ISSN 2277-2685 IJESR/Dec. 2015/ Vol-5/Issue-12/1456-1460 Sindhu BM / International Journal of Engineering & Science Research A DIGITAL CONTROLLING SCHEME OF A THREE PHASE BLDM DRIVE FOR FOUR QUADRANT OPERATION ABSTRACT Sindhu BM* 1 1 Asst. Prof., Dept. of EEE, GSSSIETW, Mysuru, Banglore, India. Electric vehicles will be one of the main transportation schemes in the coming years due to the fast exhaustion of fossil fuels. Brushless DC motors are becoming more and more popular in the area of electrical drives especially rp in the field of electrical vehicles because of its features like optimizing power density, more reliability. In this paper, a digital controlling scheme for four quadrant operation of BLDC motor with additional feature of regenerative braking is proposed. The PWM inverter fed BLDC motor and the controller models were developed and simulated in MATLAB/SIMULINK. The simulation results were verified which indicate satisfactory performance of the motor in the four quadrants. The scheme is implemented on prototype 3 phase star connected BLDC motor with pic microcontroller dspic16f877a as digital controller that perform speed control, reading hall sensor signals, rotation and direction control and commutation sequence execution for MOSFETS. The implemented system is operated and analyzed in the four quadrants. A smooth and a quick transition between the quadrants of operation is observed and measurement of the voltage generated during the regenerative braking period showed that this model can be successfully used in small and medium powered electrical vehicles. Keywords: BLDC motor, PWM inverter, pic microcontroller, hall sensors, four quadrant operation. 1. INTRODUCTION Majority of electrical drive systems call for application which require quick response and high starting torque such as electrical vehicles. BLDC motor has high range of operation, less maintenance and many other features which make it ideally suited for electric vehicle applications. Various technologies were implemented in the past to control BLDC motor. A simple but efficient method is proposed in the paper with digital controlling scheme. The efficiency of the system is also increased by the implementation of regeneration. The speed of BLDC motor drive system is controlled by digital means by programming the PIC microcontroller. The aim of this project is to propose a method of digital controlling scheme for four quadrant operation and an added feature of regenerative braking. This paper is organized as follows; Section 2 gives the detail of proposed drive system and block diagram. Section 3 gives modelling of the system in SIMULINK for no load and on load conditions. In this section analysis of the simulation results is also done. Section 4 gives out the details of hardware implementation. Section 5 deals with the hardware results and analysis and finally section VI gives conclusion. 2. PROPOSED MOTOR DRIVE SYSTEM The proposed motor drive system ( Fig 1) uses BLDC motor with built in hall sensors which is fed by PWM inverter with MOSFET as switches. The reference speed is set as input with rotor position and speed as feedback signals to the controller. The controller generates appropriate PWM signals to turn on the inverter switches. The drive is operated in all the four quadrants and the braking period energy is rectified and stored in the battery. *Corresponding Author www.ijesr.org 1456
3. SIMULATION AND RESULT ANALYSIS The proposed system is modelled in MATLAB SIMULINK platform with PI controller as speed controller and the four quadrant operation for no load and on load condition is obtained and analysed. Fig. 1: Proposed drive system With reference to the Fig 2 the simulation is carried out with at no load and the plot of reference and actual speed indicated by Fig 4 gives the transient performance of the motor. The system is modelled for closed loop operation with load in all four quadrants and the simulation results are shown in Fig 5. During braking mode of operation using the relay block subsystem, the generated energy is rectified and stored in the battery. The simulation results indicate good transient and steady state characteristics during no load as well as on load of 11 Nm. The inverter output, Stator current and PWM pulses are studied and found to be satisfactory. The State of charging of battery is also plotted and studied and found to be working satisfactorily. Fig. 2: Closed loop Simulink model of BLDC motor at No load Copyright 2015 Published by IJESR. All rights reserved 1457
Fig. 3: Closed loop Simulink Model of BLDC motor on load Fig. 4: Actual and reference no load speed Fig. 5: Actual and reference speed during Four quadrant operation on load of 11N.m Copyright 2015 Published by IJESR. All rights reserved 1458
4. HARDWARE IMPLEMENTATION Fig. 6: soc of battery during braking The proposed system is verified experimentally by building a prototype (FIG 7). For experimental set up 3- phase, star connected 36V BLDC motor with built in hall sensors is used. The microcontroller is interfaced with motor. The microcontroller performs speed and position sensing, speed controlling and commutation sequence execution. The PI controller is tuned to have Kp as 0.1 and Ki as 0.03. The digital controller is effectively used to capture the hall sensor signals, to provide appropriate PWM pulses and to aid the motor speed control. The switching frequency is 3.2 khz. Optocouplers are used to provide isolation. The basic idea behind PWM pulse generation for excitation of the phases at different switching instants depends on rotor direction of rotation. All the instruction are performed in a single cycle. For eight selectable priority levels each of the available interrupt sources of the three external interrupt sources are provided. It is used to get the hall signal output from the motor. Fig. 7: Hardware setup of BLDC motor drive 5. EXPERIMENTAL RESULTS AND ANALYSIS The drive is operated in the first quadrant the speed and torque are positive and the motor is driven in the forward motoring mode by making the switch to CW mode and by slowly increasing the RPM using a variable knob. In the pic microcontroller an error signal is generated by comparing reference speed and the actual speed of the motor and by using the PI speed regulator the motor is aided to run at the constant speed. Copyright 2015 Published by IJESR. All rights reserved 1459
On resetting the PIC for an very small instant of time the code for the reverse motoring is executed and on changing the switch position from CW to CCW and varying the RPM the motor runs in the reverse direction that is in the third quadrant where the speed and torque are negative. To observe the regenerative braking the motor running in the reverse motoring mode is brought to absolute stand still position and the dspic is reset, the power supply to the motor is turned off ensuring that no power is entering the drive from external means and the motor is made to manually rotate in the forward braking as well as reverse braking directions and as an indication of the regenerative brake energy being generated LEDs are provided in the power and driving paths which glows brightly. These LEDs glowing indicates that not only power is generated; the motor is also being driven by the aid of control units in the regenerative braking modes in both the directions. 6. CONCLUSION Mode of operation Forward braking Reverse braking Generated voltage 20V 13V This paper presents a simple yet effective and efficient method of digital speed controlling of BLDC motor in four quadrants. The system is simulated and also verified experimentally and found to have satisfactory performance both on no load and with load. For future work sensor less system can be designed and implemented using torque observers. PIC microcontroller can be replaced by sophisticated and faster controlling schemes such as digital signal processors. REFERENCES [1] Joice CS, Paranjothi SR, Kumar VJS. Practical implementation of four quadrant operation of three phase Brushless DC motor using dspic. Proc. IConRAEeCE 2011; 91 94. [2] Yedamale P. Microchip Technology Inc. Brushless DC (BLDC) motor fundamentals, 2003. [3] Singh B, Singh S. State of the art on permanent magnet brushlessdc motor drives. J. Power Electron 2009; 9(1): 1 17. [4] Elevich LN. 3-phase BLDC motor control with hall sensors using 56800/E digital signal controllers. AN1916, Application Note, Rev. 2.0, 11/2005. [5] Hashemipour AO, Saati MA, Nezamabadi MM. A new hybrid brushless DC motor/generator without permanent magnet. IJE Trans. B: Appl. 2007; 20(1): 77 86. [6] Xia C, Li Z, Shi T. A control strategy for four-switch threephase brushless DC motor using single current sensor. IEEE Trans. Ind. Electron 2009; 56(6): 2058 2066. [7] Hung CW, Lin CT, Liu CW, Yen JY. A variable-sampling controller for brushless DC motor drives with low-resolution position sensors. IEEE Trans. Ind. Electron 2007; 54(5): 2846 2852. [8] Sathyan A, Krishnamurthy M, Milivojevic N, Emadi A. A lowcost digital control scheme for brushless DC motor drives in domestic applications. Proc. Int. Electric Machines Drives Conf. 2009; 76 82. [9] Sathyan A, Milivojevic N, Lee YJ, Krishnamurthy M, Emadi A. An FPGA-based novel digital PWM control scheme for BLDC motor drives. IEEE Trans. Ind. Electron 2009; 56(8): 3040 3049. [10] Shanmugasundram R, Zakariah KM, Yadaiah N. Low-cost high performance brushless DC motor drive for speed control applications. Copyright 2015 Published by IJESR. All rights reserved 1460