Heterodyne Controlled Matrix Converter as a Direct Frequency Reduction Method for Microturbine Generators (MTG)

In this paper a control method for a matrix converter (MC) based on the heterodyne concept from the communication field is presented. The method is used to convert the high frequency of a microturbine generator's (MTG) output voltage to the utility grid's frequency. In this control method a frequency modulation (FM) of the MC's switching frequency is achieved using a DQ0 analysis of the converter's filtered output voltage with the utility grid's frequency as a reference. After filtration, the MC achieves a conversion to the reference frequency with a minimal total harmonic distortion (THD) of the output voltage while using a low switching frequency. In addition, the proposed method decouples the output frequency, phase angle and voltage amplitude, which allows them to be controlled separately. This significantly simplifies the required control, and enables a robust and low-cost design. The theoretical analysis, simulation and experimental results of the method are reported.