Control method of a compressor mechanically coupled to a turbine

A control method of a centrifugal compressor (C) mechanically coupled to an expansion turbine (TorC), the centrifugal compressor (C) being provided with at least a control system (20) of the absorbed power, said control method of the rotation speed of a turbine-centrifugal compressor assembly, comprising the following steps:

• acting on the centrifugal compressor control system (20) of the absorbed power by means of a first controller (PID-f), in order to keep constant the rotational speed of the compressor mechanically coupled to the expansion turbine;
• ensuring that the centrifugal compressor (C) remains in a stable operating condition by means of an admission valve (Vi) of the expansion turbine (TorC);
• configuring said control system (20) to operate on a suction valve (Va) of the centrifugal compressor;
• maintaining by means of a second controller (PID-s):
• a suction valve (Va) opening
• or, not concurrently:
• a variation of a mounting angle of stator blades of the centrifugal compressor (C) at values between a pumping limit of the centrifugal compressor (C) and the 100%, by acting on the admission valve (Vi) of the expansion turbine (TorC) to stabilize a desired set-point pressure.