Research On The Strategy Of Duty-cycle Space Vector Modulation Of Matrix Converter

In the field of AC variable frequency speed regulation,as a complement and substitution of the AC-DC-AC converter,matrix converter has good prospects for development because of good sinusoidal input and output characteristics,controllable input power factor,direct bidirectional energy flow,high power density and according with the development direction of modularization.At present,however,there are many factors restricting the realization of matrix converter and its application in industrialization.One of the key factors is the choice of modulation strategy.Matrix converter modulation strategy is an important link to achieve its function and ensure the stable and reliable operation of the system.Appropriate modulation strategy can improve the voltage transfer ratio,reduce the frequency of flow,save power consumption,expand the range of reactive power control,improve the quality of output waveform and so on.Different stages are based on different mathematical ideas and circuit logic,many scholars have put forward different modulation strategies.However,it has not found the common characteristic and the concrete connection between them for lacking of further research on the basis of unified control strategy.The space vector modulation strategy is a novel method based on the state of the switch.It provides two new degrees of freedom for the modulation strategy.Different modulation strategies can be realized by selecting specific free parameters and free vectors in this method,so it is of universal significance to study.In this paper,the traditional direct transfer function method,the indirect and direct space vector modulation algorithm and the dual voltage modulation strategy are analyzed.The forming idea,the duty cycle calculation and the switch state combination are analyzed,On the basis of this,the research and analysis on the strategy of space duty ratio vector modulation is carried out.Through the vector analysis method,it obtains the specific internal relations with other modulation strategies and verified the unity of the method.A practical scheme based on the modulation strategy is proposed.The scheme chooses the free parameter as zero,The new expression of free vector is constructed.It improved waveform quality and improved the input side power factor.At the same time,it can still get the maximum voltage transfer ratio 0.866 and realize minimum commutation frequency.The simulation model of matrix converter is built in MATLAB/Simulink simulation platform.The feasibility and effectiveness of the theory are verified by simulation results.At the end of this paper,based on the designed to DSP and CPLD as the main control unit circuit of a matrix converter accounted for the empty vector control system,use the platform to verify the feasibility and effectiveness of the method and further expand the converter provides the space of the control range.