[attachment=15542]
Abstract
This paper presents the performance evaluation of the fuzzy and PI control system applied to Permanent- Magnet Brushless DC Motor (PMBLDCM) with different PWM techniques. At first the comparison analysis is made between SPWM and SVPWM inverter fed PMBLDCM with the implementation of PI controller. From the analysis of Total harmonic distortion (THD) in the inverter current, SVPWM technique was found to be better than SPWM technique. However, the PI controller has some disadvantages such as: high starting overshoot, sensitivity to controller gains and sluggish response due to sudden load disturbance. Hence the Fuzzy logic controller is implemented in the feedback for SVPWM inverter fed PMBLDCM. Simulation result are presented and analyzed for both fuzzy and PI controllers. It is observed that fuzzy logic based controller gives better responses than traditional PI controller for the speed control of dc motor drives.
I. INTRODUCTION
Controllers: Conventional dc motors are highly efficient and their characteristics make them suitable as servomotor. However, it needs a commutator and brushes which are subject to wear and required maintenance. The functions of commutator and brushes were implemented by solidstate switches that can realize maintenance-free motors. These motors are now known as brushless dc motors. Brushless dc motors are widely used in various applications. Two examples of them are electric vehicle and industrial machinery. Fuzzy logic controller which is presented by Zadeh in 1965, is a new controller [1]. Besides that, fuzzy logic controller is more efficient from the other controller such as proportional-integral (PI) controller. T he comparison between them is needed to compare what the controller is efficient [2]. The reason why conventional controller low efficiency such as PI controller because the overshoot is too high from the set point and it may takes delay time to get constant and sluggish response due to sudden change in load torque and the sensitivity to controller gains Ki and Kp [3]. PWM techniques: Pulse Width Modulation variable speed drives are increasingly applied in many new industrial applications that require superior performance. Recently, developments in power electronics and semiconductor technology have lead improvements in power electronic systems. Hence, different circuit configurations namely multilevel inverters have become popular and considerable interest by researcher are given on them. Variable voltage and frequency supply to d.c drives is invariably obtained from a three-phase voltage source inverter. A number of Pulse width modulation (PWM) schemes are used to obtain variable voltage and frequency supply. The most widely used PWM schemes for three-phase voltage source inverters are carrier-based sinusoidal PWM and space vector PWM (SVPWM). There is an increasing trend of using space vector PWM (SVPWM) because of their easier digital realization and better dc bus utilization.
II.PULSE WIDTH MODULATION IN INVERTERS
Output voltage from an inverter can also be adjusted by exercising a control within the inverter itself. The most efficient method of doing this is by pulsewidth modulation control used within an inverter. In this method, a fixed dc input voltage is given to the inverter and a controlled ac output voltage is obtained by adjusting the on and off periods of the inverter components. This is the most popular method of controlling the output voltage and this method is termed as Pulse-Width Modulation (PWM) Control. PWM inverters are quite popular in industrial applications. PWM techniques are characterized by constant amplitude pulses. The width of these pulses is however modulated to obtain inverter output voltage control and to reduce its harmonic content.