<p>Digital television is one of the biggest broadcasting media available. All over the world television companies are rearranging their broadcasting from analogue to digital transmission. Former standard disagreements in the analogue era have lead to an agreement of one common European standard for digital television. Countries like USA and Japan have their own similar standards.</p><p>The report consists of two objectives; a survey of the most commonly used standards for digital television today and the construction of a prototype receiver for the second generation satellite DVB-standard.</p><p>A thorough literature study and careful design resulted in a fully functioning system. Measurements performed on the DVB-S sections gave exemplary results. Comparing these results with corresponding measurements performed on the DVB-S2 section showed much better performance for DVB-S2 with the same code rates. This shows some of the advantages of the new standard and proving the coding theory right. New coding algorithms make it possible to transmit more information on noisier channels of inferior quality. In laymen’s words; DVB-S2 gives a better picture and more television channels on the same satellite compared to DVB-S.</p>

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Diante da necessidade em aperfeiÃoar as tecnologias existentes para a conversÃo de energia elÃtrica em sistemas de alta potÃncia, este trabalho tem por finalidade projetar, analisar e implementar experimentalmente uma tÃcnica de modulaÃÃo com o intuito de reduzir o conteÃdo harmÃnico da tensÃo de saÃda em um inversor multinÃvel com capacitor flutuante de trÃs nÃveis. Algumas das diversas tÃcnicas de modulaÃÃo (PSPWM, LSPWM, HE-PWM e CSV-PWM) foram analisadas e implementadas no controlador digital FPGA a fim de comparar suas caracterÃsticas de desempenho com a tÃcnica de modulaÃÃo proposta. AlÃm disso, foi realizado o estudo de perdas da topologia de inversor multinÃvel com capacitor flutuante de trÃs nÃveis e a anÃlise teÃrica da distorÃÃo harmÃnica total da modulaÃÃo proposta. Finalmente, o desenvolvimento digital das tÃcnicas mostrou resultados coerentes, com formas de onda obtidas experimentalmente com alta qualidade de resoluÃÃo. A comparaÃÃo entre as estratÃgias de modulaÃÃo em termos de DHT resultou positivamente à modulaÃÃo proposta, cujos resultados experimentais de DHT nas tensÃes de linha na saÃda apresentaram o melhor desempenho para toda a faixa de Ãndices de modulaÃÃo comparadas Ãs tÃcnicas PSPWM, LSPWM-POD e CSV-PWM e uma reduÃÃo de atà 4,5% em relaÃÃo à HE-PWM. Isto comprova o estudo teÃrico realizado e sua aplicaÃÃo no inversor multinÃvel com capacitor flutuante de trÃs nÃveis. / Given the need to improve the existing technologies for electrical energy conversion into high power systems, this works purpose to design, analyze and implement a modulation technique that aims to reduce the output voltage harmonic content on the three-level flying capacitor multilevel inverter. Some of the various conventional modulation techniques (PSPWM, LSPWM, HE-PWM e CSV-PWM) have been analyzed and implemented in FPGA controller in order to compare their performance features with the proposed modulation technique. Furthermore, the losses study of the three-level flying capacitor multilevel inverter topology and the total harmonic distortion theoretical analysis of the proposed modulation technique have been made. Finally, the digital implementation of the techniques showed consistent results with experimentally obtained waveforms with high quality resolution. The comparison between the modulation strategies in the THD rates resulted positively for the proposed modulation, which THD experimental results in the line output voltage showed the best performance for all range of modulation indexes compared to techniques PSPWM, LSPWM-POD and CSV-PWM and the reduction of up to 4.5% better than HE-PWM. This proved the theoretical study done and its application in three-level flying capacitor multilevel inverter.

International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, Nevada / After briefly presenting the TRANSMED mission, the configuration of the Telemetry and Telecommand links is illustrated and the their dimensioning is analyzed. Both links operate at S-band with satellite grade standards. The system composition, the main equipment and the system growth potential are thereafter presented.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Visando superar os desafios inerentes à conversÃo de energia elÃtrica em sistemas de alta potÃncia, minimizando as perdas e melhorando a qualidade da energia processada, este tra-balho tem por objetivo analisar e implementar uma tÃcnica de modulaÃÃo para ser aplicada nas duas topologias de inversores multinÃveis mais disseminadas - com neutro grampeado (NPC), e com capacitor flutuante (FC) - a fim de reduzir os esforÃos nos semicondutores, bem como melhorar o Ãndice de distorÃÃo harmÃnica da tensÃo de saÃda. Ao longo do trabalho foi evidenciada a necessidade da digitalizaÃÃo da tÃcnica proposta, visto que o desenvolvimento analÃgico da mesma acarretaria em um circuito complexo e de baixa confiabilidade. Dessa forma, escolheu-se como plataforma digital um FPGA, devido à sua facilidade de programa-ÃÃo e reconfiguraÃÃo, alÃm da alta velocidade e quantidade de pinos de entrada e saÃda. AlÃm da tÃcnica proposta, foram tambÃm desenvolvidas outras modulaÃÃes para fins de compara-ÃÃo, apresentando os padrÃes de chaveamento para cada uma delas, bem como o comporta-mento da corrente atravÃs dos semicondutores em cada perÃodo de chaveamento. Foi tambÃm realizada a anÃlise teÃrica das topologias e suas respectivas etapas de operaÃÃo, caracterÃsticas e levantamento das equaÃÃes que ditam a anÃlise das perdas para as diferentes situaÃÃes de tÃcnicas aplicadas a cada uma das estruturas. O desenvolvimento digital das tÃcnicas mostrou-se correta atravÃs da anÃlise das formas-de-onda colhidas por meio de um circuito digital-analÃgico. AlÃm disso, a comparaÃÃo da aplicaÃÃo dessas modulaÃÃes em inversores a trÃs nÃveis NPC e FC de 6 kW mostrou-se favorÃvel à tÃcnica proposta em termos de eficiÃncia e reduÃÃo da distorÃÃo harmÃnica em ambas as topologias, comprovando sua utilidade em con-versores multinÃveis de alta potÃncia. Por fim, foi apresentado o desenvolvimento da tÃcnica proposta em inversores com mais de trÃs nÃveis, onde se pode comprovar sua eficiente aplica-ÃÃo para tais fins, bem como sua expansibilidade para inversores de n nÃveis. / In order to overcome the challenge of processing electric energy in high power systems with minimal losses and high energy quality, this work presents the implementation and anal-ysis of a modulation technique applicable on both most well-known multilevel inverter struc-tures - neutral point-clamped (NPC), and flying capacitors (FC) - to reduce the stresses across the semiconductors devices, and to improve the total harmonic distortion of the output volt-age. Throughout the work, the necessity to digitalize the proposed technique has been evi-denced due to the high complexity and low reliability inherent to the analogical approach. Thus, the digital controller FPGA has been chosen, as it is easy to program and reconfigure, works at high speed, and has a lot of input and output pins. Additionally, other modulation techniques were also implemented to compare their performance with the proposed one, pre-senting the switching patterns and the behavior of the electrical currents through the semicon-ductors for each modulation. A theoretical analysis was also performed for both topologies and their respective operation principle, characteristics, and equations used on the losses anal-ysis for the different combinations of modulation applied to each structure. Finally, the digital development of the various techniques has proved to be correct by observing the waveforms obtained through the digital/analogical circuit. Besides, the comparison of the modulation techniques on 6 kW NPC and FC three-level prototype inverters proved to be favorable to the proposed technique in terms of efficiency and total harmonic distortion reduction on both topologies, confirming its usefulness on high power multilevel converters. At last, it was pre-sented the application of the proposed modulation technique to inverters with more than three levels, where it was observed its eligibility for n-levels topologies.

Spectrum has been a scarce commodity in RF communication. Acoustic data communication is an alternative to RF communication where data is transmitted through sound waves. In this thesis, several different aspects of acoustic data communication are investigated. A physical test setup is built where the data communication spectrum extends up to 40 kHz. Impulse response of the acoustic channel is considered in a laboratory environment. Acoustic spectrum beyond the hearing limit between 25 kHz to 35 kHz is found as a suitable band for the developed setup. Distance and multipath components are important factors, determining the communication accuracy. The physical layer for the communication system is built by taking RF Pager system as a reference. This system is also modified to improve the performance. Dierent modulation techniques are used in order to evaluate their performances for acoustic channels. BFSK, BPSK, QPSK, GMSK, OFDM, DSSS and FHSS techniques are implemented for comparison. Total and effective bit rate are considered for the overall performance evaluation of differentt modulation techniques. Several experiments are done in laboratory environment where there are several multipath components. As the distance between the transmitter and receiver is increased, path loss and multipath increases. It is shown that certain modulation techniques are more robust to multipath and are better candidates for acoustic communication. While acoustic environment is inefficient in terms of power, it is still a good candidate for communication in short distances.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This dissertation deals with modulation techniques for multilevel diode clamped converters. The major challenge to be overcome by modulation strategies to these converters is the balance of the dc-link voltage capacitors, whilst minimizing the THD of output voltages. Among the modulation strategies reported in literature for this purpose are the carrier-based and space vector modulation techniques. Generally the space vetor methods select the nearest three vector to implement the desired output voltage vector. However, it is not always possible to remove the low frequency ripple in the dc-link voltage capacitors using this diagram vector. This work proposes a new space vector diagram that allows the elimination of the low frequency ripple in the dc-link voltage capacitors and guarantees the balance to the entire converter linear operation region, operating with any power factor load. Further constrains are derived based on the sign and magnitude of the output currents to determine the transition between the space vector diagram N3V and NS3V, making a hybrid modulation. As a result is possible to minimize the total harmonic distortion of the output voltages and to ensure the control of the averaged neutral point current. In order to make it possible to extend the results for converters with any number of levels, a carrier based modulation was proposed in this work where the modulation signals are chosen to ensure maximum use of the dc-link of the linear range of operation of converter, and eliminate low-frequency oscillation in the voltage capacitors. Moreover, it is proposed a space vector modulation strategy to back-to-back three level diode clamped converters, with the purpose to connect the wind power generation to the grid. This technique combines the utilization of the N3V and NS3V space vector diagrams for both converters connected to the same dc-link. Thus it is possible to establish a trade off between oscillation in the voltage capacitors and THD of output voltages. Experimental results and benchmarks are presented and demonstrate the good performance of the proposed methods. / Esta dissertação de mestrado trata de estratégias de modulação para conversores multiníveis com diodos de grampeamento. O principal desafio a ser superado por técnicas de modulação aplicadas a estes conversores é o de equilibrar as tensões dos capacitores do barramento CC, enquanto que minimizando a penalização da THD das tensões de saída. Dentre as principais estratégias de modulação com esse propósito abordadas na literatura, são as estratégias baseadas na comparação com portadora e as estratégias vetoriais. Geralmente os métodos de modulação vetorial utilizam os três vetores de comutação mais próximos do vetor de tensão de referência, N3V. Entretanto nem sempre é possível eliminar as ondulações de baixa frequência presentes nas tensões dos capacitores do barramento CC em toda faixa de operação do conversor utilizando essa divisão de setores. Este trabalho deriva um novo diagrama vetorial NS3V, que possibilita a eliminação das ondulações de baixa frequência das tensões dos capacitores do barramento CC na região linear do conversor, independente do fator de potência de operação. Além disso são obtidas restrições baseadas no sinal e nas magnitudes das correntes de saída para determinar a transição entre a modulação que utiliza o diagrama vetorial N3V e o diagrama vetorial NS3V, tornando a modulação híbrida. Com isto é possível minimizar a distorção harmônica das tensões de saída e assegurar o controle da corrente média sobre um período de comutação no ponto central do divisor capacitivo. Com objetivo de facilitar a extensão dos resultados para um número qualquer de níveis, a modulação baseada na comparação com portadora foi proposta nesse trabalho onde as tensões modulantes são escolhidas de forma a garantir a máxima utilização da tensão do barramento CC na faixa linear de operação do conversor, bem como eliminar as ondulações de baixa frequência presentes nas tensões dos capacitores. Ainda, é proposta uma estratégia de modulação vetorial para conversores com diodos de grampeamento de três níveis em configuração back-toback com o propósito de conectar sistemas de geração eólica à rede. Nesta estratégia de modulação é combinada a utilização dos diagramas vetoriais N3V e NS3V para ambos os conversores conectados ao mesmo barramento CC. Dessa forma é possível estabelecer um compromisso entre ondulação das tensões dos capacitores do barramento CC e THD das tensões de saída. Resultados experimentais e análises comparativas são apresentadas e demonstram a boa performance dos métodos propostos.

In order to meet the ever-growing demand for mobile data, a number of different technologies have been adopted by the fourth generation standardization bodies. These include multiple access schemes such as spatial division multiple access (SDMA), and efficient modulation techniques such as orthogonal frequency division multiplexing (OFDM)-based modulation. The specific objectives of this theses are to develop an effective feedback method for interference management in smart antenna SDMA systems and to design an efficient OFDM-based modulation technique, where an additional dimension is added to the conventional two-dimensional modulation techniques such as quadrature amplitude modulation (QAM). In SDMA time division duplex (TDD) systems, where channel reciprocity is maintained, uplink (UL) channel sounding method is considered as one of the most promising feedback methods due to its bandwidth and delay efficiency. Conventional channel sounding (CCS) only conveys the channel state information (CSI) of each active user to the base station (BS). Due to the limitation in system performance because of co-channel interference (CCI) from adjacent cells in interference-limited scenarios, CSI is only a suboptimal metric for multiuser spatial multiplexing optimization. The first major contribution of this theses is a novel interference feedback method proposed to provide the BS with implicit knowledge about the interference level received by each mobile station (MS). More specifically, it is proposed to weight the conventional channel sounding pilots by the level of the experienced interference at the user’s side. Interference-weighted channel sounding (IWCS) acts as a spectrally efficient feedback technique that provides the BS with implicit knowledge about CCI experienced by each MS, and significantly improves the downlink (DL) sum capacity for both greedy and fair scheduling policies. For the sake of completeness, a novel procedure is developed to make the IWCS pilots usable for UL optimization. It is proposed to divide the optimization metric obtained from the IWCS pilots by the interference experienced at the BS’s antennas. The resultant new metric, the channel gain divided by the multiplication of DL and UL interference, provides link-protection awareness and is used to optimize both UL and DL. Using maximum capacity scheduling criterion, the link-protection aware metric results in a gain in the median system sum capacity of 26.7% and 12.5% in DL and UL respectively compared to the case when conventional channel sounding techniques are used. Moreover, heuristic algorithm has been proposed in order to facilitate a practical optimization and to reduce the computational complexity. The second major contribution of this theses is an innovative transmission approach, referred to as subcarrier-index modulation (SIM), which is proposed to be integrated with OFDM. The key idea of SIM is to employ the subcarrier-index to convey information to the receiver. Furthermore, a closed-form analytical bit error ratio (BER) of SIM OFDM in Rayleigh channel is derived. Simulation results show BER performance gain of 4 dB over 4-QAM OFDM for both coded and uncoded data without power saving policy. Alternatively, power saving policy maintains an average gain of 1 dB while only using half OFDM symbol transmit power.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: This thesis investigates orthogonal frequency division multiplexing (OFDM) as a viable modulation technique for an ultrasonic acoustic underwater modem. The underwater environment provides a challenging setting for acoustic communications. Long delay spreads due to multipath propagation, severe Doppler frequency shifts, frequency dependent absorption and very limited bandwidth are but some of the challenges to overcome. OFDM essentially provides the parallel transmission of symbols in the frequency domain by simultaneously modulating many closely spaced orthogonal subcarriers. The resulting long parallel symbol rate together with the cyclic extension of symbols render the signal robust against intersymbol interference (ISI) caused by multipath propagation. Intercarrier interference (ICI) between the overlapping frequency responses of subcarriers is mitigated by their property of orthogonality. Doppler spread contributes to the loss of orthogonality and can result in severe ICI. A method of measuring the Doppler shift by means of including a preamble and postamble symbol with each data frame is proposed. The detected frequency offset is corrected by resampling the frame at the desired sample rate. Not only do the ambles serve as a mechanism for timing and frequency synchronisation, but they are also applied in the channel estimation process. The equalisation of channel response is required for the coherent demodulation of the received symbols. An investigation into different phase shift keying (PSK) and quadrature amplitude modulation (QAM) constellations reveal optimal arrangements for minimal symbol errors. The optimised QAM constellations do not lend themselves to Gray-coding, so that an efficient interleaving scheme is needed to mitigate the non-uniform distribution of bit errors among symbol errors. Forward error correction is provided via a Bose Chaudhuri Hocquenghem (BCH) block code. Variable code rates, together with the ability to switch between different constellations, enable the modem to perform so-called variable modulation in an attempt to maximise the throughput under specific channel conditions. The modulation/demodulation scheme is wholly defined in software as to provide flexibility and facilitate experimentation with different signal processing methods. The accompanying hardware platform allows for the transmission of a pre-generated signal and the recording of a received signal for off-line processing. The prototype design serves as a proof of concept and thus provides only simplex communication. Field tests over limited distances demonstrate the successful operation of the prototype modem. We conclude that OFDM is indeed a suitable modulation technique for acoustic underwater communication. / AFRIKAANSE OPSOMMING: Hierdie tesis ondersoek die toepassing van ortogonale frekwensiedeling multipleksering (OFDM) as modulasie tegniek op ʼn onderwater kommunikasie modem. Die onderwater omgewing bied vele uitdagings vir akoestiese kommunikasie. Lang vertraging-verstrooiings as gevolg van multipad voortplanting, Doppler frekwensieskuif, frekwensieafhanklike absorpsie, en beperkte bandwydte is van die uitdagings wat oorkom moet word. In essensie bied OFDM die parallelle versending van ʼn aantal simbole deur die gelyktydige modulasie van verskeie nou-gespasieerde subdraers in die frekwensiegebied. Die gevolglike lang parallelle simboolperiodes, tesame met die sikliese uitbreiding van simbole, verleen immuniteit teen intersimbool steurnisse (ISI) wat ontstaan as gevolg van multipad voortplanting. Die ortogonaliteit van naburige draers in die frekwensiegebied beperk interdraer steuring (ICI) tussen hul oorvleuelende frekwensie weergawes. Doppler frekwensieskuif kan egter lei tot die verlies aan ortogonaliteit en bydra tot ernstige interdraer steurings. ʼn Metode wat gebruik maak van aanhef en slot simbole, ingesluit by elke raam, word voorgestel om die Dopplerskuif te meet. Die bepaalde frekwensieafset word gekorrigeer deur die monstertempo van die raam aan te pas na die verlangde tempo. Buiten die tyd- en frekwensie-sinkronisasie funksies van die aanhef en slot simbole, speel dit ook ʼn belangrike rol in die ontrekking van die frekwensie weergawe van die kanaal. Die effening van die kanaal se frekwensieweergawe is noodsaaklik vir die koherente demodulasie van die ontvangde simbole. ʼn Ondersoek na verskillende fase verskuif sleuteling (PSK) en kwadratuur amplitude modulasie (QAM) konstellasies het optimale rangskikkings opgelewer vir minimale simboolfoute. Hierdie optimale QAM konstellasies verleen hulself egter nie na Gray-kodering nie. ʼn Effektiewe invlegtegniek is nodig om die nie-uniforme verspreiding van bisfoute tussen simboolfoute te beperk. Fout korrigering funksionaliteit word gebied deur ʼn Bose Chaudhuri Hocquenghem (BCH) blokkode. Verstelbare koderingstempo’s en die vermoë om tussen verskillende konstellasies te skakel, stel die modem in staat om sogenaamde verstelbare modulasie te gebruik in ʼn poging om die data deurset te optimeer onder spesifieke kanaal kondisies. Die modulasie en demodulasie skema is volledig in sagteware gedefinieer. Dit verleen buigbaarheid en vergemaklik eksperimentering met verskeie seinverwerkingstegnieke. Die meegaande hardeware platvorm stel die modem in staat om vooraf opgewekte seine uit te saai en rou ontvangde siene op te neem vir na-tydse verwerking. Die prototipe ontwerp dien as ʼn konseptuele bewys en bied dus slegs simplekse kommunikasie. Die suksesvolle werking van die modem is gedemonstreer deur toetsing oor beperkte afstande. Hieruit word afgelei dat OFDM inderdaad geskik is vir akoestiese onderwater kommunikasie.

This thesis aims to abstract the physical layer (PHY) performance of current and upcoming technologies, so that, their suitability for various use cases and scenarios could be evaluated within an affordable time. For the said purpose, a new effective SINR mapping technique eEESM along with the dynamic optimization of the fitting parameter is proposed. The mapping accuracy of proposed eEESM techniques is analyzed and compared against the other state-of-the-art methods in the doubly selective channel. The results show that the proposed technique is more accurate and map closest to the reference packet error rate (PER) curves. Moreover, the mapping error of eEESM is the lowest for all considered MCSs. The justification for its better performance is the tighter symbol error rate (SER) approximation used to derive effective SINR and the proposed optimization approach. The main purpose of using PLA instead of full PHY simulations is to reduce simulation time. Therefore, a novel concept is presented to abstract PHY performance depending on the time and frequency selectivity of the channel. This further reduces the number of computations required to estimate performance using PLA. To demonstrate the gain in terms of simulation time, the computation complexity of PLA is compared against full PHY simulations. Results show that PLA is roughly 1000 to 1000000 times faster (depending on the abstracted fading conditions) compared to the PHY simulator. The effective SINR mapping approach is then further extended for future candidate multi-carrier techniques (i.e., OFDM, DFT-s-OFDM, GFDM, OTFS), which could be adopted by the upcoming technologies. For this purpose, the received SINR of symbols received through these multi-carrier techniques is derived. The resultant received SINR also considers the impact of ICI due to Doppler. Subsequently, the received SINR of symbols is mapped to effective SINR considering the selectivity of the channel. By comparing the effective SINR, OTFS outperforms other techniques. The reason for the better performance of OTFS is due to the spread of symbol energy over time and frequency, which results in higher effective SINR due to higher diversity. Furthermore, evaluation results show that the proposed PLA can accurately model the performance of these multi-carrier techniques under various fading conditions. Multi-connectivity is another enhancement being considered for future technologies, as an enabler for ultra-reliable communications under harsh channel conditions. Therefore, multi-connectivity communications are also studied in this thesis. Specifically, the frequency domain multi-connectivity networks are presented. To fully exploit frequency diversity under frequency selective channels, the subcarrier-based link combing scheme is proposed. The earlier derived received SINR is then extended for the state-of-the-art link combining schemes, i.e., SC, EGC, and MRC. The multi-connectivity gain in terms of the average received SINR is derived and compared for the above-mentioned combining schemes. To abstract the performance of multi-connectivity communications, the post-combined effective SINR mapping is proposed, where effective SINR represents the combined performance of connected links. The developed PLA performance is validated against the PHY simulations for the case of MRC. Results reveal that with the increase in multi-connectivity order, the RMSE error decreases due to the decrease in the variance of mapping SINRs. In the end, various applications of PLA are demonstrated. The developed multi-carrier PLAs are used to compare the performance of multi-carrier techniques under various fading conditions. Results depict that PER of multi-carrier techniques generally decreases with the increase in time or frequency selectivity, given that, the ideal channel estimation, ICI, and inter-symbol interference (ISI) cancellation is used. The multi-connectivity evaluation results depict that with the increase in channel selectivity higher diversity gain could be achieved. Besides, the proposed subcarrier-wise combining scheme achieves better performance compared to the traditional link combining approach. The next PLA application demonstrated is the performance comparison of V2X technologies, i.e., IEEE~802.11p, LTE-V2V, IEEE~802.11bd, and NR-V2X, in an Urban NLOS communications scenario. It is observed that 802.11bd outperforms other technologies in terms of PER and packet reception ratio (PRR). Its better performance is due to lower ICI compared to LTE-V2X and NR-V2X, and due to the use of LDPC codes compared to 802.11p. In contrast, NR-V2X outperforms other technologies in terms of data rates and packet inter-arrival time. The last PLA application shown is the link adaptation for single-link and multi-connectivity communications. In single-link communication, the performance of various PLA techniques is compared in terms of achieved data rates and outage probability against the case of perfect CQI. The CQI based on the proposed eEESM technique improves the data rates and reliability of the link, compared to other schemes. Further, in the case of multi-connectivity, the post-combined effective SINR mapping proposed in this thesis is used for link adaptation in terms of both MCS selection and adapting the number of links. The proposed scheme optimizes multi-connectivity data rates while using the lowest possible number of links required for the desired quality of service.

Controlling the dynamic outputs of electrical machines has always been an essential topic in aerospace, automotive and other industries. Electrical machine control consists of several components, each of which can be controlled in various ways. Whereas the dynamic responses are mostly simulated using MATLAB/SIMULINK, Prof. Marko Hinkkanen from Aalto University has launched a project for the development of an open-source simulator called ’Motulator’, based on Python. In this thesis, we focus on developing modulation methods and related functions for the inverter in ’Motulator’ based on an existing model of a Permanent Magnet Electrical Machine (PMSM). First, the two-level and three-level inverters with the Space Vector Modulation (SVPWM) method are developed. The dynamic output performance improves significantly compared to Sinusoidal Pulse-Width Modulation (SPWM). In addition, operation under the over-modulation mode for both inverters is implemented to improve the DC-bus voltage utilisation further, allowing higher torques and speeds. The problem of neutral point voltage imbalance is solved for the three-level inverter, ensuring the difference voltage between upper and lower capacitors to fluctuate around 0. Finally, a harmonic analysis tool based on the non-uniform Fourier transform is established. / Styrning och reglering av elektriska maskiners dynamik har alltid varit ett viktigt ämne inom flyg- och bilindustrin men även för andra tillämpningar. Regleringen av elektriska maskiner består av flera delar som var och en kan styras på olika sätt. De dynamiska förhållandena simuleras vanligen i MATLAB/SIMULINK. För att inte vara beroende av kommersiell programvara har Professor Marko Hinkkanen från Aalto universitetet lanserat en simulator med öppen källkod, baserad på Python, kallad ’Motulator’. Examensarbetet fokuserar vi på att utveckla moduleringsmetoder och relaterade funktioner för växelriktaren i ’Motulator’, baserat på en befintlig modell av en permanentmagnetiserad synkronmaskin (PMSM). Först utvecklas två- och trenivåomriktare med ”Space Vector Modulation” (SVPWM). Drivsystemets dynamisk prestanda förbättras därvid avsevärt i jämförelse med Sinus-pulsbreddsstryning (Sinusoidal-PWM). Övermodulering har implementerats för båda växelriktarna i avseende att ytterligare förbättra DC-bussens spänningsutnyttjande, vilket möjliggör högre vridmoment och varvtal. Problemet med nollpunktsspänningens obalans är löst för trenivåomriktaren, vilket säkerställer att skillnadsspänningen mellan de övre och nedre kondensatorerna fluktuerar runt 0. Slutligen har ett verktyg utvecklats i syfte att analysera övertoner, baserat på en olikformig Fouriertransform.