Electricity systems are very complex systems and are composed of numerous transmission lines, generators and loads. The generating stations are generally far away from load centres and that may cause transmission line congestion and overloading. Series capacitive compensation is the most economical way to increase transmission capacity and improve transient stability of transmission grids. However, one of the impeding factors for the widespread use of series capacitive compensation is the potential risk of Subsynchronous Resonance (SSR). Subsynchronous Resonance is a phenomenon in which electrical power is exchanged with the generator shaft system in an increasing manner which may result in damage to the turbine generator shaft system. Therefore, mitigating SSR continues to be a subject of research and development aiming at developing effective SSR countermeasures.<p>This research work presents new methods of alleviating the SSR problem using a Static Synchronous Series Compensator (SSSC) and a Static Synchronous Compensator (STATCOM). These methods are based on using the SSSC and STATCOM to inject unbalanced series quadrature voltages and unbalanced shunt reactive currents in transmission line just after clearing faults. When the subsynchronous oscillations drive unsymmetrical phase currents, the developed electromagnetic torque will be lower than the condition when the three-phase currents are symmetrical. The unsymmetrical currents result in a lower coupling strength between the mechanical and the electrical system at asynchronous oscillations. Therefore, the energy exchange between the electrical and the mechanical systems at subsynchronous oscillations will be suppressed, thus, avoiding the build-up of torsional stresses on the generator shaft systems under subsynchronous resonance condition. The validity of proposed methods are demonstrated by time simulation results using the electromagnetic transient program EMTP-RV.

Electricity systems are very complex systems and are composed of numerous transmission lines, generators and loads. The generating stations are generally far away from load centres and that may cause transmission line congestion and overloading. Series capacitive compensation is the most economical way to increase transmission capacity and improve transient stability of transmission grids. However, one of the impeding factors for the widespread use of series capacitive compensation is the potential risk of Subsynchronous Resonance (SSR). Subsynchronous Resonance is a phenomenon in which electrical power is exchanged with the generator shaft system in an increasing manner which may result in damage to the turbine generator shaft system. Therefore, mitigating SSR continues to be a subject of research and development aiming at developing effective SSR countermeasures.<p>This research work presents new methods of alleviating the SSR problem using a Static Synchronous Series Compensator (SSSC) and a Static Synchronous Compensator (STATCOM). These methods are based on using the SSSC and STATCOM to inject unbalanced series quadrature voltages and unbalanced shunt reactive currents in transmission line just after clearing faults. When the subsynchronous oscillations drive unsymmetrical phase currents, the developed electromagnetic torque will be lower than the condition when the three-phase currents are symmetrical. The unsymmetrical currents result in a lower coupling strength between the mechanical and the electrical system at asynchronous oscillations. Therefore, the energy exchange between the electrical and the mechanical systems at subsynchronous oscillations will be suppressed, thus, avoiding the build-up of torsional stresses on the generator shaft systems under subsynchronous resonance condition. The validity of proposed methods are demonstrated by time simulation results using the electromagnetic transient program EMTP-RV.

There has been much effort in new design for transceiver used in mobile communications. The general approach is to combine RF functions with DSP to allow linear modulation techniques and permit flexibility of modulation format and receiver processing. In practice, with the quadrature modulation technique there is always some imbalance between the I- and Q channels of modulator and demodulator. This is mainly due to finite tolerances of capacitor and resistor values used to implement the analog components. The unavoidable imbalance between the I- and Q channels is known to degrade the performance of quadrature communication system. The main concern of this thesis is to propose a new blind scheme and with fast convergence algorithm, such as the inverse QRD-RLS algorithm, to deal with the problem described above for compensation in the transmitter and receiver. First, for the transmitter, the so-called adaptive estimation and compensation with power measurement implemented by the inverse QRD-RLS algorithm is employed. While in the receiver, a new blind adaptive filtering approach of the nonlinear parameters estimation and compensation, along with the power measurement in the receiver, is devised to adaptively compensate for the gain/phase imbalance and DC offsets in a quadrature demodulator. Where the conventional inverse QRD-RLS algorithm is employed for estimating the parameters of compensator, without using any reference signal transmitted from the transmitter. To document the merits of the proposed scheme, computer simulation for the coherent 16-PSK-communication system is carried out. With our proposed method a great improvement for eliminating the effects of the imbalance and offset over the existing techniques has verified. It has rapidly convergence rate and the smaller mean square error in steady state.

The Decimator, an SED Systems Ltd. product, is a PCI slot card that performs both time and frequency domain measurements of given input signals. It is essentially a more economical version of a bench spectrum analyzer or oscilloscope, with a PC interface. Several issues limit the speed and accuracy of the results of the Decimator, and the study of these issues is the focus of this thesis. These issues, including but not limited to, are as follows: 1) Imbalances between the received In-phase and Quadrature-phase channels; 2) The FFT and Windowing functions are performed by a microcontroller, but it is desired that they be migrated to an FPGA. While solutions to improve the first issue is being implemented and verified, the second issue is not one of simply reducing a source of error. The second issue requires a cost-benefit analysis on the migration of these signal processing algorithms from an ARM microcontroller to a Xilinx FPGA.

The Decimator, an SED Systems Ltd. product, is a PCI slot card that performs both time and frequency domain measurements of given input signals. It is essentially a more economical version of a bench spectrum analyzer or oscilloscope, with a PC interface. Several issues limit the speed and accuracy of the results of the Decimator, and the study of these issues is the focus of this thesis. These issues, including but not limited to, are as follows: 1) Imbalances between the received In-phase and Quadrature-phase channels; 2) The FFT and Windowing functions are performed by a microcontroller, but it is desired that they be migrated to an FPGA. While solutions to improve the first issue is being implemented and verified, the second issue is not one of simply reducing a source of error. The second issue requires a cost-benefit analysis on the migration of these signal processing algorithms from an ARM microcontroller to a Xilinx FPGA.

Made available in DSpace on 2015-03-26T13:42:33Z (GMT). No. of bitstreams: 1 texto completo.pdf: 244644 bytes, checksum: 7bb131def78ba69016b2b6a8a2dd140f (MD5) Previous issue date: 2014-02-27 / Linkage disequilibrium (LD) is defined as the non-random association between alleles of different loci in a population and association mapping (MA) refers to a statistically significant association between molecular marker and phenotypic trait. The objectives of this study were: (1) estimate the linkage disequilibrium in populations of popcorn related by cycles of selection using SNP markers, (2) compare the populations in the degree of LD, (3) evaluate changes in allele frequencies and (4) identify significant associations between markers and quality related characteristics of popcorn. In total 465 samples were evaluated, with 354 samples belonging to the population 'Viçosa' and 111 samples belonging to the population eija- asm Improvement Program popcorn, Federal University of Viçosa. The populations were subjected to the following cycles of selection: Viçosa cycle 1 and cycle 1 Beija-Flor, obtained after one cycle of selection among and within half-sib families, Viçosa cycle 4, obtained after four cycles of selection among and within half-sib families, Viçosa cycle 2 full-sib families (FIC), obtained after two cycles of selection among and within full-sib families, Viçosa S4, obtained by selection of progeny S4. Ninety-six SNPs markers in properly selected QTL regions for quality, already identified above were used. The following characters were measured: capacity expansion (ml/g), grain density (g/ml), sphericity of grains and 100 grains weight (g). In comparison the Viçosa c0 used as the reference population for the highest mean values for LD linking group found in Viçosa c2 fic (D' = 0,8911; r 2 = 0,1905) as well as to related and unrelated SNPs (D' = 0,8911, r 2 = 0,1905) . Regarding the MA significant associations (p < 0.05) were found for all traits, with thirteen associations related to the feature expandability, twenty three with the sphericity of the grains, eight with the weight of 100 grains and seventeen density of the grains. / Desequilíbrio de ligação (LD) é definido como a associação não aleatória entre alelos de diferentes locos em uma população e mapeamento associativo (MA) refere-se à associação estatística significativa entre o marcador molecular e a característica fenotípica. Os objetivos deste trabalho foram: (1) estimar o desequilíbrio de ligação em populações de milho pipoca relacionadas por ciclos de seleção utilizando marcadores SNP, (2) comparar as populações quanto ao grau de LD, (3) avaliar alterações de frequências alélicas e (4) identificar associações significativas entre marcadores e características relacionadas à qualidade do milho pipoca. No total foram avaliadas 465 amostras, sendo 354 amostras pertencentes à - populações pertencentes ao germoplasma do Programa de Melhoramento de Milho-Pipoca da Universidade Federal de Viçosa. As populações foram submetidas aos seguintes ciclos de seleção: Viçosa ciclo 1 e Beija-Flor ciclo 1, obtidas após um ciclo de seleção entre e dentro de famílias de meios-irmãos, Viçosa ciclo 4, obtida após quatro ciclos de seleção entre e dentro de famílias de meios-irmãos, Viçosa ciclo 2 famílias de irmãos completos (FIC), obtidas após dois ciclos de seleção entre e dentro de famílias de irmãos completos, Viçosa S 4, obtida por seleção de progênies S4. Foram utilizados 96 marcadores SNP devidamente selecionados em regiões de QTL pré-identificadas para qualidade. Os seguintes caracteres foram mensurados: capacidade de expansão (ml/g), densidade dos grãos (g/ml), esfericidade dos grãos e peso de 100 grãos (g). Em comparação a Viçosa c0, utilizada como população de referência os maiores valores médios de LD por grupo de ligação foram encontrados em Viçosa c2 fic r2=0,1905). Na análise de MA foram encontradas associações significativas (p < 0,05) para todas as características avaliadas, sendo treze associações relacionadas com a característica capacidade de expansão, vinte e três com a esfericidade dos grãos, oito com o peso de 100 grãos e dezessete com a densidade dos grãos.