Small-Signal Stability Analysis of an Open-Loop Induction Motor Drive Including the Effect of Inverter Deadtime

This paper demonstrates light-load instability in a 100-kW open-loop induction motor drive on account of inverter deadtime. An improved small-signal model of an inverter-fed induction motor is proposed. This improved model is derived by linearizing the nonlinear dynamic equations of the motor, which include the inverter deadtime effect. Stability analysis is carried out on the 100-kW415-V three-phase induction motor considering no load. The analysis brings out the region of instability of this motor drive on the voltage versus frequency (V-f) plane. This region of light-load instability is found to expand with increase in inverter deadtime. Subharmonic oscillations of significant amplitude are observed in the steady-state simulated and measured current waveforms, at numerous operating points in the unstable region predicted, confirming the validity of the stability analysis. Furthermore, simulation and experimental results demonstrate that the proposed model is more accurate than an existing small-signal model in predicting the region of instability.

Analysis of sine-triangle and zero-sequence injection modulation schemes for split-phase induction motor drive

A split-phase induction motor is fed from two three-phase voltage source inverters for speed control. This study analyses carrier-comparison based pulse width modulation (PWM) schemes for a split-phase motor drive, from a space-vector perspective. Sine-triangle PWM, one zero-sequence injection PWM where the same zero-sequence signal is used for both the inverters, and another zero-sequence injection PWM where different zero-sequence signals are employed for the two inverters are considered. The set of voltage vectors applied, the sequence in which the voltage vectors are applied, and the resulting current ripple vector are analysed for all the PWM methods. Besides all the PWM methods are compared in terms of dc bus utilisation. For the same three-phase sine reference, the PWM method with different zero-sequence signals for the two inverters is found to employ a set of vectors different from the other methods. Both analysis and experimental results show that this method results in lower total harmonic distortion and higher dc bus utilisation than the other two PWM methods.

Modelling and analysis of an open-loop induction motor drive incorporating the effect of inverter dead-time

The objective of this paper is to study the influence of inverter dead-time on steady as well as dynamic operation of an open-loop induction motor drive fed from a voltage source inverter (VSI). Towards this goal, this paper presents a systematic derivation of a dynamic model for an inverter-fed induction motor, incorporating the effect of inverter dead-time, in the synchronously revolving dq reference frame. Simulation results based on this dynamic model bring out the impact of inverter dead-time on both the transient response and steady-state operation of the motor drive. For the purpose of steady-state analysis, the dynamic model of the motor drive is used to derive a steady-state model, which is found to be non-linear. The steady-state model shows that the impact of dead-time can be seen as an additional resistance in the stator circuit, whose value depends on the stator current. Towards precise evaluation of this dead-time equivalent resistance, an analytical expression is proposed for the same in terms of inverter dead-time, switching frequency, modulation index and load impedance. The notion of dead-time equivalent resistance is shown to simplify the solution of the non-linear steady-state model. The analytically evaluated steady-state solutions are validated through numerical simulations and experiments.

O parlamento aberto na era da internet : pode o povo colaborar com o Legislativo na elaboração da leis?

Aborda as principais questões da atual reflexão sobre a democracia participativa. Tem como base o estudo de dois casos em especial de práticas participativas digitais desenvolvidas por parlamentos: o programa e-Democracia, da Câmara dos Deputados brasileira, e o projeto Senador Virtual, do Senado chileno.

The open parliament in the age of the internet : can the people now collaborate with legislatures in lawmaking?

This work seeks to address those questions and evaluate other international experiences and experiments designed to achieve the same ends. The book is based on a study of two particular cases where parliamentary bodies designed and implemented participatory digital processes, namely, the e-Democracy Program developed by the Brazilian House of Representatives, and the Virtual Senator Program developed by the Chilean Senate. The text unfolds in the form of a systematic analysis of institutional aspects embracing political and organizational elements as well as the social aspects associated to the application of digital democracy in parliaments. The investigation shows that at the stage they found themselves in 2010 those projects had only brought in very incipient results in regard to the aspects of enhancing representativity in decision making processes, aggregating collective intelligence to the legislative process or transparency to parliamentary performances, even though all of those are precious components of any democracy that deems itself to be participatory and deliberative. Nevertheless, such experiences have had the merit of contributing towards the gradual construction of more effective participatory mechanisms, complementary to the political representation system in place.

El parlamento abierto em la era de la Internet : ¿Puede el pueblo colaborar com el Legislativo en la elaboración de las leyes?

¿Es viable la coexistencia de acciones de participación y deliberación con el ejercicio de la representación parlamentaria? ¿De qué manera la tecnologia de la información y comunicación ha auxiliado el proceso de interacción entre la sociedad y el parlamento en el cotidiano dei legislativo? ¿Estamos cercanos a un sistema híbrido de democracia representativa y participativa con la incorporación en la agenda legislativa de maneras efectivas de coproducción de leyes? Esta obra intenta responder a estas preguntas, además de evaluar otras experiencias intemacionales con este mismo objetivo. El libro tiene como base el estudio de dos casos en especial de prácticas participativas digitales desarrolladas por parlamentos: el programa e-Democracia de la Cámara de Diputados brasileños y el proyecto Senador Virtual dei Senado chileno. El texto se desarrolla mediante el análisis sistemático de los aspectos institucionales que abarcan elementos organizacionales y políticos, así como de los aspectos sociales comprometidos en la aplicación de la democracia digital en parlamentos. La investigación indica que estos proyectos, en el punto en que se encontraban en el año 2010 presentaron resultados aunque incipientes en lo que concieme a la mejoría de la representatividad en la toma de decisiones, de agregación de inteligencia colectiva, en el proceso legislativo y de la transparencia por parte de la actuación parlamentaria, elementos apreciados por la democracia participativa y deliberativa. No obstante, dichas experiencias poseen el mérito de contribuir con la construcción gradual de mecanismos participativos más efectivos y complementarios ai sistema político.

Internet e educação : a compressão espaço-temporal e o civismo

Discute a relação entre a Internet e a educação para o civismo. Parte-se de uma análise do processo de compressão espaço-temporal, que se acirra com o advento das Tecnologias de Informação e Comunicação (TIC). A imaterialidade das relações e o individualismo são consequências de um mesmo processo que afasta os homens do mundo e os vincula a simulacros, e a presença da técnica tende a dar força a esse processo. Dessa forma, a velocidade das trocas simbólicas realizadas através das infovias acaba por exercer diversos impactos nos processos educacionais, destacando-se a falta de cultura política. Trata-se de uma situação difícil de ser modificada, no entanto, ao debater a relação entre a Internet e a educação, o texto também procura apontar caminhos para a constituição de um civismo a partir da presença das TIC no cotidiano.

Exigência de contratação de provedor de serviço de conexão à internet para o acesso em banda larga

Consultoria Legislativa - Área XIV - Comunicação Social, Informática, Telecomunicações, Sistema Postal, Ciência e Tecnologia.