Controle digital de velocidade de um motor de corrente contínua com conversor CA/CC em regime de condução descontínua

Abstract

This work deals with the presentation of a very simple and low cost microcomputer-based control strategy, for speed regulation and current limitation of low-power dc drives. The power suply is a single-phase full-wave dual thyrstor converter in discontinuous operation. The system's good performance was obtained by a minimal hardware structure and low cost implementation, wich confirms its economic viability. The dual-converter assembly is completely reversible, operating in the four quadrants of the torque-speed characteristic. In addition, the system presents good operating conditions over all working range. The control algorithm is made up of a classical proportional plus integral controller, without using an auxiliary current, regulation loop. Faster current transients suffer limitation by a simple procedure with saturation of its greatest value. There is another important simplification: speed measurement without the use of a mechanical transducer. The work also explains in details the project of the speed control loop entirely on the discrete domain. For this purpose, the modeling assembly includes the motor and the static converter coupling. For this mode, we make an analizys of the dc drive parametrs variation with the operation point, and finally, it is shown the project of the direct firing angle control, in the converter. Experimental results, illustrating the good performance of this system, are presented for a 2HP dc drive, which are compared with the digital simulation results.