In this paper, a power supply unit based on the Engine-Generator Set (EGS) will be discussed. The recent clear trends lead to use of more economical power sources that are able to yield maximum of fuel energy. EGS units can be considered as comparatively sophisticated mechatronic systems consisting of mechanical part, electromechanical energy conversion part, power electronics and control (feed-back) part. This paper is aimed to highlight that mobile EGS needs a speedy power buffer with back-up power supply and bi-directional dc-dc converter, to show the PID regulator design and results of EGS experimental identification and verification.@en