Joaquín Pedra

Algorithm for the study of voltage sags on induction machines

This paper proposes an algorithm for the approximate calculation of the effects caused by a voltage sag in the induction machine supply system. The algorithm computes the current and torque peaks, and the mechanical speed loss for an extensive range of voltage sags. It has a high calculation speed because it makes two simplifications. The first supposes that speed varies insignificantly during the first cycles after the voltage drop and recovery points to solve analytically the electrical transients in these cycles. The second neglects the electrical transient during the sag duration for a quick evaluation of the speed loss. Machine sensitivity to voltage sags is graphically shown. The curves can be applied to protective relay coordination.

Electrical resonance instability study in wind power plants

Wind power plant stability can be affected by the interaction between the wind turbine and the resonances in the collector grid. This paper presents an electrical resonance instability study applied to wind power plants. The influence of feedforward low pass filter bandwidth and converter filter inductance on wind power plant stability is analyzed with examples. An impedance-based representation of the wind power plant is used to identify the resonances and analyze stability problems. PSCAD/EMTDC time-domain simulations are also shown to validate the stability study.

Electrical resonance instability study in traction systems

Traction system stability can be affected by the interaction between the traction load and resonances in the railway traction grid. This paper presents an electrical resonance instability study applied to traction systems. The influence of traction section length and converter time delay on traction system stability is analyzed with examples. An impedance-based representation of the traction system is used to identify the resonances and analyze stability problems. PSCAD/EMTDC time-domain simulations are also shown to validate the stability study.