1. Direct Torque Control of Brushless DC Motor Drives With Improved Reliability Mourad Masmoudi, Bassem El Badsi, and Ahmed Masmoudi IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 50, NO. 6, NOVEMBER/DECEMBER 2014

2. ABSTRACT THIS PAPER DEALS WITH THE SYNTHESIS AND IMPLEMENTATION OF A NOVEL DIRECT TORQUE CONTROL (DTC) STRATEGY DEDICATED TO THE CONTROL OF BLDC MOTOR DRIVES. COMPARED WITH THE MOST RECENT AND HIGHLY PERFORMED DTC STRATEGY, THE PROPOSED ONE OFFERS IMPROVED RELIABILITY DUE TO THE ACHIEVEMENT OF BALANCED SWITCHING FREQUENCIES OF THE INVERTER UPPER AND LOWER INSULATED-GATE BIPOLAR TRANSISTORS, ON ONE HAND, AND THE REDUCTION IN THE AVERAGE VALUE OF THE MOTOR COMMON MODE VOLTAGE, ON THE OTHER HAND. THE TORQUE RIPPLE IS SIGNIFICANTLY DAMPED DURING SECTOR-TO-SECTOR COMMUTATIONS USING A THREE-LEVEL HYSTERESIS TORQUE CONTROLLER.

3. INTRODUCTION IN RECENT YEARS, VARIABLE SPEED DRIVES EQUIPPED WITH BLDC MOTORS HAVE BEEN EXTENSIVELY INTEGRATED IN VARIOUS APPLICATIONS, PARTICULARLY IN AUTOMOTIVE INDUSTRY UTILITIES [1] [2] [3].123 BLDC MOTORS ARE CHARACTERIZED BY A HIGH POWER FACTOR, HIGH EFFICIENCY, AND SIMPLE SENSORLESS CONTROL STRATEGIES, WHICH REPRESENT A CRUCIAL COST BENEFIT FOR DIFFERENT LARGE-SCALE PRODUCTION INDUSTRIES.

4. INTRODUCTION THE MOST RECENT AND HIGHLY PERFORMED ONE HAS BEEN PROPOSED BY ZHU AND LEONG [25].25 ALTHOUGH A NOTABLE ATTENUATION OF THE TORQUE RIPPLE HAS BEEN GAINED USING THIS STRATEGY. IT HAS BEEN NOTICED THAT IT YIELDS UNBALANCED SWITCHING FREQUENCIES OF THE INVERTER UPPER AND LOWER INSULATED-GATE BIPOLAR TRANSISTORS (IGBTS), ON ONE HAND, AND A RELATIVELY HIGH AVERAGE VALUE OF THE COMMON-MODE VOLTAGE (CMV) OF THE BLDC MOTOR.

5. PROBLEM FORMULATION

6. THE VOLTAGE SOURCE INVERTER FEEDING THE BLDC MOTOR IS THE CONVENTIONAL SIX- SWITCH THREE-PHASE INVERTER (SSTPI).

7. PROBLEM FORMULATION

8. STUDY BACKGROUND

10. ACCOUNTING FOR THE ABOVE, ONE CAN CLEARLY NOTICE THAT THE RELIABILITY OF THE INVERTER IS COMPROMISED BY THE UNBALANCED SWITCHING FREQUENCIES OF THE UPPER AND LOWER IGBTS. MOREOVER, THE RELIABILITY OF THE BLDC MOTOR TURNS TO BE AFFECTED IN SO FAR AS ITS LIFE SPAN IS LIMITED BY THE GENERATED CMV.

11. STUDY BACKGROUND

12. CASE STUDY

13. SIMULATION RESULTS

18. CONCLUSION THIS PAPER HAS PROPOSED A NOVEL DTC STRATEGY DEDICATED TO THE CONTROL OF BLDC MOTOR DRIVES. COMPARED WITH THE MOST RECENT AND HIGHLY PERFORMED DTC STRATEGY DEVELOPED BY ZHU AND LEONG, THE PROPOSED ONE MAKES IT POSSIBLE THE IMPROVEMENT OF THE DRIVE RELIABILITY DUE TO 1) THE BALANCING OF THE SWITCHING FREQUENCIES OF THE INVERTER UPPER AND LOWER IGBTS AND 2) THE SIGNIFICANT REDUCTION IN THE AVERAGE VALUE OF THE MOTOR CMV. THIS HAS BEEN CARRIED OUT THROUGH THE APPLICATION OF APPROPRIATE NULL VOLTAGE VECTORS TO DECREASE THE ELECTROMAGNETIC TORQUE.