Efficient Modeling of Synchronous Machines for Transient Simulation of Marine Electrical Power Systems

Synchronous machines are employed in various applications, including marine electric power and propulsion systems. This paper proposes a multirate constant-parameter voltage-behind-reactance (CP-VBR) synchronous machine model to improve the efficiency of electromagnetic transient (EMT) simulations of multi-machine marine electrical systems. The proposed multirate modeling technique considers the difference in transient behaviors between the stator (fast) subsystem and the rotor and mechanical (slow) subsystems. Allowing larger time steps for the slow subsystem enhances the overall computational efficiency. The proposed multirate synchronous machine model is implemented using the custom-defined library in PSCAD/EMTDC and demonstrated in transient studies of marine electrical systems. It is shown that by increasing the slow subsystem time step by a factor of five with respect to the fast subsystem, appreciable computational gains may be achieved while maintaining good numerical accuracy.