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Abstract
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Unified power flow controller (UPFC) is one of the multipurpose flexible AC transmission system devices which
controls the transmission line parameters independently and simultaneously. This study presents a novel power flow
controlling method based on terminal sliding mode control (TSMC) method using UPFC. The proposed controller has the
advantages of finite-time convergence and chattering-free properties. A chattering-free state variable controller is designed and
employed to address the problems of reference tracking, robustness against uncertainties and disturbances performance of the
proposed controller is compared with an existing sliding mode controller (SMC) and a PI controller. Chattering phenomena
and discontinuity of the sliding mode controller are also eliminated. Another objective of the proposed control scheme is to
use only locally-measurable states, and to avoid remote long distance measurements. An adaptive observer is used to estimate
the receiving end bus voltage, to avoid the data transfer problems over long distances, and to fulfil advantages such as fault
detection and isolation. The presented observer could also be used to estimate the measurable states of the system. Simulation
results demonstrate the efficiency of the proposed controllers. It is shown that the convergence time of the proposed TSMC is
lower than those of the SMC and PID controllers ’. Stability of the proposed controllers is mathematically proved. The
performance of the presented adaptive observer, in the noisy environment, is also evaluated by simulation. Finally, simulation
results of the suggested controllers under transient states and faulty conditions are presented.
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