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In view of the increasing use of variable frequency drive equipment, the active and reactive demand characteristics of a power grid with a high percentage of variable frequency loads under transient state are analyzed. Due to the fact that a large number of variable frequency motors in power grid cannot be modeled one by one, an aggregation motor model is needed to approximate them. In this paper, a variable frequency motor model is built on the MATLAB/Simulink simulation platform, and the influence of frequency converter on induction motors aggregation is analyzed. Then, an induction motors aggregation method is used to aggregate the variable frequency motors. The transient simulation of the power grid is carried out when the induction motors and the variable frequency motors respectively occupy a high proportion. The simulation results show that variable frequency motors show different load characteristics from the conventional induction motors, and a large number of them can make the system suffer the active impact after the fault recovery process. [ABSTRACT FROM AUTHOR]

This paper takes bus hinge plate damper as the research object, its working principle is studied and introduced, and the damping characteristics of throttle relief valve are analyzed. The relationship between the velocity and the load of the damper is obtained by modeling the articulated disc damper. The load characteristics of the damper are simulated by AMESIM software, and the correctness of the relationship is verified. This provides a basis for the optimization of dampers and provides reference for future research [ABSTRACT FROM AUTHOR]

Rubber-cord shock absorbers of balloon and diaphragm types that are currently used in vibration isolation systems of process equipment of petrochemical and oil and gas production do not have sufficient durability in operation. Thus, other elastic elements study, including rubber-cord shock absorbers of sleeve type, is to be considered. [ABSTRACT FROM AUTHOR]