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The application of Shifted Frequency Analysis in power system transient stability studies Martí, Andrea T.J.


Power system engineers use transient stability computer simulation programs to model the power grid’s behaviour when large disruptions cause the grid to deviate from its 60-Hz operating frequency. These programs must be able to capture these frequency dynamics around 60 Hz while being computationally efficient, as an extensive number of simulations are typically run for a given scenario. In the traditional power grid, the large mechanical inertia of the synchronous generators stabilizes the network during disturbances and maintains the system frequency close to the 60 Hz operating frequency. In the modern grid, however, the increase of renewable energy sources lowers the grid’s inertia and larger frequency deviations can occur. The phasor solution method employed in the traditional programs solves the network assuming a constant 60-Hz frequency. When deviations from 60 Hz are prominent, the Electromagnetic Transients Program (EMTP) is used as an alternative to the phasor solution to capture these fluctuations. The EMTP models the electrical network based on the differential equations of the network components, which allows the tracing of the network waveforms. However, this discretization requires small time-steps, which makes the solution method computationally expensive. The Shifted Frequency Analysis (SFA) method discussed in this work is an alternative to the traditional phasor solution and to the EMTP solution. In this work, a generalized SFA-based program is written and used for transient stability analysis. SFA is a discrete-time solution method, like the EMTP, but uses a frequency-shifting transformation to bring the solution domain down to 0 Hz. Because of this transformation, SFA can capture network dynamics around 60 Hz using large time-steps, making it suitable for transient stability analysis studies.

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