System identification and robust anti-windup control for a helium liquifier

This paper addresses the system identification and advanced control of a helium (He) liquifier supplying cooling power at liquid helium (LHe) temperatures (-269 °C). To study the dynamic response to heat load variation, a He liquifier simulation model is utilized. The main focus is to regulate the discharge pressure of the compressor station to guarantee stable system operation. System identification is first conducted to obtain plant models, and a two degree of freedom H_∞ controller is designed to achieve regulation. Moreover, saturation of the control valve is compensated via an anti-windup technique, which is suitable for regulation problem with disturbance rejection. The effectiveness of the proposed control designs is demonstrated by dynamical simulations in EcosimPro (EA International) software.