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Abstract: This paper proposes a special protection scheme to prevent power system blackout due to a sequence of relay trip events based on phasor measurement units (PMUs). In a control center, we use PMU''s to monitor the generators and the major EHV transmission lines of a power system, and apply an instability prediction algorithm for initiating a special protection schemes (SPS) to avoid a sequence of relay trip events whenever necessary. When a fault happens, we group the generators swinging coherently and reduce the system to One-Machine-Infinite-Bus (OMIB) system. The remedial control actions consist of load shedding and generation tripping. The strategy for determining the amount of remedial control actions is a proposed relay setting limited equal-area criterion for OMIB. A case study of Taiwan power system assumed to be equipped with proposed special protection scheme is conducted. Encouraging results are obtained. [Copyright &y& Elsevier]

Abstract: The tuning of the PSS parameters for a multi-machine power system is usually formulated as an objective function with constraints consisting of the damping factor and damping ratio. A novel mixed-integer ant direction hybrid differential evolution algorithm, called MIADHDE, is proposed to solve this kind of problem. The MIADHDE is improved from ADHDE by the addition of accelerated phase and real variables. The performances of three different objective functions are compared to the MIADHDE in this paper. Both local and remote feedback signals of machine speed deviation measurements can be selected as input signals to the PSS controllers in the proposed objective function. The New England 10-unit 39-bus standard power system, under various system configurations and loading conditions, is employed to illustrate the performance of the proposed method with the three different objective functions. Eigenvalue analysis and nonlinear time domain simulation results demonstrate the effectiveness of the proposed algorithm and the objective function with a remote signal. [Copyright &y& Elsevier]