Power quality and electromagnetic compatibility: special report, session 2

The scope of Session 2 (S2) has been defined as follows by the Session Advisory Group and the Technical Committee: Power Quality (PQ), with the more general concept of electromagnetic compatibility (EMC) and with some related safety problems in electricity distribution systems. Special focus is put on voltage continuity (supply reliability, problem of outages) and voltage quality (voltage level, flicker, unbalance, harmonics). This session will also look at electromagnetic compatibility (mains frequency to 150 kHz), electromagnetic interferences and electric and magnetic fields issues. Also addressed in this session are electrical safety and immunity concerns (lightning issues, step, touch and transferred voltages). The aim of this special report is to present a synthesis of the present concerns in PQ&EMC, based on all selected papers of session 2 and related papers from other sessions, (152 papers in total). The report is divided in the following 4 blocks: Block 1: Electric and Magnetic Fields, EMC, Earthing systems Block 2: Harmonics Block 3: Voltage Variation Block 4: Power Quality Monitoring Two Round Tables will be organised: - Power quality and EMC in the Future Grid (CIGRE/CIRED WG C4.24, RT 13) - Reliability Benchmarking - why we should do it? What should be done in future? (RT 15

VOLTAGE COMPENSATION USING ARTIFICIAL NEURAL NETWORK: A CASE STUDY OF RUMUOLA DISTRIBUTION NETWORK

 A study of hourly voltage log taken over a period of six months from Rumuola Distribution network Port Harcourt, Rivers State indicates that power quality problems prevalent in the Network are undervoltage/voltage sags and overvoltage/voltage swells. This paper aims at addressing these power quality problems in the distribution network using artificial neural network (ANN) controller based dynamic voltage restorer (DVR). The artificial neural networks controller engaged to controlling the dynamic voltage restorer were trained with input and output data of proportional integral (PI) controller and of unit amplitude generator obtained during simulation. All simulations and modeling were carried out in MathLab/Simulink. Proposed dynamic voltage restorer was tested with replicated model of Rumuola substation by simulating with sample of average voltage for Omerelu, Waterlines, Rumuola, Shell Industrial and Barracks feeders. Simulation results showed that DVR is effective in compensating for under-voltage and over-voltage in Rumuola Distribution network Port Harcourt, Rivers State. http://dx.doi.org/10.4314/njt.v36i1.2

Dynamic Voltage Restorer Application for Power Quality Improvement in Electrical Distribution System: An Overview

Dynamic Voltage Restorer (DVR) is a custom power device that is used to improve voltage disturbances in electrical distribution system. The components of the DVR consist of voltage source inverter (VSI), injection transformers, passive filters and energy storage. The main function of the DVR is used to inject three phase voltage in series and in synchronism with the grid voltages in order to compensate voltage disturbances. The Development of (DVR) has been proposed by many researchers. This paper presents a review of the researches on the DVR application for power quality Improvement in electrical distribution network. The types of DVR control strategies and its configuration has been discussed and may assist the researchers in this area to develop and proposed their new idea in order to build the prototype and controller

SIMULATION AND MITIGATION OF POWER QUALITY DISTURBANCES ON A DISTRIBUTION SYSTEM USING DVR

Voltage sag is the most important power quality problem faced by many industrial customers. Equipment such as process controllers, programmable logic controllers, adjustable speed drives, robotics, etc used in modern industrial plants are actually becoming more sensitive to voltage sags. Voltage sags are normally described by the magnitude variation and duration, and also characterized by unbalance, non-sinusoidal wave shape and phase angle shift. One of the most common mitigation solution is installing uninterrupted power supply (UPS). To meet the demand for more efficient mitigation solution, the Dynamic Voltage Restorer (DVR) will be deployed. When a fault occurs, either at the high voltage source end or at the consumer end, the DVR injects active and reactive power for the restoration of the voltage sags in the network. This thesis presents the power quality problems faced by the power distribution systems in general and then concentrates on analyzing an important and specific distribution system in particular. A dynamic voltage restorer (DVR) is connected on the 11KV of an utility feeder to Ipoh hospital, in reducing the voltage sags, that affect the operation of sensitive loads to the hospital. Case studies were conducted at four industrial sites (Hitachi plant and Nihoncanpack at Bemban, Filrex at Bercham and Ipoh Hospital) by monitoring and taking physical sag measurements for a period of one month. The real time measurements were carried out to identify the types power quality disturbances that exits in the various plants before providing the custom power device as a mitigation tool. The Ipoh Hospital is taken for a special case study since the hospital has to maintain high quality power supply to the medical equipments such as CT Scan, Magnetic Resonance Imaging (MRI), Magnetic Scanner, X-ray unit, and other life savingequipment. For simulation study, PSS/ADEPT and PSCAD/EMTDC software packages were used in modeling of the power distribution system. With the PSS/ADEPT simulation tool, the voltage severity is studied by introducing different types of faults. The PSCAD/EMTDC is a graphical user interface simulation tool to simulate sag waveforms for various types of faults. A DVR was modeled using the PSCAD/EMTDC software and simulated for voltage sag mitigation. The recorded waveform shows the DVR as a potential custom power solution provider. The DVR can improve the overall voltage regulation. The results obtained from the DVR show that the voltage sags are reduced by bringing the supply voltage level to 100%. The simulated results were verified for selected faults theoretically. v

Power quality enhancement in secondary electric power distr[i]bution networks using dynamic voltage restorer.

Doctoral Degree. University of KwaZulu-Natal, Durban.This research study investigates and proposes an effective and efficient method for improving voltage profile and mitigating unbalance voltage, voltage variation disturbances in rural and urban secondary distribution networks. It also proffers solutions for improving the performance of future distribution networks in order to increase the optimum functioning, security and quality of electricity supply to end users, thus making the power grid smarter. This study involves the compensation of power quality disturbance in balanced and unbalanced, short and long distribution networks. The mitigation of result of this voltage variation, poor voltage profile and voltage unbalance with an effective power electronics based custom power controller known as Dynamic Voltage Restorer (DVR) conceived. DVR is usually connected between the source voltage and customer load. An innovative new design-model of the DVR has been proposed and developed using a dq0 controller and proportional integral (PI) controller method. Model simulation was carried out using MATLAB/Simulink in Sim Power System tool box. An analysis of the results obtained when the new DVR is not connected to and tested on LV networks shows that the voltage profile, percentage voltage deviation and percentage voltage unbalance for 0.5 km for balanced and unbalanced distribution networks are within standards and acceptable limits, hence, the voltages are admissible for customers’ use. It was further established that the voltage profile, percentage voltage unbalance, voltage drop and percentage voltage deviation for distribution networks of 0.8 km to 5 km range from the beginning to the end of the feeder are less than the statutory voltage limits of -5%, 2 %, 5 % and ± 5 % respectively, hence, voltages are inadmissible for customers’ use. Others results obtained when DVR was connected recognized that for distribution feeder lengths of 0.5 km to 5 km range for balanced and unbalanced, short and long distribution networks the voltage profile, voltage variation, voltage drop and percentage voltage unbalance are within statutory voltage limits of 0.95 p.u and 1.05 p.u, -5 %, and less than 2 % respectively. Based on this investigation, and in order to achieve efficient, reliable and cost-effective techniques for improving voltage profiles, decreasing voltage variations and reducing voltage unbalances, the new DVR model is recommended for enhancing optimal performances of secondary distribution networks

Modeling and Simulation of a Dynamic Voltage Restorer (DVR)

Power quality is one of major concerns in the present era. It has become important, especially, with the introduction of sophisticated devices, whose performance is very sensitive to the quality of power supply. Power quality problem is an occurrence manifested as a nonstandard voltage, current or frequency that results in a failure of end use equipments. One of the major problems dealt here is the power sag. To solve this problem, custom power devices are used. One of those devices is the Dynamic Voltage Restorer (DVR), which is the most efficient and effective modern custom power device used in power distribution networks. Its appeal includes lower cost, smaller size, and its fast dynamic response to the disturbance. This paper presents modeling, analysis and simulation of a Dynamic Voltage Restorer (DVR) using MATLAB. In this model a PI controller and Discrete PWM pulse generator was used

Power Quality

Electrical power is becoming one of the most dominant factors in our society. Power generation, transmission, distribution and usage are undergoing signifi cant changes that will aff ect the electrical quality and performance needs of our 21st century industry. One major aspect of electrical power is its quality and stability – or so called Power Quality. The view on Power Quality did change over the past few years. It seems that Power Quality is becoming a more important term in the academic world dealing with electrical power, and it is becoming more visible in all areas of commerce and industry, because of the ever increasing industry automation using sensitive electrical equipment on one hand and due to the dramatic change of our global electrical infrastructure on the other. For the past century, grid stability was maintained with a limited amount of major generators that have a large amount of rotational inertia. And the rate of change of phase angle is slow. Unfortunately, this does not work anymore with renewable energy sources adding their share to the grid like wind turbines or PV modules. Although the basic idea to use renewable energies is great and will be our path into the next century, it comes with a curse for the power grid as power fl ow stability will suff er. It is not only the source side that is about to change. We have also seen signifi cant changes on the load side as well. Industry is using machines and electrical products such as AC drives or PLCs that are sensitive to the slightest change of power quality, and we at home use more and more electrical products with switching power supplies or starting to plug in our electric cars to charge batt eries. In addition, many of us have begun installing our own distributed generation systems on our rooft ops using the latest solar panels. So we did look for a way to address this severe impact on our distribution network. To match supply and demand, we are about to create a new, intelligent and self-healing electric power infrastructure. The Smart Grid. The basic idea is to maintain the necessary balance between generators and loads on a grid. In other words, to make sure we have a good grid balance at all times. But the key question that you should ask yourself is: Does it also improve Power Quality? Probably not! Further on, the way how Power Quality is measured is going to be changed. Traditionally, each country had its own Power Quality standards and defi ned its own power quality instrument requirements. But more and more international harmonization efforts can be seen. Such as IEC 61000-4-30, which is an excellent standard that ensures that all compliant power quality instruments, regardless of manufacturer, will produce of measurement instruments so that they can also be used in volume applications and even directly embedded into sensitive loads. But work still has to be done. We still use Power Quality standards that have been writt en decades ago and don’t match today’s technology any more, such as fl icker standards that use parameters that have been defi ned by the behavior of 60-watt incandescent light bulbs, which are becoming extinct. Almost all experts are in agreement - although we will see an improvement in metering and control of the power fl ow, Power Quality will suff er. This book will give an overview of how power quality might impact our lives today and tomorrow, introduce new ways to monitor power quality and inform us about interesting possibilities to mitigate power quality problems. Regardless of any enhancements of the power grid, “Power Quality is just compatibility” like my good old friend and teacher Alex McEachern used to say. Power Quality will always remain an economic compromise between supply and load. The power available on the grid must be suffi ciently clean for the loads to operate correctly, and the loads must be suffi ciently strong to tolerate normal disturbances on the grid

Hybrid three-phase rectifiers with active power factor correction: a systematic review

The hybrid three-phase rectifiers (HTR) consist of parallel associations of two rectifiers (rectifier 1 and rectifier 2), each one of them with a distinct operation, while the sum of their input currents forms a sinusoidal or multilevel waveform. In general, the rectifier 1 is a GRAETZ (full bridge) (can be combined with a BOOST converter) and the rectifier 2 combined with a DC-DC converter. In this HTR contest, this paper is intended to answer some important questions about those hybrid rectifiers. To obtain the correct answers, the study is conducted as an analysis of a systematic literature review. Thus, a search was carried out in the databases, mostly IEEE and IET, and 34 papers were selected as the best corresponding to the HTR thematic. It is observed that the preferred form of power distribution in a unidirectional hybrid three-phase rectifiers (UHTR) is 〖55%P〗_o (rectifier 1) and 〖45%P〗_o (rectifier 2). For the bidirectional hybrid three-phase rectifiers (BHTR) the rectifier 1 preferably takes 〖90% of P〗_o and 〖10% of P〗_o are processed by rectifier 2. It is also observed that the UHTR that employ the single-ended primary-inductor converter (SEPIC) or VIENNA converter topologies in their rectifier 2, can present sinusoidal input currents with low total harmonic distortion (THD) and high Power Factor (PF), even succeeding to comply with the international standards. The same can be said about the rectifier that employs a pulse-width (PWM) converter of BOOST topology in rectifier 2. In short, the HTR are interesting because they allow to use the GRAETZ full bridge topology in rectifier 1, thus taking advantage of its characteristics, being simple, robust and reliable. At the same time, the advantages of rectifier 2, i.e., high PF and low THD are well used. In addition, this article also points out the future direction of research that is still unexplored in the literature, thus giving opportunities for future innovation

Online Control of Modular Active Power Line Conditioner to Improve Performance of Smart Grid

This thesis is explored the detrimental effects of nonlinear loads in distribution systems and investigated the performances of shunt FACTS devices to overcome these problems with the following main contribution: APLC is an advanced shunt active filter which can mitigate the fundamental voltage harmonic of entire network and limit the THDv and individual harmonic distortion of the entire network below 5% and 3%, respectively, as recommended by most standards such as the IEEE-519