Typically gas permeation processes are designed and simulated for steady state conditions. In some applications such as biogas upgrading varying feed gas conditions demand for a fundamental understanding, description and control of membrane process behaviour. In this study we present a dynamic process model for membrane based biogas upgrading processes ln particular we report efficient process control schemes to maintain a required constant product purity. The dynamic model of a hollow fiber gas permeation module is used to analyze a three stage membrane process for biogas upgrading. Such complex configurations of gas permeation modules enable both high CH4 purities and high CH4 recoveries simultaneously. The dynamic model was programmed in Aspen Custom Modeler and exported to Aspen Plus and Aspen Plus Dynamics for dynamic process simulation. Two novel process control schemes are presented which maintain the product purity even if significant changes in the feed gas conditions are enforced. These control schemes operate within short periods and compensate changes in the feed conditions. Both control systems do not require any additional process equipment making it attractive for numerous gas permeation processes. The presented control concepts are neither limited to biogas upgrading processes nor to the three stage membrane process. (C) 2015 Elsevier B.V. All rights reserved.