Distributed low voltage ride-through operation of power converters in grid-connected microgrids under voltage sags

Abstract

Abstract-With the increasing penetration of renewable energy, microgrids (MGs) have gained a great attention over the past decade. However, a sudden cut out of the MGs due to grid fault may lead to adverse effects to the grid. As a consequence, reactive power injection provided by MGs is preferred since it can make the MG a contributor in smooth ride through the faults. In this paper, a reactive power support strategy using droop controlled converters is proposed to aid MG riding through three phase symmetrical voltage sags. In such a case, the MGs should inject reactive power to the grid to boost the voltage in all phases at AC common bus. However, since the line admittances from each converter to point of common coupling (PCC) are not identical, the injected reactive power may not be equally shared. In order to achieve low voltage ride through (LVRT) capability along with a good power sharing accuracy, a hierarchical control strategy is proposed in this paper. Droop control and virtual impedance is applied in primary control loop while secondary control loop is based on dynamic consensus algorithm (DCA). Experiments are conducted to verify the effectiveness of the proposed control strategy.

Low‐voltage ride‐through of a droop‐based three‐phase four‐wire grid‐connected microgrid

“…To facilitate the integration of high penetration level of microgrids, it is expected that the current grid codes will be updated [14,16]. The basic requirement of an LVRT scheme is to keep the electric generators connected into the utility grid.…”

“…However, the current LVRT practice for low-voltage (LV) microgrids and photovoltaic systems is to disconnect them during grid faults [15]. Nevertheless, due to increasing penetration of such systems, this practice is not sustained and is required to be extended for LV systems in the future [10,16,17].…”

“…The LVRT capability of droop-controlled VSCs is not adequately investigated in the literature. Vasquez et al [24] provide voltage support for a singlephase droop-controlled VSC, while Zhao et al [15,16] improve LVRT of three-phase three-wire VSCs using negative sequence droop and distributed controls, respectively. Many DERs are connected to an LV microgrid designed with four wires which enables the connection of single-phase loads.…”

Review of Ship Microgrids: System Architectures, Storage Technologies and Power Quality Aspects

“…The voltage sags are also closely related to the low-voltage ride-through (LVRT) or fault ridethrough (FRT) studies in microgrids; hence relevant literature reports strategies that can be used to mitigate voltage sags [44][45][46][47][48], as well as LVRT strategies for microgrids [49][50][51]. Therefore, both voltage sag mitigation strategies and LVRT strategies are discussed here.…”

“…Reactive power control is the most commonly used strategy for mitigating voltage sags in microgrids, and will also allow microgrid to ride-through faults [46]. This strategy is commonly known as Q/V droop control.…”