Tidal stream energy is seen as one of the most viable and clean energy sources in future. This paper describes the research on a cost effective tidal stream power generation system in which a group of 3-phase synchronous generators operating at diverse speeds are connected to a common DC bus via passive diode rectifiers. This power conversion and collection configuration reduce the amount of components required, while maximising efficiency, reliability and controllability, thereby facilitating reduction in capital costs and in operational costs. The output power of each tidal stream generator is regulated by controlling the field excitation of individual machines. The operational characteristics of the proposed power generation system are analysed and the control methods for maximum power extraction and maximum power limiting are outlined. (6 pages)