Simulation of three-phase short-circuit at the terminals of synchronous machine
Three-phase sudden short-circuit at the terminals of a synchronous machine under open circuit condition is simulated. The standard parameters are calculated by using the known parameters, and substituted into the analytical expression for computing short-circuit current. The curve of the relationship between the maximal armature momentary current and the rotor angle is plot. It is concluded that the armature momentary current is maximal when short-circuit occurring at the time of the terminal voltage wave is going through zero. Furthermore, a simulation model in SIMULINK environment is constructed, thus the oscillograms of the armature short-circuit currents in the three phases and the field short-circuit current are plot.
Simulation analysis of a synchronous generator system under fault conditions
In this paper, simulations of a three-phase short-circuit fault that occurs on a 230 kV bus have been carried out in a stand-alone simplified power system based on Matlab/Simulink, the results confirm the validity of the excitation control system including auxiliary control links-power system stabilizer (PSS) on stability of the power system, and the effect of the PSS2A is superior than the Genetic PSS. It also presents the changes of the first amplitude of the transient field fault current and the transient armature fault current along with different phase angles when the fault happens on the armature windings. Simulation results under different fault durations indicate that the time to reach steady-state will reduce substantially if amplitude of the armature transient fault current decreases slightly. Furthermore, this paper presents the changes of maximum deviation and steady-state time of the rotor speed along with the length of fault duration. Simulations about fault happened on different locations are also carried out in this standalone simplified power system, it turned out that the transient stability level of the system is higher when fault happens before the transformer compared with the fault happens on the point that behind the transformer.
Engineering bio-inks for 3D bioprinting cell mechanical microenvironment
Three-dimensional (3D) bioprinting has become a promising approach to construct­ing functional biomimetic tissues for tissue engineering and regenerative medicine. In 3D bioprinting, bio-inks are essential for the construction of cell microenviron­ment, thus affecting the biomimetic design and regenerative efficiency. Mechanical properties are one of the essential aspects of microenvironment, which can be char­acterized by matrix stiffness, viscoelasticity, topography, and dynamic mechanical stimulation. With the recent advances in functional biomaterials, various engineered bio-inks have realized the possibility of engineering cell mechanical microenviron­ment in vivo. In this review, we summarize the critical mechanical cues of cell micro­environments, review the engineered bio-inks while focusing on the selection princi­ples for constructing cell mechanical microenvironments, and discuss the challenges facing this field and the possible solutions for them.