International Journal of Mechanical Engineering and Technology (IJMET) Volume 9, Issue 12, December 2018, pp. 778 786, Article ID: IJMET_09_12_078 Available online at http://www.ia aeme.com/ijmet/issues.asp?jtype=ijmet&vtype= =9&IType=12 ISSN Print: 0976-6340 and ISSN Online: 0976-6359 IAEME Publication Scopus Indexed TRACK VOLTAGE APPROACH USING CONVENTIONAL PI AND FUZZY LOGIC CONTROLLER FOR PERFORMANCE COMPARISON OF BLDC MOTOR DRIVE SYSTEM FED BY CUK CONVERTER N. Mohanraj EEE, SASTRA Deemed to be University, Tirumalaisamudram, Thanjavur, India R. Sankaran EEE, SASTRA Deemed to be University, Tirumalaisamudram, Thanjavur, India ABSTRACT This research paper deals with speed control of a BrushLess DC motor (BLDC) drive system as a cost-effective solution for low-power applications. The speed of the BLDC motor is controlled by varying the dc-bus voltage of a Voltage Source Inverter (VSI), where a DC-DC converter using CUK configuration is employed. The DC link voltage is controlled in closed loop using voltage follower approach, where the output of CUK converter is controlled by using a reference voltage proportional to desired speed through variable duty ratio control of the power MOSFET switch. Here, two alternate controllers viz. PI and Fuzzy Logic controllers are utilized for generating trigger signals for gate triggering of the power MOSFET switch and the performance are compared. The performance of the entire proposed drive system is simulated for both controllers in MATLAB/SIMULINK environment covering operation over a wide range of reference speed. Keywords: BLDC motor, CUK Converter, Fuzzy Logic controller, PI Controller, Track Voltage Approach. Cite this Article: N. Mohanraj and R. Sankaran, Track Voltage Approach Using Conventional Pi And Fuzzy Logic Controller For Performance Comparison of BLDC Motor Drive System Fed by CUK Converter, International Journal of Mechanical Engineering and Technology, 9(12), 2018, pp. 778 786. http://www.iaeme.com/ijme et/issues.asp?jtype=ijmet&vtype=9&itype e=12 http://www.iaeme.com/ IJMET/index.asp 778 editor@iaeme.com
N. Mohanraj and R. Sankaran 1. INTRODUCTION BLDC motor has gained popularity due to higher reliability, simplicity in control and lesser maintenance. As far as space and weight are concerned, BLDC motors [1]. are the best choice in many applications. The construction and control architecture are also well suited for safe operation in critical applications. BLDC motors possess several merits over brushed DC motors and induction motors, such as a better speed versus torque characteristics, high dynamic response, high efficiency and reliability, longer operating life, noiseless operation and higher range of speed. In automobile industry, high demand for efficient permanent magnet motors motivated the development of BLDC motor drives and their controllers. Similarly, in aerospace applications, where space and weight are important. Quick speed response due to the higher ratio of developed torque to inertia of the BLDC motor is an added advantage. As far as the construction of the brushless DC motor is concerned, it follows an inside out construction where the rotating element carries permanent magnets [2]. Here instead of mechanical commutator, electronically switched commutation is employed through Hall sensors and power electronic based switching circuits [7], [9] in the stator supply. This also facilitates introduction of various control techniques through feedback controllers for frequency and voltage variations. The motor posses linear characteristics between current and torque and also voltage and speed. NOMENCLATURE Van, Vbn, Vcn : Phase voltages in a,b,c Volts ia, ib, ic : Phase currents in a,b,c, Amps ea, eb, ec : back-emf s in a,b,c, Volts R : Stator resistance per phase in Ω L : Stator self inductance, H M : Stator mutual inductance, H Te : Electromagnetic Torque, N-m T L : Motor s Load torque, N-m B : Motor s coefficient of viscous friction, N-m/rad/sec J : moment of inertia of rotor shaft and load, kg-m 2 ω : Angular speed of rotor, rad/sec. 2. MODELLING OF BLDC DRIVE SYSTEM The circuit equivalent of the BLDC motor is shown in Fig. 1. The back-emf waveforms are trapezoidal in nature, while current waveforms are rectangular in shape. Assuming stator windings parameters being same in all the phases and the self and mutual inductances remains constant. The corresponding voltage equations for all the three phases can be written as shown in (1) in matrix form. Fig. 1. BLDC motor equivalent Circuit. http://www.iaeme.com/ IJMET/index.asp 779 editor@iaeme.com
Track Voltage Approach Using Conventional Pi And Fuzzy Logic Controller For Performance Comparison of BLDC Motor Drive System Fed by CUK Converter Van Vbn Vcn R 0 0 ia L M 0 0 ia ea = 0 R 0ib + 0 L M 0 ib + eb. 0 0 R ic 0 0 L M ic ec (1) The electromagnetic torque produced in BLDC motor is due to interaction of stator winding current and rotor magnetic field and instantaneous torque is as shown in (2) Te =.... (2) The torque-balance equation of the rotor [2]. is shown in equation (3).! = "#"$#%! &. (3) 3. CONTROL OF BLDC DRIVE SYSTEM The entire BLDC motor drive system consisting of DC-DC converter, DC-AC converter (Inverter), Hall sensor, controller and BLDC motor as shown in Fig. 2. Rotor position feedback is required at each 60 degrees electrical for phase current commutation of six-steps in the entire drive system. Fig. 2. BLDC drive system Components. The position of the rotor and switching sequence of the stator coils must be consistent for production of the unidirectional torque. This is achieved by Hall sensors which sense the instantaneous rotor field magnets position. The Hall sensor circuitry is part of an inherent feedback arrangement for triggering the Voltage Source Inverter in 120 mode of conduction. n a speed control application of the BLDC motor [3], [4]. it is necessary to introduce a variable DC link voltage and the same is implemented using a DC-DC CUK converter [8], [9]. is employed. This control is provided for the six-pulse inverter at the front end, instead of PWM control of the stator currents is instrumental in reducing the torque ripple to a great extent on the mechanical side. 4. VOLTAGE FOLLOWER METHOD As mentioned earlier, implementation of voltage follower method is done by two alternate controllers as follows. PI controller. FUZZY logic controller. Voltage Follower Approach using PI controller The reference voltage generated is compared with the voltage generated from the dc link capacitor and obtained error will be fed to the PI controller. The PI controller output signal http://www.iaeme.com/ IJMET/index.asp 780 editor@iaeme.com
N. Mohanraj and R. Sankaran will be compared with the saw tooth carrier waveforms for generating the PWM pulses for gate triggering of the 6-pulse inverter is shown in Fig. 3. Fig. 3. Voltage follower approach using PI controller The BLDC motor MATLAB/SIMULINK model driven by a three phase six-pulse inverter which is fed by CUK converter [6]. using PI controller is shown in Fig. 4. The BLDC motor parameters shown in TABLE I is dealt. Fig. 4. Schematic of BLDC Motor Drive system incorporating Voltage Follower Approach using PI controller The schematic shown in Fig. 5. consists of PI controller and saw tooth generator. In the voltage follower method, reference voltage is generated corresponding to reference speed. The comparison is made between the reference voltage with the actual dc link voltage. The error signal generated is processed by the PI controller, for comparison with a 20 khz saw tooth carrier signal, so as to generate PWM signals for the IGBT gates of the VSI as shown in Fig. 5. Fig. 5. Schematic of PI controller Voltage Follower Approach using FUZZY controller The comparison is made between the reference voltage with the voltage generated from the dc link capacitor and obtained error will be fed to the FUZZY controller. The output signal of the FUZZY controller will be compared with the saw tooth carrier waveforms for generating the PWM pulses for gate triggering of the 6-pulse inverter is shown in Fig. 6. http://www.iaeme.com/ IJMET/index.asp 781 editor@iaeme.com
Track Voltage Approach Using Conventional Pi And Fuzzy Logic Controller For Performance Comparison of BLDC Motor Drive System Fed by CUK Converter Fig. 6. Schematic of BLDC Motor Drive system incorporating Voltage Follower Approach using FUZZY controller The BLDC motor MATLAB/SIMULINK model driven by a three phase six-pulse inverter which is fed by CUK converter [6]. using FUZZY controller is shown in Fig. 7. Fig. 7. Voltage follower approach using fuzzy controller The schematic shown in Fig. 8. consist of FUZZY controller [5]. and saw tooth generator. In the voltage follower method, reference voltage is generated corresponding to reference speed. The comparison is made between the reference voltage with actual dc link voltage and an error signal is processed by the FUZZY controller, for comparison with a 20 khz Saw tooth carrier signal, so as to generate PWM signals for the IGBT gates of the VSI. Fig. 8. Schematic of FUZZY controller 5. SIMULATION RESULTS Fig. 9. Shows the speed variation of the entire BLDCM drive system for a step change of reference speed from 2000 RPM to 1500 RPM and its corresponding Backemf and current waveforms using PI controller. http://www.iaeme.com/ IJMET/index.asp 782 editor@iaeme.com
N. Mohanraj and R. Sankaran Fig. 9. Rotor speed, Back EMF and Stator Current waveforms using PI controller Fig. 10. Shows the speed variation of the entire BLDCM drive system for a step change of reference speed from 1500 RPM to 1000 RPM and its corresponding Backemf and current waveforms using PI controller. Fig. 10. Rotor speed, Back EMF and Stator Current waveforms using PI controller Fig. 11. Shows the speed variation of the entire BLDCM drive system for a step change of reference speed from 1000 RPM to 500 RPM and its corresponding Backemf and current waveforms using PI controller. Fig. 11. Rotor speed, Back EMF and Stator Current waveforms using PI controller Fig. 12. Shows the Shows the speed variation of the entire BLDCM drive system for a step change of reference speed from 2000 RPM to 1500 RPM and its corresponding Backemf and current waveforms using FUZZY controller. http://www.iaeme.com/ IJMET/index.asp 783 editor@iaeme.com
Track Voltage Approach Using Conventional Pi And Fuzzy Logic Controller For Performance Comparison of BLDC Motor Drive System Fed by CUK Converter Fig. 12. Rotor speed, Back EMF and Stator Current waveforms using FUZZY controller Fig. 13. Shows the speed variation of the entire BLDCM drive system for a step change of reference speed from 1500 RPM to 1000 RPM and its corresponding Backemf and current waveforms using FUZZY controller. Fig. 13. Rotor speed, Back EMF and Stator Current waveforms using FUZZY controller Fig. 14. Shows the speed variation of the entire BLDCM drive system for a step change of reference speed from 1000 RPM to 500 RPM system and its corresponding Backemf and current waveforms using FUZZY controller. Fig 14. Rotor speed, Back EMF and Stator Current waveforms using FUZZY controller Fig. 15. Shows the speed variation of the entire BLDCM drive system simulated waveform for the step change of reference speed for both the controllers viz PI controller and FUZZY controller. It can be observed that smoothness is obtained in actual speed following the reference speed, Backemf and current waveforms using FUZZY controller is far superior than PI controller in the BLDC motor drive system over the time period 2 seconds. http://www.iaeme.com/ IJMET/index.asp 784 editor@iaeme.com
N. Mohanraj and R. Sankaran Fig.15. Rotor speed, Back EMF and Stator Current waveforms using (a) PI Controller (b) FUZZY controller 6. CONCLUSION In this research paper, the entire drive system is simulated over duration of certain time period. Comparison is made on both controller viz. PI controller and FUZZY controller. This is done by analyzing various parameters in simulated waveforms of the entire drive system. Finally, these simulated results shows that the FUZZY controller has better performance and smoothness in waveforms in all aspects as compared to PI controller. ACKNOWLEDGMENT I am deeply indebted to our vice chancellor Prof V. Sethuraman, SASTRA University, for providing me the facilities to do this work and my gratefulness for his excellent support. TABLE 1 BLDC motor Specifications Motor Rating 5 Horse Power Voltage 400 Volts Rated Speed 3000 Revolution Per Minute Phase resistance 1.875 ohms Phase inductance 8.5 milli Henry Number of pole pairs 2 Back EMF Trapezoidal http://www.iaeme.com/ IJMET/index.asp 785 editor@iaeme.com
Track Voltage Approach Using Conventional Pi And Fuzzy Logic Controller For Performance Comparison of BLDC Motor Drive System Fed by CUK Converter REFERENCES [1] N. Mohanraj, R. Sankaran. "Converter Control Strategy for Torque Ripple Minimization in BLDC Motor", Energy Procedia, 2017. [2] P. Pillay and R. Krishnan, Modeling, simulation, and analysis of permanent- magnet motor drives, part II: The brushless dc motor drive, IEEE Trans. Ind. Appl., vol. IA-25, no. 2, pp. 274 279, Mar./Apr. 1989. [3] C. Sheeba Joice, S. R. Paranjothi, and V. J. Senthil Kumar, Digital control strategy for four quadrant operation of three phase BLDC motor with load variations, IEEE Trans. Ind. Informat., vol. 9, no. 2, pp. 974 982, May 2013. [4] T.J.E. Miller, Brushless Permanent Magnet & Reluctance Motor Drives Clarendon Press, Oxford, Vol.2, pp: 192-199, 1989. [5] Timothy J. Ross Fuzzy Logic with Engineering Applications,McGraw Hill, Inc., 1997. [6] J. F. Gieras and M.Wing, Permanent Magnet Motor Technology Design and Application. New York, NY, USA: Marcel Dekker, Inc, 2002. [7] N. Mohan, T. M. Undeland and W. P. Robbins, Power Electronics: Converters, Applications and Design, 3rd Edition, John Wiley and Sons Inc, USA, 2002 [8] B. K Bose, Power Electronics and Variable Frequency Drives, Technology and Applications, IEEE Press, 1997. [9] G. K. Dubey, Power Semiconductor Controlled Drives", Prentice Hall, New Jersey, 1989. http://www.iaeme.com/ IJMET/index.asp 786 editor@iaeme.com