Capacitor-Current Proportional-Integral Positive Feedback Active Damping for LCL-Type Grid-Connected Inverter to Achieve High Robustness Against Grid Impedance Variation

2019 ◽  
Vol 34 (12) ◽  
pp. 12423-12436 ◽  
Author(s):  
Yuying He ◽  
Xuehua Wang ◽  
Xinbo Ruan ◽  
Donghua Pan ◽  
Xingping Xu ◽  
...  
Keyword(s):  
Positive Feedback ◽  
Active Damping ◽  
Proportional Integral ◽  
Impedance Variation ◽  
Grid Impedance ◽  
Grid Connected Inverter

scholarly journals Research on Novel Control Strategy for Grid-Connected Inverter Suitable for Wide-Range Grid Impedance Variation

Electronics ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 623 ◽  
Author(s):  
Xiaohuan Wang ◽  
Yang Liu ◽  
Xudong Zhang ◽  
Qingshou Yang ◽  
Chunjiang Zhang
Keyword(s):  
Control Strategy ◽  
Active Damping ◽  
Damping Coefficient ◽  
Current Loop ◽  
Grid Current ◽  
Impedance Variation ◽  
Grid Impedance ◽  
Wide Range ◽  
Simulation And Experiment ◽  
Grid Connected Inverter

With the higher penetration of renewable energy, the influence of grid equivalent distribution cable impedance on grid-connected inverter stability is attracting increasing attention. In order to suppress the interaction between grid distribution cable impedance and output impedance of the grid-connected system, the active damping strategy is often used. When a capacitive current loop is used, the damping coefficient increases with the grid impedance increasing. However, the excessive damping coefficient will cause the unstable operation of the system. In order to enhance the robustness of the system, a novel control strategy which is suitable for wide-range grid impedance variation is proposed. In this strategy, the capacitor current inner loop is combined with the grid current inner loop, and grid voltage feedforward is included. Since the virtual impedance, active damping and voltage feed-forward are normalized, the changing tendency of the damping coefficient of the grid-current inner loop is opposite to that of capacitor current inner-loop. The overall damping coefficient of the system remains relatively constant when the grid impedance changes, and this effectively suppresses the resonance of the system. In this paper, the method is analyzed and the parameters are designed and optimized. Finally, the simulation and experiment are presented to verify the analysis.

Adaptive Notch Filter Based Active Damping Control for Grid-Connected Inverter

2014 ◽  
Vol 986-987 ◽  
pp. 1169-1172
Author(s):  
Ping Wang ◽  
Meng Meng Cai
Keyword(s):  
Notch Filter ◽  
Active Damping ◽  
Band Pass Filter ◽  
Pass Filter ◽  
Adaptive Notch Filter ◽  
Attenuation Characteristic ◽  
Damping Control ◽  
Grid Impedance ◽  
Grid Connected Inverter ◽  
Active Damping Control

The LCL filter is widely applied as interface between grid-connected inverter and grid due to the preferable high frequency attenuation characteristic. Under the condition of weak grid, impedance value of grid model cannot be ignored, the existence of grid impedance results in different LCL resonant frequencies, which will arise challenges of traditional active damping control. Based on the analysis of band pass filter using active damping control strategy, an adaptive active damping control is proposed in this paper by introducing the application of active notch filter, which can adjust the position of negative resonance point adaptively so as to manage sudden grid changes. Theoretical analysis and simulation results presented on the platform of grid-connected PV inverter system indicate the effectiveness and adaptability of this active damping strategy.

scholarly journals Improved PR Control Strategy for an LCL Three-Phase Grid-Connected Inverter Based on Active Damping

2021 ◽  
Vol 11 (7) ◽  
pp. 3170
Author(s):  
Yahui Li ◽  
Jing Zhang ◽  
Zhenghang Hao ◽  
Peng Tian
Keyword(s):  
Coordinate System ◽  
Control Strategy ◽  
Reactive Power ◽  
Current Control ◽  
Active Damping ◽  
Power Calculation ◽  
Frequency Method ◽  
Proportional Integral ◽  
Three Phase ◽  
Grid Connected Inverter

Aiming at the problem of power coupling and complicated decoupling in the d-q coordinate system of a three-phase grid-connected inverter, a current closed-loop control strategy based on an improved QPIR (quasi-proportional integral resonant) controller in the α-β two-phase static coordinate system is proposed. Firstly, the mathematical model of an LCL three-phase grid-connected inverter is established, and its instantaneous power calculation equation is deduced. Secondly, the frequency method is applied to compare and analyze the proportional resonant, quasi-proportional resonant, and improved current controller, and the appropriate improved controller parameters are obtained according to the traditional proportional integral controller parameter design method and the weight coefficient. Finally, the improved controller is compared with the traditional controller in the simulation model of the LCL three-phase grid-connected inverter based on active damping. The results show that the proposed improved current control strategy has good dynamic response characteristics, can realize the non-static error control of grid-connected current, and realizes the decoupling control of active power and reactive power when the load jumps. At the same time, the results also prove the superiority of the proposed control strategy and verify its effectiveness.

scholarly journals A Control Parameters Design Method With Multi-Constrains for an LCL-Filtered Grid-Connected Inverter in a Weak Grid

2022 ◽  
Vol 9 ◽  
Author(s):  
Fuyun Wu ◽  
Zhuang Sun ◽  
Weiji Xu ◽  
Zhizhou Li ◽  
Jianguo Lyu
Keyword(s):  
Steady State ◽  
Design Method ◽  
Dynamic Performance ◽  
Active Damping ◽  
Parameter Design ◽  
Control Parameters ◽  
Weak Grid ◽  
Current Controller ◽  
Grid Impedance ◽  
Grid Connected Inverter

Under weak grid conditions, the variation of the grid impedance will affect the steady-state and dynamic performance of the LCL-filtered grid-connected inverter and even make the inverter unstable. To ensure the system stability and further improve the dynamic performance in a weak grid, a control parameter design method with multi-constrains considering the system bandwidth for the current controller and active damping is proposed in this paper. First, based on the current controller and active damping with only grid current feedback, the effects of control parameters and grid impedance on the LCL resonant suppression and the performance of the inverter are analyzed. Moreover, the parameter constraints of the controllers are derived considering the grid impedance, including stability, resonance suppression, and margin constraints. Furthermore, as the system bandwidth affects the dynamic performance of the inverter, combined with the obtained multi-constraints, the optimal control parameters are determined by achieving the maximum bandwidth of the system against the impedance variation. Compared with other two methods, when the proposed method is applied, the system can operate with a better dynamic and steady-state performance. Finally, experiments are performed on a 2 kW three-phase grid-connected inverter in the weak grid, which verify the effectiveness of the parameter design method proposed in this paper.

scholarly journals Single-Phase Photovoltaic Grid-Connected Inverter Based on Fuzzy Neural Network

2021 ◽  
Vol 25 (3) ◽  
pp. 310-316
Author(s):  
Shenping Xiao ◽  
Zhouquan Ou ◽  
Junming Peng ◽  
Yang Zhang ◽  
Xiaohu Zhang ◽  
...  
Keyword(s):  
Neural Network ◽  
Pid Controller ◽  
Fuzzy Neural Network ◽  
Single Phase ◽  
Fuzzy Inference ◽  
Learning Ability ◽  
Proportional Integral ◽  
Fuzzy Neural ◽  
Grid Connected Inverter ◽  
Self Learning

Based on a single-phase photovoltaic grid-connected inverter, a control strategy combining traditional proportional–integral–derivative (PID) control and a dynamic optimal control algorithm with a fuzzy neural network was proposed to improve the dynamic characteristics of grid-connected inverter systems effectively. A fuzzy inference rule was established after analyzing the proportional, integral, and differential coefficients of the PID controller. A fuzzy neural network was applied to adjust the parameters of the PID controller automatically. Accordingly, the proposed dynamic optimization algorithm was deduced in theory. The simulation and experimental results showed that the method was effective in making the system more robust to external disruption owing to its excellent steady-state adaptivity and self-learning ability.

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