Research On The Modulation And Control Technique Of Multilevel Current Source Converter

In recent years,the concept of green travel has promoted the rapid development of electric vehicles.Large capacity energy storage and electric vehicle charging piles have become the focus of research.These need the support of low voltage and high current technology,multi-level current source converter happens to have this characteristic.Therefore,with the development of superconducting energy storage technology,the problem of inductive energy storage efficiency is solved,and the multilevel current source converter will have a broad application prospect.In this paper,the current research status of multilevel current source converters at home and abroad is summarized,the advantages and disadvantages of a typical multilevel current source converter are generalized,the characteristics of step wave modulation,specific subharmonic elimination modulation,carrier pulse width modulation and multilevel space vector modulation are analyzed,the current sharing algorithm of the inductor shunt multilevel current source converter is induced.Aiming at the advantages and disadvantages of multilevel current source converter topology and modulation method,a cascade topology based on nearest level approximation modulation(NLM)and pulse width modulation(PWM)hybrid modulation is introduced.The NLM unit sub modules share the DC current source,and the PWM unit sub module is parallel to the NLM unit,the modulation combination of low frequency and high frequency synthesizes the advantages of the two modulation methods in the aspect of the switching loss and the harmonic wave content respectively.The low-frequency module uses the sorting algorithm to balance the current of the shunt inductors to ensure the normal operation of the converter.The high frequency PWM modulation module plays the role of compensating the harmonic of the output current of the low frequency module and reducing the harmonic distortion.In Matlab/Simulink,the topology and control algorithm proposed in this paper are simulated,and the dSPACE/DS1006 controller is used to carry out the hardware experiment,the simulation and experimental results show that the proposed topology and the control algorithm are effective.Then,the mathematical model of the three-phase current type PWM rectifier and the three-value logic modulation method are introduced in this paper.The MATLAB/Simulink is used to compare the direct control strategy under the three-phase stationary coordinate and the two-phase rotating coordinate system.Finally,a three-phase current type modular multilevel converter topology is introduced in this paper.The working principle and mathematical model are analyzed.In view of the unequal inductance current of the possible submodules,an inductor current equalization algorithm for sub modules is proposed.And the three-phase current model MMC simulation model is built in MATLAB/Simulink to verify the effectiveness of the current equalization algorithm of the sub module inductance.