Design and simulation of speed controller using ac-dc buck boost converter for dc motor drive with soft starter

Abstract

In this paper a model is developed to run a separately excited direct current (d.c) motor using a single phase alternating current (a.c) source by converting the a.c source into variable d.c source using a buck-boost converter. Main problem d.c motor drive is the starting current due this insulation may damage and also efficiency will decrease so that here in this paper it is solved by using soft starter. The variable Pulse Width Modulation (PWM) is used to regulate the voltage at the end of ac dc buck boost converter. Here the speed of the d.c motor is also controlled using a speed controller which is connected to the soft starter. Thus a MATLAB simulink model is developed where speed of the d.c motor is controlled using a soft starter. PWM based rectifiers are efficiently employed in low to medium power applications. Since the ac-dc buck boost converter can produce voltages higher or lower than the supply voltages, they are most useful in variable dc drives. In a traditional dc motor system a resistor starter is used to monitor the armature current of the motor. This is because initially armature current is high which damages the motor. Instead of a three point starter, a MOSFET based soft starter is used to limit the starting current. And also a PI controller is used to control the speed of the dc motor. This controller calculates the reference current based on the reference speed of the motor and feeds it into the soft starter. As a result in this Simulink model of a separately excited dc motor runs on a single phase a.c source with better control. The main advantage is that the motor becomes independent of the input voltage level as it can be adjusted. The speed of the d.c motor can also be controlled. The circuit becomes small with less switching and copper losses and the armature current can also be controlled because of the soft starter.