VRV oil return control method and system

An oil return control method for a multi-split air conditioner, the multi-split air conditioner including:

• an outdoor unit;
• a plurality of indoor units;
• and expansion valves respectively disposed on connecting pipes between each of the indoor units and the outdoor unit;
• wherein the method includes:
• (1) calculating an average exhaust pressure within an oil return period Pd_AVG
• Pd_AVG
• =
• ∑
• i
• =
• 1
• Count
• ⁢
• (
• Ratio
• i
• *
• Pd
• i
• )
• Count
• *
• RatioX
• wherein RatioX is a set load rate, Count is either the number of times that exhaust pressure of a compressor is collected within the oil return period or the number of times power-on indoor unit load rate is calculated within the oil return period;
• Pdi is the exhaust pressure of the compressor collected for the ith time within the oil return period;
• Ratioi is the power-on indoor unit load rate calculated for the ith time within an oil return period,
• Ratioi=On_Hpi/ALL_HP, On_HPi is a sum of capacities of all power-on indoor units when calculating Ratioi;
• and ALL_HP is a sum of capacities of all indoor units;
• (2) determining whether the average exhaust pressure Pd_AVG is greater than or equal to a set threshold Pdthreshold;
• if Pd_AVG is greater than or equal to Pdthreshold, maintaining the multi-split air conditioner working in heating mode and entering into a heating oil return process;
• if Pd_AVG is less than Pdthreshold, activating the multi-split air conditioner to work in cooling mode, stopping a fan within those power-on indoor units and entering into a cooling oil return process, activating the multi-split air conditioner to work in the heating mode again until the cooling oil return process ends.