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Distributed Energy Resources (DERs) have disrupted the traditional electrical system. Grid-connected photovoltaic (PV) systems deliver electric energy closer to the consumer, shifting the paradigm from centralized to distributed generation. The impact of the stochastic PV output power gives rise to potentially rapid voltage fluctuations. Reactive power compensation is needed to regulate the voltage profile to meet the relevant standards. Traditional approaches like switched capacitors cannot provide reactive power that is continuously adjustable at short time scales. This paper examines an alternative distribution static synchronous compensator (D-STATCOM) based on a matrix converter (MC) for the low voltage distribution networks with high PV penetration. This technology can extend service life by using inductors for energy storage. The converter being studied provides ancillary services, including reactive power support; the impact on reliability, operational constraints, and electrical behavior is demonstrated. The contribution of this paper is a detailed analysis and impact study of the capacitor-less D-STATCOM in high PV penetration distribution networks. The significance of this paper is that it studies the behavior of the power electronics converter and its interaction with the power systems without assuming or neglecting details of either. Compensation effects and reliability comparisons between the proposed capacitorless D-STATCOM and the incumbent D-STATCOM technology are also studied in this paper.

Electrical insulation performance of compressed gas insulated switchgear (GIS) is adversely affected by metallic particle contaminants with a loss of up to 90% of the gas dielectric strength. Such particles play a crucial role in determining the system insulation integrity. Coating of the inside surface of GIS enclosures with a dielectric material such as epoxy resin can alleviate the adverse effect of contaminating metallic particles on the insulation, as the coated electrodes in compressed gas result in a somewhat higher breakdown voltage. Such coatings have the effect of "smoothing" the surface and reducing the pre-breakdown current in the gas gap. Also, in the presence of metallic particles, the electrostatic particle charging is impeded; hence, the maximum particle excursion in a coaxial GIS is significantly reduced for a given applied AC voltage. In this paper, the effect of the dielectric coatings is analyzed with a theoretical model which is confirmed in the high-voltage experiments. The results show the effectiveness of dielectric coating in mitigating the contamination due to the particles. The influence of other factors such as gas pressure and particle size are also discussed. [ABSTRACT FROM PUBLISHER]

In the post-industrial digital-economy, motors powering manufacturing have been replaced by computers powering ecommerce - with significant financial losses attributable to poor power quality (PQ). At the same time, increasing penetration of distributed generation and constant power loads complicate the job for the electric utilities to deliver high-quality electrical power. Traditionally, voltage source converters provide PQ compensation; the backbone of these converters, however, are large electrolytic capacitors (e-caps), which have well-known failure rates. A D-STATCOM that does not use e-caps was shown to increase the converter service life and increase the reliability of the power system; finite control set model predictive control (MPC) was shown to achieve high fidelity tracking for multi-objective cost functions. However, high fidelity (to achieve low total harmonic distortion) results in high switching frequency, which increases losses and device stresses, and reduces the overall converter reliability. This paper improves the capacitorless D-STATCOM by investigating an adaptive MPC that trades-off high-fidelity performance and switching frequency, subject to IEEE 519 THD standards, to achieve good-enough performance. The method is verified experimentally in a 7.5 kVA D-STATCOM hardware prototype. The results show a reduction in switching frequency by over 30% compared with the MPC methods that prioritize high-fidelity alone.

Finite control set model predictive control (MPC) is a model-based control method that can include multi-objective optimization, constrained control, adaptive control, and online auto-tuning of weighting factors all in a single controller that exhibits fast dynamic tracking. This paper utilizes the model-based framework of MPC to develop a sensorless current maximum power point tracking (MPPT) algorithm. Eliminating the current sensor can reduce the cost and improve the reliability of the photovoltaic system. This paper also utilizes constrained control and online auto-tuning of MPC to develop an adaptive perturbation MPPT to reduce steady-state oscillation and improve dynamic performance. This paper builds in a single framework the different layers of the MPPT problem: control, estimation, and MPPT. The proposed adaptive perturbation sensorless current mode MPPT (ASC-MPPT) technique performance is compared to the well-known incremental conductance (InCon) MPPT technique. The EN50530 European industrial test standards were used to demonstrate performance.

The Irish Electricity Supply Board's (ESB) Shannon Hydro Electric Scheme joined the ranks of world-recognized engineering feats on 29 July 2002 when it received Milestone and Landmark Awards to mark its 75th Anniversary. The Shannon Scheme was officially opened at Parteen Weir on 22 July 1929. One of the largest engineering projects of its day, it was successfully executed by Siemens to harness the Shannon River. It subsequently served as a model for large-scale electrification projects worldwide. Operated by the Electricity Supply Board of Ireland, it had an immediate impact on the social, economic and industrial development of Ireland and continues to supply significant power beyond the end of the 20th century. [ABSTRACT FROM PUBLISHER]

This letter proposes a gaming model with coalition among producers in subgroups for the market setting with multiple producers. The possible number of coalitions is obtained for a total number of N(N≥3) producers. The generic spatial gaming model with coalition has a vector as its objective function, with each vector element representing a coalition profit. Various constraints are formulated, including the spatial constraints (e.g., the DC power flow equations). The Cournot gaming strategy is adopted. A small system is used for testing the model with satisfactory results. [ABSTRACT FROM PUBLISHER]

A method utilizing prony algorithm and artificial neural networks (ANNs) is presented to locate faults on loop systems. Fault simulation is implemented using the ATP-EMTP. The loop system is represented by a line with generator units on both ends. The proposed method accounts for the anticipated changes in the traveling-wave characteristics. Proposed modifications are limited to the type of ANN inputs. The modified scheme provided good accuracy in locating the faults. [ABSTRACT FROM AUTHOR]

A method is proposed to utilize the dynamic-line rating system on old transmission lines to up-rate ampacity without replacing old conductors or increasing line voltage. A DLR system applicable to double-circuit transmission lines is designed based on maximum-allowable conductor temperature, conductor temperature at the limit-dip (sag) margin, and transformer maximum load. The improved performance of the system is reported. [ABSTRACT FROM PUBLISHER]

Two adaptive fuzzy systems are developed for identification and location of short-circuit faults on one phase of the phase- modulation brushless dc motors. Motor performance is computed by a discrete-time numerical model. The waveform of line-to-neutral voltages summation is monitored for feature extraction. Diagnostic indices are derived by processing the characteristic signal using discrete Fourier transform (DFT) and short-time Fourier transform (STFT). Testing results show an acceptable diagnosing performance of the proposed scheme. [ABSTRACT FROM AUTHOR]

An automatic scheme for fault diagnosis and location of stator-winding interturns in permanent-magnet brushless dc motors is presented. System performances under healthy and faulty operation are obtained via a discrete-time model. Waveform of the electromagnetic torque is monitored and processed using discrete Fourier transform and short-time Fourier transform to derive proper diagnostic indices. Two adaptive neuro-fuzzy inference systems (ANFIS) are developed to automate the fault diagnosis process. Test results show an acceptable performance for ANFIS in detecting the fault. [ABSTRACT FROM AUTHOR]

An adaptive neuro-fuzzy inference system (ANFIS) is developed to diagnose open switch faults of PM brushless dc motor drives. Features extracted under healthy and faulty operations using wavelet transform are used to train ANFIS. Testing of the proposed diagnostic system shows it could not only diagnose the fault but identify the faulty switch as well. Good agreement between experimentation and simulation is obtained. [ABSTRACT FROM AUTHOR]

A summary of the actual state of battery charger harmonics is presented. The effect of harmonic distortion on the distribution system, especially on distribution transformers, is analyzed. A program was developed that allows the consideration of the transformer life consumption as a function of the battery charger characteristics and charging algorithm. The program is considered to be a distribution planning and management tool. The proposed tool can be easily applied to determine the optimum charging time as a function of the existing load, ambient temperature, and time of day. From the study it can be deduced that a direct connect-and-charge scheme can be detrimental to the transformer life, especially under high temperature and large load. Calculations show the existence of a quadratic relationship between the transformer life consumption and the total harmonic distortion (THD) of the battery charger current. Furthermore, the current THD should be limited to 25 30% in order to have a reasonable transformer life expectancy. [ABSTRACT FROM PUBLISHER]

Thunderstorms and lightning are large contributors to fault occurrence due to the fact that the spark stroke is repeated several times during a very short time interval. Lightning bolts are not the only origin for repetitive faults. Reclosers and recloser circuit breakers are among several types of cyclic loads that submit the system to a similar current pattem. The connected equipment may be able to withstand the first voltage sag but will drop out with the following one, if it arrives before the equipment reaches a stable situation or if the equipment self-recovers. The concept of recovering time was originally presented 62 ten years ago without turther development. The Computer Business Equipment Manufacturing Association (CBEMA) curve is the most widespread power acceptability or equipment sensitivity graph; however, its values are given in a one-event base so they cannot be applied for repetitive sag studies. The undervoltage part of the CBEMA curve follows very closely the expression Jv2dt = k, which allows the extension of this criterion to repetitive sags. Results obtained are in good agreement with those previously published. [ABSTRACT FROM PUBLISHER]

Considerations for the remaining life of the Aluminum Stranded Conductors Steel Reinforced (ACSR) in transmission lines have become gradually important to hold the reliability and the stability of the electric power supply. The useful life of the ACSR exposed to the atmosphere for a long period may be dependent on deterioration caused by such factors as atmospheric corrosion, galvanic corrosion, crevice corrosion, or fatigue corrosion. Forest fires for any overhead transmission lines built nearly on the ridge of the mountains may significantly reduce to the mechanical strength of the ACSR and lead to failure or accident. In this paper, material and mechanical deterioration performances of ACSR due to forest fires are presented through several sample tests. Data analysis for tension load and extension of ACSR after blazed are reported. [ABSTRACT FROM PUBLISHER]

This paper presents a simple model for the nonlinear magnetization characteristics of a switched reluctance motor (SRM). The flux linkage is given as a continuous mathematical expression depending on the phase current and rotor position. This expression can then be differentiated or integrated easily without computer use; it allows finding a mathematical formula for the instantaneous torque of each phase. The model is valuable for computer-aided designs, especially for sizing and initial estimates where accuracy can be traded with time saving. The model was implemented to verify its degree of accuracy. The simulation program has the ability to calculate numerous parameters that can be very useful for quick estimates of the efficiency for a particular SRM drive or even to choose a particular motor. [ABSTRACT FROM PUBLISHER]

Coating the inside surface of GIS enclosures with a dielectric film reduces the deleterious effect of electrode surface roughness, impedes the development of metallic particle initiated microdischarges, increases the field required to lift particles, and reduces the charge acquired by particles, all of which help alleviate the adverse effect of contaminating metallic particles on insulation withstand. The performance of particle-contaminated compressed gas systems with dielectric coated electrodes is analyzed. Two mechanisms for the transfer of charge from electrodes to contaminating particles are considered, namely, conduction through the coating layer and microdischarges in the surrounding gas. This paper presents an electrostatic study of the particle lifting fields with dielectric covered electrodes. The overall breakdown strength of the system is evaluated and the results are discussed in the light of experimental findings. [ABSTRACT FROM PUBLISHER]

An experimental study and some calculations on induction motor behavior were carried out. The effects due to short interruptions and voltage sags were investigated. A standard three-phase squirrel-cage motor of 5.5 kW, 1500 rpm, 380 V was used. The presence of induction motor changes the voltage sag waveform and duration. Protection characteristic curves and contactor ride-through capability together with their improvement are also studied. The interaction between motor load, system hot-load pickup, and voltage sag magnitude determine the motor reacceleration duration and magnitudes. Besides, on-sag and post-sag currents can reach levels higher than the direct start values. Post-sag overcurrent duration can last more than twice the normal start time period, having specific energies in the same order of magnitude. [ABSTRACT FROM PUBLISHER]

Increasing interest in power quality has evolved in the past decade. This article surveys the literature for current applications of advanced artificial intelligence techniques in power quality. Applications of some advanced mathematical tools in general, and wavelet transform in particular, in power quality are also reviewed. An extensive collection of literature covering applications of fuzzy logic, expert systems, neural networks, and genetic algorithms in power quality is included. Literature exposing the use of wavelets in power quality analysis as well as data compression is also cited. [ABSTRACT FROM PUBLISHER]