Harmonic Analysis on the Input Current of Indirect Matrix Converter Under Different Modulation Strategies

In order to clarify the characteristics of input current harmonics, moreover suppress harmonics and improve power grid quality for the indirect matrix converter (IMC), the mathematical model is established based on the transfer function of IMC and the harmonic components are ascertained. Furthermore, the pulse barycentre concept, in which the amplitude, width and distribution position of a pulse are all considered, is introduced to analyze and determine the frequencies and magnitudes of main harmonic components. In addition, the principle of the output voltage vector pulse proportional symmetric distribution, which is able to attenuate input current harmonics, is discovered in the process of theoretical analysis and utilized under different modulation strategies. Simulation and experimental results show that, by using either dual space vector modulation (SVM) or two-stage pulse-width-modulation (PWM) with the pulse proportional symmetric distribution, the input currents mainly contain (6n±1)th low order harmonics, which are irrelevant to the output frequency, and the harmonic contents decrease as the frequency increases. Simulation and experimental results coincide with the theoretical results, which demonstrate the validity of the theoretical analysis.