• a second connection line having a first end connected to the internal condenser and a second end connected to the gas injection device,
• wherein flow of the refrigerant is controlled depending on at least one mode for a temperature adjustment of a vehicle interior.