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Advisor(s)
Abstract(s)
A dificuldade de controlo de um motor de indução, bem como o armazenamento de energia CC e posterior utilização como energia alternada promoveram o desenvolvimento de variadores de frequência e inversores. Assim, como projeto de tese de mestrado em Automação e Sistemas surge o desenvolvimento de um variador de frequência.
Para elaboração do variador de frequência efetuou-se um estudo sobre as técnicas de modulação utilizadas nos inversores. A técnica escolhida e utilizada é a Sinusoidal Pulse Width Modulation (SPWM). Esta técnica baseia-se na modelação por largura de impulso (PWM), o qual é formado por comparação de um sinal de referência com um sinal de portadora de elevada frequência. Por sua vez, a topologia escolhida para o inversor corresponde a um Voltage Source Inverter (VSI) de ponte trifásica completa a três terminais. O desenvolvimento da técnica de modulação SPWM levou ao desenvolvimento de um modelo de simulação em SIMULINK, o qual permitiu retirar conclusões sobre os resultados obtidos.
Na fase de implementação, foram desenvolvidas placas para o funcionamento do variador de frequência. Assim, numa fase inicial foi desenvolvida a placa de controlo, a qual contém a unidade de processamento e que é responsável pela atuação de Insulated Gate Bipolar Transistors (IGBTs). Para além disso, foi desenvolvida uma placa para proteção dos IGBTs (evitando condução simultânea no mesmo terminal) e uma placa de fontes isoladas para alimentação dos circuitos e para atuação dos IGBTs. Ainda, foi desenvolvida a técnica de SPWM em software para a unidade de controlo e finalmente foi desenvolvida uma interface gráfica para interação com o utilizador.
A validação do projeto foi conseguida através da variação da velocidade do motor de indução trifásico. Para isso, este foi colocado a funcionar a diversas frequências de funcionamento e a diferentes amplitudes. Para além disso, o seu funcionamento foi também validado utilizando uma carga trifásica equilibrada de 3 lâmpadas de forma a ser visualizada a variação de frequência e variação de amplitude.
The difficulty of control of an induction motor and DC energy storage and subsequent use as AC energy promoted the development of variable frequency drives (inverters). Thus, as project of master's thesis in Automation and Systems arose the development of a frequency inverter. For the development of a frequency inverter was made a study of modulation techniques used in inverters. The technique used and chosen was the Sinusoidal Pulse Width Modulation (SPWM). This technique is based on the use of Pulse Width Modulation (PWM), which is generated by comparing the reference signal with a high frequency carrier signal. In turn, the chosen topology for the inverter was the Voltage Source Inverter (VSI) and the complete three-phase bridge with three terminals. The development of SPWM modulation technique led to the development of a SIMULINK simulation model, which allowed taking conclusions about the results. In the implementation phase was developed boards for the operation of the frequency inverter. Thus, initially was developed the control board that contains the processing unit and is responsible for the actuation of Insulated Gate Bipolar Transistors (IGBTs). In addition, a board was developed for protection of IGBTs (avoiding simultaneous conduction in the same terminal), and another board was developed to supply circuit boards and gates of IGBTs. Moreover, the SPWM technique software was developed to the control unit and finally it was developed a graphical interface for interaction with the user. The validation of the project was achieved by varying the speed of a three phase induction motor. To this end, the motor was placed operating at various frequencies and different amplitudes. In addition, the operation has also been validated using balanced three-phase load lamps so as frequency and amplitude variation would been visually seen.
The difficulty of control of an induction motor and DC energy storage and subsequent use as AC energy promoted the development of variable frequency drives (inverters). Thus, as project of master's thesis in Automation and Systems arose the development of a frequency inverter. For the development of a frequency inverter was made a study of modulation techniques used in inverters. The technique used and chosen was the Sinusoidal Pulse Width Modulation (SPWM). This technique is based on the use of Pulse Width Modulation (PWM), which is generated by comparing the reference signal with a high frequency carrier signal. In turn, the chosen topology for the inverter was the Voltage Source Inverter (VSI) and the complete three-phase bridge with three terminals. The development of SPWM modulation technique led to the development of a SIMULINK simulation model, which allowed taking conclusions about the results. In the implementation phase was developed boards for the operation of the frequency inverter. Thus, initially was developed the control board that contains the processing unit and is responsible for the actuation of Insulated Gate Bipolar Transistors (IGBTs). In addition, a board was developed for protection of IGBTs (avoiding simultaneous conduction in the same terminal), and another board was developed to supply circuit boards and gates of IGBTs. Moreover, the SPWM technique software was developed to the control unit and finally it was developed a graphical interface for interaction with the user. The validation of the project was achieved by varying the speed of a three phase induction motor. To this end, the motor was placed operating at various frequencies and different amplitudes. In addition, the operation has also been validated using balanced three-phase load lamps so as frequency and amplitude variation would been visually seen.
Description
Keywords
Variador de frequência SPWM SIMULINK VSI Topologia de ponte trifásica completa Variable frequency drives Three-phase inverter topology
Citation
Publisher
Instituto Politécnico do Porto. Instituto Superior de Engenharia do Porto