Desenvolvimento de um retificador pwm para sistemas de acionamento de motores de indução na irrigação de lavouras de arroz

Abstract

Due to the great importance of agribusiness for the national economy, irrigation systems are widely used for the maintenance of plantations, mainly in the western border of Rio Grande do Sul, where much of the rice production is achieved using irrigation. These irrigation systems have a high demand for electricity, since most of them are driven by electromechanical groups. Consequently, the quality of energy supply in these rural regions is crucial, as the only locally available drive systems are using diodes for voltage rectifying, thus becoming susceptible to failures caused by poor power quality. In this context, in partnership with the company Esco GD, this work proposes the use of a PWM rectifier to rectify the input voltage, on account of the low distortion in the input currents, power factor close to unity and lower ripple in the output voltage. Firstly, the rice plantation in the western border of Rio Grande do Sul is characterized, then, important aspects about the power quality standards and regulatory agencies are described, topologies of industrially used motor drive systems are also described. Subsequently, the state-space representation of the PWM rectfier in the synchronous reference frame is calculated, to obtain the transfer function that relates the input currents with the duty cycle of each leg of the rectfier and to obtain the transfer function that relates the DC bus voltage with the input currents. These functions are use to design the voltage and current control loops, both of wich are based in proportional-integral controllers. Thereafter, the grid synchronization method DSOGI-PLL is shown along with its implementation parameters. The simulation results are divided in three stages, system start up, where the performance of the system during the charging of the DC bus and starting the control system is evaluated, steady state, where the performance of the system during its nominal operation was assessed, and transient state, in wich the performance of the PWM rectifier was evaluated during low power quality phenomena. Lastly, the design of the energy storage elements and the preload resistors are described in the attachments.