Power Quality Characteristics Research Articles

Обработка данных экспериментальных измерений показателей качества электрической энергии на примере уровней отклонений напряжений

Обработка данных экспериментальных измерений показателей качества электрической энергии на примере уровней отклонений напряжений

Power Quality Characteristics of a Multilevel Current Source With Optimal Predictive Scheme From More-Electric-Aircraft Perspective

Revolutionary design power architectures into electric aircraft system are being actively discussed to cope with the issues of a present state-of-the-art technology. The two demanding objectives in more-electric-aircraft (MEA) concept are power quality enhancement and increased level of redundancy despite of higher on-board power supply requirement throughout aircraft operation. In addressing the open challenges, this study outlines an operational characteristics of a three-phase multilevel shunt active filter (SAF) deployed for distribution power system in emerging MEA. The introduced shunt active filter is based on modular multilevel converter configuration for harmonic-current compensation purposes. On this foundation, a current control strategy for SAF is designed with a finite-control-set model predictive control technique. The developed solution provides several merits into aircraft electrical network as easy implementation on embedded platforms, controllable feature with a wide range of current frequencies, producing exact current harmonic replica onto the supply side over a given prediction horizon, and modular design with redundancy functionality. Dedicated predictive control system helps to better execution-time efficiency together with low sensitivity over the constraints imposed upon the optimization formulation through an integrated perturbation analysis and sequential quadratic programming solver. Simulation and experimental verifications for the three-phase four-level shunt active power filter are discussed, where robust behavior of handling harmonic currents with respect to the supply impedance and fundamental frequency variations is achieved, when the harmonic distortion levels fulfill the IEEE Standard 519 recommendations.

Analysis of Energy Storage Characteristics of Power Quality Integrated Control System based on MMC

MMC as a new type of voltage source converter is used more and more widely, its essence is a distributed storage system, there are many advantages by using the topological structure of MMC on power quality integrated control system, the power quality control system of voltage sag mitigation is the important use of MMC energy storage system for power quality compensation process. In this paper, based on the analysis of the topology of MMC, firstly analyzes the essence of energy conversion power quality integrated control system of voltage sag compensation, then the energy storage characteristics were calculated and analyzed, the performance index of voltage sag compensation, finally, the simulation method is used to verify the voltage sag compensation characteristics of power quality integrated control system.

Analysis of the Investment Situation of Biomass Power Generation Industry in China

The biomass resources represented by crop residue is abundant in China, taking it as raw material to generate electricity has the characteristics of good power quality, high reliability and relatively mature technology. It plays an important role in maintaining energy security, optimizing energy structure, alleviating environmental pollution and promoting rural economy development. China’s biomass power generation industry is a policy-supporting industry in the industry start-up period, which has been rapidly developed in recent years under the stimulation of a variety of policies by the government. Although China’s biomass power generation industry has great potential for development, there are some problems in industrial investment. This paper analyzes the investment situation of China’s biomass power generation industry from the aspects of industrial investment source, investment area, and investment scale and investment economy in order to improve the investment scientificity of biomass power generation industry and provide evidence for the rapid and healthy development of biomass power generation industry in China.

An Fundamental Current Reference Control Strategy for DSTATCOM under Various Load Situations

Effort for power quality enhancement is gradually raised in power transmission and distribution system. In a distribution system, it is a pre-requisite consumer related concern which is addressed by evading the mis-operation of massive power electronic load apparatus. Due to this, voltage/current harmonic distortions are acquired at common coupling point, which influences the disruption of quality power in a distribution system. A reliable and efficient active power conditioner is utilized for acquiring the power quality features in a three phase distribution system with attractive control objective. Over the classical conditioning techniques, a D-STATCOM plays a key role in a distribution system for power quality enhancement. Formal control objectives are adversed with incredible switching losses due to extreme harmonized frequencies in a reference current component. This paper proposes the imperative reference current extraction scheme for optimal functioning of DSTATCOM with reduced switching losses and gaining the incredible efficiency. The validation of DSTATCOM with proposed control strategy under several load situations (linear/non-linear & balanced/un-balanced) is evaluated by using Matlab/Simulink platform and simulation results are conferred.

A Critical Evaluation of Power Quality Features using Dual APF under Grid Interfaced DG Scheme

This paper presents the concept of power quality enhancement reducing the harmonic distortion with power distribution system consisting of balanced and unbalanced non-linear type of loads. This paper presents power quality enhancement using dual active power filters (APF’s) under grid connected distributed generation scheme. Acive power filters effectively generate compensating signals for harmonic abolition and this paper presents APF for compensating currents to be induced in to distribution grid for harmonic elimination under balanced and unbalanced non-linear load conditions. Distributed generation (DG) feeds the grid and the scheme of grid interfaced DG was explained. APF is controlled using instantaneous P-Q theory and DG inverter is controlled using simple control strategy. Proposed system was developed and the results are obtained using MATLAB/SIMULINK software.

POWER QUALITY ANALYSIS BY THE RIPPLE TECHNIQUE

Characteristics of Power quality has been with us since the inception of the electrical Power system. However, the topic of power quality has attracted particular attention in recent years due to the increase of electronically controlled. Power quality problems caused disruptions to electrical or electronic equipment and the resulting consequences are very expensive. Ripple techniques will be studied in this paper for analysing power quality monitoring. In the case study based on the measurement of the site of the Asian Institute of Technology (AIT) and it was examined using the proposed ripple technique.

Synthetic evaluation of steady-state power quality based on combination weighting and principal component projection method

With integration of renewable energy and use of non-linear loads in power systems, the power quality problem is increasingly attracting attention of researchers. In China, standards for individual power quality indexes are set. However, when evaluating power quality in practice, individual indexes cannot directly reflect a comprehensive level of power quality. In this paper, a comprehensive analysis of various indexes is conducted to obtain a unified parameter for describing the characteristics of power quality from an overall perspective. First, weight values of power quality indexes are calculated by combining the subjective and objective weight. Then, based on the principal components of the projection method, projection values of boundary data and data to be evaluated are obtained. Finally, using these projection values, a grade range for power quality data is located. A practical case study is presented to show the validity of the proposed method for evaluating power quality.

Single‐phase solar grid‐interfaced system with active filtering using adaptive linear combiner filter‐based control scheme

This study deals with a control scheme for single-stage solar photovoltaic (SPV) grid-interfaced system. The voltage-source inverter (VSI) is a power electronic interface between SPV array and the grid. The VSI provides power quality features, i.e. harmonics mitigation, power factor correction and perturb and observe maximum power point tracking for single-stage SPV grid-interfaced system. The SPV array supplies active power to the non-linear load and grid through VSI, during daytime only or when SPV generation is more than the load power. To increase the utilisation of VSI, it is used as an active power filter at night, to mitigate harmonics and to provide active power to the load from the utility grid. The proposed adaptive linear combiner filter has the capability to extract harmonics and enhances the power quality in SPV grid-interfaced system. It has also satisfied an IEEE-519 standard of harmonics by improving the quality of power of SPV grid-integrated system. Simulation results of the SPV system are presented, which are simulated using MATLAB and response of system under non-linear load and varying environmental condition are also studied experimentally on a developed prototype in the laboratory.

Adaptive neuron detection‐based control of single‐phase SPV grid integrated system with active filtering

This study deals with an adaptive neuron detection-based control technique for single-phase, single-stage solar photovoltaic (SPV) array grid integrated system using a voltage-source converter (VSC). The VSC also provides power quality features such as harmonics mitigation, power factor correction and perturb and observation-based maximum power point tracking for an SPV grid-interfaced system. With this approach, the VSC has the active power flow from the SPV array to the grid and it also performs the non-linear load current harmonic compensation by keeping the grid current almost sinusoidal. On the other hand, in the night mode, if the SPV power is not available, the VSC works as an active power filter for the harmonics elimination and reactive power compensation. This increases the effective utilisation of the VSC. The adaptive neuron detection technique has lesser noise and oscillation in extraction of fundamental component in comparison of conventional adaptive control algorithm. It has also satisfied an IEEE-519 standard of harmonics by improving the quality of power of SPV grid integrated system. The proposed system is modelled and simulated using MATLAB/Simulink and the response of the system under non-linear loads and varying environmental conditions are evaluated experimentally on a prototype developed in the laboratory.

Light Wavelength and Power Quality Characteristics of CFL and LED Lamps under Different Voltage Harmonic Levels

Conventional light sources are less efficient as compared to the light emitting diode and compact fluorescent lamps. Conventional incandescent filament lamps are resistive and therefore do not depend on power quality parameters. In the electric power system, nonlinear loads are increasing rapidly and the high content of harmonic due to the nonlinear loads cannot be neglected. Harmonic generation from the light emitting diode and the compact fluorescent lamp is one of the main problems for power quality. In this study, the light efficiency and electrical characteristics of the light emitting diode lamps and compact fluorescent lamps are evaluated under various voltage harmonic levels. The results show that light emitting diode, produces more harmonics as compared to the compact fluorescent lamps, with the increase of the voltage harmonic distortion from 0.7% to 3.52% in the light emitting diode, current harmonic increased from 140% to 192%. The results also show that increase in voltage harmonic distortion just not only increase current harmonics distortion but also affect the light wavelength of the lamp.

Prototype of an Electric Drive Elevator

Abstract The research purpose of the authors is reducing the energy consumption of the main worldwide consumer - the electric motors- by useful utilization of the input energy through the Regenerative Electric Drive System having also the power quality features. The prototype of the electric elevator consists mainly of two trolley: one serve for the active load, and the other as counterweight, gearbox, power converter, induction machine and chain transmission. The elevator is driven by using 4kW three-phase induction machine through AC-AC power converter and has the capacity of 450 kg. The numerical simulation results and the experimental platform are shown.

Power Quality in Railway Traction and Compensation by Combining Shunt Hybrid Filter and TCR

This paper analyses the quality of electricity in railway traction. Power quality characteristics have been measured as a case study in a traction sub-station in Tamil Nadu, India, where 1400 KVAR capacitor bank is installed. The actual data has been obtained through direct supply of traction load. Harmonics and various power quality problems are generated through the load of current. The emerging power problems need attention to rectify the polluting sites. Issues are measured by providing power quality analyzer and compared with IEEE standards 519-1992. Simulation has been done to improve the power quality issues such as harmonics, power factor and reactive power by using a combination of shunt hybrid filter and Thyrsitor Control Rectifier.

Electrical machines based DC/AC energy conversion schemes for the improvement of power quality and resiliency in renewable energy microgrids

The power quality and resiliency (or self-healing capacity) characteristics of a renewable energy based microgrid (REM) are limited majorly due to their inherent dependency on the static power electronics based energy conversion devices. Whereas, conventional electrical machines based power plants possess good power quality and resiliency characteristics due to their high inertia and control features. So, the REMs’ research need to be shifted towards making its operation similar to conventional electrical machines based power plant. With this intent, this paper proposes two DC/AC energy conversion schemes that are designed based on the theory of electrical machines such as DC Motor (DCM) and Doubly Fed Induction Generator (DFIG). The first scheme is a rotary inverter (named as RDCMIGI) that replaces the conventional static power electronic inverter with a real DCM-DFIG set. The second scheme is a static inverter (named as VDCMIGI) that uses a pulse width modulated power electronic inverter, whose modulating signals are generated through a closed loop virtual DCM-DFIG based control system. These two schemes emulate the behavior of electrical machines based conventional power plant in REM, which leads to the improvement of power quality through the smooth control of voltage/frequency and resiliency through the injection of necessary moment of inertia. For the analysis, the conventional/proposed energy conversion schemes are modeled in MATLAB/Simulink® and are tested during various uncertainties. From the results, it is observed that the proposed DC/AC energy conversion schemes have effectively improved the power quality and resiliency, and thereby, leverages REMs as better future grids.

Power Quality Investigation of Distribution Networks Embedded Wind Turbines

In recent years a multitude of events have created a new environment for the electric power infrastructure. The presence of small-scale generation near load spots is becoming common especially with the advent of renewable energy sources such as wind power energy. This type of generation is known as distributed generation (DG). The expansion of the distributed generators- (DGs-) based wind energy raises constraints on the distribution networks operation and power quality issues: voltage sag, voltage swell, voltage interruption, harmonic contents, flickering, frequency deviation, unbalance, and so forth. Consequently, the public distribution network conception and connection studies evolve in order to keep the distribution system operating in optimal conditions. In this paper, a comprehensive power quality investigation of a distribution system with embedded wind turbines has been carried out. This investigation is carried out in a comparison aspect between the conventional synchronous generators, as DGs are widely in use at present, and the different wind turbines technologies, which represent the foresightedness of the DGs. The obtained results are discussed with the IEC 61400-21 standard for testing and assessing power quality characteristics of grid-connected wind energy and the IEEE 1547-2003 standard for interconnecting distributed resources with electric power systems.

A PCA-based approach for substation clustering for voltage sag studies in the Brazilian new energy context

Voltage Sags are the most disturbing power quality deviation to the sensitive industrial loads causing production losses and other impacts to the equipment end users and distributors of electricity. A new methodology for estimation of voltage sag patterns and clustering of distribution substations with similar features for voltage sags is the main contribution of this paper. The focus is on the regulation of this phenomenon in Brazil. Network modeling and faults simulations in transmission and distribution levels were performed in a Brazilian actual distribution system with 17 substations in order to get information regarding the number of voltage sags caused in the substations bus bars. Principal Component Analysis was applied on a significant number of variables containing relevant information of power quality and design features of the substations and storing the major Principal Components Scores. Furthermore, Clusters of substations with similar characteristics to voltage sags were formed and assigned a specific Membership to each substation. The expected annual number of voltage sags is the solution. A 95% Confidence Interval for the total number of voltage sags was estimated, leading to the classification of the main variables related to the voltage sags by clusters formed. Clusters of Substations with similarities for regulatory purpose of voltage sags were the principal results, followed by classification of the main variables associated with voltage sags by the clusters formed. A critical analysis of the results and a comparison among different Clustering Methods reaffirmed the assertiveness of the proposed methodology for the management of power quality associated with voltage sags, by the Regulator and the distribution utilities in Brazil.

Feature Selection of Power Quality Disturbance Signals with an Entropy-Importance-Based Random Forest

Power quality signal feature selection is an effective method to improve the accuracy and efficiency of power quality (PQ) disturbance classification. In this paper, an entropy-importance (EnI)-based random forest (RF) model for PQ feature selection and disturbance classification is proposed. Firstly, 35 kinds of signal features extracted from S-transform (ST) with random noise are used as the original input feature vector of RF classifier to recognize 15 kinds of PQ signals with six kinds of complex disturbance. During the RF training process, the classification ability of different features is quantified by EnI. Secondly, without considering the features with zero EnI, the optimal perturbation feature subset is obtained by applying the sequential forward search (SFS) method which considers the classification accuracy and feature dimension. Then, the reconstructed RF classifier is applied to identify disturbances. According to the simulation results, the classification accuracy is higher than that of other classifiers, and the feature selection effect of the new approach is better than SFS and sequential backward search (SBS) without EnI. With the same feature subset, the new method can maintain a classification accuracy above 99.7% under the condition of 30 dB or above, and the accuracy under 20 dB is 96.8%.

Overview of power quality analysis and control technology for the smart grid

With the wide application of non-linear loads and the large-scale access of distributed energy generations based on power electronics equipments, power quality problems in the distribution network are increasingly serious with new characteristics. Further in-depth research is of great significance in theory and practice. This paper provides an overview of power quality analysis, compensators, and control technologies under the new situation of smart grid. It focuses on the topologies and control methods for power quality conditioners, especially new characteristics of power quality and applicable control technologies in microgrids and distributed power plants. Finally, trends and prospects of power quality control technology are introduced, which is important to achieve security and efficient operation of the smart grid.

Power Quality in Railway Traction and Compensation by Combining Shunt Hybrid Filter and TCR

This paper analyses the quality of electricity in railway traction. Power quality characteristics have been measured as a case study in a traction sub-station in Tamil Nadu, India, where 1400 KVAR capacitor bank is installed. The actual data has been obtained through direct supply of traction load. Harmonics and various power quality problems are generated through the load of current. The emerging power problems need attention to rectify the “polluting” sites. Issues are measured by providing power quality analyzer and compared with IEEE standards 519–1992. Simulation has been done to improve the power quality issues such as harmonics, power factor and reactive power by using a combination of shunt hybrid filter and Thyrsitor Control Rectifier.

电气化铁路电能质量问题分析

电气化铁路具有高速化、重载化、能源利用率高、经济效益好等优点。但电气化铁路牵引负荷属于大功率非线性单相负荷，接入电网后会对给其供电的电力系统带来谐波、三相不平衡等电能质量问题，不利于公用电网安全、经济运行。本文首先介绍了电气化铁路接入电网电能质量特性，主要对电气化铁路牵引负荷引起的两大主要电能质量问题谐波和负序进行详细分析；然后对电气化铁路接入电网后产生的谐波、负序对电力系统各环节的影响进行了总结；最后对目前常用的改善公用电网电能质量措施进行分类，为电气化铁路接入电网电能质量评估、治理提供参考依据。 Railway electrification has advantages such as high speed, heavy load, high energy utilization and good economic benefits. But the traction load of electrified railway is a high power, single phase and nonlinear load, its access to the grid will bring about power quality problems such as harmonics, three-phase imbalance which go against safe and economic operation of power system. Firstly after electrified railway connects to power system the characteristics of power quality are introduced in this paper. The main problems, harmonic and negative sequence caused by the traction load of electrified railway, are analyzed in detail. Then, the influence of harmonic and negative sequence on power system is summarized. Finally, the current measures to improve the power quality of the utility grid are classified. A reference is provided for the power quality evaluation and treatment after the electrified railway connects to power system.