Stability analysis on parallel of LCL-filter-based grid-connected converters in MW-level direct-drive wind generation using complex vector

With the individual capacity of wind power generation system increasing, the demand for high power grid-connected converters is growing, which is usually limited by the available semiconductor technology. One solution is multiple lower power units connected in parallel. LCL filters can provide much better ripple and harmonic attenuation. Therefore, they are more suitable for high power conversion systems. However, LCL filters may result in resonance, and thus cause the closed-loop control system unstable, especially in the parallel of LCL-filter-based converters which are connected to the grid by one transformer. In this paper, complex vector model of parallel of two LCL-filter-based converters is first introduced in details. Then using the superposition theorem, the performance of LCL filter imposed by separate excited sources is analyzed. Furthermore, current reference step response and voltage feedforward control are discussed. Finally, the related results are verified by simulation and experiment.

[1]  F. Briz,et al.  Analysis and design of current regulators using complex vectors , 1997, IAS '97. Conference Record of the 1997 IEEE Industry Applications Conference Thirty-Second IAS Annual Meeting.

[2]  Zhe Chen,et al.  Overview of different wind generator systems and their comparisons , 2008 .

[3]  Henk Polinder,et al.  Basic Operation Principles and Electrical Conversion Systems of Wind Turbines , 2005 .

[4]  Christian Wessels,et al.  Limitations of Voltage-Oriented PI Current Control of Grid-Connected PWM Rectifiers With $LCL$ Filters , 2009, IEEE Transactions on Industrial Electronics.

[5]  M. Liserre,et al.  A stable three-phase LCL-filter based active rectifier without damping , 2003, 38th IAS Annual Meeting on Conference Record of the Industry Applications Conference, 2003..

[6]  Fei Zhou,et al.  Parallel interleaved grid-connected converters in MW-level wind power generation , 2009, 2009 IEEE International Electric Machines and Drives Conference.

[7]  Fei Zhou,et al.  Design algorithm of grid-side LCL-filter for three-phase voltage source PWM rectifier , 2008, 2008 IEEE Power and Energy Society General Meeting - Conversion and Delivery of Electrical Energy in the 21st Century.

[8]  Poh Chiang Loh,et al.  Exploring inherent damping characteristic of LCL-filters for three-phase grid-connected voltage source inverters , 2010, 2010 IEEE Energy Conversion Congress and Exposition.