1,583 research outputs found

    New advanced methods for the spectral analysis of time-varying waveforms in power systems

    Get PDF
    This thesis presents new advanced methods for the spectral analysis of time-varying waveforms in power systems. First, the main non-parametric, parametric and hybrid methods are presented in details under an analytical review of the state of the art, stressing both their advantages and their weaknesses. Then, a new advanced modified parametric method and three new advanced hybrid methods are presented in this thesis. All of the proposed methods guarantee an accuracy typical of the parametric methods, though with a significantly lower computational efforts

    Interharmonics Analysis and Mitigation in Adjustable Speed Drives

    Get PDF

    Software Algorithms to Coordinate and Improve Voltage Sag Ridethrough Capabilities of Networked Industrial Processes

    Get PDF
    For those who design, operate, and troubleshoot industrial processes, electric power quality is a subject that requires much consideration. Processes that use electronic sensors, actuators, and computation devices are heavily reliant on a stable, consistent input power source. When a power quality event such as a voltage fluctuation occurs, automation equipment often behaves unpredictably and causes process malfunction or failure. Because industrial power consumers often blame their electric utility for these events, some utilities offer process susceptibility studies as a service for their customers. During a typical study, utility technicians and engineers perform in-house tests on suspect components or systems using voltage sag generating equipment. These tests determine device malfunction thresholds and establish an event failure timeline. Test results provide data for applying mitigation solutions, where the most critical or susceptible loads receive a higher priority for improvement. While effective, this approach often requires the addition of costly hardware. This study presents novel software algorithms that coordinate and improve process ridethrough capabilities of network connected industrial processes. An add-on PC interfacing with an automation network executes a routine that detects voltage sags, performs a fast measurement of sag parameters, and determines an expected process response. Rather than implement a `cure all\u27 reaction for every disturbance scenario, mitigation routines are executed based upon the expected response. Underlying design constraints of this study are to minimize or avoid the installation of conventional ridethrough hardware and adhere to a software architecture that is unintrusive to existing controllers. Voltage sag detection is performed with a real-time analysis of incoming voltages and is triggered from RMS voltage derivative threshold crossings. Having recognized the presence of a voltage sag, the algorithm determines the sag magnitude with a peak detection method, and can associate the measured magnitude/phase combination with previously recorded process data. Either the sag characteristics or historical process response data is then analyzed to determine the expected process response. Sags that can potentially force motor drives to trip offline cause the process to respond to an expected shutdown. Voltage sag magnitude/phasing combinations that have been shown to cause no process disruption are ignored. Combinations which have caused only instrument signal corruption and significant process variable deviations trigger the mitigation routine to address faulted control signals only. Drive fault mitigation responses consist of a software-only drive coast routine and an improved drive coast routine requiring the addition of basic switching hardware. Out of tolerance process errors are mitigated with output control command substitution or input signal substitution routines. Verification of software functionality is achieved with an experimental automated process - - a textile unwind/rewind system that operates at a controlled linespeed and tension. Detailed analysis and simulation is performed on both component and system-wide levels. Unmitigated and mitigated process voltage sag responses are recorded and matched with the theoretical process model. Although customization is required to apply the algorithms to the specific design of the textile tension control process, experimentation with this test bed system serves as a satisfactory proof of concept for the software routines. As a result, the methods developed in this study can improve the task of process power quality mitigation by customizing solutions for individual processes, avoiding the application of power quality mitigation solutions where they are not required, coordinating corrective actions by utilizing existing automation network functionality, and ultimately reducing the need for costly hardware installation and maintenance

    Power quality analysis for renewable power generation in household

    Get PDF
    Power quality is becoming essential part of Power Industry. The introduction of smarter and more sensitive equipment at both grid and residential level has created performance issues that need investigation. The cost of the power losses is rising due to power quality problems. The other significant factor that is proving vital is the customer dissatisfaction. The introduction of Renewable Energy (RE) into modern grids has also created Power Quality (PQ) problems. A study is required to narrow down the factors that can cause these PQ issues. The power companies are buying electricity back from the consumer produced by these RE sources. The power produced by RE sources coming into the electrical grid needs to be monitored. The research will focus on the factors that impact PQ especially the Total Harmonic Distortion in a electrical grid powered by renewable sources. The factors impacting power quality will be studied in detail by using an simulation approach aided by an experimental set up. The simulation approach will be used to test the hypothesis that total harmonic distortion increases by changing the nature and size of the load in the electrical system. The load type used for the research will be linear and nonlinear loads. The simulation will use single and three phase electrical system. The simulation results will be analysed and discussed. The experimental setup will be used to verify the simulation result. The experiment will be conducted on different set of load to observe the impact on the total harmonic distortion in particular. The experimental result will be collected over period of time enabling the researcher to study in detail the impact of weather, temperature, and inclination of solar panels. These factors will impact the research result. The collected data will be presented for discussion

    Power quality analysis for renewable power generation in household

    Get PDF
    Power quality is becoming essential part of Power Industry. The introduction of smarter and more sensitive equipment at both grid and residential level has created performance issues that need investigation. The cost of the power losses is rising due to power quality problems. The other significant factor that is proving vital is the customer dissatisfaction. The introduction of Renewable Energy (RE) into modern grids has also created Power Quality (PQ) problems. A study is required to narrow down the factors that can cause these PQ issues. The power companies are buying electricity back from the consumer produced by these RE sources. The power produced by RE sources coming into the electrical grid needs to be monitored. The research will focus on the factors that impact PQ especially the Total Harmonic Distortion in a electrical grid powered by renewable sources. The factors impacting power quality will be studied in detail by using an simulation approach aided by an experimental set up. The simulation approach will be used to test the hypothesis that total harmonic distortion increases by changing the nature and size of the load in the electrical system. The load type used for the research will be linear and nonlinear loads. The simulation will use single and three phase electrical system. The simulation results will be analysed and discussed. The experimental setup will be used to verify the simulation result. The experiment will be conducted on different set of load to observe the impact on the total harmonic distortion in particular. The experimental result will be collected over period of time enabling the researcher to study in detail the impact of weather, temperature, and inclination of solar panels. These factors will impact the research result. The collected data will be presented for discussion

    Enhance OF SOGI-FLL and SOGI-PLL response to voltage sags and swells perturbations

    Get PDF
    The scope of this thesis is related to the enhancement of the operation of distributed generators (DGs) based on renewable energies (REs) when connected to the conventional grid network. Synchronization of those DGs, i.e. their front-end inverters, with the grid is critical for injecting power into the grid. Internal control loops of voltage source inverters (VSIs) monitor parameters such as the utility voltage's phase, amplitude, and frequency to achieve proper synchronization and inject power into the grid. Therefore, an appropriate estimation of the grid parameters is needed for completing the mentioned goals. The different existing monitoring techniques still face technical challenges when appearing faults on the grid, particularly voltage sags and voltage swells. From those techniques, SOGI-FLL and SOGI-PLL are widely spread in power inverters. In the mentioned faulty conditions, a degradation of the estimated parameters occurs due to the impact of the grid defaults on the dynamic performance of the SOGI-FLL and SOGI-PLL estimators. In the literature, it was not found contributions to those problems. This research aimed to contribute by providing a fast and accurate detection of the faults, yielding a robust dynamical response of the VSIs control structure in front of such perturbations, thanks to a fast and precise estimation of grid parameters. This faults detection strategy was accompanied by minimization of the monitored parameters drift due to inherent harmonic pollution of the faults. Then a first contribution has been the design and implementation of a Finite State Machine on a synchronization structure known as SOGI-PLL and in SOGI-FLL, enhancing their dynamical response regarding transient time and steady-state response in front of voltage sags. A second contribution has been implementing the strategy to face the problems derived from voltage swells with satisfactory results. The research was carried out in the E3PACS laboratory facilities of EEBE-UPC. This work is organized as follows: In Section 1, the study is contextualized. Section 2 describes Power Quality indexes benchmarking for assessing the problem to solve and the obtained results. It is then followed by Section 3, where the SOGI-FLL response against voltage sags and swells is analyzed. Therefore, Section 4 summarizes the different approaches and results for mitigating the grid faults studied. Section 5 is devoted to showing SOGI-PLL amelioration by applying SOGI Error-Based algorithm. Finally, Section 6 summarizes the main contributions of this work, along with the general conclusions. Section 7 lists future work, in Section 8 are listed the published JCR indexed papers.L'abast d'aquesta tesi està relacionat amb la millora del funcionament dels generadors distribuïts (DG, distributed generation en anglès) basats en energies renovables quan es connecten a la xarxa elèctrica convencional. La sincronització d'aquests DG amb la xarxa és fonamental per injectar energia a aquesta, especialment quan es tracta d'inversors de potència. Els llaços de control interns dels inversors de font de tensió (VSI, Voltage Source Inverters en anglès) controlen paràmetres com ara la fase, l'amplitud i la freqüència de la tensió de la xarxa per aconseguir una sincronitzaciórequerida. Per tant, es necessita una estimació adequada dels paràmetres del bus de tensió per assolir els objectius esmentats. Les diferents tècniques de monitorització existents encara s'enfronten a reptes tècnics a l'hora d'aparèixer fallades a la xarxa, especialment caigudes i augments abruptes de tensió ("Voltage sags" i "Voltage swells" en anglès, respectivament). En el cas dels inversors, les tècniques basades en estructures SOGI-FLL i SOGI-PLL estan àmpliament esteses i, en les esmentades condicions de fallada, es produeix una degradació dels paràmetres estimats a causa de l'impacte dels defectes de la xarxa en el seu comportament dinàmic . A la literatura, no es van trobar contribucions rellevants per mitigar aquests problemes. Aquesta investigació pretén doncs contribuir proporcionant una detecció ràpida i precisa de les fallades, donant una resposta dinàmica robusta de l'estructura de control dels VSI davant d'aquestes pertorbacions, gràcies a una estimació ràpida i precisa dels paràmetres de la xarxa. Aquesta estratègia de detecció de fallades s'acompanya de la minimització de la deriva dels paràmetres monitoritzats a causa de la contaminació harmònica inherent de les fallades. Així doncs, una primera contribució ha estat el disseny i la implementació d'una màquina d'estats finits en una estructura de sincronització coneguda com SOGI-PLL i en SOGI-FLL, millorant la seva resposta dinàmica pel que fa al temps transitori i la resposta en estat estacionari davant les caigudes de tensió. Una segona aportació ha estat la implementació de l'estratègia per afrontar amb resultats satisfactoris els problemes derivats de les pujades de tensió (voltage swells). La investigació es va dur a terme a les instal·lacions del laboratori E3PACS de l'EEBE-UPC. Aquest treball s'organitza de la següent manera: A l'apartat 1 es contextualitza l'estudi. La secció 2 descriu el la referenciació dels índexs de qualitat de l'energia per avaluar el problema a resoldre i els resultats obtinguts. A continuació, segueix la Secció 3, on s'analitza la resposta SOGI-FLL contra les caigudes i les inflors de tensió. Per tant, la Secció 4 resumeix els diferents enfocaments i resultats per mitigar les falles de la xarxa estudiades. La secció 5 està dedicada a mostrar la millora SOGI-PLL aplicant l'algorisme SOGI basat en errors. Finalment, l'apartat 6 resumeix les principals aportacions d'aquest treball, juntament amb les conclusions generals. La secció 7 enumera els treballs futurs, a la secció 8 s'enumeren els articles indexats JCR publicats.Postprint (published version

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

    Get PDF
    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

    Optimised design of isolated industrial power systems and system harmonics

    Get PDF
    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
    corecore