Short-circuit analysis in large-scale distribution systems with high penetration of distributed generators

Strezoski, Luka; Prica, Marija

doi:10.1109/jas.2017.7510517

Cited by 22 publications

(12 citation statements)

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“…The doubly-fed induction generator wind turbine (DFIG-WT) is one of the most popular wind turbine generators due to its low manufacturing cost, high efficiency, and high flexibility, and is extensively applied on wind farms [1][2][3]. In earlier studies, DFIG-WT was regarded as a load or synchronous generator for short-circuit calculation, as the capacity of wind farms is small [4,5]. However, with the increasing capacity of wind power access to the grid, the influence of the short-circuit current (SCC) of DFIG-WT can no longer be ignored.…”

Section: Introductionmentioning

confidence: 99%

Short-Circuit Current Calculation and Harmonic Characteristic Analysis for a Doubly-Fed Induction Generator Wind Turbine under Converter Control

Zheng

Wang

2018

Energies

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An accurate calculation of short-circuit current (SCC) is very important for relay protection setting and optimization design of electrical equipment. The short-circuit current for a doubly-fed induction generator wind turbine (DFIG-WT) under excitation regulation of a converter contains the stator current and grid-side converter (GSC) current. The transient characteristics of GSC current are controlled by double closed-loops of the converter and influenced by fluctuations of direct current (DC) bus voltage, which is characterized as high order, multiple variables, and strong coupling, resulting in great difficulty with analysis. Existing studies are mainly focused on the stator current, neglecting or only considering the steady-state short-circuit current of GSC, resulting in errors in the short-circuit calculation of DFIG-WT. This paper constructs a DFIG-WT total current analytical model involving GSC current. Based on Fourier decomposition of switch functions and the frequency domain analytical method, the fluctuation of DC bus voltage is considered and described in detail. With the proposed DFIG-WT short-circuit current analytical model, the generation mechanism and evolution law of harmonic components are revealed quantitatively, especially the second harmonic component, which has a great influence on transformer protection. The accuracies of the theoretical analysis and mathematical model are verified by comparing calculation results with simulation results and low-voltage ride-through (LVRT) field test data of a real DFIG.

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Section: Introductionmentioning

confidence: 99%

Short-Circuit Current Calculation and Harmonic Characteristic Analysis for a Doubly-Fed Induction Generator Wind Turbine under Converter Control

Zheng

Wang

2018

Energies

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“…The dynamic model of the recloser can be imitated by inverse-time OCR characteristics. This consists of the reset time (F 1 (I)) and the pickup time (F 2 (I)), which are expressed in Equations (1) and (2), respectively [21]:…”

Section: Dynamic Model Of Recloser-fusementioning

confidence: 99%

“…Distributed generators (DGs) have rapidly spread around the world because of advantages such as reduced carbon emissions, decreased line losses, and improved voltage profiles [1]. Although DGs provide many benefits, they can disrupt the coordination of protective devices.…”

Section: Introductionmentioning

confidence: 99%

Separated Phase–Current Controls Using Inverter-Based DGs to Mitigate Effects of Fault Current Contribution from Synchronous DGs on Recloser–Fuse

2019

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Synchronous distributed generators (SDGs) significantly affect recloser–fuse coordination due to the high fault current contribution. This paper proposes a separated phase–current control using inverter-based distributed generators (IBDGs) to remove the effects of fault current contributions from SDGs during unsymmetrical faults. The three-phase current produced by IBDGs is independently controlled. While the total fault current is reduced by adjusting the current phase angle in the faulty phase, the energy in the DC-link capacitor (Cdc) is delivered to the grid in order to avoid the rise of DC-link voltage (Vdc) by means of injection of the active current into the nonfaulty phase. To maintain the proper grid voltage, the voltage regulation feature is installed in the IBDGs. Moreover, current estimations programmed within the IBDGs are introduced to avoid the performance degradation of separated phase–current controls caused by phasor measurement units (PMUs). The dynamic performance of the separated phase–current controls using IBDGs was evaluated using an IEEE 34-node radial test feeder. According to the simulation results, the IBDGs could eliminate the effects of fault current contributions from the SDG without interruption since the disconnections caused by excessive Vdc were prevented. They could also regulate the grid voltage in the nonfaulty phase.

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“…17. After comparing three load models that consist of (a) neglecting, (b) pre‐fault loading, and (c) constant impedance in distribution systems with high‐capacity DG systems, neglecting of loads could result in inaccuracy in calculating short‐circuit currents 18 . When a low resistance grounding system experienced a single ground fault, the effect of loads on the zero‐sequence short‐circuit current was analyzed in Ref.…”

Section: Introductionmentioning

confidence: 99%

A short‐circuit analysis algorithm capable of analyzing unbalanced loads and phase shifts through transformers using the Newton‐Raphson power‐flow calculation, sequence, and superposition methods

Kim

2020

Int Trans Electr Energ Syst

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Summary Load in short‐circuit analyses is usually neglected because the short‐circuit current magnitude that flows from conventional rotating machines is significantly greater than the short‐circuit current magnitude changed by the loads. However, as distributed loads unbalanced in phases have been connected to a grid, the current that flows from them affects the magnitude and angle of the short‐circuit current. Thus, the objective of this study is to develop a short‐circuit algorithm able to analyze the effect of unbalanced loads and phase shifts through transformers on the short‐circuit current. For this purpose, this study adds the steady‐state short‐circuit models of loads unbalanced in phases to the sequence network. To determine the accurate short‐circuit current, this study proposes the superposition principle that superimposes the contribution of pre‐ and post‐fault conditions. To calculate the pre‐ and post‐fault voltages, this study also combines the three‐phase Newton‐Raphson and sequence methods. In addition to the superposition principle, this study takes phase shifts through three‐phase transformers in the sequence network into account. The case studies indicate that the proposed method could be more accurate because of not ignoring loads unbalanced in phases and the phase shift through transformers.

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Short-circuit analysis in large-scale distribution systems with high penetration of distributed generators

Cited by 22 publications

References 0 publications

Short-Circuit Current Calculation and Harmonic Characteristic Analysis for a Doubly-Fed Induction Generator Wind Turbine under Converter Control

Short-Circuit Current Calculation and Harmonic Characteristic Analysis for a Doubly-Fed Induction Generator Wind Turbine under Converter Control

Separated Phase–Current Controls Using Inverter-Based DGs to Mitigate Effects of Fault Current Contribution from Synchronous DGs on Recloser–Fuse

A short‐circuit analysis algorithm capable of analyzing unbalanced loads and phase shifts through transformers using the Newton‐Raphson power‐flow calculation, sequence, and superposition methods

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