The control method of preventing over-temperature in the middle part of the condenser when DC frequency conversion multi-connected external units are refrigerated

Abstract

The invention discloses a control method for preventing overtemperature in the center of a condenser of a direct current (DC) multi-frequency conversion outdoor machine during refrigeration. The control method comprises the following steps of: detecting the central temperature Tc of an outdoor condenser coil pipe; when the Tc is less than 59 DEG C and more than or equal to 57 DEG C, prohibiting afrequency-conversion pressing machine from frequency raising, and prohibiting a constant-frequency pressing machine from being started; when the Tc is less than 57 DEG C, making the frequency-conversion pressing machine quit from the protection; when the Tc is less than 62 DEG C and more than or equal to 59 DEG C, making the frequency-conversion pressing machine reduce the frequency at the rate of 0.8 to 1.2HZ / 10s; when the Tc is less than 65 DEG C and more than or equal to 62 DEG C, making the frequency-conversion pressing machine reduce the frequency at the rate of 0.8 to 1.2HZ / s; when the frequency of the frequency-conversion pressing machine is reduced to the lowest frequency and the Tc which is less than 65 DEG C and more than or equal to 59 DEG C is maintained for more than 1min, stopping the constant-frequency pressing machine, and continuously operating the frequency-conversion pressing machine at the lowest frequency; when the Tc is more than or equal to 65 DEG C, immediatelyshutting down the frequency-conversion pressing machine and the constant-frequency pressing machine; and when the Tc is less than 57 DEG C and the downtime of the constant-frequency pressing machine is maintained for more than 3min, starting the constant-frequency pressing machine. The control method has the advantages of no hysteresis quality and stable systems, and makes compressors difficultlyburned out.

Description

technical field [0001] The present invention relates to the technical field of DC frequency conversion multi-connected air-conditioning systems, specifically a control method for protection when the temperature in the middle of the condenser (using the temperature in the middle of the condenser to simulate high pressure) is too high when the DC frequency conversion multi-connected external unit is refrigerated. Only for the combination of DC frequency conversion multi-unit external unit frequency conversion compressor and fixed frequency compressor, that is, the control method for preventing over-temperature in the middle of the condenser when DC frequency conversion multi-unit external unit is cooling. Background technique [0002] At present, many DC frequency conversion multi-connected air conditioners on the market are combined with a frequency conversion compressor and a fixed frequency compressor to form an external unit. Compressor plus 2 fixed-frequency compressor co...

AI Technical Summary

Problems solved by technology

And because of the hysteresis of the high pressure simulated by the temperature (that is, when the pressure is very high, the temperature that may be detected is still the temperature before the high pressure, resulting in the phenomenon that the temperature is lagging behind the pressure), therefore, it may make the protection adopted The time of frequency reduction or shutdown is not very accurate, resulting in large fluctuations in the system

This kind of fluctuation is more obvious especially for DC frequency conversion multi-line, because the DC frequency conversion external unit is a combination of frequency conversion compressor and fixed frequency compressor. Due to protection, the fixed frequency compressor will be continuously and frequently started and stopped. This will not only affect the cooling effect, but also lead to system instability, and the continuous start and stop of the fixed frequency compressor will easily burn out the compressor