Design of an observer and speed controller for a DC motor fed by fuel cells and DC to DC converters

This paper presents a method to control the speed of a separately excited D.C. motor using a D.C. to D.C. converter. The energy source of the system is a Fuel Cell (FC), for which a mathematical model describing its electrical characteristics is also presented. By controlling the duty cycle of the converter, the input power of the motor is also controlled; thus controlling the speed of the motor. Depending on the operating characteristics of the FC used, the motor may or may not be controlled due to the restrictions imposed on the duty cycle. The range of existence of the duty cycle is derived based on the analysis of impedances of the system. A state observer is designed for sensorless current estimation. Simulations are made using the system´s dynamic equations to demonstrate the obtained results.