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

Optimised design of isolated industrial power systems and system harmonics

This work has focused on understanding the nature and impact of non-linear loads on isolated industrial power systems. The work was carried out over a period of 8 years on various industrial power systems: off-shore oil and gas facilities including an FPSO, a wellhead platform, gas production platforms, a mineral processing plant and an LNG plant. The observations regarding non-linear loads and electrical engineering work carried out on these facilities were incorporated into the report.A significant literature describing non-linear loads and system harmonics on industrial power systems was collected and reviewed. The literature was classified into five categories: industrial plants and system harmonics, non-linear loads as the source of current harmonics, practical issues with system harmonics, harmonic mitigation strategies and harmonic measurements.Off-shore oil and gas production facilities consist of a small compact power system. The power system incorporates either its own power generation or is supplied via subsea cable from a remote node. Voltage selection analysis and voltage drop calculation using commercially available power system analysis software are appropriate tools to analyse these systems. Non-linear loads comprise DC rectifiers, variable speed drives, UPS systems and thyristor controlled process heaters. All nonlinear loads produce characteristic and non-characteristic harmonics, while thyristor controlled process heaters generate inter-harmonics. Due to remote location, harmonic survey is not a common design practice. Harmonic current measurements during factory acceptance tests do not provide reliable information for accurate power system analysis.A typical mineral processing plant, located in a remote area includes its own power station. The power generation capacity of those systems is an order of magnitude higher than the power generation of a typical off-shore production facility. Those systems comprise large non-linear loads generating current and voltage interharmonics. Harmonic measurements and harmonic survey will provide a full picture of system harmonics on mineral processing plants which is the only practical way to determine system harmonics. Harmonic measurements on gearless mill drive at the factory are not possible as the GMD is assembled for the first time on site.LNG plants comprise large non-linear loads driving gas compressor, however those loads produce integer harmonics. Design by analysis process is an alternative to the current design process based on load lists. Harmonic measurements and harmonic survey provide a reliable method for determining power system harmonics in an industrial power system

Power Quality Issues in Distributed Generation

This book deals with several selected aspects of electric power quality issues typically faced during grid integration processes of contemporary renewable energy sources. In subsequent chapters of this book the reader will be familiarized with the issues related to voltage and current harmonics and inter-harmonics generation and elimination, harmonic emission of switch-mode rectifiers, reactive power flow control in power system with non-linear loads, modeling and simulation of power quality issues in power grid, advanced algorithms used for estimating harmonic components, and new methods of measurement and analysis of real time accessible power quality related data

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

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

Two methods for controlling three-time fundamental frequency neutral-point voltage oscillation in a hybrid VIENNA rectifier

This study presents two methods of controlling neutral-point voltage oscillation in a hybrid VIENNA rectifier, which is composed of the parallel association of a three-phase single-switch Boost rectifier with a VIENNA-type rectifier. The neutral-point oscillation reason has been analysed with a mathematical model. Meanwhile, the two neutral-point control methods of a simplified method based on a zero-sequence component injection and a dual-carrier pulse-width modulation (PWM) method are proposed to control the voltage deviation of the split DC-link and three-time fundamental frequency neutral-point voltage fluctuation with a decrease from ±1.6 to ±1 V, respectively. Moreover, the significant oscillation in the neutral-point voltage caused by unbalanced loads or asymmetric capacitor parameters can also be effectively suppressed by using the dual-carrier PWM method. Furthermore, the performance comparison between these two methods is provided. The experimental results show that the system after being introduced the proposed two methods still exhibits a low-order input current harmonic such as second, third, and fourth harmonics as well as the input current total harmonic distortion is lower than the standard 5%

Desenvolvimento de um Retificador Trifásico Híbrido Unidirecional com Conversor Boost

O trabalho apresentado neste documento incide sobre o tema do desenvolvimento de um retificador trifásico híbrido unidirecional com conversor Boost. O retificador trifásico híbrido (RTH) com conversor Boost é constituído por dois retificadores (retificador 1 e 2) e transformador de isolamento na entrada de cada fase do retificador 2, de forma a mitigar as interações de corrente. A mesma configuração sem os transformadores de isolamento é considerada inviável devido às interações de corrente entre os módulos do retificador 2. O RTH permite combinar as vantagens do retificador 1 (ponte GRAETZ) com as vantagens do retificador 2 (correção do fator de potência), apresentando vantagens em diversas aplicações. Analisando o RTH com conversor Boost e transformador de isolamento, existente na literatura, está provado que essa solução "clássica" apresenta maior peso, volume e elevado custo. Sendo assim, torna interessante e desafiador projetar um RTH com conversor Boost sem o transformador de isolamento. Assim, é proposto o RTH aqui descrito, com conversor Boost, mas sem transformador de isolamento. Para tal, foi necessário substituir o indutor Boost de cada módulo do retificador 2, pelo indutor acoplado. Uma simulação preliminar do RTH proposto foi executada no software PSIM (20 kW). Foi construído um protótipo do retificador trifásico (RT) modular com conversor Boost e correção do fator de potência (PF), i.e., retificador 2 do RTH proposto, de 3 kW, com objetivo de validar a mitigação da interação de corrente. Os resultados do RTH proposto, pela simulação, mostram não haver interação de corrente e funciona de forma correta, tendo apresentado um elevado PF de 99,92% e baixa distorção harmónica total (THD) de 3,96%. De igual modo, o protótipo do RT modular também mostrou não haver interação de corrente entre as fases e um funcionamento ao previsto, tendo apresentado um elevado PF (99,8%) e baixo valor da THD (3,7%). Assim, fica comprovado que é possível implementar um RTH com conversor Boost e indutor acoplado.The work presented in this document focuses on the development of a three-phase unidirectional hybrid rectifier with Boost converter. The three-phase hybrid rectifier (RTH) with Boost converter is composed of two rectifiers (rectifier 1 and 2) and isolation transformer at the input of each phase of rectifier 2, to mitigate current interactions. The same configuration without isolation transformers is considered unfeasible due to current interactions between rectifier 2 modules. RTH allows combining the advantages of rectifier 1 (GRAETZ bridge) with the advantages of rectifier 2 (power factor correction), thus presenting advantages in several applications. Analyzing the RTH, based on Boost converter with an isolation transformer existing in the literature, it is proved that this "classic" solution presents a heavier weight, larger volume, and higher cost. Therefore, it turns up more interesting and challenging to design an RTH with Boost converter, without the isolation transformer. Thus, an RTH with a Boost converter, but without the isolation transformer, is here proposed. For this, it was necessary to replace the Boost inductor of each module of rectifier 2, with a coupled inductor. The proposed RTH implementation was first simulated in PSIM software (20 kW). A prototype of the modular three-phase rectifier with Boost converter and power factor (PF) corrector, i.e., the rectifier 2 of the proposed RTH of 3 kW, was also built, to validate the mitigation of current interaction. The proposed RTH results simulations show that there is no current interaction and work correctly, having presented a high power factor of 99.92% and low total harmonic distortion (THD) of 3.96%. Likewise, the modular three-phase rectifier prototype also is showing no current interaction between phases and equal to the previewed operation, having presented a high PF (99.8%) and low THD value (3.7%). Thus, it is proved that it is possible to implement an RTH with Boost converter and coupled inductor

A comprehensive study of key Electric Vehicle (EV) components, technologies, challenges, impacts, and future direction of development

Abstract: Electric vehicles (EV), including Battery Electric Vehicle (BEV), Hybrid Electric Vehicle (HEV), Plug-in Hybrid Electric Vehicle (PHEV), Fuel Cell Electric Vehicle (FCEV), are becoming more commonplace in the transportation sector in recent times. As the present trend suggests, this mode of transport is likely to replace internal combustion engine (ICE) vehicles in the near future. Each of the main EV components has a number of technologies that are currently in use or can become prominent in the future. EVs can cause significant impacts on the environment, power system, and other related sectors. The present power system could face huge instabilities with enough EV penetration, but with proper management and coordination, EVs can be turned into a major contributor to the successful implementation of the smart grid concept. There are possibilities of immense environmental benefits as well, as the EVs can extensively reduce the greenhouse gas emissions produced by the transportation sector. However, there are some major obstacles for EVs to overcome before totally replacing ICE vehicles. This paper is focused on reviewing all the useful data available on EV configurations, battery energy sources, electrical machines, charging techniques, optimization techniques, impacts, trends, and possible directions of future developments. Its objective is to provide an overall picture of the current EV technology and ways of future development to assist in future researches in this sector

Efficacy of Smart PV Inverter as a Strategic Mitigator of Network Harmonic Resonance and a Suppressor of Temporary Overvoltage Phenomenon in Distribution Systems

The research work explores the design of Smart PV inverters in terms of modelling and investigates the efficacy of a Smart PV inverter as a strategic mitigator of network harmonic resonance phenomenon and a suppressor of Temporary Overvoltage (TOV) in distribution systems. The new application and the control strategy of Smart PV inverters can also be extended to SmartPark-Plug in Electric Vehicles as the grid becomes smarter. As the grid is becoming smarter, more challenges are encountered with the integration of PV plants in distribution systems. Smart PV inverters nowadays are equipped with specialized controllers for exchanging reactive power with the grid based on the available capacity of the inverter, after the real power generation. Although present investigators are researching on several applications of Smart PV inverters, none of the research-work in real time and in documentation have addressed the benefits of employing Smart PV inverters to mitigate network resonances. U.S based standard IEEE 519 for power quality describes the network resonance as a major contributor that has an impact on the harmonic levels. This dissertation proposes a new application for the first time in utilizing a Smart PV inverter to act as a virtual detuner in mitigating network resonance. As a part of the Smart PV inverter design, the LCL filter plays a vital role on network harmonic resonance and further has a direct impact on the stability of the controller and rest of the distribution system. Temporary Overvoltage (TOV) phenomenon is more pronounced especially during unbalanced faults like single line to ground faults (SLGF) in the presence of PV. Such an abnormal incident can damage the customer loads. IEEE 142-“Effective grounding” technique is employed to design the grounding scheme for synchronous based generators. The utilities have been trying to make a PV system comply with IEEE 142 standard as well. Several utilities are still employing the same grounding schemes even now. The attempt has resulted in diminishing the efficacy of protection schemes. Further, millions of dollars and power has been wasted by the utilities. As a result, the concept of effective grounding for PV system has become a challenge when utilities try to mitigate TOV. With an intention of economical aspects in distribution systems planning, this dissertation also proposes a new application and a novel control scheme for utilizing Smart PV/Smart Park inverters to mitigate TOV in distribution systems for the first time. In other words, this novel application can serve as an effective and supporting schema towards ineffective grounding systems. PSCAD/EMTDC has been used throughout the course of research. The idea of Smart inverters serving as a virtual detuner in mitigating network harmonic resonance and as a TOV suppressor in distribution systems has been devised based on the basic principle of VAR injection and absorption with a new control strategy respectively. This research would further serve as a pioneering approach for researchers and planning engineers working in distribution systems

Power quality requirements and responsibilities at the point of connection

In the present power delivery environment, electricity as a product has become more competitive than before. Modern electrical devices are complex in terms of their functionalities and are more sensitive to the quality of the supplied electricity. A disturbance in supply voltage can cause significant financial losses for an industrial customer. Moreover, there are increasing number of disputes in different countries of the world among the network operators, the customers and the device manufacturers regarding their individual responsibility concerning 'Power Quality' (PQ) problems and solutions. In addition, the existing standards on PQ give very limited information about responsibility sharing among the involved parties. PQ disturbances can be originated in the network as well as at the customer's premises and can propagate to other parts of the network. The PQ level in the network is also highly influenced by PQ emission behaviors of customer's devices and the network characteristics. During the last decades, PQ related complaints have increased largely. Inadequate PQ can lead to various technical and financial inconveniences to the customers and the network operators. This research aims to find out a socio-economically optimum solution to PQ problems. The main objectives of this thesis are defined as: "Analyze main PO problems and their consequences to various involved parties in the network. Next, define optimal PQ criteria at the customer's point of connection (POC) and finally specify responsibilities of the involved parties". The thesis is based on practical field measurements of PQ parameters in the network, on analyzing the developed network models by using computer simulations and laboratory experiments. The most important part of the work is the verification of simulation results with thepractical measurements. Further, the obtained results are compared with the values given in the available standards. Lastly optimal PQ parameters at a poc are defined for flicker, harmonics and voltage dips. A summary of the research work reported in this thesis is as follows: • Obtained a deeper insight in PQ problems around the world • Developed typical network models for computer simulations on different PQ phenomena (such as flicker, harmonics and voltage dips) and verified the results with field measured data • Gathered practical information on various technical and financial consequences of inadequate PQ for different parties namely: the network operators, the customers and the equipment manufacturers • Made an inventory on various existing (and developing) standards and technical documents on PQ around the world. Then, compared the limits given on various PQ parameters in those standards/documents and discussed their relevance and applicability in the future • A proposal is given about optimal PQ limits (for flicker, harmonics) at the low voltage (LV) customer's POC Also, the average and maximum values of voltage dips in the networks are estimated • Suitable planning level limit values for flicker, harmonics and voltage dips are proposed • PQ related responsibilities of the customers, network operators and device manufacturer at the customer's POC are defined The main conclusions and thesis contributions are: • It is found that a harmonization among the presently available PQ standards is required and a dedicated set of global standards is needed to get optimal PQ at the customer's POC Various limiting values on different PQ parameters (e.g. flicker emission and harmonic current emission limits for a customer) at a POC are proposed in this thesis. Also, the average and maximum numbers of voltage dips in the Dutch high voltage (HV) and medium voltage (MV) networks are estimated. • A new set of planning level values for flicker severities at different voltage levels of a network is proposed. For harmonics, a proposal is given to change the planning level values for 'triple n' harmonic voltages and new values are suggested for the MV and LV networks. Moreover, it was proposed that the 3rd harmonic summation coefficient value of the standard can be modified to a higher value as sufficient diversity is found in the system. Regarding voltage dips, the numbers of planning and compatibility levels are proposed for a MV network in the Netherlands. In this thesis, PQ responsibility sharing procedures are defined for a network operator, customer and a device manufacturer. Network impedance is identified as an important parameter in deciding flicker and harmonics at a POC The network operator should provide information on the approximate number of occurrence of voltage dips in a year at a customer's POC To maintain sufficient PQ level in the network, all the involved parties should follow certain rules and duties. It was concluded that PQ regulation can be successfully implemented in the electricity business when all the involved parties are aware of their respective responsibilities in the network