| Permanent magnet motor has been more and more widely used in various AC drive systems for its high performance and reliability.Direct Torque Control(DTC)method is always the research focus when it is linked with permanent magnet motor as an advanced control method proposed by foreign scholars in the end of last century.At present,the two-level converter is more popular in this field.Compared with two-level converter,permanent magnet motor using Direct Torque Control method based on three-level converter owns less research results.Replacing two-level converters with three-level converters is proposed for its advantages compared with two-level converters.Based on existing research results of PMSM-DTC,a new method which is used to compound voltage space vectors of three-level converters.after this new method,a permanent magnet motor three-level direct torque control scheme is proposed based on the priority of torque and flux linkage.The whole work of this paper are briefly summed up as follows:(1)Using three-level converters to replace two-level converters means more rich choices in choosing voltage space vectors,which is expected in sinusoidal motor.Meanwhile,when using three-level converters,how to meet their controlling requirements is needed to be considered seriously.Based on existing voltage space vectors compounding methods,a new compounding method is proposed which is a closed-loop method and does not bring the distortion of the final compounded voltage space vectors.(2)Based on typical PMSM-DTC scheme,a new control method is proposed which in named as permanent magnet motor optimal direct torque control considering the priority of torque compared with flux linkage and the safety of motor.Using Simulink software simulates this new control scheme.The simulation results show that this new control method is feasible an effective.The results show that when the load torque of motor is heavy,direct torque control is actually direct self control in this new control scheme. |
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