An algorithm for optimal sizing of the capacitor banks under non-sinusoidal and unbalanced conditions

In non-sinusoidal and unbalanced systems, optimal sizing of the capacitor banks is not a straightforward task as in sinusoidal and balanced systems. In this paper, by means of qualitative and quantitative analysis, it is interpreted that the classical capacitor selection algorithm widely implemented in Reactive Power Control (RPC) relays does not achieve optimal power factor improvement in non-sinusoidal and unbalanced systems. Accordingly, a computationally efficient algorithm is proposed to find the optimal capacitor bank for smart RPC relays. It is further shown in a simulated test case by using Matlab software that the proposed algorithm provides better power factor improvement when compared with the classical algorithm. It is also figured out from the simulation results that both algorithms cause almost the same harmonic distortion and unbalance deterioration levels in the system

A filter design approach to maximize ampacity of cables in nonsinusoidal power systems

This paper presents an optimal design of the C-type passive filters for the effective utilization of the power cables under nonsinusoidal conditions based on maximization of the harmonic derating factor (HDF) of a power cable, where maintaining the load true power factor at an acceptable range is desired. According to IEEE Standard 519, the total harmonic distortions of the voltage and current measured at the point of common coupling are taken into account as main constraints of the proposed approach. The presented numerical results show that the proposed approach provides higher current carrying capacity, or ampacity of the cables under nonsinusoidal conditions when compared to the traditional approaches based on minimization of the current total harmonic distortion and maximization of the true load power factor. A numerical case study is presented to demonstrate the proposed approach

Optimal design of single-tuned passive filters using response surface methodology

This paper presents an approach based on Response Surface Methodology (RSM) to find the optimal parameters of the single-tuned passive filters for harmonic mitigation. The main advantages of RSM can be underlined as easy implementation and effective computation. Using RSM, the single-tuned harmonic filter is designed to minimize voltage total harmonic distortion (THDV) and current total harmonic distortion (THDI). Power factor (PF) is also incorporated in the design procedure as a constraint. To show the validity of the proposed approach, RSM and Classical Direct Search (Grid Search) methods are evaluated for a typical industrial power system

Optimal multiple-steps single-tuned harmonic filters under time-varying conditions

Nowadays, considering the time-varying nature of harmonic sources is a significant trend in the power quality studies. In this research, the optimum sizing of multiple-steps passive LC compensator for maximum power factor and minimum transmission loss for non-linear loads under time varying conditions of background harmonic voltages, system impedance, and load impedance, is determined. The source harmonic voltages are varying in time independently of each other. The equivalent system impedance is given by varying the Thevenin impedance over a finite period. The functioning of the concerned LC filter is explained through a representative case study. Simulation results illustrate the viability of the suggested approach

A new switched DC –link capacitor based multilevel converter (SDC2MLC)

At present, one of the most common techniques for high power conversion in medium voltage applications is the use of cascaded multilevel converters. In this article, a new Switched DC-Link Capacitor Multilevel converter (SDC2MLC) with considerably few numbers of power electronics switches (IGBTs) is proposed, where keeping the total harmonic distortion (THD) of the output voltage waveforms as low as possible is desired. The proposed topology is configured using two separate basic units. Each unit consists of four switches with a series-parallel combination of isolated DC sources. The performance of the presented topology for both configurations is described. The required number of switches, power diodes, gate driver circuits and voltage stresses across the switches are compared with those of other recent published techniques. Furthermore, operation and performance of the proposed SDC2MLC are illustrated with the aid of experimental results of a single-phase 11-level converter to clarify the viability of the proposed topology

A Methodology for Low-Cost Optimization of Energy Efficient Passive Filters in Distribution Networks

ABSTRACT: In power distribution networks, nonlinear loads produce harmonic currents that can pass through other sensitive locations in the power system and eventually back to the source. Harmonic currents can produce a variety of effects that are harmful to a power system structure. Consequentially, the deployment of new cost and energy efficient passive, active and hybrid filtering techniques is important for the utilities and consumers alike. This paper presents an application of the Genetic Algorithm toolbox (GA) provided by MatLab software in order to find the optimal sizing of parameters of C-type passive filters based on minimization of the total investment cost of the proposed filters. Load power factor (PF), load voltage total harmonic distortion (THD V ) and supply current total demand distortion (TDD) are considered as the main constraints in this paper. Besides, capacitor loading duties are taken into account in compliance with IEEE Standard 18-2002 guidelines. Various numerical results are presented to validate the proposed approach

Novel Sequence Variants in the NPC1 Gene in Egyptian Patients with Niemann-Pick Type C

BACKGROUND: Niemann-Pick disease type C (NPC) is a rare, autosomal recessive, progressive neuro-visceraldisease caused by biallelic mutations in either NPC1gene (95% of cases) or NPC2 gene. AIM: This caseseries study aimed at the molecular analysis of certain hot spots of NPC1 genein NPC Egyptian patients. METHODS: The study included 15 unrelated NPC patients and selected parents,as well as20 healthy controls of matched sex and age. Clinical investigations were performed according to well established clinical criteria. Assessment of the chitotriosidase level, as an initial screening tool for NPC, was done in all cases. Polymerase chain reaction amplification of NPC1 exons (17–25) encountering the hotspot residues (855–1098 and1038–1253) was carried out followed by direct sequencingfor mutational analysis. RESULTS: All includedpatients with mainly neurovisceral involvement were characterized. The onset of the disease varied from early-infantile (58.3%) to late-infantile (26.7%) and juvenile-onset (6.7%). Ahigh chitotriosidase level wasobservedin all patients. Molecular analysis of NPC1 (exons 17–25) confirmed 15 mutant alleles out of 30 studied ones. They included two novel homozygous missense variants (p.Ser1169Arg and p.Ser1197Phe) and previously reportedfour mutations (p.Arg958*, p.Gly910Ser, p.Ala927Glyfs*38, and andp.Cys1011*). CONCLUSION: The two studied amino acid residues (855–1098 and 1038–1253) could beconsidered aspotential hotspot regions in NPC1 Egyptian patients