Compressor system including a plurality of compressors

A compressor system, comprising at least one variable-speed compressor, at least one fixed-speed compressor, a main suction pipe and a main discharge pipe;

• wherein respective suction pipes of the variable-speed compressor and the fixed-speed compressor are connected to the main suction pipe in parallel, and respective discharge pipes of the variable-speed compressor and the fixed-speed compressor are connected to the main discharge pipe in parallel;
• wherein the main suction pipe is configured with an oil-gas separation fitting structure, and the oil-gas separation fitting structure comprises:
• a first opening connected with the main suction pipe, configured to introduce oil-gas mixture from the main suction pipe into the oil-gas separation fitting structure;
• a second opening which is in communication with the fixed-speed compressor, configured to introduce gas of the oil-gas mixture from the main suction pipe into the fixed-speed compressor;
• a third opening which is only in communication with the variable-speed compressor, configured to introduce most of the oil of the oil-gas mixture from the main suction pipe only into the variable-speed compressor, and to make the variable-speed compressor stay in an oil-rich state;
• and
• the first opening, the second opening and the third opening are configured in such a way that the oil-gas mixture enters the first opening, passes the third opening and then flows to the second opening.