Limit Cycle Occurrence During Reactive Power Generation by Interlinking Converter in Hybrid Microgrids

Abstract

This paper is concerned with the analysis of an instability phenomenon, known as limit cycle, in hybrid microgrids (HMGs). The rapid growth of distributed energy resources and their integration into existing distribution networks has opened a new era for electricity generation and distribution markets. The appearance of microgrids, both in the form of ac and dc, is the result of this integration. When both ac and dc microgrids (AC-MGs and DC-MGs) are in the vicinity of each other, they can be interconnected via ac-dc converters, also known as interlinking converters (ICs). Such a structure allows more efficient use of all resources in the system by enabling energy exchange between DC-and AC-MGs. In this paper, it is shown how the reactive power compensation method in IC leads to unstable operation of the HMG. Detailed analysis of this instability reveals that it is caused by a phenomenon known as limit cycle. By knowing the roots of instability, it is possible to eliminate it. Then we studied how the limit cycle that occurred is avoided by nonlinear control techniques support. The analytical studies are backed up by the simulation of a sample HMG. Résumé-Cet article porte sur l'analyse d'un phénomène d'instabilité, connu sous le nom de cycle limite dans les micro-réseaux hybrides (MRHs). La croissance rapide des ressources énergétiques distribuées et de leur intégration dans les réseaux de distribution existants a ouvert une nouvelle ère aux marchés de production et de distribution d'électricité. L'apparition de micro-réseaux, à la fois sous forme de courant alternatif et continu, est le résultat de cette intégration. Lorsque les deux micro-réseaux CA et CC (CA-MRs et CC-MRs) se trouvent à proximité l'un de l'autre, ils peuvent être reliés entre eux par des convertisseurs CA-CC, aussi connu comme convertisseurs interconnectés (CI). Une telle structure permet une utilisation plus efficace des ressources dans le système en permettant l'échange d'énergie entre CC-et CA-MRs. Dans cet article, il a été montré comment la méthode de compensation de puissance réactive dans un CI conduit à un fonctionnement instable du MRHs. Une analyse détaillée de cette instabilité révèle qu'elle est causée par un phénomène connu sous le nom de cycle limite. En connaissant les racines de l'instabilité, il est possible de l'éliminer. Ensuite, nous avons étudié la façon dont le cycle limite produit est évité par le support des techniques de contrôle non linéaire. Les études analytiques sont soutenues par la simulation d'un échantillon de MRH.

Comprehensive review on the strategies for controlling the interconnection of AC and DC microgrids

“…[39], [43], [44], [45], [46], [47], [48], [49], [50], [51], [52], [53], [54], [55], [56], [57], [58], [59], [60], [61], [62], [63], [64], [65], [66], [67], [68], [69], [70], [71], [72], [73], [74], [75] SST An SST is used to interconnect AC and DC microgrids. This method provides more degree of freedom in power transfer performance.…”

“…[59], [60], [48], [61], [62], [58], [63] Virtual Impedance [64] Adaptive, Improved and Robust [50], [53], [51], [52], [39], [49], [54], [65], [56], [66] Intelligent [47], [55], [70], [45], [44] Active Power Sharing Master-Slave [71], [72], [73]…”

A Probe into Reactive Power Management in Renewable Energy System using Facts Devices

“…Subsequently, an enhanced droop control method through online virtual impedance adjustment is presented in [16]. Furthermore, power sharing control strategies of DG units are based on communication embrace concentrated control debated in [17]. In [18], master/slave control and distributed control is considered.…”

An improved power control strategy for hybrid AC-DC microgrids

“…In (7), Qic* is the reference reactive power generation of IC, Vac,ic is the voltage magnitude of IC ac bus and nic is droop characteristic slope which is inversely proportional to IC rated power [10,18].…”

“…This results in better reactive power support and voltage quality. This participation can be accomplished by using a proper Q-V droop characteristic in IC control system [10,18,19].…”