Double Line Voltage Synthesis Of Matrix Converter Under Unbalanced Supply

The matrix converter is a single-stage ac/ac converter. Due to the lack of reactive component, the matrix converter has compact structure and high power density; however, the disturbulances in the input side can degrade the output performance for the same reason. Recently, many improved modulation strategies have been proposed which provide satisfactory output waveforms, but the input currents are distorted according to the input/output balance equation.On the basis of analyzing the double line voltage synthesis (DLVS) and space vector modulation (SVM) strategies, this paper proves the consistency of the two strategies. The sector partition of input current and output voltage vectors is analyzed, which implies that the original switch also exists in SVM. The link between the space vectors and three-phase instantaneous values is built, based on which the consistency between the duty cycles of active switches and active vectors is proved.Based on the consistency analysis, this paper proposes two improved double line voltage synthesis (DLVS) strategies utilizing the dynamic input current modulation methods of space vector modulation (SVM) strategy. Both of them apply the dynamic input current modulation methods to DLVS aiming at improving input and output waveforms at the same time. The dynamic input current modulation methods are represented in scalar view, and the instantaneous input current expressions are given, according to which the input current quality of different modulation methods is analyzed. The impact of unbalance degree and output voltage amplitude on input current is discussed. To verify the theoretical analysis, the simulation model of matrix converter is built, and the simulation is performed. The simulation results verify the improvement of the proposed strategies and the variation trend of input current THD with various unbalance degree and output voltage amplitude.A 10-kW matrix converter prototype is built, and experiments are carried out. The contrast experiment verifies the effectiveness of the proposed strategies. It is also verified that the operation time of the proposed strategies is much shorter than that of dynamic input current modulation methods based on SVM.