Modelling 1

Simulation Models of Triple Switched Reluctance Motors Parallel Drive System Hao Chen, Fengfeng Zhuang, Xiuli Ju

China University of Mining & Technology, Xuzhou 221008, China Abstract The structure and principles of the triple Switched Reluctance motors parallel drive system was described. The developed simulation models for the triple Switched Reluctance motors parallel drive system were presented. The simulated rotor speed curves, the simulated phase current waveform and simulated electromagnetic torque waveform were also presented.

II. STRUCTURE OF SYSTEM AND PRINCIPLES

I. INTRODUCTION

In some industry applications for the large power electrical drive, the double motors parallel drive, the triple motors parallel drive, and the multiple motors parallel drive could be adopted to enhance the reliability, save space and make the distribution of the drive reasonably. The Switched Reluctance motor drive is a novel electrical drive. The Switched Reluctance motor drive has the soft mechanical properties [1]. It contributes to balance the loads and synchronize the rotor speeds while the double Switched Reluctance motors parallel drive [2], the triple Switched Reluctance motors parallel drive or the multiple Switched Reluctance motors parallel drive [3] were developed. The Switched Reluctance motor drive has the high capability of fault tolerance since each phase is independent in magnetic paths and in circuit. The capability of fault tolerance in the four-phase Switched Reluctance motor drive is higher than that in the threephase Switched Reluctance motor drive since the number of phase in the four-phase Switched Reluctance motor drive is bigger than that in the three-phase Switched Reluctance motor drive [4]. There are commonly fourphase 8/6 structure Switched Reluctance motor and fourphase 16/12 structure Switched Reluctance motor [5]. Considering the manufactural technique and capability of fault tolerance, the four-phase 8/6 structure Switched Reluctance motor with the four-phase asymmetric bridge power converter is the choice for the triple Switched Reluctance motors parallel drive system. MATLAB-SIMULINK simulation platform is an effective tool for the analysis of the motor drive. In the paper, the developed simulation models for the triple Switched Reluctance motors parallel drive system were presented. The authors would like to thank for the project supported in part by the Higher College or University of Jiangsu Province High & New Technology Industry Development Project (JH03-002), the 333 Engineering Training Programme Foundation for New Century Science & Technology Leaders of Jiangsu Province Grant No. 2003-16, the Indigo Blue Engineering Training Programme Foundation for MiddleYoung Academic Leaders by the Education Department of Jiangsu Province Grant No. [2002]60 and International Cooperation Project of Jiangsu Province Grant No. BZ2005015.

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The triple Switched Reluctance motors parallel drive system is made up of the triple four-phase 8/6 structure Switched reluctance motor, the triple four-phase asymmetric bridge power converter in parallel and the controller. There are eight stator poles and six rotor poles in the motor. There are only centralized coils in the stator, and there is no winding, no magnet and no brush in the rotor. There is a rotor position detector fixed to the case of the motor that is made up of the slotted disk coaxial with the rotor and the transducers. The photograph of the one Switched Reluctance motor was shown in Fig. 1.

Fig. 1. Photograph of the Switched Reluctance motor.

There are eight main switches and eight flywheel diodes in the main circuit of the four-phase asymmetric bridge power converter. The photograph of the one unit four-phase asymmetric bridge power converter was shown in Fig. 2. The amplitude of the phase current, the turn-on angle of the main switches and the turn-off angle of the main switches in the power converter could be used for the electromagnetic torque control and the rotor speed control. In the system, the phase current chopping control (CCC) could be implemented within the low rotor speed range from 100 rlmin to 500 rlmin, and the angle position control strategy (APC) could be implemented within the high rotor speed range from 500 rlmin to 1500 rlmin. Within the low rotor speed range from 100 rlmin to 500 rlmin, the turn-on angle of the main switches and the turn-

off angle of the main switches in the power converter are fixed. While the measured amplitude of the phase current is bigger that the limit, the main switches in the power converter are turned off a certain time, and then the main switches are turned on. If the amplitude of the phase current is still bigger than the limit, the main switches are turned off the certain time again, and then the main switches are turned on again, and so on. The balance of the loads and the synchronization of the rotor speeds in the triple Switched Reluctance motors could be implemented by regulating the limit of the current chopping, and the PID algorithm could be adopted. Within the high rotor speed range from 500 rlmin to 1500 rlmin, the turn-off angle of the main switches in the power converter is fixed at the optimum range, the balance of the loads and the synchronization of the rotor speeds in the triple Switched Reluctance motors could be implemented by regulating the turn-on angle of the main switches in the power converter, and the PID algorithm could also be adopted.

Fig. 2. Photograph of the one unit power converter.

III. SIMULATION MODELS

The simulation models for the triple Switched Reluctance motors parallel drive system developed by the MATLAB-SIMULINK platform was based on the nonlinear model of the electrical network of the power converter main circuit integrated with the two dimensions finite element model of the Switched Reluctance motor, which was shown in Fig. 3.

Fig. 3. Simulation models for the triple Switched Reluctance motors parallel drive system.

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In the simulation model, "Xon" is the turn-on angle of the main switches in the power converter, "X' is the rotor position, "W' is the angular speed of the motor, "TLJ", "TL2", and "TL3" are the loads for the triple Switched Reluctance motors, respectively, "Tel" are the electromagnetic torque for the triple Switched Reluctance motors, respectively, "f' is the inertia movement of the motor, "D" is the viscous coefficient of friction, "ni", "n2", and "n3" are the rotor speed for the triple Switched Reluctance motors, respectively, "SRMJ", "SRJM2", and

"SRAM3" are the triple Switched Reluctance motors, respectively. The simulation model for one unit Switched Reluctance motor was shown in Fig. 4. Where, "Ta", "Ib", "Tc", and "Td' are the electromagnetic torque in each phase, respectively, "Te" is the incorporated electromagnetic torque, "Us" is the supplied voltage of the phase windings, "Xoff' is the turn-off angle of the main switches in the power converter, "Im" is the limit of the current chopping, "Ia", "Ib", "Ic", and "Id' are the phase current in each phase, respectively.

Fig. 4. Simulation model for one unit Switched Reluctance motor.

The simulation model of phase current calculation and electromagnetic torque calculation module was shown in Fig. 5. Where, "Position Conversion" is used to convert the absolute rotor position of each phase as the relative rotor position within one rotor period, "Current Hysteresis" is used to implement the phase current chopping control, "i" is phase current, "a0 / 8i" and " 0 VL / ao" could be obtained by the magnetization curves of the Switched Reluctance motor, "R" is the phase resistance.

IV. SIMULATION RESULTS A triple Switched Reluctance motors parallel drive system with the triple four-phase 8/6 structure Switched reluctance motor and the triple four-phase asymmetric bridge power converter in parallel was simulated by the developed simulation models. The DC supply voltage of the prototype system is DC 132 V. At the operational condition of CCC, the turn-on angle of the main switches in the power converter was fixed at 00 (0° is the rotor 550

position that the axis of the rotor slot is aligned with that of the stator pole of the conducted phase), and the turn-off angle of the main switches in the power converter was fixed at 30°. At the operational condition of APC, the turn-off angle of the main switches in the power converter was fixed at 22.50. The simulated rotor speed curves were given in Fig. 6, while the given rotor speed of the triple Switched Reluctance motors parallel drive system is 300 rlmin, and

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the loads were 1. 60N.m x 3. The simulated phase current waveform in the triple Switched Reluctance motors were given in Fig. 7, respectively. The given rotor speed of the triple Switched Reluctance motors parallel drive system is 807 rlmin, the simulated rotor speed curves were given in Fig. 8, while the loads 1. 60N. m x 3 was added suddenly, and the simulated phase current waveform in the triple Switched Reluctance motors were given in Fig. 9, respectively.

C rrlOh

Fig. 5. Simulation model of phase current and electromagnetic torque calculation module.

1 2r

Ordinate: 2.0 A, Abscissa: 0. 01 s a) motor 1

1- motor 1: the load was 1. 44 N. m 2- motor2: the load was 1. 60 N.m 3- motor 3: the load was 1. 76 N. m Ordinate: 50 rlmin, Abscissa: 0. 05 s

Fig. 6. Simulated rotor speed curves.

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1

Ordinate: 2.0 A, Abscissa: 0.01 s b) motor 2

Ordinate: 1.OA, Abscissa: 0.01 s a) motor 1

Ordinate: 2.0 A, Abscissa: 0. 01 s c) motor 3

Ordinate: 5.0 A, Abscissa: 0. 01 s b) motor 2

Fig. 7. Simulated phase current waveform.

Ordinate: 5. 0 A, Abscissa: 0. 005 s c) motor 3

1- motor 1: the load was 1. 44 N. m 2- motor2: the load was 1. 60 N.m 3- motor 3: the load was 1. 76 N. m Ordinate: 5 rlmin, Abscissa: 0. 01 s

Fig. 9. Simulated phase current waveform.

Fig. 8. Simulated rotor speed curves.

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V. CONCLUSION

REFERENCES

The simulation models for the triple Switched Reluctance motors parallel drive system had been developed by the MATLAB-SIMULINK platform. It was based on the nonlinear model of the electrical network of the power converter main circuit integrated with the two dimensions finite element model of the Switched Reluctance motor. It provides with an applied and effective tool for the design and analysis of the triple Switched Reluctance motors parallel drive system. The choice of the control algorithm, the optimization in structure parameters and control parameters for the balance of the loads and the synchronization of the rotor speeds in the triple Switched Reluctance motors could be made based on the simulation models. The developed simulation models could be extended for the multiple Switched Reluctance motors parallel drive system.

[1] H. Chen, D. Zhang and G. Xie, "Study of the mechanical properties for the switched reluctance motor drive," Journal of China University of Mining & Technology, vol.30, no.5, pp. 458-462, Sept. 2001. [2] H. Chen, "The parallel drive system of the double switched reluctance motors based on fuzzy logic," in Proc. of 35th Annual IEEE Power Electronics Specialists Conference, Aachen, Germany, June 2004, pp.3306-3310. [3] H. Chen, D. Zhang, F. Xiao and T. Su, "The Multiple Electrical Machines System of the Switched Reluctance Drive," in Proc. of IEEE International Conference on Industrial Technology, Vol.1, Bangkok, Thailand, Dec. 2002, pp. 610-613. [4] H. Chen, J. Jiang, C. Zhang and G. Xie, "Analysis of the four-phase switched reluctance motor drive under the lacking one phase fault condition," in Proc. of IEEE 5th Asia-Pacific Conference on Circuit and Systems, Tianjin, China, Dec. 2000, pp. 304-308. [5] H. Chen, D. Zhang, T. Su and F. Xiao, "A four-phase 16/12 structure switched reluctance motor drive system," in Proc. of IEEE International Conference on Industrial Technology, Vol. 1, Bangkok, Thailand, Dec. 2002, pp. 600-603.

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