Research On Modulation Strategy And Raising The Voltage Transfer Ratio For Two-stage Matrix Converter

Compared with traditional AC-DC-AC power converter, matrix converter hasmany advantages, including the simple topology of circuit, absence of large DC linkstorage elements, good input and output characteristics, bidirectional energytransmission, unity power factor and very low pollution on the grid. Thereinto,two-stage matrix converter have more excellent performance than direct matrixconverter: independent of rectifier and inverter side could be controlled separately; inmulti-drive system, a rectifier stage can be connected multiple inverter stage, so thatreducing the cost; and no need complex four-step commutation. Because of theexcellent performance of two-stage matrix converter, it will definitedly obtain rapiddevelopment in the field of power electronics in the future.However, although reaserchers work hard many years, so that matrix converterachieved the expected results, there are still a number of issues. Nowadays matrixconverter remains in the theoretical study and laboratorial prototype stage, almost hasno practical application in the industrial, these issues also become hot research. Thisthesis reaserch the common-mode voltage problem and frequency modulated PWM inorder to reduce EMI and noise for two-stage matrix converter, its development hasimportant engineering significance.Firstly, two-stage matrix converter is modulated with non-zero vector of rectifierside of the dual space vector modulation strategy, that is, rectifier stage employ PWMmodulation strategy and inverter stage employ SVPWM modulation strategy to fulfillvariable frequency output, in addtion to analyse the common-mode voltage generationprinciple and distribution rule of two-stage matrix converter in detail.Secondly, Use four modulation strategy to restrain common-mode voltage,including rearranging zero vector modulation method, using adjacent vector instead ofzero vector modulation method, none zero vector modulation method of inverter sideand changing the intermediate DC voltage modulation method, all of its reducetwo-stage matrix converter’s common-mode voltage amplitude by experiment.Moreover, study its switching times in a PWM period, whether or not zero-currentconverter and voltage transfer ratio changes.Then, this paper proposed the method of periodic modulated PWM, randomizedmodulated PWM and Chaotic modulated PWM to solve the problem of EMI and noise.Hope that the method of periodic modulated PWM, randomized modulated PWM andChaotic modulated PWM are able to reduce the amplitude of harmonic waveformobviously, meaning these method can restain EMI and noise in effect. And comparedanalyse the method of periodic modulated PWM, randomized modulated PWM and Chaotic modulated PWM.Lastly, study on inherent defect of two-stage matrix converter, its max voltagetransfer ratio is0.866, designing Buck-BoostMC circuit increase the voltage transferratio of two-stage matrix converter. The basic principle, control strategy andcommutation strategy are studied.