Abstract-An offshore wind turbine usually has the grid step-up
transformer integrated in the nacelle. This increases mechanical
loading of the tower. In that context, a transformer-less, high
voltage, highly-reliable and compact converter system for
nacelle installation would be an attractive solution for large
offshore wind turbines. This paper, therefore, presents a
transformer-less grid integration topology for PMSG based
large wind turbine generator systems using modular matrix
converters. Each matrix converter module is fed from three
generator coils of the PMSG which are phase shifted by 1200.
Outputs of matrix converter modules are connected in series to
increase the output voltage and thus eliminate the need of a
coupling step-up transformer. Moreover, dc-link capacitors
found in conventional back-to-back converter topologies are
eliminated in the proposed system. Proper multilevel output
voltage generation and power sharing between converter
modules are achieved through an advanced switching strategy.
Simulation results are presented to validate the proposed
modular matrix converter system, modulation method and
control techniques.
Index Terms-Modular matrix converter, transformer-less grid
connection, wind power.