Study On Overmodulation And Fault Tolerant Control Strategies Of Indirect Matrix Converter Fed Dual Three Phase Pmsm Drives

On the ground of indirect matrix converter(IMC)applied in low voltage and high power drive system,this thesis established the Dual Three Phase Permanent Magnet Synchronous Motor(PMSM)drive system fed by indirect matrix converter(IMC),which possesses both advantages of multiphase motor and indirect matrix converter.In the thesis,different control schemes are proposed to realize the normal operation of drive system under normal and abnormal conditions,detailed research and verification are clarified later.In order to better reflect the experiment performance of the proposed fault tolerant control strategies under abnormal conditions,the space vector modulation(SVM)strategy is firstly introduced which is the most commonly used control method of indirect matrix converter(IMC)under normal condition.The space vector modulation(SVM)is applied in both the rectifier stage and inverter stage of IMC,appropriate coordinated control strategy is also required to assure the steady and safe operation of IMC,the average virtual DC link voltage is constant and the modulation index need not to be modified instantly,which is suitable for the closed loop control of dual three phase PMSM.To overcome the limitation of the maximum voltage transfer ratio(VTR)of indirect matrix converter which is only 0.866 when it is under the linear modulation,a novel over-modulation strategy is proposed in this thesis,the main principle is to synthesis the reference current vector and reference voltage vector by changing the weight coefficient of the hexagon vector and the basic vector.This over-modulation strategy can meet the demand when the input voltage source is dropped which may lead to difficulty in motor load under low output voltage.Considering the existence of input LC filter which can produce LC resonance,causing great current harmonic on grid side and damaging the stability of power grid,the active damping control based on power balance is proposed to restrain the grid side current harmonic.The key method is to extract the high frequency component of current and add it into the input reference current,and then using the new reference current to implement over-modulation control so that the whole system can achieve high voltage transfer ratio as well as low current harmonic.For further research on indirect matrix converter fed dual three phase PMSM drive system,the mathematical model of dual three phase PMSM need to be established,the modeling methods based on dual dq transformation and vector space decoupling are elaborated in detail,relevant motor vector control strategies for both methods are introduced in the thesis,by applying over-modulation and active damping control,the voltage transfer ratio can be increased and grid side current harmonic can be suppressed.To enhance the reliability of indirect matrix converter fed dual three phase PMSM drive system,fault tolerant control strategy under abnormal condition that open-phase circuit of PMSM appears,assuming that only one phase of PMSM is open,a voltage compensation strategy is put forward to assure the motor operate normally without changing any structure of the whole system.The correctness of theoretical analysis and research is validated by both simulation and experiment.