Novel Fault Models for Electronically Coupled Distributed Energy Resources and Their Laboratory Validation

Strezoski, Luka; Dumnić, Boris; Popadić, Bane; Prica, Marija; Loparo, Kenneth A.

doi:10.1109/tpwrs.2019.2943123

Cited by 25 publications

(21 citation statements)

References 25 publications

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“…As IBDERs are connected to the network through inverters, their behavior is completely controlled by the inverter's controller. In normal operating conditions, IBDERs, in most cases, operate with a unity power factor, in order to generate as much real power as possible [9]. As every fault in a microgrid is accompanied by voltage dip at the IBDER's connection point, IBDER controller must respond in order to satisfy various grid-code requirements for voltage stabilization.…”

Section: Inverter-based Dersmentioning

confidence: 99%

“…After the inverter's controller detects a fault occurrence, it limits fault current to a predefined value, and employs a predefined control strategy to manage the active to reactive fault currents ratio. In most cases, the IBDER injects a positive sequence symmetrical currents, even in case of unbalanced faults, and reacts to positive sequence voltage drops [9]. The IBDER control strategies that manage fault currents are dictated by the requirements defined in specific grid codes, including the Fault Ride Through (FRT) and Reactive Current Injection requirements [9].…”

Section: Inverter-based Dersmentioning

confidence: 99%

“…In most cases, the IBDER injects a positive sequence symmetrical currents, even in case of unbalanced faults, and reacts to positive sequence voltage drops [9]. The IBDER control strategies that manage fault currents are dictated by the requirements defined in specific grid codes, including the Fault Ride Through (FRT) and Reactive Current Injection requirements [9].…”

Section: Inverter-based Dersmentioning

confidence: 99%

“…In the grid-connected mode, the most significant fault current source by far is the utility grid, whereas DERs contribute to the fault current in a range of 10-20%, depending on their type and locations [7,8]. As most of the DERs in emerging microgrids are completely or partially decoupled from the grid by an inverter-so called inverter-based DERs (IBDERs), or doubly-fed induction machines (DFIMs), respectively, and as their fault currents in the transient period are in most cases limited to no more than 1.5 of their rated values, the fault current supplied by DERs is almost negligible when compared to the one coming from the utility grid [9,10]. On the other hand, in the islanded mode, the only fault current sources are DERs and therefore the total fault current is significantly lower when compared to the grid-connected mode.…”

Section: Introductionmentioning

confidence: 99%

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Short-Circuit Analysis of DER-Based Microgrids in Connected and Islanded Modes of Operation

2021

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Since microgrids should be able to smoothly operate in two distinct modes—grid-connected and islanded, their fault currents can widely fluctuate depending on the operational mode. When the microgrid is connected to the grid, the highest fault current, by far, is supplied by the utility grid. In this mode, the fault current contribution from distributed energy resources (DERs) is less than 20%. However, when the microgrid switches to the islanded mode, the fault current contribution from the utility grid is lost and DERs are the sole fault current sources. Thus, the overall fault current in the islanded mode is multiple times lower when compared to the grid connected mode. Moreover, most of the DERs are inverter-based, with limited fault currents, which further reduces the overall fault current in the islanded mode. With the rapid rise of the microgrid penetration around the globe, this phenomenon can adversely influence the relay protection, and thus the microgrid fault current needs to be precisely analyzed. Therefore, the main purpose of this paper is to thoroughly analyze the fault current differences in two distinct operation modes of a microgrid, and to consequently derive conclusions regarding the required improvements in fault calculations and relay protection analysis in emerging microgrids. A representative microgrid test bed is developed and modelled using the in-house developed software as well as in a state-of-the-art hardware-in-the-loop environment. Several different short-circuit faults were simulated and analyzed in both grid-connected and islanded modes. The results show that the fault currents significantly differ depending on the operating mode, and thus highly influence the protection system. Moreover, test results show that the fault calculation algorithms aimed at radial distribution grids, mostly used for microgrid fault calculations in the available literature, need to be further improved to provide precise and time-efficient results when the emerging microgrids are considered. These results provide a valuable insight into the current state of the microgrids’ fault calculation and protection and reveal several important directions for future research.

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Section: Inverter-based Dersmentioning

confidence: 99%

Section: Inverter-based Dersmentioning

confidence: 99%

Section: Inverter-based Dersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Short-Circuit Analysis of DER-Based Microgrids in Connected and Islanded Modes of Operation

2021

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“…У оквиру тих правила дефинисани су и посебни захтеви "Fault Ride Through -FRT", односно детаљније "Low Voltage Ride Through -LVRT". Ови захтеви дефинишу услове и начин рад ДЕР приликом појаве сниженог напона на месту његовог прикључења на мрежу [3].…”

Section: правила о погону дистрибутивних мрежаunclassified