Propagation of unbalance in electric power systems

Chindris, M.; Cziker, A.; Miron, Anca; Bălan, Horia; Iacob, Ana; Sudria, A.

doi:10.1109/epqu.2007.4424221

Cited by 46 publications

(30 citation statements)

References 1 publication

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“…where; Z 11:m k , Z 22:m k positive-sequence and negative-sequence impedances 7 of the induction motor connected to the k th busbar respectively. Scenario II: The distribution network is modified by placing the induction motor at the j th busbar and the unbalanced load at the k th busbar in the network given in Fig.…”

Section: Impact Of Induction Motors On Voltage Unbalance Emissionmentioning

confidence: 99%

Attenuation and propagation of voltage unbalance in radial distribution networks

Perera

Ciufo

Meegahapola³

et al. 2015

Int. Trans. Electr. Energ. Syst.

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Recently published International Electrotechnical Committee (IEC) technical reports IEC 61000-3-13 provides detailed methodologies for managing voltage unbalance (VU) in electric power systems. A key aspect in the VU emission allocation process is the estimation of VU propagation in different parts of the network. Although the VU propagation from upstream networks to downstream networks is adequately addressed, the attenuation of VU when propagating from downstream to upstream networks at the same voltage level has not been properly taken into account in the aforementioned methodologies. Furthermore, mains connected three-phase induction motors are known to attenuate VU, and there is no methodology currently available to quantify the attenuation provided by such motors. The main motivation behind the current research is to investigate the VU propagation and attenuation in radial distribution networks and to quantify the attenuation provided by induction motor loads. This paper reports that the VU propagation from downstream to upstream in a radial distribution network with symmetrical distribution lines can be conservatively approximated by the ratio of fault levels of upstream and downstream network. Moreover, an influence coefficient has been introduced as a means of appraising the impact of induction motor loads. The theoretical work presented is verified using unbalanced load flow analysis. The outcomes presented in the paper are useful for the further development of IEC technical report on VU emission allocation. AbstractRecently published International Electrotechnical Committee (IEC) technical reports IEC 61000-3-13 provides detailed methodologies for managing voltage unbalance (VU) in electric power systems. A key aspect in the VU emission allocation process is the estimation of VU propagation in different parts of the network. Although the VU propagation from upstream networks to downstream networks is adequately addressed, the attenuation of VU when propagating from downstream to upstream networks at the same voltage level has not been properly taken into account in the aforementioned methodologies. Furthermore, mains connected three-phase induction motors are known to attenuate VU and there is no methodology currently available to quantify the attenuation provided by such motors. The main motivation behind the current research is to investigate the VU propagation and attenuation in radial distribution networks and to quantify the attenuation provided by induction motor loads. This paper reports that the VU propagation from downstream to upstream in a radial distribution network with symmetrical distribution lines, can be conservatively approximated by the ratio of fault levels of upstream and downstream network. Moreover, an influence coefficient has been introduced as a means of appraising the impact of induction motor loads. The theoretical work presented is verified using unbalanced load flow analysis. The outcomes presented in the paper are useful for the further development of IEC techni...

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Section: Impact Of Induction Motors On Voltage Unbalance Emissionmentioning

confidence: 99%

Attenuation and propagation of voltage unbalance in radial distribution networks

Perera

Ciufo

Meegahapola³

et al. 2015

Int. Trans. Electr. Energ. Syst.

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“…Nowadays, the unbalance problem has gained lots of attention from utility companies and customers [3,5]. For example, Bollen [6], Kim et al [7], Chindris et al [8] and Ghijselen and Van den Bossche [9] studied the definition, generating mechanism, standards, propagation and mitigation measures for the voltage unbalance. In 2008, the International Electro-Technical Commission (IEC) published a technical report that stipulates the unbalance emission limits for loads when they are connected to the high voltage, medium voltage and low voltage systems [10].…”

Section: Introductionmentioning

confidence: 99%

Contribution Determination for Multiple Unbalanced Sources at the Point of Common Coupling

Sun

et al. 2017

Energies

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Three-phase unbalance is an important power quality issue that can cause many negative effects to the power system. Effective mitigation and management of voltage unbalance will benefit from the knowledge of how the unbalanced sources contribute to the voltage asymmetry at the point of evaluation (POE). In this paper, a method is proposed to assess the overall unbalance contribution of the multiple unbalanced sources at the point of common coupling (PCC). Firstly, the equivalent circuit for analysis is established and the unbalance contribution indices are proposed. Then a method is proposed to determine whether the dominant unbalanced polluter is at the upstream or downstream of POE. If the main unbalanced source is identified to be downstream of POE, a procedure is further proposed to determine the individual contribution of the multiple unbalanced sources. Moreover, for the multiple unbalanced source condition, the current flowing in each feeder is proposed to be used for the contribution estimation instead of the current actually emitted by the unbalanced source. Finally, a method is proposed to estimate the equivalent negative sequence impedance of the aggregate loads. Simulation and field analysis results validate the effectiveness and accuracy of the method.

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“…Besides, unequal single phase loads over three phase distribution systems cause unbalanced power flow. This induces additional losses to electrical equipment which restrict their tolerances (i.e., shorter lifespan) in terms of stability and reliability [4]. The aforementioned phenomena also appear to be more significant in weak power system with high grid impedance [3].…”

Section: Introductionmentioning

confidence: 99%

Flyback Cascaded Multilevel Inverter Based SHE-PWM Control for STATCOM Applications

Law¹,

Ng²,

Wong³

2017

IJPEDS

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This paper presents the closed loop DC-DC flyback converter with multilevel cascaded H-bridge inverter (MCHI) for transformer-less static synchronous compensator (STATCOM) system. The STATCOM system is proposed to be controlled using decoupled dq vector control incorporating the new reactive current reference algorithm and multi-level selective harmonic elimination pulse width modulation (MSHEPWM) technique. This ensures transient performance enhancement as well as simpler control and modulation technique implementation for dynamic systems. As the proposed MSHEPWM solely depends on adjustable DC-link voltage levels, flyback converter is designed for that purpose to suit wider applications. In current work, a single phase five-levels CHI based STATCOM system incorporated with the aforementioned converters are presented to compensate the reactive power (VAR) at the point of common connection (PCC). The dynamic as well as the transient performances of the developed STATCOM control system and the proposed voltage closed loop control of each converter are investigated to meet different VAR demands at balanced loading conditions. Simulation studies are performed to verify the effectiveness and theoretical analysis of the approaches presented. Keyword:Cascaded H-Bridge inverter (CHI) Reactive power (VAR) Compensation Selective harmonic elimination pulse width modulation (SHEPWM) Static synchronous compensator (STATCOM)

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Propagation of unbalance in electric power systems

Cited by 46 publications

References 1 publication

Attenuation and propagation of voltage unbalance in radial distribution networks

Attenuation and propagation of voltage unbalance in radial distribution networks

Contribution Determination for Multiple Unbalanced Sources at the Point of Common Coupling

Flyback Cascaded Multilevel Inverter Based SHE-PWM Control for STATCOM Applications

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