Converting thermal energy to electricity is one of the most common energy conversions in the field of electricity production. This transformation of energy is essential for both renewable and non-renewable heat sources. One of the main parameters of such a system that is responsible for this conversion is its efficiency. Many improvements have been made to the old methods, and new techniques were developed to have an efficient transformation. One of these new methods that will be discussed here is a combined system of a Free Piston Stirling Engine (FPSE) with a Permanent Magnet Linear Synchronous Machine (PMLSM). The two purposes of presenting such a system are: first, the theoretical efficiency of a Stirling engine is high, and second, some of the losses will be removed by eliminating the crank-shaft from this system compared to the standard Stirling engine system. To study this system, a thermodynamic model of a RE-1000 FPSE was presented and validated. Then it was coupled with a PMLSM, and the combined system was controlled. The total efficiency of this system in the steady state is 14.4%. Furthermore, a sensitivity study is done to see the impact of different parameter variations on the system response. This study is valuable from a practical point of view when the theoretical model is going to be validated with the experimental setup. In this case, which parameters must be measured or estimated with more accuracy should be known.