Modeling and Simulation Proportional-Integral (Pi) Controller for a Dc Motor with Improvement Performance.
This report is about a simulation study of modeling classical control technique of dc motor drive with improvement in proportional-integral (PI) control which is used closed-loop operation to control speed of motor. The speed regulator uses a PI controller in order to obtain the electromagnetic torque needed to reach the desired speed. Current controller controls the armature current by computing the appropriate thyristor firing angle or by using the firing gate angle. This generates the rectifier output voltage needed to obtain the desired armature current and thus the desired electromagnetic torque. This report also includes the work already completed and work planned for the next semester.
Figure1: Proportional Integral control (PI)
Figure 2: main idea of PI controller
The control schematic of PI control dc motor converter-controlled separately-excited dc motor drive is shown above. The motor drive shown is a speed-controlled system. The thyristor bridge converter gets its ac supply through single-phase transformer thus the dc output is fed to the armature of the dc motor. The field is separately excited, and the field supply can be kept constant or regulated. The dc motor has a tachogenerator whose output is utilized for closing the speed loop. The output of the tachogenerator is filtered to remove the ripples to provide the signal, ωmr. The speed command ωr* is compared to the
Speed signal to produce a speed error signal. This signal is processed through a Proportional-integral (PI) controller to determine the torque command. The torque command is limited, to keep it within the safe current limits, and the current command is obtained by proper scaling. The armature current command ia* is compared to the actual armature current ia to have a zero current error. Since there is an error, PI current
References:  Sen, P.C., Thyristor DC Drives, J.Wiley and Sons, 1981.  Mohan, Undeland and Robbins, Power Electronics 3rd edition, John Wiley & Son, INC, 2003  Nondahl, Thomas A., Microprocessor Control of Motor Drives and Power Converters, tutorial course, IEEE Industry Application Society, October 1993.  Cyril W.Lander., Power Electronics 3rd edition, McGraw-Hill, 1993.  Muhammad H. Rashid., Power Electronics Circuits, Devices, and Applications 3rd edition, Pearson Prentice Hall, 2004.  R. Krishnan. Electric Motor Drives, Modeling, Analysis, and Control, Prentice Hall, 2001  http://www.powerdesigners.com/InfoWeb/resources/pe_html/ch05s6/intro.html  http://www.mathworks.com/ [pic]