108 research outputs found
Effective Utilization of Distributed Power Sources under Power Mismatch Conditions in Islanded Distribution Networks
Get PDFThe integration of distributed generation (DG) into a power distribution network allows the establishment of a microgrid (MG) system when the main grid experiences a malfunction or is undergoing maintenance. In this case, the power-generating capacity of distributed generators may be less than the load demand. This study presents a strategy for the effective utilization of deployed active and reactive power sources under power mismatch conditions in the islanded distribution networks. Initially, the DGs’ and capacitors’ optimal placement and capacity were identified using the Jaya algorithm (JA) with the aim to reduce power losses in the grid-connected mode. Later, the DG and capacitor combination’s optimal power factor was determined to withstand the islanded distribution network’s highest possible power demand in the event of a power mismatch. To assess the optimal value of the DG–capacitor pair’s operating power factor (pfsource) for the islanded operation, an analytical approach has been proposed that determines the best trade-off between power losses and the under-utilization of accessible generation. The test results on 33-bus and 69-bus IEEE distribution networks demonstrate that holding the islanded network’s load power factor (pfload) equal to pfsource during the power imbalance conditions allows the installed distributed sources to effectively operate at full capacity. As expected, the proposed strategy will assist the utility companies in designing efficient energy management or load shedding schemes to effectively cope with the power mismatch conditions
Harmonic measurement and simulation to improve power supply quality at Faculty Electrical Engineering, UTM
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No full textAuthor at head of title.I. Un bourgeois de Rome. Le pour et le contre. La crise péril en la demeure. Le village. La Fée le roman d'un jeune homme pauvre -- II. Le cheveu blanc. La tentation. ReÌdemption. Montjoye -- III. Le belle au bois dormant. Le cas de conscience. Julie. Dalila. L'acrobate -- IV. Le sphinx. Un roman parisien. La partie de dames. Chamillac -- V. Echec et mat. Palma ou la nuit du vendredi saint. La vieillesse de Richelieu. York.Mode of access: Internet
Photovoltaic system DC series arc fault: a case study
Get PDFPhotovoltaic (PV) systems are becoming increasingly popular; however, arc faults on the direct current (DC) side are becoming more widespread as a result of the effects of aging as well as the trend toward higher DC voltage levels, posing severe risk to human safety and system stability. The parallel arc faults present higher level of current as compared with the series arc faults, making it more difficult to spot the series arc. In this paper and For the aim of condition monitoring, the features of a DC series arc fault are Analyzed by analysing the arc features, performing model’s simulation in PSCAD, and carrying out experimental studies. Various arc models are simulated and investigated; for low current arcs, the heuristic model is used where a set of parameters established. Moreover, the heuristic model’s simulated arc has been shown to be compatible with the experimental data. The features of arc noise in the electrode separation region and steady-arcing states with varied gap widths are investigated. It has been discovered that after an arc fault occurs, arc noise increases, notably in the frequency range below 50 kHz; where this property is useful for detecting DC series arc faults. Besides that, variations in air gap width are more sensitive to frequencies under 5 kHz
Towards hybrid AC/DC microgrids: Critical analysis and classification of protection strategies
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A fault current limiting approach for commutation failure prevention in LCC-HVDC transmission systems
No full textCommutation failure is one of the most frequent failures in line-commutated converter based high-voltage direct-current (LCC-HVdc) systems which may lead to the outage of HVdc links, and thus affect the performance of the power system. Most commutation failures are caused by voltage reduction due to ac system faults. In this paper, a commutation failure prevention module (CFPM) is developed, which inserts the optimal value of resistance proportional to the reduced extinction angle in series with the fault current path using a simple switching method. When a fault occurs at the inverter ac side, a self turn-off switch starts switching with a pre-specified frequency and controlled modulation index, which limits the fault current to the desired value and inhibits commutation failure. The salient feature of the proposed CFPM is that it is fully controllable. In addition, despite the available controller modification methods which are not effective for low-impedance faults, the proposed CFPM can prevent commutation failure regardless of the fault severity. The practical performance and feasibility of the developed CFPM is validated through laboratory testing, using the real-time Opal-RT hardware prototyping platform. The experimental results demonstrate that the proposed strategy can effectively eliminate the commutation failure or repetitive commutation failures under different fault types
Towards hybrid AC/DC microgrids: Critical analysis and classification of protection strategies
No full textHybrid AC/DC microgrids are arising as an interesting approach as they combine the prominent features of AC and DC networks and do not require excessive modifications in the distribution network. However, protection of such microgrids suffers from several challenges including limited fault current contribution of inverter-based DG sources in the islanded mode, inability of single-setting overcurrent relays in protection of dual-mode microgrids, selection of a proper grounding system, and lack of natural zero-crossing current. The aim of this paper is to provide a comprehensive review of the available strategies for protection of hybrid AC/DC microgrids. Apart from describing the most relevant options presented to date and classifying them into specific groups, a critical analysis is performed, in which the main challenges of each approach are presented. Finally, some conclusions and recommendations for the protection of future hybrid AC/DC microgrids are pointed out
A compact design of multi-feeder data logging system for power quality measurement with a multiplexer and a single PQ transducer
Get PDFThis paper presents a simple and costs effective equipment design multi-feeder data logger for recording and monitoring power quality. The system design uses remote supervising and multi-feeder data logging system (RESMOS). The data collected through resmos portable unit (RMPU) will automatically be saved with the format as binary and comma separated value (CSV). The time setting on the RMPU can be configured with minimum one minute per logging. This data logger uses a single transducer with a multiplexer for recording and monitoring ten channels of power quality at busbar. The system design has been validated with national metrology laboratory scientific and industrial research institute of Malaysia (SIRIM). This tool has the advantage that it can be used to measure harmonic data more than 21st at the same time for ten channels and equipped with software making it easier for analysis data with low operational costs versus another power quality equipment. The experimental results indicate that the proposed technique can accelerate data reading with conversion rate one sample per second for each channel. The device can be used to measure harmonic level and power quality with a confidence level above 95% and percentage error under 2.43% for total harmonics distortion (THD) and 1.72% for voltage harmonics
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