EFFICIENCY OPTIMIZATION CONVERTER TO DRIVE BRUSHLESS DC MOTOR

Transcription

1 EFFICIENCY OPTIMIZATION CONVERTER TO DRIVE BRUSHLESS DC MOTOR Darshan K 1, Ms.Deepa N P 2 1,2 Dayananda Sagar College Of Engineering Abstract- Power factor correction based efficiency optimization converter fed BLDC motor drive is presented in this paper. To obtain unity power factor at AC mains using single voltage sensor, the converter is operated in DICM. To control the speed of BLDC motor it is electronically commutated such that VSI has been operated by fundamental frequency switching. The proposed model shows a valid increase in efficiency compared with existing system which is in acceptable range of IEC with less number of components used.. Keywords: BL CSC bridgeless canonical switch cell, VSI voltage source inverter, DICM discontinuous inductor current mode, CCM continuous conduction mode, PFC power factor correction, BLDC brushless dc motor, EMF electro motive force, EMI Electromagnetic interference and DBR diode bridge rectifier. I. INTRODUCTION The proposed system is converter based VSI fed BLDC motor driver, the conduction losses are reduced by partial elimination of DBR in this converter. A DBR followed by a high value of dc link capacitive feeding VSI based BLDC motor, draws peak current from supply and injects high amount of harmonics in the supply system, therefore PFC converts are used for improving power quality at AC mains. The proposed converter have low loses because of less number of components used. The cost of the proposed converter is less, because the converter is operated in DCM using voltage follower approach with requirement of single voltage sensor. II. CONVENTIONAL-TUNING METHOD Proportional controller (P-controller), integral controller (I-integral controller), derivative controller, combination of P-I controller, P-D controller, PID controller are the various tuning methods, out of which P-I controller is used in this proposed system III. EXISTING SYSTEM Converter to drive BLDC motor: Using a front end DBR and a high value of dc link capacitor draws high peak current which induces harmonics in the system. The speed control of BLDC motor is made by PWM based VSI. In the existing model there is increase in EMI in PFC converter. These EMI is classified into two categories as Conducted EMI at low frequency, Radiated EMI at high All Rights Reserved 549

2 Converter to drive BLDC motor EMI causes problems such as skin effect, high overshoot transient, eddy current loss, and Voltage drop which affect overall efficiency and performance of system. IV. PROPOSED SYSTEM When ac supply is given to diode bridge rectifier (DBR), it converts ac signal to dc signal.the dc filter has the function to reduce the harmonic from the DBR. The bridgeless canonical switching cell (BL-CSC) is used to reduce the usage of diodes, no conduction loss occurs. From BL-CSC converter, the voltage source inverter is fed into the BLDC motor, and the motor rotates.the PIC microcontroller and driver units are used to trigger the voltage source inverter. Fig.1 Block diagram of proposed method The PIC microcontroller has the voltage of minimum 5v, so driver unit is connected to the BL-CSC and VSI.Fig.1 shows the block diagram of proposed All Rights Reserved 550

3 V. OPERATING PRINCIPLE OF THE CONVERTER Fig.2 Circuit diagram of proposed method This bridgeless converter is designed such that two switches operate for positive and negative halfcycles of the supply voltage. During positive half cycle Sw1 is turned on and during negative half cycle Sw2 is tuned on, the operation for complete cycle is explained in terms of modes. Mode 1 When switch Sw1 is turned on, the input side inductor Li1 starts charging via diode Dp and current ili increases. Whereas, the intermediate capacitor C1 starts discharging via switch Sw1 to charge the DC link capacitor Cd. Therefore, the voltage across intermediate capacitor VC1 decreases, while DC link voltage, Vdc increases. Fig below shows the operation of mode I. Mode 2 When switch Sw1 is turned off, the energy stored in inductor Li1 discharges to DC link capacitor Cd via diode D1.The current ili reduces, whereas the DC link voltage continues to increase in this mode of operation. Intermediate capacitor C1 starts charging and the voltage VC1 increases. Fig below shows the operation of mode II. Mode 3 This mode is the discontinuous conduction mode of operation as the current in input inductor Li1 becomes zero. The intermediate capacitor C1 continues to hold energy and retains its charge, while the DC link capacitor Cd supplies the required energy to the load. The similar behavior of the converter is realized for the other negative half cycle of supply voltage. Fig below shows the operation of mode All Rights Reserved 551

4 Mode 4 When switch Sw2 is turned on, the input side inductor Li2 starts charging via diode Dn and current ili increases. Whereas, the intermediate capacitor C2 starts discharging via switch Sw2 to charge the DC link capacitor Cd. Therefore, the voltage across intermediate capacitor VC2 decreases, while DC link voltage, Vdc increases. Fig below shows the operation of mode IV. Mode 5 When switch Sw2 is turned off, the energy stored in inductor Li2 discharges to DC link capacitor Cd via diode D2.The current ili reduces, whereas the DC link voltage continues to increase in this mode of operation. Intermediate capacitor C2 starts charging and the voltage VC2 increases. Fig below shows the operation of mode V. Mode 6 This mode is the discontinuous conduction mode of operation as the current in input inductor Li2 becomes zero. The intermediate capacitor C2 continues to hold energy and retains its charge, while the DC link capacitor Cd supplies the required energy to the load. The similar behavior of the converter is realized for all the negative half cycle of supply voltage. Fig below shows the operation of mode All Rights Reserved 552

5 VI.Control of BLDC motor Hall-effect position sensors are used to sense the rotor position to achieve electronic commutation of BLDC motor. A standard commutation technique is used for this trapezoidal back electromotive force (EMF) BLDC motor, where only two stator phases conduct at any given instant of time. With the help of rotor position information, the switches in the VSI are switched ON and OFF to ensure proper direction of flow of current in respective windings. Hall-effect position sensors (Ha, Hb, and Hc) are used for sensing the rotor position on a span of 60 for electronic commutation. The conduction states of two switches (S1 and S4) are shown in Fig. 6. A line current iab is drawn from the dc link, whose magnitude depends on the applied dc link voltage Vdc, back EMFs (ean and ebn), resistances (Ra and Rb), and mutual and self-inductances (M and La and Lb) of the stator windings. Table II shows the different switching states of the VSI feeding a BLDC motor based on the Hall-effect position signals (Ha Hc). Switching modes to operate inverter VII. SELECTED-TUNING METHOD Proportional controller (P-controller), integral controller (I-integral controller), the combination of P-I controller is used to obtain constant speed and efficient working of BLDC MOTOR. 7.1 P-controller: P-controller decreases the rise time and steady state error of the system. For a 1 st order system as shown in Fig-3. Fig.3 Proportional controller The response of the closed loop transfer function is given in Fig-4 Fig.4 Response with proportional controller There is a steady state offset between the desired response and the output response. This offset can be reduced by increasing the proportional gain, but that may also cause increased oscillations for higher order systems. 7.2 I- controller: The closed loop system with integral controller is represented as All Rights Reserved 553

6 Fig.5 Integral controller action only The step response of this system with integral action is shown below. Fig.6 Step response with integral control action 7.3 PI controller: P-I controller is mainly used to eliminate the steady state error resulting from P controller Fig.7 Proportional plus integral control action P-I action provides the dual advantages of fast response due to P-action and the zero steady state error due to I-action. Fig.8 Transient responses with P, I and P-I All Rights Reserved 554

7 VIII. SIMULATION CIRCUIT AND WAVEFORM Fig.9 simulation circuit Fig.10 rotor speed waveform IX. CONCLUSION A PFC based BL-CSC converter fed BLDC motor drive has been proposed with improved power quality at the AC mains. A bridgeless configuration of a CSC converter has been used for achieving reduced conduction losses in PFC converter. The speed control of BLDC motor and power factor correction at AC mains has been achieved using a single voltage sensor. The switching losses in the VSI have been reduced by the use of fundamental frequency switching by electronically commutating the BLDC motor. Moreover, the speed of BLDC motor has been controlled by controlling the DC link voltage of the VSI. The proposed drive has shown an improved power quality at the AC mains for a wide range of speed control and supply voltages. A satisfactory performance of the proposed drive has been obtained and it is a recommended solution for low power application. REFERENCES 1. A. Barkley, D. Michaud, E. Santi, A. Monti and D.Patterson, Single Stage Brushless DC Motor Drive with High Input Power Factor for Single Phase Applications, 37th IEEE Power Electr.Spec.Conf., (PESC), pp.1-10, June T. Gopalarathnam and H.A.Toliyat, A new topology for unipolar brushless DC motor drive with high power factor, IEEE Trans. Power Elect., vol.18, no.6, pp , Nov A.Fardoun, E. H. Ismail, A. J. Sabzali, M. A. Al-Saffar, New Efficient Bridgeless Cuk Rectifiers for PFC Applications, IEEE Trans. Power Electron., vol.27, no.7, pp , July B. Singh and V. Bist, An Improved Power Quality ridgeless Cuk Converter Fed BLDC Motor Drive for Air Conditioning System, IET Power Elect., Volume 6, issue 5, pp , M.Mahdavi and H. Farzaneh-Fard, Bridgeless CUK power factor correction rectifier with reduced conduction losses, IET power Electron. Vol.5 no.9,pp ,Nov A. J. Sabzali, E. H. Ismail, M. A. Al-Saffar and A. A. Fardoun, New Bridgeless DCM Sepic and Cuk PFC Rectifiers With Low Conduction and Switching Losses, IEEE Trans. Ind. Appl., vol.47, no.2, pp ,march-april M. Mahdavi and H. Farzanehfard, Bridgeless SEPIC PFC Rectifier with Reduced Components and Conduction Losses, IEEE Trans. Ind Electron., vol 58 no,9,pp ,Sept V. Bist and B. Singh, A Reduced Sensor PFC BL-Zeta Converter Based VSI Fed BLDC Motor Drive, Electric Power System Research, vol.98,pp.11-18,may All Rights Reserved 555

8 9. B. Williams, Generation and Analysis of Canonical Switching Cell DCto-DC Converters, IEEE Trans. Ind. Electron, vol.61, no.1, pp , Jan About The Authors: Mr.Darshan K 1 is pursuing M.Tech at Dayananda Sagar College of Engineering in DEC (Digital Electronics and Communication). The areas of interests are control system and Electronic drives. Ms. Deepa N P 2 is working as Assistant professor at Dayananda Sagar College of Engineering, Bangalore. She have got more than 4 years of teaching experience. Her research interests are Power Electronics and drives, Renewable All Rights Reserved 556