Three-phase Power Quality Research Articles

Researches regarding power quality at the hot rolling mills’ power supply

The study described in the paper was carried out through measurements taken at a feed station in a hot rolling line. The aforementioned measures are appropriate for the purpose of analyzing power quality. The measurements were taken using a three-phase power quality analyzer. Measurements were taken for voltage and current values, as well as for active, reactive, and apparent powers. The analysis of the measurements taken indicates that the power quality is affected by the nonlinearity of the load. As a consequence, the level of reactive power becomes higher, leading to a reduced power factor.

Three-Phase Four-Wire Transformerless Unified Power Quality Conditioner Based on AC-DC-AC Nine-Leg Converter and Shunt Converter

Three-Phase Four-Wire Transformerless Unified Power Quality Conditioner Based on AC-DC-AC Nine-Leg Converter and Shunt Converter

All-in-one three-phase smart meter and power quality analyzer with extended IoT capabilities

The traditional power grid is evolving into a new smart grid that requires better coordination of supply and demand, making it necessary to establish precise monitoring strategies in order to determine grid status in real-time. With the aim of providing a low-cost device based on open-hardware and open-source software to the technicians, engineers, and scientists around the world, this paper presents the three-phase openZmeter (3Ph-oZm), an all-in-one device that allows measuring and computing electrical data related to energy and power quality features in three-phase power networks. It has been designed to perform advanced computations for voltage, current, frequency, power, and energy. 3Ph-oZm is able to process high order harmonics, and log power quality disturbance events defined according to the recommendations of some international standards organizations. The data and its associated features are processed on-site using custom software specifically designed and programmed for this purpose that relies on advanced signal analysis techniques. This smart meter significantly improves the capabilities of the single-phase version, and overcomes certain shortcomings of other commercial devices, both in terms of versatility and data acquisition and processing capabilities. The system has been calibrated and validated using laboratory testing set-up and real-world applications, such as long-term photovoltaic power plant metering. The capabilities of 3Ph-oZm can also support a variety of other electrical applications, such as three-phase induction motor health monitoring, energy savings, or microgrid state estimation.

Artificial Lighting Photoperiod Manipulation Approach to Improve Productivity and Energy Use Efficacies of Plant Factory Cultivated Stevia rebaudiana

Stevia rebaudiana cultivated in non-native tropical conditions tends to flower early, halting vegetative growth, resulting in lower biomass and yields of its valued steviol glycoside metabolites. While indoor cultivation allows manipulation of artificial lighting to mimic optimal conditions, it introduces an additional energy cost. The study objectives were to assess photoperiod manipulation as a lighting strategy to increase overall biomass and metabolite yields as well as to improve the efficacy of the electrical energy used for indoor cultivation of Stevia rebaudiana in non-native environmental conditions. Stevia was grown under artificial lighting with red, green, and blue wavelengths with photoperiods of 8 h, 12 h, 16 h, and intermittent light amounting to 16/24 h, each with a constant Daily Light Integral (DLI) of 7.2 mol m−2 day−1. Yield was measured as leaf dry weight biomass in combination with Liquid chromatography–mass spectrometry (LCMS) analysis of Stevioside and Rebaudioside A content. The photon flux density of the artificial and natural light as measured by a spectroradiometer, and the energy use data collected with a three-phase power quality logger, were compared for each treatment tested and to that from plants grown under natural light irradiation in a greenhouse. Yield and energy data were used to determine the efficacies of the lighting systems tested. Stevia plants under a continuous 16-h photoperiod (16H) had the highest productivity, resulting in the highest biomass accumulation and metabolite concentrations. The Stevioside and Rebaudioside A yields per plant were 975% higher than those obtained under natural daylight and day-neutral tropical photoperiod. Overall energy use and photon conversion efficacies were also highest under 16H at 65.10 g kWh−1 for biomass accumulation, 12.40 g kWh−1 for metabolite yields and 7.5 mg mol−1 for photon conversion. These findings support the application of photoperiod manipulation as a viable approach to increase productivity and improve energy use efficacies for indoor cultivation of Stevia rebaudiana plants under artificial lighting in non-native environments with the 16-h photoperiod under red and blue artificial light supplemented with green spectrum as the best option.

Predictive direct power control of three-phase three-level four-leg unified power quality conditioner

In this paper, a predictive direct power control for three-phase three-level four-leg unified power quality conditioner (UPQC) has been proposed. The proposed three-level four-leg UPQC is capable o...

Effects of Waveforms Distortion for Household Appliances on Power Quality

Harmful effect of harmonics is considered one of the main factors that badly affect the electricity meters’ accuracy and power quality of distribution systems. In this paper, the impact of harmonics generated by various household appliances has been investigated. Household appliances have been divided into four groups according to the similarity of their current and voltage waveforms. The appliances have been collected together according to the reason of the year and time to analyze their waveform. Experimental measurements have been performed using a standard CALMET-TE30 three-phase power quality analyzer. Measurement uncertainty calculations have been taken into consideration to acquire the actual measurement results. The waveforms of these results have been precisely plotted using a specially designed MATLAB program.

Power factor improvement in three-phase networks with unbalanced inductive loads using the Roederstein ESTAmat RPR power factor controller

The paper presents the analysis of a power factor with capacitors banks, without series coils, used for improving power factor for a three-phase and single-phase inductive loads. In the experimental measurements, to improve the power factor, the Roederstein ESTAmat RPR power factor controller can command up to twelve capacitors banks, while experimenting using only six capacitors banks. Six delta capacitors banks with approximately equal reactive powers were used for experimentation. The experimental measurements were carried out with a three-phase power quality analyser which worked in three cases: a case without a controller with all capacitors banks permanently parallel connected with network, and two other cases with power factor controller (one with setting power factor at 0.92 and the other one at 1). When performing experiments with the power factor controller, a current transformer was used to measure the current on one phase (at a more charged or less loaded phase).

Study on Compressing Data for Three-Phase Power Based on Adaptive Two-Dimensional Wavelet Packet

This paper presents a method based on adaptive two-dimensional wavelet packet for three-phase power quality data. In this paper, we shall briefly introduce the method of dq0 transformation. First, the original data is converted by the method of dq0 transformation, its purpose may be to eliminate redundancy between the three-phases alternating data, then change the one-dimensional date converted into a two-dimensional matrix by the integral multiple of cycles, which aims to eliminate redundant between cycles. Finally, use the method of two-dimensional adaptive wavelet packet decomposition, image SPIHT coding and DEFLATE coding to compress the data. The simulation result shows that the algorithm effectively compress the three-phase power quality data, and it has a good compression effect.

The Design and Application of SVG for Low Voltage Distribution Networks

SVG can compensate reactive power deficiency, suppress harmonics, improve three-phase imbalance and power quality more flexibly. There are very few small volume SVG products available for low voltage distribution network in the past. The generic SVG products are very expansive, thus not suitable for low voltage distribution network. Therefore, it is an urgent task to design a new generation distribution network SVG product that offers good value for money. This paper studied a SVG digital controller based on TMS320F28335 DSP chip. The fast and powerful computing and parallel operation capability of TMS320F28335 can satisfy the real-time, multifunction and multiple objective coordination control of SVG. Applied the instantaneous reactive power theory and adopted current direct control mode, an enhanced filtering algorithm to filter instantaneous sampling value is proposed. Automatic bi-directional compensation control strategy effectively reduced voltage variation at the user side. Its effectiveness is verified by an engineering project.

Current Control Scheme for Three-Phase Power Quality Conditioner Under Balanced and Unbalanced Condition

The three-phase shunt active power filter eliminates harmonic currents and compensates reactive power for non-linear loads. A current control scheme based on the time-domain approach for three-phase shunt active power filters is analysed in this paper. A basic outline and evaluation of the performance of existing current control methods for active power filters are presented. According to different complicated power quality issues and various compensation requirements, a current control scheme based on time domain approach is proposed. Comparing with existing methods this algorithm has very short response time delay. Different compensation current references can thus be accurately and easily obtained by adopting the proposed current control scheme. The simulation results show the excellent performance and effectiveness of the proposed method.

Current control scheme for three-phase power quality conditioner under balanced and unbalanced conditions

Current control scheme for three-phase power quality conditioner under balanced and unbalanced conditions

A Novel Active Interphase Transformer Scheme to Achieve Three-Phase Line Current Balance for 24-Pulse Converter

A new active interphase transformer (IPT) scheme to achieve three-phase line current balance for a 24-pulse converter is proposed in this paper. The proposed active IPT scheme consists of three IPT and a current-controlled inverter with required rating only 1.16% of system power rating. A current injection method for an active IPT is also proposed in this paper. The balance of three-phase current and high power quality can be achieved by injecting compensation current into the secondary winding of the active IPT. Moreover, the proposed scheme can operate in flexible load configurations, by which separated loads can be connected to the separated outputs of the converter independently. The operation criteria for flexible load arrangements are analyzed to obtain better performance. System simulation is conducted and a 6-kW laboratory prototype is built both for evaluation and test. Both simulation and experimental results demonstrate the validity of the proposed scheme.

The effect of IEC grouping algorithms on frequency domain noise

In this paper, noise propagation through a two-stage nonlinear algorithm for measurement of harmonic distortion in power systems according to IEC 61000-4-7 is analyzed. Noise generated in the instrument’s input circuitry is considered as an aggregated noise source without detailed characterization of its origin. The first stage of the measurement algorithm is the discrete Fourier transform (DFT) of the input signal. Noise propagation through the DFT is analyzed by means of probability theory. The result of this analysis, the probability density function (pdf) of the DFT spectrum amplitudes, is used for characterization of the second stage of the measurement algorithm – the root-sum-square grouping of several spectrum components into a single harmonic distortion index. In this way, pdfs of the most common harmonic indices are derived and analyzed. The study presented reveals that noise generated in the input stage produces, besides the already known variance of the results, an offset in the harmonic distortion indices. Analysis of the resulting pdfs implies that an increase in the number of components in the grouping procedure increases the offset error, whereas the standard deviations are essentially independent of the number of components included in the group. The validity of the model derived has been tested with a prototype of a low-cost portable instrument for three-phase power quality measurements.

Kalman filter and wavelets transform based three-phase power quality disturbances detection, classification and diagnosis tool implementation-hardware and software

Kalman filter and wavelets transform based three-phase power quality disturbances detection, classification and diagnosis tool implementation-hardware and software

Analysis of electromagnetic pollution produced by line frequency coreless induction furnaces

This paper presents the electromagnetic pollution produced by the line frequency coreless induction furnaces in the power supply network. We analyzed a furnace with 12.5 t capacity of cast-iron. The measurements have been made in the secondary of the furnace transformer, using the CA8334 three-phase power quality analyser. Experimental results emphasized the presence of harmonics and interharmonics in the phase voltages and harmonics in the currents absorbed from the network. The operation of analyzed furnace also produces unbalance. Further to the harmonic analysis of the signals measured in the furnace installation, we have been proposed some optimization methods for its operation, in such way to comply with the European norms of Electromagnetic Compatibility (EMC).

Application of a three-level NPC inverter as a three-phase four-wire power quality compensator by generalized 3DSVM

A two-level four-leg inverter has been developed for the three-phase four-wire power quality compensators. When it is applied to medium and large capacity compensators, the voltage stress across each switch is so high that the corresponding dv/dt causes large electromagnetic interference. The multilevel voltage source inverter topologies are good substitutes, since they can reduce voltage stress and improves output harmonic contents. The existing three-level neutral point clamped (NPC) inverter in three-phase three-wire systems can be used in three-phase four-wire systems also, because the split dc capacitors provide a neutral connection. This paper presents a comparison study between the three-level four-leg NPC inverter and the three-level NPC inverter. A fast and generalized applicable three-dimensional space vector modulation (3DSVM) is proposed for controlling a three-level NPC inverter in a three-phase four-wire system. The zero-sequence component of each vector is considered in order to implement the neutral current compensation. Both simulation and experimental results are given to show the effectiveness of the proposed 3DSVM control strategy. Comparisons between the 3DSVM and the 3-D hysteresis control strategy are also achieved.

Analysis and implementation of three-phase power quality compensator under the balanced and unbalanced load conditions

An active power filter with asymmetric inverter legs are presented to eliminate harmonics, compensate reactive power and draw the balanced line current from the AC source under balanced and unbalanced load conditions. Three inverter legs are used in the adopted voltage source inverter. In each leg, four active switches are adopted to achieve three-level pulse-width modulation (PWM). No clamped diode or flying capacitor is used in the proposed inverter. In the adopted control algorithm, a classical proportional-integral voltage controller and hysteresis current controller are used to maintain DC-link voltage constant and to track line current commands, respectively. A voltage compensator is added in the inner control loop to compensate the neutral point voltage variation due to load variation. Based on the proposed PWM control scheme, a three-level voltage pattern is generated on the AC terminal of the inverter. The system configuration and mathematical analysis are discussed in the paper. Finally, the experimental results based on a laboratory scaled down prototype are provided to verify the effectiveness of the control algorithm.

Injected voltage calculation in three-phase series power quality controllers

A three-phase series power quality controller (SPQC) is a device designed for eliminating voltage disturbances. It compensates load-voltage fluctuation by injecting an appropriate voltage into the distribution system. The maximum output voltage of an SPQC is constrained by its voltage limit, which is determined by the configuration of the SPQC and its DC link voltage. Based on discussions about unbalanced voltage sags using the phasor-diagram approach, a rotation-transform-based control strategy is designed. With the new method, the active power injected by an SPQC is minimised and the output voltages of the SPQC are kept within its voltage limit while the supply voltage distortion can be completely compensated. A two-phase compensation method especially for a 3-phase 3-wire system is also proposed in this paper. A new control strategy, a shift-transform-based control strategy for the two-phase compensation method, is designed. The new control strategy allows the compensation range of an SPQC to be significantly expanded without increasing the voltage limit of the device. The performance of the two new control strategies is verified by simulation.

Three-Phase Power Quality Compensator Under the Unbalanced Sources and Nonlinear Loads

A three-phase voltage-source inverter for a power quality compensator under the unbalanced mains and nonlinear loads is proposed to provide balanced three-phase source current and improve input power factor. The proposed converter is based on the conventional three-phase voltage-source inverter with three additional ac power switches to achieve three-level pulsewidth modulation. The voltage stress of three ac power switches is clamped to half the dc-link voltage. The balanced reference mains currents are estimated using the dc-bus voltage and load currents. A proportional-integral voltage controller is used in the outer loop to compensate the switching losses of the voltage-source inverter. To perform the integrated power quality compensation, a hysteresis current control scheme is adopted to track the balanced line current command in phase with mains voltage. Three voltage levels are generated on the ac terminal of the proposed inverter. Computer simulation and experimental results are provided to verify the effectiveness of the proposed control scheme.