Switching-Loss Optimized Modulation Strategy for Multi-Level Matrix Converter

A direct three-level matrix converter has much lower switching frequency harmonic content than a conventional matrix converter. Existing literature for controlling the former relies on the indirect approach of mathematically decomposing the converter into a two-level front-end converter and a three-level neutral-point-clamped inverter. The switching sequence for these two converters is independently synthesized before merging them to get the switching sequence for the direct three-level matrix converter. This decomposition obfuscates the redundancies in the switching vector duty cycle equations that govern this converter. The indirect approach produces significantly higher switching losses in the direct three-level matrix converter than the conventional matrix converter despite having additional voltage levels, as demonstrated in this paper. A new switching-loss optimized modulation strategy is proposed to overcome this limitation. The proposed method does not rely on mathematically decomposing the converter, thus being able to exploit the redundancies in the duty cycle equations. The proposed strategy leads to much lower switching loss than a conventional matrix converter while retaining the benefit of lower harmonic content. The proposed method is verified in simulation and hardware using a 5 kW laboratory prototype.