The invention discloses a method for controlling an electronic expansion valves during multi-connected
air conditioning unit heating. The method includes the following steps that firstly, the target air suction superheat degree Tr and the target
supercooling degrees Tl of the expansion valves are set; secondly, whether the actual air suction superheat degree Ts-Tdef is equal to Tr or not is judged, if the actual air suction superheat degree Ts-Tdef is equal to Tr, the third step continues to be executed, and if the actual air suction superheat degree Ts-Tdef is not equal to Tr, the sixth step is executed; thirdly, whether the actual
supercooling degrees tem-liq of the expansion valves are all in the Tl range or not is judged, if the actual
supercooling degrees tem-liq of the expansion valves are all in the Tl range, the fourth step is executed, if the actual supercooling degrees tem-liq of the expansion valves are not all in the Tl range, the fifth step is executed, no adjustment is made, and the second step is executed; fifthly, when the actual supercooling degree tem-liq of a certain expansion valve is larger than the upper limit of T1, the valve is opened to a certain degree, when the actual supercooling degree tem-liq of a certain expansion valve is smaller than the
lower limit of Tl, the valve is closed to a certain degree, and the second step is executed after adjustment is completed; sixthly, whether the actual supercooling degrees tem-liq of the expansion valves are all in the Tl range or not is judged, if the actual supercooling degrees tem-liq of the expansion valves are all in the Tl range, the seventh step continues to be executed, and if the actual supercooling degrees tem-liq of the expansion valves are not all in the Tl range, the eighth step is executed; seventhly, the step numbers of all the expansion valves are adjusted, and the second step is executed after adjustment is completed; and eighthly, when Ts-Tdef is larger than Tr, the expansion valves with tem-liq larger than the upper limit of Tl are opened to a certain degree, if Ts-Tdef is smaller than Tr, the expansion valves with tem-liq smaller than the
lower limit of Tl are closed to a certain degree, and the second step is executed after adjustment. The method has the beneficial effects that a
refrigerant is reasonably distributed, and a balance
heating effect is achieved.