Bond graph approach for port-controlled Hamiltonian modeling for SST

Abstract

Energy-based modeling is often very appropriate for physical system modeling for development and analysis of multi domain dynamic system models. One such tool for modelling of system is bond graph (BG), which allows to model complex system, with clear interconnection rules and preserving the physical structure of the system. In various engineering system, operation is carried out on various time scale. One such area of generic system is microgrid, where multidisciplinary microgrid components operating on various time scales. In such hybrid system, flows and efforts comprise a very good choice of variables to link components for system stability and performance analysis. Since components are typically connected through various power electronics devices, mathematical modeling capable of capturing high frequency behavior is of utmost concern in stability analysis. Solid state transformer (SST) is one such device playing a key role in bi-directional power flow between the grid and various renewable sources. This paper proposes the use of the BG approach to recognize the energy representation of the microgrid in port-Hamiltonian form by looking at the energy transformation aspects of microgrid components. The port-controlled Hamiltonian systems (PCHS) are the mathematical description of bond graphs which allows integration of subsystems of hybrid microgrid using energy as the linking concept. To illustrate the utility of BG in hybrid systems, basic PI controller is implemented. The aim of the paper is to show how to model complex systems in bond graph domain.