Method for controlling direct current frequency conversion air-conditioner while operating in refrigeration mode

Abstract

The invention discloses a method for controlling a direct current frequency conversion air-conditioner while operating in a refrigeration mode. The method is used for controlling the direct current frequency conversion air-conditioner when the lowest capacity output of the outdoor unit is higher than the capacity requirement of the inner unit, and comprises the following steps: step 1, setting different target low pressure values for various sections of the outdoor ambient temperature; step 2, reducing the operation frequency of a direct current frequency conversion compressor to the lowest operation frequency during the operation process of the direct current frequency conversion air-conditioner according to the requirements on the capability of the indoor unit; and step 3, controlling a first throttle electronic expansion valve, a second throttle electronic expansion valve and an unloading electromagnetic valve to execute corresponding actions according to the low pressure values when the direct current frequency conversion compressor operates in the lowest operation frequency, or controlling the direct current frequency conversion air-conditioner to be started or stopped. With the adoption of the method, the excess capacity output of the outdoor unit is counterbalanced, so that capacity output of the outdoor unit is matched with the lowest capacity requirement of the indoor unit, the normal and stable operation of the direct current frequency conversion air-conditioner is maintained, and the phenomenon that a small trolley is drawn by a horse having large power is prevented.

Description

technical field [0001] The invention relates to the technical field of frequency conversion air conditioners, in particular to a control method when the minimum capacity output of an outdoor unit is higher than the capacity requirement of an indoor unit when a DC frequency conversion air conditioner operates in cooling mode. Background technique [0002] Since one outdoor unit can drive multiple indoor units, and the series and specifications of indoor units can be freely combined, DC inverter air conditioners have developed rapidly and have a wide range of applications, becoming the product with the most promising market prospects in the field of central air conditioners. The outdoor unit of the DC variable frequency air conditioner is composed of a DC variable frequency compressor and multiple fixed frequency compressors in parallel. The nominal capacity of the selected DC variable frequency compressor is usually below 6 horsepower. The operating frequency range of the DC v...

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Problems solved by technology

[0004] However, a problem brought about by the use of large-capacity DC inverter compressors is that the operating frequency range of large-capacity DC inverter compressors (such as 30 hp) is between 20 and 120Hz, and the operating frequency corresponding to the nominal capacity is 90Hz. When the operating frequency is 20Hz, the minimum output capacity is 5 horses. Then, when only one indoor unit of the indoor units is turned on, the minimum output capacity of the outdoor unit is 4 horses higher than the capacity requirement of the indoor unit, resulting in "Malaysia". "pull the trolley" phenomenon

When the minimum output capacity of the outdoor unit is higher than the capacity requirement of the indoor unit, the flow rate of refrigerant returning to the compressor through the indoor unit is lower than the flow rate of refrigerant discharged from the compressor. In this way, the air return port of the system compressor will appear in the DC inverter air conditioner. The low voltage drops rapidly and reaches the low voltage protection value, causing the entire DC inverter air conditioner to shut down. The consequence is that the DC inverter air conditioner shuts down and starts frequently, which reduces the comfort of the air-conditioned room and also affects the service life of the DC inverter air conditioner.

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