Modeling and real-time control of an industrial air multi-compressor system

This paper presents a control algorithm for an air multi-compressor system. The goal is to achieve adequate performance in terms of air pressure regulation by properly coordinating a set of compressors driven by fixed speed motors. The coordination is required to impose an upper bound to the activation frequency of electric drives. A multi-compressor system is intended to be a viable alternative to compressor systems based on Variable Speed Drives (VSD) operated by inverters, which suffer of several technical and economic drawbacks. The control strategy is based on the evaluation of the timing associated to activations/deactivations of each compressor. Such evaluation is determined by the values of physical variables that determine the system behavior, including air flows, pressures and temperature. The periodic measurement of the actual pressure is performed to dynamically adjust the estimation of relevant time instants in case of variations of working conditions. The algorithm takes into account the dynamics of the air pressure, as well as timing constraints on the minimum period between two subsequent activations of each compressor. The effectiveness of the multi-compressor solution is evaluated by simulation.