Multirate VBR Model of Synchronous Machines for EMTP-Type Simulation Programs

Models of electrical machines are essential in electromagnetic transient programs (EMTP) that are commonly used for studies of power systems. Recently, a voltage-behind-reactance (VBR) model has been developed for synchronous machines as an alternative to the conventional qd0 model which has advantageous properties in terms of interfacing and accuracy when using large simulation time steps. This paper presents a multirate implementation method for the VBR models of the synchronous machines in EMTP solution. The multirate algorithm separates the VBR machine model into fast subsystem (that includes the stator interfacing circuit and uses small time steps) and slow subsystem (that includes the rotor history terms and mechanical subsystem and uses larger time steps). The presented computer studies demonstrate the computational gains offered by the proposed multirate VBR model.