Combined finite element and network modeling methods provide a time efficient instrument to simulate multi-physics systems. In this work, the Combined Simulation is applied to a nonlinear electromagnetic energy harvester with electrical interface circuit and capacitive energy storage. The energy harvester consists of two cylindrical permanent magnets placed in a cylinder with opposite directions to each other, whereas one magnet is fixed and the other magnet is freely movable in the vertical direction within the cylinder. A coil surrounds the cylinder and transforms the magneto-mechanical energy into electrical energy by means of electromagnetic induction. An external force with a certain wave-form excites the system.
Finite element and network modeling methods are combined to determine concentrated and distributed network parameters and to describe the nonlinear system as an equivalent circuit, whereas Finite element modeling of the two permanent magnets reveals the repulsive force at different distances. The position-dependent electromagnetic coupling coefficient is employed by calculating the linked magnetic flux gradient. The system performance, including the interface circuit and an energy storage component, is then predicted using the numerical network simulator LTspice. A voltage doubler is used to charge a capacitor and compared with a one-way and two-way rectifier. The voltage doubler shows the best results and charges the capacitor to the highest voltage. The presented method helped to understand the overall system behavior. Physical quantities can be quickly determined in the network. The method can be applied to other multi-physics systems and to more complex interface circuits, easily.