DELAY MARGIN COMPUTATION FOR LOAD FREQUENCY CONTROL SYSTEM WITH PLUG-IN ELECTRIC VEHICLES

Ashraf Khalil and Ang S. Peng

Keywords

Communication time delays, delay margin, delay-dependent stability, electric vehicle, load frequency control system, sweeping test

Abstract

The demands and generation are balanced through the load frequency control (LFC). The introduction of the plug-in electric vehicles (PEVs) in the LFC loop improves the performance and reduces the fluctuations resulting from the renewable energy sources. The time delay is inevitable in the LFC system. In this paper, we propose a new method for computing the delay margin in an LFC system with PEVs and communication delay. The model of the system with time delay is transformed to the frequency domain. A combination of the sweeping test and the binary iteration algorithm is used to find the crossing frequencies and hence calculate the exact delay margin. The results of the proposed method are tested using time domain simulation using Matlab/Simulink. The impacts of the PI controller gains and the PEVs in terms of the gain and the time constant have been investigated.

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