Co-simulation of electrical networks by interfacing EMT and dynamic-phasor simulators

The paper presents a hybrid co-simulator comprising EMT and dynamic phasor-based simulators. The EMT simulator models portion(s) of the network wherein fast transients are prevalent and detailed modeling is necessary. The dynamic phasor solver models the rest of the network using extended-frequency Fourier components. Specialized algorithms are developed and presented to accurately map instantaneous EMT and counterpart dynamic phasor samples. Interfacing requirements for co-simulation using different time-steps in the two solvers are also discussed along with implications on accuracy and numerical stability. The paper demonstrates the developed co-simulation algorithm using an example of the IEEE three-phase 118-bus network in which a wind farm is included. The wind farm and the network in its vicinity are modeled in the PSCAD/EMTDC electromagnetic transient simulator, and are interfaced to the rest of the system modeled in a dynamic phasor-based solver. The paper demonstrates the accuracy of the proposed co-simulation for a range of time-step ratios of the two solvers, and also reports the substantial computational time savings obtained using the hybrid simulator.