Control method for non-stop defrosting of air source variable frequency heat pump

Abstract

The invention relates to a control method for non-stop defrosting of an air source variable frequency heat pump. Comprising the following unit operation steps that when the unit meets the defrosting entering condition, the frequency of a compressor is reduced to 30 Hz from the current frequency at the speed of 1 Hz / s, after the frequency is maintained for 40 S, a four-way valve is powered on for reversing, meanwhile, the frequency of the compressor is increased at the speed of 1 Hz / s, the frequency is increased to 70 Hz to operate, the operation is maintained till defrosting operation is finished, and an external fan is shut down while the four-way valve is reversed; after the unit meets the defrosting ending condition, the compressor is reduced from the current frequency to 30 Hz at the speed of 2 Hz / s, after the frequency is maintained for 10 S, the four-way valve is powered off and reversed, and automatic control is conducted according to the heating frequency; before the four-way valve is switched, when it is detected that the high-pressure saturation temperature Tpd is larger than the judgment temperature T1, the draught fan is started to operate, and when it is detected that the high-pressure saturation temperature Tpd is smaller than or equal to the judgment temperature T2, the draught fan is closed to operate; and when the four-way valve is subjected to power-down reversing, the fan is re-judged according to the initial rotating speed condition.

Description

technical field [0001] The invention relates to the technical field of variable frequency heat pumps, in particular to a control method for non-stop defrosting of an air source variable frequency heat pump. Background technique [0002] When the air source heat pump unit is operated for heating in winter, the air-side heat exchanger will be frosted. When the frosting condition is reached, the unit will enter the defrosting mode operation; The non-stop defrosting method is adopted. When the unit operates in the heating mode and meets the defrosting entry conditions, the compressor will immediately reduce the frequency to 30HZ (the minimum operating frequency set by the unit). After maintaining for 40s, the four-way valve will change direction and the fan Shut down the operation, the unit will enter the defrosting mode operation; when the unit operation meets the defrosting end condition, the compressor will immediately reduce the frequency to 30HZ (the minimum operating frequ...

AI Technical Summary

Problems solved by technology

[0003] Compared with the shutdown defrosting method, this control method has the advantage of reducing the waiting time for the shutdown defrosting unit to stop and restart, but there are still some hidden dangers in the control: when the heat pump unit is defrosting, in order to quickly remove the heat on the fin heat exchanger Frost, the fan of the unit will stop running (the fan will take away the heat of the refrigerant and increase the defrosting time), and the fan will not start until the four-way valve changes direction; when the frosting of the unit is uneven (such as the back of the unit is blocked by objects resulting in uneven frosting), defrosting cannot ensure that the frost layer is removed at the same time (some heat exchangers have been removed from the frost, while some heat exchangers have not been removed), resulting in a continuous increase in system pressure (the frost has been removed) The pressure of the gaseous refrigerant in the clean part of the heat exchanger will continue to rise), if it is higher than the system protection pressure, the unit will shut down for protection, affecting the normal use of users, and the high pressure in repeated defrosting modes will also affect the life of the unit

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