The invention discloses a gas supplementing and
enthalpy increasing control method of a low-temperature type direct-current variable-frequency
heat pump system. The key of the method is as follows, anexhaust temperature of the
system is detected, when the exhaust temperature is larger than or equal to 70 DEG C, and when an exhaust superheat degree is larger than or equal to 25 DEG C, an enthalpyspraying
electromagnetic valve (10) is electrified and started, and an
enthalpy spraying auxiliary path is circulated; an
enthalpy spraying
electronic expansion valve (11) is started, an initial opening degree is 100 PLS and kept for 3 minutes, then adjusting is carried out according to an actual
supercooling degree, when the actual
supercooling degree is larger than or equal to a target
supercooling degree, the opening valve control of the enthalpy spraying
electronic expansion valve (11) is carried out; and when the actual supercooling degree is less than the target supercooling degree, theclosing valve control of the enthalpy spraying
electronic expansion valve (11) is carried out, when the exhaust superheat degree is less than 20 DEG C, the enthalpy spraying electronic expansion valve(11) is closed, the enthalpy-spraying auxiliary path is not circulated, and the safety and reliability of a compressor are guaranteed. According to the gas supplementing and enthalpy increasing control method of the low-temperature direct-current variable-frequency
heat pump system, the problems that in an actual application project, the heating performance of the variable-frequency
heat pump system is attenuated and the system reliability is poor in a low-temperature use environment are solved.