103 research outputs found
Transient Stability Analysis for Grid-Forming Inverters Transitioning from Islanded to Grid-Connected Mode
This paper addresses the transient stability of grid-forming (GFM) inverters when transitioning from the islanded to grid-connected mode. It is revealed that the reconnection of the GFM inverters to the main grid can be equivalent to a step change of the active power reference, whose impact is closely related with the local load, active power reference of GFM inverter, and short-circuit ratio (SCR) of the grid. Such equivalent disturbance may cause GFM inverters lose the synchronism with the grid. To avoid loss of synchronization, the existence of equilibria of GFM inverter after reconnecting it with the grid is examined, considering the varying SCR. Then, the parametric effects of power controllers on the transient stability are characterized by using phase portraits, which shed clear insights into the controller design for reliably reconnecting GFM inverters with grid. Lastly, all the theoretical findings are confirmed by experimental tests
A Current Limiting Method for Single-Loop Voltage-Magnitude Controlled Grid-Forming Converters During Symmetrical Faults
Observation of Ultrahigh Mobility Surface States in a Topological Crystalline Insulator by Infrared Spectroscopy
Topological crystalline insulators (TCIs) possess metallic surface states
protected by crystalline symmetry, which are a versatile platform for exploring
topological phenomena and potential applications. However, progress in this
field has been hindered by the challenge to probe optical and transport
properties of the surface states owing to the presence of bulk carriers. Here
we report infrared (IR) reflectance measurements of a TCI, (001) oriented
in zero and high magnetic fields. We demonstrate that the
far-IR conductivity is unexpectedly dominated by the surface states as a result
of their unique band structure and the consequent small IR penetration depth.
Moreover, our experiments yield a surface mobility of 40000 ,
which is one of the highest reported values in topological materials,
suggesting the viability of surface-dominated conduction in thin TCI crystals.
These findings pave the way for exploring many exotic transport and optical
phenomena and applications predicted for TCIs
Transient Stability Analysis of Droop-Controlled Grid-Connected Converters With Inertia Emulating Low-Pass Filters
Transient Stability of Voltage-Source Converters With Grid-Forming Control:A Design-Oriented Study
Adaptive Reactive Power Control of PV Power Plants for Improved Power Transfer Capability under Ultra-Weak Grid Conditions
Adaptive reactive power control of PV power plants for improved power transfer capability under ultra-weak grid conditions
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