On Energy Conversion in Port-Hamiltonian Systems

We study port-Hamiltonian systems with two external ports, and the strategies and limitations for conversion of energy from one port into the other. It turns out that, apart from the cyclo-passivity of port-Hamiltonian systems, this is related to the internal connection structure of port-Hamiltonian systems. A source of motivation for energy conversion is provided by thermodynamics, in particular the Carnot theory of conversion of thermal into mechanical energy. This is extended to general port-Hamiltonian systems which are satisfying structural conditions on their topology; thus generalizing the Carnot-Clausius theory of heat engines. In particular, the operation of Carnot cycles is extended, which is illustrated by the example of a precursor to the Stirling engine, as well as an electromagnetic actuator. Furthermore, alternative energy conversion control schemes such as energy-routers are discussed.