Research On Common-mode Suppression And Control Strategy For AC-DC Matrix Converter

As a new type of "green" AC-DC power converter for its controllable power factor,sinusoidal input current,no need of large volume storage devices and other excellent advantages,the AC-DC matrix converter(MC),which is suitable for use in such as aerospace and ship system,has been a research hotspot in the field of po wer electronics in recent years.However,the large common-mode voltage(CMV)of the AC-DC matrix converter will seriously damage the leakage protection devices of the system,and the excessive power devices in the bidirectional switch require higher capaci ty for the fault tolerance of the converter.Meanwhile,there is no need of large volume storage devices makes the converter more sensitive to external disturbances.Therefore,in order to solve the problem about high common-mode voltage,poor fault tolerant performance and low disturbance resistance for the AC-DC matrix converter,the thesis selects this converter as the object to analyze and research the converter topology,modulation algorithm and control strategy deeply with the current space vector modulation(SVM).Firstly,the evolution process of the AC-DC matrix converter topology is introduced,then the space vector modulation mode and the corresponding vector synthesis principle are elaborated,and the generation mechanism of the CMV for the conver ter is also studied deeply.Because the CMV of the traditional zero vector for AC-DC matrix converter is too large,a three-phase seven-switch AC-DC matrix converter topology with a bidirectional continuous current loop has been proposed in this thesis.Co mpared with using two symmetrical effective vector to replace the traditional zero vector,the proposed topology,which uses an external freewheeling loop to construct virtual zero vector,can not only reduce CMV effectively,but also can reduce the switch ing commutations and switching loss,implement safety commutation and have a better quality of the input and output waveforms.Secondly,the operation mode and vector synthesis in the case of switch failures for AC-DC matrix converter are analyzed in detail,then the thesis finds the main reason why the converter waveforms distorted in the failure state is that the synthetic vector can not appear or appear error.For this,the I type,II type and III type of AC-DC matrix converter fault-tolerant control systems,which are based on redundant phase,redundant arm and reverse circuit,have been designed in this thesis respectively.The three kinds of redundant systems,which achieve the error vector appear normally again,all can make the converter resume normal operation,and have a good fault tolerance ability.Then,the application of sliding mode control(SMC)in AC-DC matrix converter is studied well.Firstly,based on the current space vector modulation,the mathematical model of the converter is modeled,then the system characteristics of the converter are analyzed in detail,and the traditional sliding mode control model of the converter is derived.To restrain the chattering in sliding mode and improve the overall robustness of the system,the sliding mode control function can be replaced by a continuous hyperbolic tangent function,then this thesis presents a global sliding mode control(GSMC)based on the hyperbolic tangent function with a input power factor(IPF)sliding mode compensation for AC-DC matrix converter.Comparing the chattering and the dynamic response speed between the traditional SMC and GSMC,the results show that the proposed approach has global robustness with a unity IPF,and the sliding mode chattering can be suppressed well,which improves the quality of input and output waveforms effectively.Finally,a simulation model is built on the MATLAB/Simulink platform,then a corresponding laboratory prototype is built by DSP+FPGA,and the correctness and effectiveness of the above methods are both verified by simulation and experiment.Furthermore,the thesis hopes that the research results can solve some problems that hinder the development of AC-DC matrix converter,which would provide some technical support for the industrial application of AC-DC matrix converter in the future.