On-line reactive power compensation schemes for unbalanced three phase four wire distribution feeders

Lee, San-Yi; Wu, Chi‐Jui

doi:10.1109/61.248308

Cited by 54 publications

(13 citation statements)

References 5 publications

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“…Considering that Equation (16) refers to Phase A, and decomposing this expression into real and imaginary parts, Equations (20) and (21) are obtained. The angle of X aF is π 2 when it is a coil, and − π 2 when it is a capacitor.…”

Section: Negative-sequence Current Compensatormentioning

confidence: 99%

“…Squaring Equations (20) and (21), adding both equations, and regrouping the terms, we obtain (22). To simplify, we consider that ∝ a+ = 0.…”

Section: Negative-sequence Current Compensatormentioning

confidence: 99%

“…He used a single-phase load with known data, and compensated it with a coil and capacitor and we believe that the voltages in the study were balanced. This study has been extended by many authors [16][17][18][19][20][21][22][23][24].Gyugyi et al[25] studied compensation through passive compensators for a three-wire linear system with unbalanced load and balanced voltages. For this purpose, they categorised the line currents into symmetric component values, and proposed two delta-connected compensators: one for compensating the imaginary part of the positive-sequence current and the other for compensating the negative-sequence current.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

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Compensation of Reactive Power and Unbalanced Power in Three-Phase Three-Wire Systems Connected to an Infinite Power Network

et al. 2019

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The compensation of an electrical system from passive compensators mainly focuses on linear systems where the consumption of charges does not vary significantly over time. In three-phase three-wire systems, when the network voltages are unbalanced, negative-sequence voltages and currents appear, which can significantly increase the total apparent power supplied by the network. This also increases the network losses. This paper presents a method for calculating the compensation of the positive-sequence reactive power and unbalanced powers caused by the negative-sequence line currents using reactive elements (coils and/or capacitors). The compensation is applied to three-phase three-wire linear systems with unbalanced voltages and loads, which are connected to an infinite power network. The method is independent of the load characteristics, where only the line-to-line voltages and line currents, at the point where compensation is desired, need to be known in advance. The solution obtained is optimal, and the system observed from the network behaves as one that only consumes the active power required by a load with a fully balanced current system. To understand the proposed method and demonstrate its validity, a case study of a three-phase three-wire linear system connected to an infinite power network with unbalanced voltages and currents is conducted.Appl. Sci. 2020, 10, 113 2 of 17 these inefficient powers. According to [13,14], imbalances at one point in the system can help offset some of the imbalances at another point. Such situations cannot be analyzed if only the modules of voltages and currents are known.The application of electronics, in the compensation of electrical systems, indicates that most industries today mainly focus on the use of active compensators. The advantages of these compensators or filters cannot be denied, especially for the compensation of non-linear systems. As compared to passive compensators, the active compensators are more expensive, less robust, and consume more energy. In certain situations, for linear systems, where the load does not vary with time, the use of passive compensators is a good alternative. They are configured from reactive elements (coils and/or capacitors). In this study, passive compensators are used to compensate for the reactive and unbalanced power resulting from the negative-sequence current of any three-wire system.The concept of compensation of an electrical system by passive compensators is not new. Steinmetz [15] developed a passive compensator to obtain a system of balanced line currents. He used a single-phase load with known data, and compensated it with a coil and capacitor and we believe that the voltages in the study were balanced. This study has been extended by many authors [16][17][18][19][20][21][22][23][24].Gyugyi et al.[25] studied compensation through passive compensators for a three-wire linear system with unbalanced load and balanced voltages. For this purpose, they categorised the line currents into symmetric component values, and proposed...

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Section: Negative-sequence Current Compensatormentioning

confidence: 99%

“…Squaring Equations (20) and (21), adding both equations, and regrouping the terms, we obtain (22). To simplify, we consider that ∝ a+ = 0.…”

Section: Negative-sequence Current Compensatormentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Compensation of Reactive Power and Unbalanced Power in Three-Phase Three-Wire Systems Connected to an Infinite Power Network

et al. 2019

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“…The DSTATCOM mitigates power quality problems by injecting current to the system. DSTATCOMs for three-phase four-wire systems with neutral conductor have been successfully developed at the customer end for unbalanced systems and reported in the literature [6]. However, DSTATCOMs for three-phase three-wire systems are still under investigation.…”

Section: Introductionmentioning

confidence: 99%

Design of DSTATCOM Controller for Compensating Unbalances

Kullan¹,

Muthu²,

Mervin³

et al. 2016

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In a three phase power system, the voltages at the generation side are in sinusoidal and equal in magnitude with 120˚ phase difference between the phases. However, at the load side voltages may become unbalanced due to unequal voltage magnitudes at the fundamental frequency, phase angle deviations or unequal distribution of single phase loads. The voltage unbalance is a major power quality issue, because a small unbalance in the phase voltages can cause a larger unbalance in the phase currents. A completely balanced three-phase three wire system contains only positive sequence components of voltage, current and impedance, whereas unbalanced system contains both positive and negative sequence components of voltages and currents. The negative sequence component of current in the unbalanced system increases the temperature and losses in the equipments. Hence, it is necessary to mitigate this problem by supplying the negative sequence current to the load at the load side and keep the source side balanced. This paper proposes the shunt connected, current injecting Distribution Static Synchronous Compensator (DSTATCOM) with appropriate controller to mitigate the unbalanced load current. The symmetrical components based Hysteresis Current Controller (HCC) is designed for DSTATCOM to diminish the unbalances in a three-phase three-wire system. The performance of the controller is studied by simulating the entire system in the MATLAB/Sim-ulink environment. The DSTATCOM with HCC is found to be better than other controllers because it is suitable for compensating both balanced and unbalanced loads.

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A practical approach for distribution network load balancing by optimal re‐phasing of single phase customers using discrete genetic algorithm

Homaee

Najafi

Dehghanian

et al. 2019

Int Trans Electr Energ Syst

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Summary Voltage and current imbalance have adverse impacts on power systems such as power loss increase, communication interference, and component lifetime reduction. This paper attempts to look at unbalance impacts from distribution system operator's (DSO) viewpoint in order to understand them and then mitigate the impacts. Since solving the unbalance conditions is influenced by the way the imbalance is defined, standard unbalance indexes are studied, and new indexes are proposed in this paper. Re‐phasing of the customers is selected to reduce the level of unbalance in distribution feeders. Due to the huge number of customers, a wide variety of choices can be selected for re‐phasing of customers, which makes the solution questionable. Therefore, discrete genetic algorithm (DGA) as a metaheuristic method has been utilized in order to distribute customers among the network phases optimally considering the fact that DSO has a limitation for the re‐phasing practice. The aim is to reduce the unbalance indexes and power losses throughout the network. Simulations have been carried out on a real test case network, which shows the importance of load balancing and its effects on the power losses, voltage profile, and current flow in that network. The effectiveness of the proposed indexes has also been demonstrated for the four‐wire multigrounded distribution system. Since re‐phasing of the majority of customers in distribution networks seems impractical, a re‐phasing limitation is also investigated in this paper, and some practical suggestions of optimal load balancing in a real‐world low‐voltage distribution system have been presented here. Results show the importance of load balancing in power loss reduction and voltage unbalance improvement in the low‐voltage four‐wire multigrounded distribution system. They also illustrate that by changing phases of a few customers, power losses and unbalance indexes will be improved significantly.

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On-line reactive power compensation schemes for unbalanced three phase four wire distribution feeders

Cited by 54 publications

References 5 publications

Compensation of Reactive Power and Unbalanced Power in Three-Phase Three-Wire Systems Connected to an Infinite Power Network

Compensation of Reactive Power and Unbalanced Power in Three-Phase Three-Wire Systems Connected to an Infinite Power Network

Design of DSTATCOM Controller for Compensating Unbalances

A practical approach for distribution network load balancing by optimal re‐phasing of single phase customers using discrete genetic algorithm

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