| The diversity of rotor structure of permanent magnet synchronous motors,the highly proposed of the rotor permanent magnet materials and the continuous optimization of control methods,making speed control system of permanent magnet synchronous motor has been a great developent.Permanent magnet synchronous motor are widely used in many industries such as electric vehicles,aerospace and military engineer and other fields due to their many attractive characteristics of high efficiency,small volume and particularly wide flied-weakning refion.Due to the system constrained by inverter capacity,when the motor running at high speed,the output voltage of current regulator is saturated,and accoringly the torque,current and speed performance will be deteriorated.Using field-weakening control method can make the permanent magnet synchronous motor has a wide speed range,obtain greater outtput torque and better dynamic performance in the case of a contrained inverter capacity.Therefore,it is great significance to research a field-weakening control method for PMSM to expend the range of flied-weakening operation and improve its control performance.The main purpose of this study is to imporve the field-weakening ability of interior permanent magnet synchronous motor,expending the operating range of the system,increasing its maximum torque output capability and effectively imporve the dynamic response performance.In order to fully utilize the DC-link voltage of inverter,a field-weakening control method based on voltage difference feedback at overmodulation region for PMSM is proposed;In order to realize flux-weakening control,the strategy of Maximum Torque Per Voltage control(MTPV)will be used in this paper,then the whole control system is discussed.Firstly,the marhematical model of permanent magner synchronous motor in three coordinates system is established,the principle of coordinate transformation is described,the operation restrictions of PMSM and the current setpoint of the weakening work intorval elaborate cnstraints weakening control is detailed.Based on this analysis,an optimal path weak magnetic control strategy is proposed.Secondly,the method of field-weakening control for traditional voltage feedback is detailedly analyzed,in which the DC-link voltage is not fully utilized.For this disadvantage,a field-weakening control based on voltage difference feedback at overmodulation region for PMSM is proposed.In the modulation voltage difference feedback field-weakening control system,in order to fully utilize the DC-link,the SVPWM has been extended to the modulation area using the amplitude value following the modulation technology;In order to maximize use of SVPWM modulation of dynamic voltage difference before and after,using gradient descent method to estabilish the mathematical model conrol algorithm to adjust the phase angle of current vector to realize the speed operation range of PMSM is extended.The field-weakening property of the field-weakening control based on voltage difference feedback at overmodulation region is analyzed in detail,the analysis results show that the system without puls PI resistance under the condition of saturated link,can avoid PI integral saturation,geratly improves the dynamic performance of permanent magnet synchronous motor.Used for direct axis current limiter,after clipping the difference as alternating current adjustment quantity.Made the current track run along MTPV corp,curve broaden the operation area of the permanent magner synchronous motor,then linearization of the MTPV corp simplifies the calculation process.Finally,the simulation experiment has been performed by building the system simulation model based on Matlab/Simulink.The simulation result were compared with the traditional method,the results reflected the proposed approach can make full use of DC-link voltage,improves the torqu output capacity,imporved the dynamic rsponse performance of control system.Using TI’s DSP chip to build the hardware platform,given the software design program diagram of the field-weakening control,on this basis to build the experimantal platform,simulation results verify the feasibility and the correctness of the control method. |
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