Wave energy converter (WEC) harnesses energy from the ocean to produce electrical power. The electrical power produced by the WEC is fluctuating and is not maximized as well, due to the varying ocean conditions. As a consequence, without any intermediate power conversion stage, the output power from the WEC can not be fed into the grid. To feed WEC output power into the grid, a two-stage power conversion topology is used, where the WEC output power is first converted into DCpower through rectification, and then a DC-AC converter (inverter) is used to supply AC power into the grid. The main motive of this research is to extract maximum electrical power from the WEC by active rectification and smoothing the power fluctuation of the wave energy converter through a hybrid energy storage system consisting of battery and flywheel. This research also illustrates active and reactive power injection to the grid according to load demand through a voltage source inverter.

Analysis of the dead-time effect and other nonlinearities of the voltage source inverter was carried out in the introduction of the doctoral thesis. Three compensation strategies for vector controlled PMSM were proposed based on the analysis. The voltage disturbance observer with cost function of current errors is based on the model of PMSM, known machine parameters and easily measurable quantities. The second observer which estimates the dq- axes currents and the value of the voltage error with one parameter only is designed based on the harmonic analysis and Kalman filter algorithm. The third method combines an adaptive approach with feedback and voltage disturbance observer that is based on the PMSM model. Furthermore, the two compensation methods for vector controlled induction motor were proposed. In the first case, the standard compensation strategy is extended by a harmonic compensator that suppresses the residual 6th harmonic component in dq- axes currents. The last strategy detects the polarity of the estimated phase currents that are obtained by the Kalman filter. All compensation strategies have been verified by MATLAB/Simulink simulations and by experiments on real drives.

This thesis deals with modeling, simulation and implementation of Load Commutated SCR based current source Inverter (LCI) fed squirrel cage induction motor drive with sinusoidal voltage and sinusoidal current. In the proposed system, the induction motor is fed by an LCI. A three level diode clamped voltage source inverter (VSI) is connected at the motor terminal with ac chokes connected in series with it. The VSI currents are controlled in such a manner that it injects the reactive current demanded by the induction motor and the LCI for successful commutation of the SCRs in the LCI. Additionally, it absorbs the harmonic frequency currents to ensure that the induction motor draws sinusoidal current. As a result, the nature of the motor terminal voltage is also sinusoidal. The concept of load commutation of the SCRs in the LCI feeding an induction motor load is explained with necessary waveforms and phasor diagrams. The necessity of reactive compensation by the active filter connected at the motor terminal for the load commutation of the thyristors, is elaborated with the help of analytical equations and phasor diagrams. The requirement of harmonic compensation by the same active filter to achieve sinusoidal motor current and motor voltage, is also described. Finally, to achieve the aforementioned induction motor drive, the VA ratings of the active filter (VSI) and the CSI with respect to VA rating of the motor, are determined theoretically. The proposed drive scheme is simulated under idealized condition. Simulation results show good steady state and dynamic response of the drive system. Load commutation of the SCRs in the LCI and the sinusoidal profile of motor current and voltage, have been demonstrated. As in LCI fed synchronous motor drives, a special mode of operation is required to run up the induction motor from standstill. As the SCRs of the LCI are load commutated, they need motor terminal voltages for commutation. At standstill these voltages are zero. So, a starting strategy has been proposed and adopted to start the motor with the aid of the current controlled VSI to accelerate until the motor terminal voltages are high enough for the commutation of the SCRs in the LCI. The proposed drive is implemented on an experimental setup in the laboratory. The IGBT based three level diode clamped VSI has been fabricated following the design of the standard module in the laboratory. A generalized digital control platform is also developed using a TMS320F2407A DSP. Two, three phase thyristor bridges with necessary firing pulse circuits have been used as the phase controlled rectifier and the LCI respectively. Appropriate protection scheme for such a drive is developed and adopted to operate the drive. Relevant experimental results are presented. They are observed to be in good agreement with the simulation results. The effect of capacitors connected at the output of the LCI in the commutation process of the SCRs in the LCI is studied and analyzed. From the analysis, it is understood that the capacitors form a parallel resonating pair with filter inductor and the motor leakage inductance, which results in an undesired oscillation in the terminal voltage during each of the commutation intervals leading to commutation failure. So, in the final system, the capacitors are removed to eliminate any chance of commutation failure of the SCRs in the LCI. It is shown by experiment that the commutation of the SCRs takes place reliably in the absence of the capacitors also. The commutation process is studied and analyzed without the capacitors to understand the motor terminal voltage waveform of the experimental results.

Durant ces dernières années, l'intérêt pour les technologies des véhicules à faibles émissions de carbone a fait un bond important à travers l'Union européenne (UE) et au-delà, encouragé en cela par les gouvernements et les constructeurs automobiles. De grands espoirs ont été mis plus récemment dans les véhicules électriques (VE) et les véhicules électriques hybrides (VEH) en tant que technologies clés pour atténuer le changement climatique, améliorer la sécurité énergétique et favoriser une nouvelle branche de l'industrie dans le secteur automobile. Ainsi, l'électrification des transports a été considérée comme une stratégie clé pour réduire les émissions de CO2 dans le secteur des transports. Le principal défi est d’augmenter l’autonomie des véhicules (ce qui a toujours été au coeur de la concurrence des industries du transport), ainsi que la durée de vie des volumineuses et coûteuses batteries. Par conséquent, ceci indique que le rendement du convertisseur de puissance est un des points clés à développer pour les générations des véhicules électriques à venir. L’autre paramètre influant est la qualité de la tension et du courant (en particulier la suppression des harmoniques basses fréquences) qui permet de réduire la taille des filtres d'entrée et de sortie de ces convertisseurs. L'objectif de cette thèse est de parvenir à un meilleur rendement en proposant de nouvelles structures de convertisseur de puissance et des commandes vectorielles modifiées ; le choix de deux onduleurs alimentant un moteur ouvert aux deux extrémités. Après l'analyse étape par étape, modèle théorique, simulation et enfin une mise en oeuvre expérimentale, il a été constaté que les nouvelles méthodes proposées sont compétitives et peuvent s’appliquer aux cas des VEH et des VE afin d’apporter des caractéristiques supérieures en termes d’efficacité et de qualité de tension et de courant. / Over the last decade, the interest for low-carbon vehicle technologies has surged among both governments and automotive manufacturers across and beyond the European Union (EU). Great hopes have been put, first, on biofuel vehicles and more recently on electric vehicles (EVs) and hybrid electric vehicles (HEVs) as key technologies to mitigate climate change, enhance energy security and nurture new industry branches within the automotive sector. So electrification of vehicles has been seen as a key strategy to reduce CO2 emissions from the transport sector. The main challenge toward EVs and HEVs is to keep driving for longer distance (which has been always fields for competition among traction industries) as well as lifetime battery cells as storage system. As a result, these indicate importance of power converter efficiency as a key gate for next generations of these up-coming vehicles. The next parameter is the quality of output voltage/current (especially by suppressing low-order harmonics) to reduce the size of filtering. The aim of this thesis is to achieve better efficiency and output voltage/current Total Harmonic Distortion (THD) by proposing novel power converter and associated Pulse Width Modulation (PWM) methods while imposing modification on power converter topology. As a result, dual-inverter is proposed to supply open-end motor from both sides. To this aim, three PWM methods are suggested as: The first one, Modified Space Vector Modulation (MSVM) for dual-inverter supplied by single dc source, improves efficiency by 4-5% (while having lower switching losses), and reduces Common Mode Voltage (CMV) levels by 66%, as well. The voltage/current harmonics are analytically analyzed which shows mainly better performance. Effective switching frequency is also reduced by 66% due to the reduction of number of commutations. In the second one, Near State PWM (NSPWM) is adapted for dual-inverter supplied by single dc source in order to eliminate triplen harmonics (therefore Zero Sequence Voltage, ZSV) and improve efficiency (by 3-4%) compared to Space Vector Modulation (SVM). Additionally due to avoiding use of zero vectors, CMV is improved by 66%. While having 8 commutations instead of 12 in SVM, effective switching frequency is improved by 33%. And finally, the third proposed method deals with NSPWM for dual-inverter supplied by two isolated dc sources wherein efficiency and CMV levels show the same performance as previous one. However, in this method, voltage THD is highly reduced compared to SVM. Triplen harmonics of the output voltage are inherently suppressed by the structure. These 3 proposed methods are analytically studied and their performances are step by step simulated in Matlab/Simulink environment. Then the methods are implemented in dualinverter fed open-end motor in laboratory setup; and the results are compared with these of SVM. Finally, it is found that novel proposed methods are so competitive solutions to be applied in HEVs and EVs and bring superior efficiency and voltage/current harmonic features.

Je jasné, že nejúspěšnější konstrukce zahrnuje postup vícefázového řízení, ve kterém každá fáze může být považována za samostatný modul. Provoz kterékoliv z jednotek musí mít minimální vliv na ostatní, a to tak, že v případě selhání jedné jednotky ostatní mohou být v provozu neovlivněny. Modulární řešení vyžaduje minimální elektrické, magnetické a tepelné ovlivnění mezi fázemi řízení (měniče). Synchronní stroje s pulzním tokem a permanentními magnety se jeví jako atraktivní typ stroje, jejíž přednostmi jsou vysoký kroutící moment, jednoduchá a robustní konstrukce rotoru a skutečnost, že permanentní magnety i cívky jsou umístěny společně na statoru. FS-PMSM jsou poměrně nové typy střídavého stroje stator-permanentní magnet, které představují významné přednosti na rozdíl od konvenčních rotorů - velký kroutící moment, vysoký točivý moment, v podstatě sinusové zpětné EMF křivky, zároveň kompaktní a robustní konstrukce díky umístění magnetů a vinutí kotvy na statoru. Srovnání výsledků mezi FS-PMSM a klasickými motory na povrchu upevněnými PM (SPM) se stejnými parametry ukazuje, že FS-PMSM vykazuje větší vzduchové mezery hustoty toku, vyšší točivý moment na ztráty v mědi, ale také vyšší pulzaci díky reluktančnímu momentu. Pro stroje buzené permanentními magnety se jedná o tradiční rozpor mezi požadavkem na vysoký kroutící moment pod základní rychlostí (oblast konstantního momentu) a provozem nad základní rychlostí (oblast konstantního výkonu), zejména pro aplikace v hybridních vozidlech. Je předložena nová topologie synchronního stroje s permanentními magnety a spínaným tokem odolného proti poruchám, která je schopná provozu během vinutí naprázdno a zkratovaného vinutí i poruchách měniče. Schéma je založeno na dvojitě vinutém motoru napájeném ze dvou oddělených vektorově řízených napěťových zdrojů. Vinutí jsou uspořádána takovým způsobem, aby tvořila dvě nezávislé a oddělené sady. Simulace a experimentální výzkum zpřesní výkon během obou scénářů jak za normálního provozu, tak za poruch včetně zkratových závad a ukáží robustnost pohonu za těchto podmínek. Tato práce byla publikována v deseti konferenčních příspěvcích, dvou časopisech a knižní kapitole, kde byly představeny jak topologie pohonu a aplikovaná řídící schémata, tak analýzy jeho schopnosti odolávat poruchám.