Paper:

# Stability Regions of Nonlinear LCL-Filtered Converter with Converter-Current-Feedback Control Without Damping

## Qingyi Wang^{*,**}, Xuefen Wang^{*,**}, Min Ding^{*,**,†}, Quan Yin^{***}, and Haichun Li^{***}

^{*}School of Automation, China University of Geosciences

No. 388, Lumo Road, Wuhan 430074, China

^{**}Hubei Key Laboratory of Advanced Control and Intelligent Automation for Complex Systems

Wuhan 430074, China

^{***}School of Automation, Huazhong University of Science and Technology

1037 Luoyu Road, Wuhan 430074, China

^{†}Corresponding author

The stability regions of a LCL-filtered converter adopting converter-current-feedback control without damping are analyzed. The nonlinear LCL-filtered model is presented to investigate its influence on the system stability. The stability analysis is performed by means of the Nyquist diagram in s domain. It reveals that three factors have the dominant effects on the system stability, including internal loss of LCL-filtered model, PWM transport delay and controller parameters. The undamped stability boundaries of the system gain calculated by the symmetrical optimum method are obtained. It can be found that stable regions for the nonlinear LCL-filtered system are extended into a continuous region of ratios of LCL filter resonance frequency to control frequency from three distinct regions. Finally, the stable regions are validated by the nonlinear model simulation, and experimental results verify the theoretical analysis.

*J. Adv. Comput. Intell. Intell. Inform.*, Vol.22 No.5, pp. 629-639, 2018.

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