A comparative study on AC/DC analysis of an operational low voltage distribution system

In the near future, the digitalizing world will continue to improve and the need for DC based devices will be increased beyond doubt. Today’s electrical grid is strictly dependent on AC-DC rectifiers. Each conversion process means additional power losses and signal quality deteriorations for the network. In addition, networks which are fed by batteries and renewable sources such as solar panels, and wind turbines are suffering from conversion-based power losses. In this respect, the idea of switching to DC on the low voltage side of the networks has become an intriguing subject. In this study, the applicability and efficiency of the low voltage direct current (LVDC) concept for low voltage distribution systems is discussed and a sample LVDC distribution system is analyzed. In this operational residential application electrical transient analyzer program (ETAP) is employed for comparison of different voltage levels such as 110 V<sub>DC</sub>, 250 V<sub>DC</sub>, 320 V<sub>DC</sub> and conventional 220/380 V<sub>AC</sub>. As a novel approach different DC voltage levels are compared with typical AC system in detail. Comparative analysis is conducted for safety regulations, voltage drops, current carrying capacities, power consumption and harmonic calculation of the proposed system. In this respect applicability, possible drawbacks and future aspects of LVDC systems are interpreted.

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On the Conflict between LVRT and Line Protection in LV Distribution Systems with PVs: A Current-Limitation-Based Solution

Energies ◽

10.3390/en12152909 ◽

2019 ◽

Vol 12 (15) ◽

pp. 2909 ◽

Cited By ~ 1

Author(s):

Aristotelis Tsimtsios ◽

Dionisis Voglitsis ◽

Ioannis Perpinias ◽

Christos Korkas ◽

Nick Papanikolaou

Keyword(s):

Distribution System ◽

Distribution Systems ◽

Low Voltage ◽

Energy Resource ◽

Distribution Networks ◽

Voltage Distribution ◽

Current Limitation ◽

Protection Scheme ◽

Low Voltage Ride Through ◽

Photovoltaic Generators

The upcoming adoption of low-voltage-ride-through requirements in low-voltage distribution systems is expected to raise significant challenges in the operation of grid-tied inverters. Typically, these inverters interconnect photovoltaic units, which are the predominant distributed energy resource in low-voltage distribution networks, under an umbrella of standards and protection schemes. As such, a challenging issue that should be considered in low-voltage distribution network applications, regards the coordination between the line protection scheme (typically consisting of a non-settable fuse) and the low-voltage-ride-through operation of photovoltaic generators. During a fault, the fuse protecting a low-voltage feeder may melt, letting the generator to continue its ride-through operation. Considering that the efficacy/speed of the anti-islanding detection is affected by ride-through requirements, this situation can lead to protracted energization of the isolated feeder after fuse melting (unintentional islanding). To address this issue, this paper proposes a fault-current-limitation based solution, which does not require any modification in the existing protection scheme. The operation principles, design, and implementation of this solution are presented, while, its effectiveness is supported by extensive simulations in a test-case low-voltage distribution system. A discussion on the presented results concludes the paper.

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A Novel Optimal Shunt Capacitors Placement and Sizing Technique for Cost Minimization

10.36227/techrxiv.18141971.v1 ◽

2022 ◽

Author(s):

Thomson Mtonga ◽

Keren K. Kaberere ◽

George Kimani Irungu

Keyword(s):

Radial Distribution ◽

Distribution System ◽

Distribution Systems ◽

Cost Minimization ◽

Computation Time ◽

Search Space ◽

Power Losses ◽

Stability Margins ◽

Novel Approach ◽

Shunt Capacitors

<div>The installation of shunt capacitors in radial distribution systems leads to reduced branch power flows, branch currents, branch power losses and voltage drops. Consequently, this results in improved voltage profiles and voltage stability margins. However, for efficient attainment of the stated benefits, the shunt capacitors ought to be installed in an optimal manner, that is, optimally sized shunt capacitors need to be installed at the optimum buses of an electrical system. This article proposes a novel approach for optimizing the placement and sizing of shunt capacitors in radial distribution systems with a focus on minimizing the cost of active power losses and shunt capacitors’ purchase, installation, operation and maintenance. To reduce the search space, hence the computation time, the prroposed approach starts the search process by arranging the buses of the radial distribution system under consideration in pairs. Thereafter, these pairs influence each other to determine the optimum total number of buses to be compensated. The proposed approach was tested on the 34- and 85-bus radial distribution systems and when the simulation results were compared with those obtained by other approaches, it was established that the developed approach was a better option because it gave the least cost.</div>

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An Innovative Operation Strategy of ESS for Capacity Expansion of Renewable Energy and Customer Load with Electric Vehicle Chargers in Low Voltage Distribution Systems

Energies ◽

10.3390/en12244668 ◽

2019 ◽

Vol 12 (24) ◽

pp. 4668

Author(s):

Kyung-Sang Ryu ◽

Dae-Jin Kim ◽

Yang-Hyun Nam ◽

Heesang Ko ◽

Byungki Kim ◽

...

Keyword(s):

Renewable Energy ◽

Electric Vehicle ◽

Distribution System ◽

Distribution Systems ◽

Low Voltage ◽

Energy Resource ◽

Operation Strategy ◽

Voltage Distribution ◽

Allowable Limit ◽

Bidirectional Power Flow

This paper proposes an innovative operation strategy to extend the acceptance of EVC (Electric Vehicle Charger) and RES (Renewable Energy Resource) in LVDS (Low Voltage Distribution System) by introducing an ESS (Energy Storage System). In conventional LVDS, the load and RES capacity are designed not to exceed the pole transformer capacity. However, when the ESS is connected to the end of LVDS and the bidirectional power flow becomes possible, the linkable capacity of the load and renewable energy can be improved up to twice the capacity of the pole transformer. In addition, even though the power consumption of the load and the power generation of RES exceed the pole transformer capacity, it is possible to maintain the feeder capacity and grid voltage within the allowable limit by the appropriate operation of the ESS. The simulations are performed in the environment of PSCAD/EMTDC, and the ability of the proposed strategy is assessed and discussed.

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Voltage Reduction in Medium Voltage Distribution Systems Using Constant Power Factor Control of PV PCS

Energies ◽

10.3390/en13205430 ◽

2020 ◽

Vol 13 (20) ◽

pp. 5430

Author(s):

Daisuke Iioka ◽

Takahiro Fujii ◽

Toshio Tanaka ◽

Tsuyoshi Harimoto ◽

Junpei Motoyama

Keyword(s):

Power Factor ◽

Distribution System ◽

Power Flow ◽

Distribution Systems ◽

Low Voltage ◽

Voltage Distribution ◽

Constant Power ◽

Voltage Rise ◽

Pv Systems ◽

Power Factor Control

Reverse power flow from a photovoltaic (PV) system in a distribution system causes a voltage rise. A relative study regarding the reduction in the distribution feeder voltage depending on system conditions and the magnitude of reverse power flow has been conducted. Several methods for mitigating voltage rise have been proposed; however, the influence of these methods on the voltage in the distribution system, where the voltage is reduced due to reverse power flow, remains to be determined. In this study, the effect of constant power factor control in low-voltage PV systems, which are widely used as voltage rise countermeasures in distribution systems, was analyzed under the condition that the distribution line voltage decreases due to reverse power flow. Consequently, the constant power factor control of the low-voltage distribution system was found to adversely reduce voltage in the medium voltage distribution system due to the consumption of lagging reactive power by the PV systems.

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