An Online Modulation Strategy to Control the Matrix Converter Under Unbalanced Input Conditions

Due to absence of a dc-link energy storage element in the direct matrix converter (MC), any abnormality/disturbance in the input voltages is directly reflected on the output voltages. In this paper, a new modulation strategy to control the 3x3 MC under unbalanced input voltage conditions is proposed. The proposed strategy is based on modification of the space vector modulation strategy, which formulates and solves an optimization problem to determine the best switching states and their corresponding optimal duty cycles, such that the errors in the output voltages and the input currents under unbalanced input voltage conditions are minimized. The salient feature of the proposed strategy is its capability to extend the output operating range of the MC. The proposed strategy ensures that optimal performance of the MC over the entire operating range, including the case when the converter operates with an output voltage greater than the maximum attainable balanced output voltage under unbalanced input voltage conditions, is achieved. Performance of the proposed strategy is evaluated and validated based on time-domain simulation studies in the MATLAB/Simulink software environment and experimentation on a scaled-down laboratory prototype.