Steam heat pump system with combined cold and heat supply

The invention relates to the technical field of heat pumps, and particularly discloses a steam heat pump system with combined cold and heat supply. The steam heat pump system comprises a low-temperature heat pump unit, a water supply pipeline, a high-temperature heat pump unit, a third circulation loop, a flash tank, a first-stage water vapor compressor and a water supplementing pipeline, wherein the low-temperature heat pump unit comprises a low-temperature heat pump evaporator, a low-temperature heat pump compressor, a low-temperature heat pump condenser and a low-temperature heat pump expansion valve which are sequentially connected in series to form a first circulation loop; the high-temperature heat pump unit comprises a high-temperature heat pump evaporator, a high-temperature heat pump compressor, a high-temperature heat pump condenser and a high-temperature heat pump expansion valve which are sequentially connected in series to form a second circulation loop; the water supply pipeline is connected wit