Modelling and performance evaluation of a pseudo-random impulse sequence for in situ parameter estimation in energy applications
dc.contributor.advisor | Vermeulen, H. J. | en_ZA |
dc.contributor.author | Mwaniki, Frederick Mukundi | en_ZA |
dc.contributor.other | Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering. | en_ZA |
dc.date.accessioned | 2020-02-25T08:54:28Z | |
dc.date.accessioned | 2020-04-28T12:10:47Z | |
dc.date.available | 2020-02-25T08:54:28Z | |
dc.date.available | 2020-04-28T12:10:47Z | |
dc.date.issued | 2020-03 | |
dc.description | Thesis (PhD)--Stellenbosch University, 2020. | en_ZA |
dc.description.abstract | ENGLISH ABSTRACT: System identification and parameter estimation procedures involve the use of experiments to find an accurate model for a target system. These experiments typically involve excitation of the target system with a perturbation signal and recording and analysing the system’s input and output waveforms. The time- and frequency-domain characteristics of the perturbation signal can have a significant influence on the system response and the accuracy of the parameter estimation experiment. An optimal perturbation signal should persistently excite all the relevant modes of the target system. Although a significant amount of research has been carried out on perturbation signals, the case of a suitable signal for high power, high voltage, in situ applications has not been thoroughly investigated. This study discusses the novel concept of a Pseudo-Random Impulse Sequence (PRIS) as a wideband perturbation signal for in situ parameter estimation in energy field applications. The time- and frequency-domain properties of the PRIS are analyzed and the effects of the various model parameters, including the time constants, sequence length and clock frequency are investigated through mathematical analysis and simulations to determine the suitability of the signal for system identification and parameter estimation applications. It is demonstrated that the time- and frequency-domain properties of the PRIS can be controlled by manipulating the associated clock frequency, time constants and sequence length. This controllability of the PRIS is highly desirable as it allows the user to focus the perturbation energy to suit a wide range of applications. Perturbation signals for use in the high power applications should be generated efficiently using circuit topologies that are compatible with the associated high voltage environment. A perturbation source circuit topology for generating the proposed PRIS signal is developed and analysed. It is shown that the PRIS can be generated using a compact and efficient design with highly reduced average losses compared to conventional sources such as the Pseudo-Random Binary Sequence (PRBS) topologies. The circuit topology is, furthermore, demonstrated to be optimal for in situ high power, high voltage applications. The circuit design considerations for the proposed PRIS source are discussed in detail. Accurate information on the grid impedance characteristics, especially from a particular Point of Connection (POC) is essential for harmonic penetration studies, compliance with harmonic limits for the grid integration of renewable energy sources, transient analysis, harmonic filter design and controller design. The performance of the PRIS signal is demonstrated successfully for an in situ case study application involving wideband characterization of the The venin equivalent grid impedance of a supply network. A novel experimental approach is proposed to improve the grid impedance estimation results by minimizing the effects of the non-stationary nature of the grid. | en_ZA |
dc.description.abstract | AFRIKAANSE OPSOMMING: Stelselidentifikasie en parameterberamingsprosedures behels die gebruik van eksperimente om ’n akkurate model vir ’n teikensisteem te vind. Hierdie eksperimente behels tipies die aandryf van die teikenstelsel met ’n steursein en die opname en ontleding van die stelsel se intree- en uittreegolfvorms. Die tyd- en frekwensiegebied eienskappe van die steursein kan ’n beduidende invloed hê op die stelselweergawe en die akkuraatheid van die parameterestimasie eksperiment. ’n Optimale steursein moet al die relevante modusse van die teikenstelsel volhoudend aktiveer. Alhoewel ’n beduidende hoeveelheid navorsing oor steurseine uitgevoer is, is die geval van ’n geskikte sein vir hoëdrywing, hoogspanning, in situ toepassings nie deeglik ondersoek nie. In hierdie studie word die nuwe konsep van ’n Kwasie-Lukrake Impuls Reeks (KLIR) as ’n wyeband steursein vir in situ parameter afskatting in energie toepassings bespreek. Die tyd- en frekwensiegebied eienskappe van die KLIR word ontleed en die uitwerking van die verskillende modelparameters, insluitende die tydkonstantes, reekslengte en klokfrekwensie, word ondersoek deur wiskundige analise en simulasies om die geskiktheid van die sein vir stelselidentifisering en parameterafskatting te b epaal. Daar word gedemonstreer dat die tyd- en frekwensiegebied eienskappe van die KLIR beheer kan word deur die gepaardgaande klokfrekwensie, tydkonstantes en reekslengte te manipuleer. Hierdie beheerbaarheid van die KLIR is uiters wenslik, aangesien dit die gebruiker in staat stel om die steurenergie te fokus om ’n wye verskeidenheid toepassings te pas. Steurseine vir gebruik in die hoëdrywing toepassings moet doeltreffend opgewek word deur gebruik te maak van stroombaantopologieë wat versoenbaar is met die gepaardgaande hoogspanningsomgewing. ’n stroombaantopologie vir die opwekking van die voorgestelde KLIR sein word ontwikkel en ontleed. Daar word aangetoon dat die KLIR opgewek kan word met ’n kompakte en effektiewe ontwerp met hoogs verminderde gemiddelde verliese in vergelyking met konvensionele bronne soos die Kwasi-Lukrake Binêre Reeks (KLBR) topologieë. Verder word aangetoon dat die stroombaantopologie optimaal is vir in situ hoëdrywing, hoogspanning toepassings. Die stroombaan ontwerpsoorwegings vir die voorgestelde KLIR bron word breedvoerig bespreek. Akkurate inligting oor die netwerk impedansie-eienskappe, veral vanuit ’n bepaalde punt van verbinding, is noodsaaklik vir harmoniese penetrasiestudies, die nakoming van harmoniese limiete vir die netwerkintegrasie van hernubare energiebronne, dinamiese analise, harmoniese filterontwerp en die ontwerp van beheerstelsels. Die gedrag van die KLIR sein word suksesvol gedemonstreer vir ’n in situ gevallestudie toepassing wat die wyebandkarakterisering van die Thevenin ekwivalente netwerkimpedansie van ’n toevoernetwerk behels. ’n Nuwe eksperimentele benadering word voorgestel om die afskatting van die netwerkimpedansie te verbeter deur die uitwerking van die nie-stasionêre aard van die netwerk te minimeer. | af_ZA |
dc.description.version | Doctoral | en_ZA |
dc.format.extent | xiii, 110 leaves : illustrations (some color) | |
dc.identifier.uri | http://hdl.handle.net/10019.1/107948 | |
dc.language.iso | en | en_ZA |
dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
dc.rights.holder | Stellenbosch University | en_ZA |
dc.subject | Pseudo-Random Impuls Sequence | en_ZA |
dc.subject | Peturbation (Mathematics) | en_ZA |
dc.subject | Parameter estimation | en_ZA |
dc.subject | Impuls differential equations | en_ZA |
dc.subject | High voltages | en_ZA |
dc.subject | UCTD | en_ZA |
dc.subject | Electric power systems -- Evaluation | en_ZA |
dc.subject | Electric power systems -- Mathematical models | en_ZA |
dc.title | Modelling and performance evaluation of a pseudo-random impulse sequence for in situ parameter estimation in energy applications | en_ZA |
dc.type | Thesis | en_ZA |