Sang-Hyouk Lee, Hea-Gwang Jung, Kyo-Beum Lee, Se-Wan Choi, and Woo-Jin Choi, "Three-Parallel System Operation and Grid-Connection Technique for High-Power Wind Turbines using a PMSG," The Transactions of the Korean Institute of Power Electronics, vol. 15, > Paper

This paper proposes a design of the three-parallel converter system and grid-connection technique for a PMSG based wind turbine

systems. The back-to-back converter of the PMSG based wind turbine system is directly connected to the grid so that both the

power devices and the filters are needed to have large power ratings. The three-parallel converter configuration can reduce the

required power ratings of the devices and filters. However, the three-parallel converter can cause circulating currents. These

circulating currents can be suppressed by sellecting proper inner inductance at each leg. An LCL filter design is used to meet the

THD regulations. The latent resonance caused by the LCL filter is compensated by an active damping method without additional loss.

The decline of the power quality caused by the unbalanced and distorted grid voltages is also compensated with an additional

compensation algorithm. The simulation and experimental results show that the proposed system and compensation methods are

effective for the wind turbine systems.