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X. Hu,X. Zhang,X. Lou,X. Meng,J. Zhang,T. Li,S. Pan 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
The increasing amount of the integration of distributed generations (DG) will bring about some adverse effects on the static and transient voltage stability, or even threaten the reliability and the safety of the whole power grid. The integration capacity of DGs is the main fact that contributes to the impact on the voltage stability. As DGs are connected to the grid through electronic interface, different kinds of control methods affect voltage stability significantly as well. This work mainly focuses on the DG integration to Yuhang power grid, and the outside part of this grid can be equivalent to a Thevenin circuit. The analytic expressions of the voltage and the power penetration rate at the DG connected node are derived. On this basis, the stability characteristics of the load voltage under different DG penetration rates are analyzed. Moreover, the effects of different reactive power control strategies on voltage static stability are compared with each other, and the transient voltage stabilities under different DG penetration rates are also discussed. Finally, the allowed penetration rate for Yuhang power grid is determined after checking the static and transient stability. The results show that the system can support more loads if the penetration of DG is increased appropriately.
Load-Displacement Formulations of Low-rise Unbounded RC Shear Walls with or without Openings
Lou, K. Y.,Cheng, F. Y.,Sheu, M. S.,Zhang, X. Z. Computational Structural Engineering Institute of 2001 Computational structural engineering Vol.1 No.2
Investigations of low-rice unbounded reinforced concrete shear walls with or without openings are performed with comparison of analytical and experimental results. Theoretical analysis is based on nonlinear finite element algorithm, which incorporates concrete failure criterion and nonlinear constitutive relationships. Studios focus on the effects of height-to-length ratio of shear walls, opening ratio, horizontal and vertical reinforcement radios, and diagonal reinforcement. Analytical solutions conform well with experimental results. Equations for cracking, yielding and ultimate loads with corresponding lateral displacements are derived by regression using analytical results and experimental data. Also, failure modes of low-rise unbounded shear walls are theoretically investigated. An explanation of change in failure mode is ascertained by comparing analytical results and ACI code equations. Shear-flexural failure can be obtained with additional flexural reinforcement to increase a wall's capacity. This concept leads to a design method of reducing flexural reinforcement in low-rise bounded solid shear wall's. Avoidance of shear failure as well as less reinforcement congestion leer these walls is expected.
Optimal design of multiple tuned mass dampers for vibration control of a cable-supported roof
X.C. Wang,Q. Teng,Y.F. Duan,C.B. Yun,S.L. Dong,W.J. Lou 국제구조공학회 2020 Smart Structures and Systems, An International Jou Vol.26 No.5
A design method of a Multiple Tuned Mass Damper (MTMD) system is presented for wind induced vibration control of a cable-supported roof structure. Modal contribution analysis is carried out to determine the dominating modes of the structure for the MTMD design. Two MTMD systems are developed for two most dominating modes. Each MTMD system is composed of multiple TMDs with small masses spread at multiple locations with large responses in the corresponding mode. Frequencies of TMDs are distributed uniformly within a range around the dominating frequencies of the roof structure to enhance the robustness of the MTMD system against uncertainties of structural frequencies. Parameter optimizations are carried out by minimizing objective functions regarding the structural responses, TMD strokes, robustness and mass cost. Two optimization approaches are used: Single Objective Approach (SOA) using Sequential Quadratic Programming (SQP) with multi-start method and Multi-Objective Approach (MOA) using Non-dominated Sorting Genetic Algorithm-II (NSGA-II). The computation efficiency of the MOA is found to be superior to the SOA with consistent optimization results. A Pareto optimal front is obtained regarding the control performance and the total weight of the TMDs, from which several specific design options are proposed. The final design may be selected based on the Pareto optimal front and other engineering factors.
Intelligent hybrid controlled structures with soil-structure interaction
Zhang, X.Z.,Cheng, F.Y.,Lou, M.L. Techno-Press 2004 Structural Engineering and Mechanics, An Int'l Jou Vol.17 No.3
A hybrid control system is presented for seismic-resistant building structures with and without soil-structure interaction (SSI). The hybrid control is a damper-actuator-bracing control system composed of passive and active controllers. An intelligent algorithm is developed for the hybrid system, in which the passive damper is designed for minor and moderate earthquakes and the active control is designed to activate when the structural response is greater than a given threshold quantity. Thus, the external energy for active controller can be optimally utilized. In the control of a multistory building, the controller placement is determined by evaluating the optimal location index (OLI) calculated from six earthquake sources. In the study, the soil-structure interaction is considered both in frequency domain and time domain analyses. It is found that the interaction can significantly affect the control effectiveness. In the hybrid control algorithm with intelligent strategy, the working stages of passive and active controllers can be different for a building with and without considering SSI. Thus SSI is essential to be included in predicting the response history of a controlled structure.