Model predictive control: First application of a novel control strategy for adjustable speed drive compressors

The stabilization of pressure fluctuation is of paramount importance in the management of compressed air systems. In a multi compressor room where load/unload controlled machines can operate along with adjustable speed ones (ASD), the latter usually operate with a set point activation level which lays in between the upper and the lower thresholds of the network operating pressure. By keeping such set point as low as possible, further savings in energy consumptions can be achieved. The presented work deals with the application of a new strategy for the control of an ASD screw air compressor. This strategy-if compared with a PI strategy- can reduce pressure swings, consequently the AS compressor set point, while ensuring the network pressure´s requirements. To the utmost, such value can be set equal to the lowest network operative pressure. The above objective is pursued by controlling the ASD screw compressor with a model predictive control scheme (MPC). The comparison with a PI regulated control shows the potential of MPC both from a pressure stabilization standpoint and, slightly, also from an energy saving standpoint. For a comprehensive implementation of the control scheme, forecasting techniques need to be applied to assess end-users air requirements: this topic, though, is not investigated in the current work.