Gu Bowen

Abstract: The Microgrid (MG) is a flexible system composed of paralleled inverters. When the MG runs in grid-connected mode, the first step is to synchronize with the grid stably. However, the weak grid may interact with the synchronization loops and result in instability issues, where the steady-state instability of the MG coming from the loss of equilibrium points remains to be studied. Concretely, the synchronization loop of each inverter determines the equilibrium point. While, when the paralleled inverters work together, interactions among synchronization loops complicate the steady-state analysis. To recognize the synchronization mechanism and steady-state stability of the MG, a kind of hybrid quasi-static models of synchronization loops in the MG is developed in this paper. Studies show that the stable grid-injected currents of current-controlled inverters (CCIs) in a MG are greatly increased, while the allowed grid-injected power of the voltage-controlled inverter (VCI) are decreased obviously and it is closely dependent on the operating currents of the CCIs. Therefore, it is essential to recognize the operating points of each inverter in a MG considering the steady-state stability. Finally, the simulations are carried out to verify the analysis.

TL;DR: In this paper, a method for establishing a subsynchronous oscillation defense line of a power grid system, which relates to a Power Grid system protection technology, is proposed.

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TL;DR: In this article, a test system for secondary equipment detection in a cold region is presented, which solves the problem that low-temperature influence detection evaluation cannot be performed on secondary equipment in the prior art, and belongs to the technical field of power equipment.