This thesis utilize pulse shaping in characterization of ultra-broad bandwidth laser pulse and multi-pulse generation. Using angle-dithering technique, time-integrating phase-matching bandwidth can be increased significantly even with a thin crystal. We also characterize the pulse by angle-dithered MIIPS( intrapulse interference phase scan ) technique. An addition advantage of using a thick crystal is increased signal strength. In addition, we provide a method to generate multi-pulses and proceed Michelson interferometeric autocorrelator by controlling the spectral amplitude and phase of the pulse. To compare with the past method, the efficiency was obtained from 33% to 80% , and the stability and time resolution of delay time can be improved. We expect this method applied to narrow-band frequency-tunable THz wave genetration will be better.

Multi-pulse transformer/rectifier systems are becoming increasingly popular in power distribution systems. These topologies can be found in aircraft power systems, motor drives, and other applications that require low total harmonic distortion (THD) of the input line current. This increase in the use of multi-pulse transformer topologies has led to the need to study large systems composed of said units and their interactions within the system. There is also an interest in developing small-signal models so that stability issues can be studied. This thesis presents a procedure for the average model of multi-pulse transformer/rectifier topologies. The dq rotating reference frame was used to develop the average model and parameter estimation is incorporated through the use of polynomial fits. The average model is composed of nonlinear dependent sources and linear passive components. A direct benefit from this approach is a reduction in simulation time by two orders of magnitude. The average model concept demonstrates that it accurately predicts the dynamics of the system being studied. In particular, two specific topologies are studied, the 12-pulse hexagon transformer/rectifier (hex t/r) and the 18-pulse autotransformer rectifier unit (ATRU). In both cases, detailed switching model results are used to verify the operation of the average model. In the case of the hex t/r, the average model is further validated with experimental data from an 11 kVA prototype. The hex t/r output impedance, obtained from the linearized average model, has also been verified experimentally. / Master of Science

International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, Nevada / A new kind of telemetry ground data system--Multi-Pulse PPK (Pulse Position Keying) Telemetry System Based on PC(MPPK-PCTS) is presented in this paper. Being Aimed at the lower bit rate which is the essential shortcoming of Single-Pulse PPK(SPPK), Multi-Pulse PPK(MPPK) signal is introduced to this system. Its signal forms, bit rate, energy efficiency and error probability have been analysed in detail. The symmetric Bi-Pulse PPK(BPPK) signal with fixed reference pulse can be practised in engineering. In this system, front-ends are intelligent and modular, all modules are integrated in a personal computer chassis through EISA/PCI bus. The system operates under multi-media WINDOWS environment, with intelligent user interface. Faults can be detected and located automatically. With flexible performance, good expandibility and small size, the system can be used in reentry telemetry and many other fields where higher rate and lower power are both required.

Multipulse pulse position modulation (MPPM) has been widely proposed to improve data rate over the traditional pulse position modulation (PPM) in free-space optical communication systems. However, there is no known efficient method of encoding MPPM codewords. Furthermore, MPPM is not the optimal coding scheme (in terms of data rate) given the two main constraints of optical systems (duty cycle and zero runlength). In this work, an improved encoding technique for MPPM is provided as well as an analysis of regions where significant rate gain over MPPM is achievable. A new coding technique based on constrained coding is introduced that allows construction of codes which achieves considerable rate gain over comparable MPPM systems. In addition, our new codes allow for convenient concatenation with an outer-code and are suitable for iterative decoding. Simulation results show that these codes can achieve a $6$ dB coding gain over comparable MPPM systems.

Multipulse pulse position modulation (MPPM) has been widely proposed to improve data rate over the traditional pulse position modulation (PPM) in free-space optical communication systems. However, there is no known efficient method of encoding MPPM codewords. Furthermore, MPPM is not the optimal coding scheme (in terms of data rate) given the two main constraints of optical systems (duty cycle and zero runlength). In this work, an improved encoding technique for MPPM is provided as well as an analysis of regions where significant rate gain over MPPM is achievable. A new coding technique based on constrained coding is introduced that allows construction of codes which achieves considerable rate gain over comparable MPPM systems. In addition, our new codes allow for convenient concatenation with an outer-code and are suitable for iterative decoding. Simulation results show that these codes can achieve a $6$ dB coding gain over comparable MPPM systems.

Orientador: Falcondes José Mendes de Seixas / Resumo: A utilização de conversores com baixa distorção harmônica na corrente de entrada melhora significativamente o fator de potência de equipamentos e instalações elétricas. Este trabalho apresenta a proposta de desenvolvimento de um conversor multipulso com estágio CC-CC SEPIC, que apresenta baixa distorção na corrente de entrada, regulação da tensão na saída, podendo ainda apresentar isolamento em alta frequência. Propõe-se a utilização do conversor proposto em aplicações industriais em inversores para acionamento de máquinas elétricas de corrente alternada, em substituição aos retificadores convencionais, técnica conhecida como retrofit, em barramentos CC regulados, fontes de tensão CC, entre outras aplicações. O conversor é baseado em um autotransformador não isolado de 18 pulsos, que disponibiliza três saídas trifásicas independentes e apresenta reduzido peso e volume quando comparados com os tradicionais transformadores isolados. Este conversor já apresenta significativa melhoria no fator de potência, porém não possibilita a regulação da tensão na saída, que dependerá unicamente da tensão de entrada, estando sujeita às variações que nela ocorram. As saídas independentes, após retificação, devem ser conectadas para poder alimentar a carga. A forma mais comum de possibilitar essa conexão é utilizando elementos magnéticos adicionais, chamados de transformadores interfase (IPTs). A utilização de conversores CC-CC é outra forma de realizar a conexão, resultando em um estágio CC-C... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Converters with low harmonic distortion of input current can improve significantly the power factor at electrical equipment and plants. This work proposes the development of a multipulse converter with DC-DC SEPIC stage, with low distortion in the input current, and may also provide high frequency isolation. It could be used in industrial applications to replace conventional rectifiers in Adjustable Speed Drives (ASDs), a technique known as retrofit. It can be used also in regulated DC bus, DC voltage power supply, among other applications. The converter is based on a non-isolated 18-pulse autotransformer that provides three independent three-phase outputs and has reduced weight and size. The autotransformer improves the power factor, but does not allow the regulation of the load voltage output. The independent outputs must be connected to the load. The most common way of providing this connection is by using additional magnetic elements, called interphase transformer (IPTs). The use of DC-DC converters is another way to perform the outputs connections, resulting in a DC-DC stage that control the voltage and current, thus enabling parallel connect loads. In this work, the SEPIC converter was selected, because it can be used with few modifications to the original structure. SEPIC converter can easily be isolated, allowing the use of multipulse converters in applications that require isolation between power supply and load. Prototypes with isolated and non-isolated SEPIC conver... (Complete abstract click electronic access below) / Doutor

Submitted by ANGELO CESAR DE LOURENÇO null (angelo.lourenco@ifms.edu.br) on 2016-09-26T13:09:26Z No. of bitstreams: 1 Tese-Angelo César de Lourenço_Final.pdf: 7849728 bytes, checksum: 5e7ebce190155dba447176e825a55a34 (MD5) / Approved for entry into archive by Felipe Augusto Arakaki (arakaki@reitoria.unesp.br) on 2016-09-27T17:21:40Z (GMT) No. of bitstreams: 1 lourenco_ac_dr_ilha.pdf: 7849728 bytes, checksum: 5e7ebce190155dba447176e825a55a34 (MD5) / Made available in DSpace on 2016-09-27T17:21:40Z (GMT). No. of bitstreams: 1 lourenco_ac_dr_ilha.pdf: 7849728 bytes, checksum: 5e7ebce190155dba447176e825a55a34 (MD5) Previous issue date: 2016-07-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A utilização de conversores com baixa distorção harmônica na corrente de entrada melhora significativamente o fator de potência de equipamentos e instalações elétricas. Este trabalho apresenta a proposta de desenvolvimento de um conversor multipulso com estágio CC-CC SEPIC, que apresenta baixa distorção na corrente de entrada, regulação da tensão na saída, podendo ainda apresentar isolamento em alta frequência. Propõe-se a utilização do conversor proposto em aplicações industriais em inversores para acionamento de máquinas elétricas de corrente alternada, em substituição aos retificadores convencionais, técnica conhecida como retrofit, em barramentos CC regulados, fontes de tensão CC, entre outras aplicações. O conversor é baseado em um autotransformador não isolado de 18 pulsos, que disponibiliza três saídas trifásicas independentes e apresenta reduzido peso e volume quando comparados com os tradicionais transformadores isolados. Este conversor já apresenta significativa melhoria no fator de potência, porém não possibilita a regulação da tensão na saída, que dependerá unicamente da tensão de entrada, estando sujeita às variações que nela ocorram. As saídas independentes, após retificação, devem ser conectadas para poder alimentar a carga. A forma mais comum de possibilitar essa conexão é utilizando elementos magnéticos adicionais, chamados de transformadores interfase (IPTs). A utilização de conversores CC-CC é outra forma de realizar a conexão, resultando em um estágio CC-CC que condiciona a tensão e a corrente e assim possibilita o paralelismo das cargas. Neste trabalho, o conversor CC-CC selecionado é o SEPIC, que por suas características de entrada e saída não requer grandes modificações em relação à estrutura original. Além da regulação da tensão de saída, o conversor SEPIC é uma estrutura de potência que pode ser facilmente isolada, possibilitando a utilização dos conversores multipulsos em aplicações que requerem isolamento entre a fonte e a carga. Foram construídos protótipos de conversores SEPIC isolados e não isolados com os quais foram realizados ensaios experimentais e os resultados são apresentados e discutidos. / Converters with low harmonic distortion of input current can improve significantly the power factor at electrical equipment and plants. This work proposes the development of a multipulse converter with DC-DC SEPIC stage, with low distortion in the input current, and may also provide high frequency isolation. It could be used in industrial applications to replace conventional rectifiers in Adjustable Speed Drives (ASDs), a technique known as retrofit. It can be used also in regulated DC bus, DC voltage power supply, among other applications. The converter is based on a non-isolated 18-pulse autotransformer that provides three independent three-phase outputs and has reduced weight and size. The autotransformer improves the power factor, but does not allow the regulation of the load voltage output. The independent outputs must be connected to the load. The most common way of providing this connection is by using additional magnetic elements, called interphase transformer (IPTs). The use of DC-DC converters is another way to perform the outputs connections, resulting in a DC-DC stage that control the voltage and current, thus enabling parallel connect loads. In this work, the SEPIC converter was selected, because it can be used with few modifications to the original structure. SEPIC converter can easily be isolated, allowing the use of multipulse converters in applications that require isolation between power supply and load. Prototypes with isolated and non-isolated SEPIC converters were built, experimental tests were performed and the results are presented and discussed. / Novo Prodoutoral: 1459525

abstract: Multi-pulse particle tracking velocimetry (multi-pulse PTV) is a recently proposed flow measurement technique aiming to improve the performance of conventional PTV/ PIV. In this work, multi-pulse PTV is assessed based on PTV simulations in terms of spatial resolution, velocity measurement accuracy and the capability of acceleration measurement. The errors of locating particles, velocity measurement and acceleration measurement are analytically calculated and compared among quadruple-pulse, triple-pulse and dual-pulse PTV. The optimizations of triple-pulse and quadruple-pulse PTV are discussed, and criteria are developed to minimize the combined error in position, velocity and acceleration. Experimentally, the velocity and acceleration fields of a round impinging air jet are measured to test the triple-pulse technique. A high speed beam-splitting camera and a custom 8-pulsed laser system are utilized to achieve good timing flexibility and temporal resolution. A new method to correct the registration error between CCDs is also presented. Consequently, the velocity field shows good consistency between triple-pulse and dual-pulse measurements. The mean acceleration profile along the centerline of the jet is used as the ground truth for the verification of the triple-pulse PIV measurements of the acceleration fields. The instantaneous acceleration field of the jet is directly measured by triple-pulse PIV and presented. Accelerations up to 1,000 g's are measured in these experiments. / Dissertation/Thesis / M.S. Mechanical Engineering 2014

Multi-pulse converters have been widely used for a multi-megawatt scale power generating system to comply with harmonic regulations. Among all types of multi-pulse converters, a 12-pulse converter is the most widely used due to the simple structure, which consists of a delta-delta and a delta-wye phase-shift transformer pair and it effectively mitigates undesirable harmonics from the nonlinear load. In the early 2000s, a shunt type passive front-end for a shipboard power system was proposed. By shunting the two gensets with 30° phase angle difference, a single phase-shift transformer effectively eliminates 5th and 7th harmonics. It achieves a significant size and weight reduction compared to a 12-pulse converter while keep the comparable harmonic cancellation performance. Recently, a hybrid type front-end was proposed. On top of the passive front-end, 3 phase active power filter was added and an additional harmonic cancellation was achieved to further eliminate 11th and 13th harmonics. However, the performance of both the passive and hybrid type front-end are highly dependent on the size of the line reactor in ac mains. A back to back active power filter is proposed in this dissertation to replace the phase-shift transformer in the multi-generator power architecture. The proposed front-end does not include phase-shift transformer and the size and the weight of the overall front-end can be significantly reduced. Due to the active harmonic compensation, the back to back front-end achieves better power quality and the line reactor dependency is improved. The number of required dc-link capacitors is reduced by half by introducing a back to back configuration and the capacitor size is reduced by adjusting the phase angle difference of genset to cancel out the most significant voltage harmonics in the shared dc-link bus. The overview of the existing shunt type front-end is provided and the concept of back to back active power filter is validated by simulation and prototype hardware. The comparison between existing front-end and the proposed front-end is provided to highlight the superior performance of back to back active front-end. The dc-link bus current and voltage ripple analysis is provided to explain the dc-link ripple reduction mechanism. / Doctor of Philosophy / The transportation electrification has gained more and more attention due to its smaller carbon dioxide emission, better fuel efficiency. The recent advances in power devices, microcontrollers, and transducers accelerate the electrification of transportation. This trend is shown in the propulsion system in marine transport as well and the electric propulsion system has been widely used to meet the strict environmental regulations. However, the non-linear circuit components such as capacitor and diode in the electric propulsion system draw non-linear current and significantly deteriorate power quality and lead to critical problems such as reduced life span of circuit components Accordingly, a front-end is required to improve power quality. Also, it is desired to have compact and lightweight front-end for installation flexibility and fuel efficiency improvement. In this dissertation, several front-ends using a phase-shift transformer are reviewed and a detailed analysis is provided to help understand the harmonic cancellation principle of the existing front-end through equivalent circuit analysis, quantitative analysis, and a phasor diagram representation. Based on the analysis of the existing front-ends and shipboard power architecture, lightweight and high-performance front-end is proposed and verified by simulation and prototype hardware. The performance, size comparison between existing front-end and the proposed front-end is provided to show the advantage of the proposed front-end.

This work focuses on the safe and stable operation of an autonomous power system interconnecting an AC source with various types of power electronic loads. The stability of these systems is a challenge due to the inherent nonlinearity of the circuits involved. Traditionally, the stability analysis in this type of power systems has been approached by means of small-signal methodology derived from the Nyquist stability criterion. The small-signal analysis combined with physical insight and the adoption of safety margins is sufficient, in many cases, to achieve a stable operation with an acceptable system performance. Nonetheless, in many cases, the margins adopted result in conservative measures and consequent system over designs. This work studies the system stability under large-perturbations by means of three different tools, namely parameter space mapping, energy functions, and time domain simulations. The developed parameters space mapping determines the region of the state and parameter space where the system operation is locally stable. In this way stability margins in terms of physical parameters can be established. Moreover, the boundaries of the identified stability region represent bifurcations of the system where typical nonlinear behavior appears. The second approach, based on the Lyapunov direct method, attempts to determine the region of attraction of an equilibrium point, defined by an operation condition. For this a Lyapunov function based on linear matrix inequalities was constructed and tested on a simplified autonomous system model. In Addition, the third approach simulates the system behavior on a computer using a detailed system model. The higher level of model detail allows identifying unstable behavior difficult to observe when simpler models are used. Because the stability of the autonomous power system is strongly associated with the characteristics of the energy source, an improved voltage controller for the generator is also presented. The generator of an autonomous power system must provide a good performance under a wide variety of regimes. Under these conditions a model based controller is a good solution because it naturally adapts to the changing requirements. To this extent a controller based on the model of a variable frequency synchronous generator has been developed and tested. The results obtained show a considerable improvement performance when compared to previous practices. / Ph. D.