Dong-Keun Yoon, “풍력발전시스템의 전력변환부 3병렬 운전을 위한 LCL-필터 설계,” 아주대학교 공학석사 학위 논문, 2010. > Paper

PermanentMagnet Synchronous Generators (PMSG) are widely used in variable-speed wind turbines. However, the power devices

Must support high currents to get their high-power ratingbecause the PMSG is connected directly to the grid through a back-to-ack

converter.Therefore,the rated current of the power device can be reduced to one third of the rated value by using a three-parallel

operation.The low switching frequencyof ahigh power systemmay cause an increase in the harmonics found in the output current.

This paper proposes a design scheme for an LCL-filter used for three-parallel operation of a power converter in 2MW-wind turbines.

An appropriate design method of the delta configured LCL-filter is also proposed to improve the output power quality in the system.

A novel design method for the inner inductance of the LCL-filter is proposed in order to overcome the existing trial and error

Methods sed in designing the filter. LCL-filters typically have a problem with a reduced power factor (PF), due to the capacitor used.

To improve the poor PF, a simple compensation method is also proposed. The simulation and experimental results demonstrate that

the grid current harmonics are low and the PF is improved.