Electrical Energy Parameters Research Articles

Voltage conditioner & power flow controller based on bipolar matrix-reactance choppers

Voltage amplitude is one of the most important parameters of electrical energy, particularly from the viewpoint of sensitive loads connected to the grid. The dynamic state in a power grid (voltage sags/swells/interrupts) originating from dynamic loads, uncontrolled power flow, switching effects, adverse weather condition, etc., might cause defects in sensitive loads and financial losses. The annual damages in Europe due to voltage perturbations is estimated at 10billion €. This paper presents a three-phase voltage conditioner and power flow controller without DC energy storage unit for the control of phase and voltage amplitude. In comparison to conventional solutions, such as DVR or UPFC, the power electronic AC/AC converter is based on a bipolar matrix-reactance chopper. The main aim of this paper is to analyse the basic properties of the presented solution, especially from the point of view of the ability to compensate voltage sag/swell and interruption and to control phase shift in bidirectional power flow control. The studies have been carried out on a three phase system with passive and active load (two-source system). On the basis of the authors’ research, it can be stated that the described solution gives the possibility to compensate deep voltage sag (50% of nominal voltage), overvoltages (up to 150% of nominal voltage) and single phase interruption. Simultaneously the solution allows independent control of the phase angle of output voltage in the range±π/3. The paper presents an operational description, theoretical analysis, simulation and the experimental test results of a 1kVA laboratory model using a conventional PWM control strategy.

A holistic approach to power quality parameter optimization in AC coupling Off-Grid systems

The development of autonomous energy systems has been accompanied by a number of challenges related to the specific characteristics of these systems, such as power flow control, development of protection systems respecting the dynamic changes in short-circuit power and the issue of compliance with power quality parameters. To keep the power quality parameters of electrical energy in Off-Grid systems within the limit is highly complicated with regards to the supply of electrical energy from renewable sources of a stochastic nature, which are used as dominant sources of electric or heat energy. Variations in short-circuit power may significantly affect the system stability and may have a negative impact on the operation in case of sensitive appliances. We developed tools and methods to keep the power quality parameters in Off-Grid systems within the limits using an intelligent approach based on an artificial intelligence technique. Our computational model is able to predict disturbances in power quality and perform a set of proper reactions to avoid such disturbances with over 60% success rate in time horizon of 15min ahead. As a result, it is subsequently possible to optimize the operation of Off-Grid systems and thus contribute to improvements in the power quality parameters in Off-Grid systems.

Hybrid Transformer With Matrix Converter

This paper deals with an ac–ac voltage regulator/compensator based on a hybrid transformer with a matrix converter realizing electrical coupling in the hybrid transformer unit. The parameters of electrical energy, such as voltage amplitude, are very important, particularly from the viewpoint of the final consumer and sensitive loads connected to the grid. Furthermore, a hybrid transformer using a matrix converter can be used for power-flow control and for transient stability improvement in ac transmission systems. Active power flow and voltage magnitude in transmission lines can vary by using a conventional mechanical or thyristor-controlled regulator. However, the control parameters can be executed only in steps depending on the taps available in the electromagnetic transformer. An approach for obtaining continuous control of the voltage magnitude and phase shift using a conventional transformer with two windings and a pulsewidth-modulated matrix converter is presented in this paper. The operating principles and steady-state properties are discussed. Detailed computer simulation results are presented in this paper. Furthermore, experimental test results obtained from a three-phase 3 kVA laboratory model are also presented.

Hybrid Voltage Sag\/Swell Compensators: A Review of Hybrid AC\/AC Converters

The parameters of electrical energy, such as supply voltage amplitude, are very important, especially from the viewpoint of the final consumer with respect to sensitive loads connected to the grid. Dynamic states in the power grid?voltage sags and swells?might cause faults and defects to develop in sensitive loads. To mitigate unwanted effects, many topologies of ac/ac converters are implemented as voltage compensators. This article presents a review of hybrid ac/ac converters designed to compensate voltage sags and swells with the aim of protecting sensitive loads against sudden and severe changes in supply voltage amplitude. In this article, only solutions without galvanic separation between source and load are described. To assess the properties and to compare different topologies of voltage compensators, some common parameters, such as range of voltage sag and swell compensation, reliability, quantity of switches and transformers, and required power ratings of power electronic units in relation to power of load, are introduced. In addition, we discuss possibilities for compensation of voltage interruption, time of compensation, the efficiency, and the effect on the supply network of the described circuits. The results of the analysis have been collected and compared in tabular form and represented in graphical form. Furthermore, we show potential areas of application for particular solutions of ac voltage compensators.

Effect of Se addition on optical and electrical properties of chalcogenide CdSSe thin films

Compositional dependence of optical and electrical properties of chalcogenide CdSxSe1−x (0.4≥x≥0.0 at. %) thin films was studied. Cadmium sulphoselenide films were deposited by thermal evaporation technique at vacuum (8.2×10−4 Pa) onto preheated glass substrates (523 K). The evaporation rate and film thickness were kept constant at 2.50 nm/s and 375 ± 5 nm, respectively. X-ray diffractograms showed that, the deposited films have the low crystalline nature. Energy dispersive analysis by X-ray (EDAX) was used to check the compositional elements of deposited films. The absorption coefficient was determined from transmission and reflection measurements at room temperature in the wavelength range 300–2500 nm. Optical density, skin depth, optical energy gap and Urbach's parameters of CdSSe thin films have also been estimated. The direct optical energy gap decreased from 2.248 eV to 1.749 eV when the ratio of Se-content was increased from 0.60 to 1.00 . Conduction band and valance band positions were evaluated. The temperature dependence of dc-electrical resistivity in the temperature range (293–450 K) has been reported. Three conduction regions due to different conduction mechanisms were detected. Electrical sheet resistance, activation energy and pre-exponential parameters were discussed. The estimated values of optical and electrical parameters were strongly dependent upon the Se-content in CdSSe matrix.

A Remote Monitoring System for Voltage, Current, Power and Temperature Measurements

Abstract This paper presents a study and design of a monitoring system for the continuous measurement of electrical energy parameters such as voltage, current, power and temperature. This system is designed to monitor the data remotely over internet. The electronic power meter is based on a microcontroller from Microchip Technology Inc. PIC family. The design takes into consideration the correct operation in the event of an outage or brown out by recording the electrical values and the temperatures in EEPROM internally available in the microcontroller. Also a digital display is used to show the acquired measurements. A computer will remotely monitor the data over internet.

Technical and economic comparison of direct converters of electric energy parameters

Technical and economic comparison of direct converters of electric energy parameters

Development of a Real Time Energy Monitoring Platform User-Friendly for Buildings

This study introduces the development of a user-friendly and quite effective energy monitoring system installed in the building of School Engineering at the Universidad Autónoma de Querétaro since 2008. The metering and control software, that processes and analyzes the digitalized signals, has been developed in Integrated Development Environment (IDE) primarily MonoDevelop designed for C#, under the Linux embedded server operating system with a real time kernel. This system allows the measurement of the electric energy parameters of within a building, where the main power source has been divided into several sections for individual analysis. Measuring electric energy in sections allows the identification of higher consumption areas, the detection of abnormal conditions in voltage and current of the building. The consumption of electric energy parameters are displayed by means of an easily understood graphic interface which can be consulted via the Internet. Users who know exactly when energy consumption occurs and where it takes place are able to take more informed decisions about how to lower their energy consumption.

Valve-type converters of electric energy parameters

It is given classification of valve-type converters of electric energy parameters according to multiplicity of modulation by alternating current switches.

The role of glial cells in regulation of neurotransmitter amino acids in the external environment. I. Transmembrane electrical and ion gradients and energy parameters in cultured glial-derived cell lines

Studies of energy parameters and intracellular ion concentrations were carried out on two glial cell lines, one derived from an astrocytoma (C6) and the other from an oligodendroglioma (TR33B), to elucidate the mechanism of transport of amino acid neurotransmitters by glial cells. Respiratory rate was 2.7–2.9 nmol/min/mg dry wt.; cytochrome c at 0.035–0.041 nmol/mg dry wt., was 23–29% reduced with a calculated turnover number 4.7–5.1 e −/s at 23 °C. ATP levels were high, 5.0–6.5 mM and [CrP]/[Cr] was almost 2. Membrane potentials at [K +] e = 5mM were approximately −90 mV for C6 cells and −72 mV for TR33B. [K +] i was measured as approximately 100 mM for TR33B and 150 mM for C6 which indicated that the K + diffusion potential was the major source of the membrane potential. [Na +] i was 5.8 mM for C6 and 20 mM for TR33B cells while free calcium was about 100 nM. Near Nernstian relationships were found in both types of cell between [K +] e and membrane potential over a range of 3.5–75 mM for TR33B and 5–110 mM for C6 cells. It is concluded that C6 and TR33B cell lines may be useful models for in vitro studies of some aspects of glial behavior.

Effects of differences between channels on the accuracy in measuring the quality parameters of three-phase electrical energy

Effects of differences between channels on the accuracy in measuring the quality parameters of three-phase electrical energy

Ionic determinants of membrane potential of cells presumed to be glia in cerebral cortex of cat.

Ionic determinants of membrane potential of cells presumed to be glia in cerebral cortex of cat.

Physiological properties of glial cells in the central nervous system of amphibia.

Physiological properties of glial cells in the central nervous system of amphibia.