Several concepts of a liquid-metal magnetohydrodynamic (LMMHD) power conversion system performing single and dual cycles (LMMHD-topping cycle, steam or organic Rankine turbine-bottoming cycle) are considered. The working thermodynamic fluid in the LMMHD system can also be noncondensible (inert gas) and in this case a modified Brayton cycle is performed. The main advantages, especially superiority in efficiency, are discussed. These advantages stem from thermal properties of liquid metals and in particular from the possibility of performing a cycle with isothermal expansion of the thermodynamic fluid. Results of parametric studies for LMMHD systems in the megawatt range (up to 10 MW//E ) are presented and discussed. Substantial increase of conversion efficiency in comparison with conventional systems is demonstrated.