Chennai Office: JP INFOTECH, Old No.31, New No.86, 1st Floor, 1st Avenue, Ashok Nagar, Chennai-83. Landmark: Next to Kotak Mahendra Bank/Bharath Scans Landline: (044) - 43012642 / Mobile: (0)9952649690 Pondicherry Office: JP INFOTECH, #45, Kamaraj Salai, Thattanchavady, Puducherry - 9 Landmark: Opp. to Thattanchavady Industrial Estate & Next to VVP Nagar Arch. Landline: (0413) - 4300535 / Mobile: (0)8608600246 / (0)9952649690

1. Wide Damping Region for LCL-Type Grid-Connected
Inverter with an Improved Capacitor-Current-Feedback
Method
ABSTRACT
This project has presented a stability analysis of a LCL type grid-connected
inverter in the discrete-time domain. It has been found that even though the system
is stable when the resonance frequency fr is higher than one-sixth of the sampling
frequency (fs/6), an effective damping scheme is still required due to the potential
influence of the grid impedance. With a conventional proportional capacitor-
current-feedback active damping (AD), the valid damping region is only up to fs/6.
This however is not sufficient in the design process for obtaining a high quality
output current and the system can easily become unstable due to the resonance
frequency shifting. Considering the resonance frequency design rules of the LCL
filter, this project proposes an improved capacitor-current-feedback AD method.

2. CIRCUIT DIAGRAM
EXISTING SYSTEM
The grid-connected power generation unit normally has a pulse-width-modulation
(PWM) controlled voltage source inverter, which can inject regulated active and
reactive power to the grid. In order to reduce the harmonics of the inverter output
current, output filters are often required. The LCL-type filter is increasingly
adopted due to its better attenuation of the switching harmonics, especially in high-
power systems with lower switching frequencies.

3. PROPOSED SYSTEM
In order to ensure robustness against grid impedance variation, an improved
capacitor-current-feedback AD is proposed. The influence of damping coefficient
R on damping performance is studied. Unlike the passive damping, due to the
calculation delay and ZOH, the optimal damping is obtained at the actual
resonance frequency. Further, an approximate calculation for the optimal R is also
given. Theoretical analysis and experimental results have verified the effectiveness
of the proposed method.
TOOLS AND SOFTWARE USED:
 MP LAB
 ORCAD/PSPICE
 MATLAB/SIMULINK
OUTPUT:
 HARDWARE
 SIMULATION
REFERENCE:
Xiaoqiang Li, Xiaojie Wu, Yiwen Geng, Xibo Yuan, Member, IEEE, Chenyang
Xia, and Xue Zhang, “Wide Damping Region for LCL-Type Grid-Connected
Inverter With an Improved Capacitor-Current-Feedback Method”, IEEE

4. TRANSACTIONS ON POWER ELECTRONICS, VOL. 30, NO. 9,
SEPTEMBER 2015.