Direct matrix converter based on improved quasi-Z source network

This study proposes a three-phase direct matrix converter (DMC) topology based on an improved quasi-Z source (QZS) network. The proposed topology shows the following features: (i) Improve the voltage transmission ratio of traditional DMC. (ii) The voltage and current on the output side can be affected by the input side to the minimum, which minimises the harmonic content of the output current. (iii) Due to the existence of the improved QZS network, the three bidirectional switches of each output phase bridge arm are turned-on at the same time, which improves the reliability of the system. (iv) The improved QZS network has an input LC filter function, and no additional filter circuit is required on the input side. This study analyses the topological structure of the improved QZS-DMC and elaborates its boost working principle. On this basis, an improved dual space vector modulation strategy with shoot-through zero vector is proposed, which can effectively reduce the loss of the switch tube and improve the output waveform quality of the converter. Simulation and experimental results verify the proposed topology and strategy.