Researsh On Carrier-based Pulse-width Modulation Strategy Of Five-phase Two-stage Matrix Converter Under Unbalanced Load

In recent decades,multi-phase motors have been widely used in AC systems due to its own advantages.As a result,multi-phase motor drive systems have developed rapidly.As a ‘green' AC-AC converter,multiphase matrix converters(MC)have been widely studied and applied,and have great potential in the appliment and development of AC-AC converters.In this paper,the topology of five-phase two-stage MC is taken as the research object under balanced load,studying its space vector pulse width modulation(SVPWM)strategy.In the case of unbalanced load,the carrier-based pulse width modulation(CPWM)strategy is used to modulated the improved topology of five-phase two-stage MC.In terms of topology,in order to make three-to-five phase two-stage MC operate under unbalanced load,the topology of the three-to-five phase two-stage MC needs to be improved.Add a bridge(N-phase bridge),connecting to the neutral of the five-phase loads in the inverter stage for controlling the voltage of neutral point.The three-to-five phase two-stage MC is changed to five-phase six-bridge two-stage MC.At the same time,in order to reduce the switching losses,the "supplementary" idea from three-to-five phase two-stage MC to five-phase six-bridge two-stage MC is proposed to control the five-phase six-bridge two-stage MC.In terms of modulation strategy,the output voltages are analyzed and the duty ratios function expression of each bridge are derived,based on the SVPWM strategy.Then a symmetrical triangular carrier signal is constructed and combined with the duty ratios function to derive the expression of the modulation waves for power switch of each bridge.Finally,the CPWM strategy is implemented by logic operation.This method can simplify the calculation from three-dimensional space coordinate system to two-dimensional plane coordinate system,and can avoid the complexity of sector division and combination of duty ratios with the SVPWM strategy.The CPWM strategy can decrease calculation and can be easy to implement.Finally,the simulation model of three-to-five phase two-stage MC and five-phase six-bridge two-stage MC are built by MATLAB/Simulink.The three-to-five phase two-stage MC are modulated by SVPWM strategy,and the five-phase six-bridge two-stage MC are momulated by CPWM method.The simulation results prove the feasibility and validity of CPWM strategy.