Based on mathematical modelling and numerical simulations, the control strategy for a molten carbonate fuel cell hybrid system (MCFC-HS) is presented. Adequate maps of performances with three independent parameters are shown. The independent parameters are as follows: stack current, fuel mass flow and compressor outlet pressure. Those parameters can be controlled by external load, fuel valve and turbine-compressor shaft speed, respectively. The control system is purposed to meet many constraints: e.g. stack temperature, steam-to-carbon ratio, compressor surge limitation, etc. The aim is to achieve maximum efficiency of power generated within those constraints. Governing equations of MCFC-HS modelling are given. An adequate simulator for the MCFC module was produced and described. Based on this simulator, the control strategy was obtained. The performance of this MCFC-HS is shown in various working environments. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.