Indirect Matrix Converters as Generator–Grid Interfaces for Wind Energy Systems

Switched-inductor and quasi-Z-source indirect matrix converters are proposed as generator-grid interface for wind energy systems. Voltage levels of gearless ac generators typical for such systems are low. Thus, power electronic interfaces linking the generator with the grid must provide significant voltage boost. Switched-inductor Z-source network employs a brief shoot-through state to boost the voltage of inverters. The quasi-Z-source network offers other advantages, such as lower component ratings, reduced source stress and switch count, and simpler control strategies. The generator-grid interfaces described in this paper are based on the ultrasparse matrix topology characterized by the minimum number of semiconductor switches. The boosting networks are located between the front-end rectifier and back-end inverter. A space vector modulation technique has been developed to achieve high boosting flexibility and minimum switching losses in the converter. The fast Fourier transform analysis for the input/output currents of the converters with respect to the boost factor is carried out. The simulation and experimental results verify the effectiveness of the proposed topologies and control strategies in providing high boosting capability, while the input/output current quality is maintained within an acceptable range.