Variable-speed-drive-based soft sensor for the twin-rotary screw-compressor output pressure

Compressed-air systems account for a notable share of the industrial electricity consumption. At the same time, a significant potential to improve the energy efficiency of compressed-air generation has been recognized. Variable-speed drives provide an efficient and flexible way to regulate the output of a screw compressor and to match the typically intermittent demand of compressed air. In addition to capacity control, drive estimates for the electric motor operation can be used in soft-sensing methods. This paper proposes a novel soft sensor, which can monitor the output pressure of a twin-rotary screw compressor based on the variable-speed drive's estimates for the compressor's rotational speed and shaft torque. First, the working principle of the soft sensor is explained in detail and suggestions for commissioning, i.e. tuning it, are given. Finally, the feasibility of the soft sensor is verified with laboratory measurements.