A strategy is presented for the self-tuning of a voltage source converter (VSC) based Flexible AC Transmission Systems (FACTS) according to the prevailing system condition. L-index, which is a power system voltage stability status indicator, and its associated parameters are used to automatically regulate the modulation signal of the VSC. This will lead to a proportionate adjusting of the magnitude of the current injected into, or absorbed from, the interconnected load bus by the FACTS device. This regulating scheme will enhance seamless and optimal reactive power compensation by utilizing the dynamic operational nature of present day distressed power system networks. Results obtained using this method when applied to selected load buses of the IEEE 14 bus system under varying practical scenarios showed its capability to appropriately control FACTS devices operation to accommodate system changing conditions. It is hoped that the outcome of this work will provide efficient tools for the determination of power system status, ensure optimal utilization of the dynamic reactive power compensation devices and reduce system outages.
During a short circuit condition, core of a Current Transformer (CT) may become saturated due to large primary current containing a significant DC component. The saturation of the core distorts the secondary current which may cause malfunction of the protective devices connected to the CT. As a result of significant advances in the technology and deployment of digital relays in the last decade, the distorted secondary current can be reconstructed in a very short time. Several methods, which take into account the non-linear behavior of the CT, have been researched in the recent past. Processing time, accuracy, and online implementation are of prime importance while selecting a particular algorithm. In this paper, a comprehensive review of the different algorithms used for the detection of saturation as well as reconstruction of the distorted secondary current is presented.
A new methodology for a possible fast evaluation of a power flow is presented. The proposed method involves a transient stability constrained line-flow-based (LFB) fast contingency screening. This direct method incorporates transient energy function (TEF) to carry out the evaluation of a power system. The proposed LFB method was tested on the WECC 9-bus, three machine, the IEEE 14-bus, five machine, and the IEEE 39-bus, ten machine systems. Results of the proposed LFB were compared with those obtained from the conventional Newton-Raphson (N-R) method. It was observed that the stable re-dispatch could be obtained by the LFB method within half the computation time as compared to the time required for the N-R method. Since the LFB method was based upon identification of the stable equilibrium points of the TEF, the proposed method appears to be inherently capable of delivering a stable power dispatch. In addition, a new index called critical energy performance index (CEPI) has been introduced to indicate the level of stability and to assist in the decisions related to the re-dispatch.
This paper establishes a new method that adopts the line-flow-based (LFB) approach to develop a transient stability constrained optimal power flow (OPF) analysis called LFB-TSCOPF. The transient energy function (TEF) serves as a direct means of carrying out the stability analysis. The reduction technique was adopted in which the classical machine model was reduced to the internal node model. The proposed method was tested on the WECC 9-bus, three-machine, IEEE 14-bus, five-machine, and the New England 39-bus, ten-machine test systems. The results were compared with other known results from different methods in literature. The results of the active power and total optimal costs are quite promising and consistent with other known methods. The LFB-TSCOPF re-dispatches real power by applying the energy margin performance index as an indication of the generator unit(s) to be rescheduled. The LFB-TSCOPF provides a more comprehensive linear model, reduces computation time and can be useful for online stability studies.
Heterogeneous energy prosumers are aggregated to form a smart grid based energy community managed by a central controller which could maximize their collective energy resource utilization. Using the central controller and distributed energy management systems, various mechanisms that harness the power profile of the energy community are developed for optimal, multi-objective energy management. The proposed mechanisms include resource-aware, multi-variable energy utility maximization objectives, namely: (1) maximizing the net green energy utilization, (2) maximizing the prosumers’ level of comfortable, high quality power usage, and (3) maximizing the economic dispatch of energy storage units that minimize the net energy cost of the energy community. Moreover, an optimal energy management solution that combines the three objectives has been implemented by developing novel techniques of optimally flexible (un)certainty projection and appliance based pricing decomposition in an IBM ILOG CPLEX studio. A real-world, per-minute data from an energy community consisting of forty prosumers in Amsterdam, Netherlands is used. Results show that each of the proposed mechanisms yields significant increases in the aggregate energy resource utilization and welfare of prosumers as compared to traditional peak-power reduction methods. Furthermore, the multi-objective, resource-aware utility maximization approach leads to an optimal energy equilibrium and provides a sustainable energy management solution as verified by the Lagrangian method. The proposed resource-aware mechanisms could directly benefit emerging energy communities in the world to attain their energy resource utilization targets.
This article presents ultrasound assisted carbonization method for the synthesis of calcium carbonate nanoparticles (nano calcite). The effect of different surfactants, such as polyacrylic acid, steric acid, sodium tripolyphosphate and myristic acid, on the synthesis of nano CaCO3 was investigated. Concentration of surfactants ranged from 0.2-1.0g/L. X-ray diffraction patterns (XRD) confirmed cubic structure of nano CaCO3 showing characteristic reflection of calcite phase. Transmission electron microscopy (TEM) images showed that the particles are cubical in nature. The use of an ultrasound probe during synthesis leads to narrow distribution of particles. The conductivity and pH value of reaction mixture was measured during the reaction. The time required for the completion of reaction changes with different surfactants was also found. The crystallite size was found to be dependent on surfactant concentration. The minimum time was noted for sodium tripolyphosphate which was 40 min. The crystallite size was found to increase as per the trail sequence of the surfactant, sodium tripolyphosphate, steric acid and polyacrylic acid, myristic acid. The myristic acid shows the biggest crystallite size due to its hydrophobic nature, while sodium tripolyphosphate plays an important role in crystal growth inhibition giving lower crystallite size. Finally, the results presented here demonstrate that nano-calcite crystals can be synthesized, for high potential industrial applications such as filler in the paper and polymer industry.
A V2G facility has the potential to reduce losses and loading in the power distribution network, thereby effecting savings and an increase in the generator, line and substation capacity for additional loading. In this paper, economic models are developed to compute the amount of economic incentives accruable from the penetration of V2G into the distribution network subject to two potential benefits of V2G: released generation capacity and reduced energy losses. The developed models were tested using IEEE test systems. Results from the test systems reveal that operational choice affects economic incentives. Hence, further analytical expression was developed to model operational formulation that will lead to economic incentives. This principal model was formulated to indicate the manner in which economic incentives can be impacted by decision variables, namely: loading pattern, V2G location and capacity injection. More than 95% released generation capacity was obtained. In addition, $37,775/year of economic incentive due to reduced power losses in the IEEE 123 Node test Feeder was observed. The results from the principal model showed that V2G promises significant economic incentives. It may be concluded, based on the results obtained, that proper system studies are necessary at the planning stage before installing a V2G facility.
Electric distribution feeders are inherently unbalanced and therefore have potential for severe power loss. The penetration of vehicle-to-grid (V2G) into the distribution feeders is expected to impact the power losses in the system. This is a pressing issue since power loss affects the operations, economics, and quality of service for the electric power systems. In this article, the impact of V2G parking lots on power losses of a radial distribution network is investigated. Two test networks were used in the study, namely: IEEE 13 and IEEE 123 Node test feeder networks. The test feeders and the V2G facilities were modeled in Radial Distribution Analysis Package (RDAP). Load flow results provided information on the power losses of the network. Results show that for a given penetration level, the impact of 3-phase and system-wide V2G integration on the power loss results in less power losses than 1-phase V2G integration. Results also indicate that operating the entire system such that V2G facilities will not compromise “near-balanced” state of operation and will have an improved impact on the power loss than highly unbalanced operation. The results obtained will be a useful tool for studying the impact of V2G on the power loss of a distribution network.
The penetration of Vehicle-to-Grid (V2G) into the electrical distribution system has potential to create room for many operational benefits. A V2G facility installed on a distribution feeder line segment may affect power loss in the distribution system. Mathematical models are developed to study how magnitude of V2G reactive power injection and different mixes of uniformly distributed loads and lumped loads can impact power loss on a distribution system feeder. The V2G facilities assumed in this research are V2G parking lots with provision for injecting reactive currents into the feeder of a distribution network. It is shown that loss reduction can be greatly influenced by the pattern of loading, the amount of V2G reactive injection as well as position and number of V2G parking lot along the feeder segment. Useful results are obtained, with a promise that more than 95% power loss reduction (relative to power loss in the system without V2G installed) is possible by optimally locating a V2G parking lot along the feeder. It is observed that location and capacity injection of a V2G facility are the most critical for loss reduction. It was concluded that proper system planning and operational practice are required in order to reduce power losses.
This paper presents a methodology to evaluate transient stability constrained available transfer capability (ATC). A linear and fast line flow–based (LFB) method was adopted to optimize the ATC values. This enabled the direct determination of the system source–sink locations. This paper formulated different market transactions considering bilateral and multilateral impacts in the stability constrained ATC. The proposed method was demonstrated on the WECC 9-bus and IEEE 39-bus systems. The critical energy performance index (CEPI) enabled the direct identification of candidates for contingency screening based on ranking. This index helped to reduce the list of credible contingencies for ATC evaluation and, therefore, the computation time. The results of the proposed ATC method are consistent with the literature and can be deployed for fast assessment of the impact of transactions in an electric power system.