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SUMMARYA finite element method is presented for predicting the coupled structural-acoustic response of a flexible cylinder, which contains an acoustic medium and is excited by mechanical forces. The cylinder is represented by an existing axisymmetric, cylindrical shell element. The acoustic space inside the cylinder is modelled using a new axisymmetric, acoustic ring element. The cross-secton of the ring takes the form of an eight node, isoparametric element. The coupled equations of motion for the cylinder and acoustic field are solved using modal analysis techniques. The numerical results obtained are compared with results from an experimental investigation which is also described.

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The high penetration of converter-based distributed generations (DGs) to power system can give rise to the lack of rotational inertia while replacing the conventional synchronous generators (SGs), which provide the primary frequency reserve (PFR) in power systems. As the result, the decrease in PFR aggravates the frequency stability. To overcome this problem, the droop coefficients of governors in the remaining conventional SGs must be re-determined newly and properly. This paper proposes a new solution based on the grey wolf optimization (GWO) method to optimally select the droop coefficients of SG governors in the low-inertia large-scale power system due to the high penetration of renewables. The proposed solution is very effective for reducing the computational effort significantly, and it is able to recover not only the steady-state but also the transient frequency stability. To verify the effectiveness of proposed optimization solution based on the GWO method, several case studies are carried out on the practical Korea electric power system with the penetration of wind power plants of 4 GW.INDEX TERMS Computational effort, distributed generations, droop coefficients, frequency stability, grey wolf optimization, large-scale power system.

In this paper, we propose active vibration control of a strip in a continuous galvanizing line (CGL) using positive position feedback (PPF) control. The control system includes five pairs of electromagnetic actuators and controllers. First, the overall system was modeled using the three-dimensional finite element modeling (FEM) package ANSYS. The Krylov subspace technique was then used to reduce the order of the model. Finally, PPF control was applied to control the vibration. The stability condition was derived from the stiffness matrix concept, which shows the relationship between the DC gain of the controller and that of the system. Root locus analysis was performed to validate the stability condition derived. The results of the software simulations and the experiments demonstrate the effectiveness of the proposed controller under various tension conditions.

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