Oil return control method during high-temperature refrigeration of direct current variable frequency multi-unit machine

Abstract

The invention provides an oil return control method during high-temperature refrigeration of a direct current variable frequency multi-unit machine. The method comprises the following steps of: (1) initializing parameters; (2) when a system operates for the time which is greater than or equal to Tb from previous oil return, and Fb is less than or equal to Fx, making that Fb is equal to Fx and operation time T is equal to Ty; and if frequency reduction protection is not available in the operation time T of the system, finishing the oil return; (3) if the frequency reduction protection is available in the system, recording the time Tf for the system to operate at the current frequency and calculating unfinished time T-Tf; (4) making that Fb is equal to Fb-f and operation time T is equal to 2(T-Tf); then if the frequency reduction protection is not available during operation time T of the system, finishing the oil return, and if the frequency reduction protection is available in the system, returning to the step (3) until the current operation frequency Fb is reduced to the minimum frequency Fmin for the operation of the compressor. By adopting the oil return control method, the compressor is not burnt down, the system is not damaged, and high reliability is guaranteed.

Description

technical field [0001] The invention relates to the technical field of DC frequency conversion multi-connection air-conditioning systems, in particular to an oil return control method for DC frequency conversion multi-connection high-temperature refrigeration. Background technique [0002] When the current DC frequency conversion multi-connected air conditioning system is used for high-temperature refrigeration (generally refers to the ambient temperature above 40°, such as Africa), due to the high system pressure, high compressor exhaust temperature and large current, in order to ensure the normal operation of the system, DC frequency conversion The multi-connected air conditioning system has frequency reduction protection for excessive exhaust temperature, frequency reduction protection for current overcurrent, and frequency reduction protection for excessive temperature in the middle of the condenser to ensure the normal operation of the system. This makes the entire syst...

AI Technical Summary

Problems solved by technology

However, due to the frequency reduction protection of the system during high-temperature cooling, the compressor cannot run at high frequency at the oil return frequency Fx, which makes the oil return effect ineffective, resulting in burnout of the compressor. The frequency reduction protection of the system is shielded to ensure oil return, which may cause damage to the entire system