Analysis And Optimization Of Modulation Strategies For Matrix Converters In Multi-Scenario Applications

Compared with traditional AC-DC-AC converters,matrix converters(MCs)eliminate the need for large-capacity capacitors on the DC side,resulting in a more compact and reliable structure.In recent years,they have received widespread attention from academia and industry.Particularly in applications such as more electric aircrafts that require high power density and reliability,MCs have outstanding advantages.This thesis focuses on improving the power factor regulation and fault tolerance capabilities of MCs,and has achieved the following innovative results:(1)The modulation mechanism of MCs is studied,and a generalized expression for the modulation matrix and its common-mode component is proposed.Based on the degrees of freedom and constraints of the modulation matrix,the inherent connections between traditional modulation strategies are revealed.(2)A load information-based reactive power optimization modulation strategy for MCs is proposed.The projection and constraint relationship of the degrees of freedom of the modulation matrix on a two-dimensional modulation plane are established,achieving maximum input reactive power range.(3)An overmodulation strategy for unbalanced input voltages is proposed,and the analytical expressions for the low-frequency harmonic amplitudes of the output voltage and input current are derived based on the double Fourier integrals.The maximum fundamental amplitude of the output voltage is achieved under constraints on the waveform quality of the output voltage and input current.(4)A fault-tolerant modulation strategy for MCs is proposed,which reduces the duty cycle of faulty devices by modifying the modulation matrix,enabling fault-tolerant operation in case of open-circuit faults.Compared with the model predictive control and reinforcement learning control,it effectively reduces the total harmonic distortion of the output current when the sampling frequency is limited.The validity of the above theoretical research results is verified and improved through experiments.