Optimized Controller Design for $LCL$-Type Grid-Connected Inverter to Achieve High Robustness Against Grid-Impedance Variation

2015 ◽  
Vol 62 (3) ◽  
pp. 1537-1547 ◽  
Author(s):  
Donghua Pan ◽  
Xinbo Ruan ◽  
Chenlei Bao ◽  
Weiwei Li ◽  
Xuehua Wang
Keyword(s):  
Controller Design ◽  
Impedance Variation ◽  
Grid Impedance ◽  
Grid Connected Inverter ◽  
Formula Type

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.

scholarly journals A novel current controller design for grid-integrated PV inverter system

2021 ◽  
Vol 3 (3) ◽  
Author(s):  
Ayaz Ahmad ◽  
L. Rajaji ◽  
A. Iqbal
Keyword(s):  
Controller Design ◽  
Vital Role ◽  
Current Feedback ◽  
Lcl Filter ◽  
Design Algorithm ◽  
Grid Voltage ◽  
Pv Inverter ◽  
Current Controller ◽  
Experimental Implementation ◽  
Grid Connected Inverter

AbstractDistributed generators are playing a vital role in supporting the grid in ever-increasing energy demands. Grid code regulation must be followed when integrating the photovoltaic inverter system to the grid. The paper investigates and analyzes a controller model for grid-connected PV inverters to inject sinusoidal current to the grid with minimum distortion. To achieve better tracking and disturbance rejection, a DSP-based current controller is designed with LCL filter. The controller gets the current feedback from the grid, compares it with reference current, and calculates duty cycle to generate PWM pulses to trigger H-bridge converters. The grid voltage is loaded to the initial value in proposed PR controller to ensure the initial inverter voltage to match the grid voltage. The paper presents a novel current controller algorithm for grid-connected inverter system, and simulation is done. A detailed analysis has been carried out to validate the proposed design algorithm. Experimental implementation of the current controller in the DC/AC converter circuits with an LCL filter is done for 5.4 kW to validate and match the simulation model.

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 Application of Improved Droop Control Based on Grid Impedance in Photovoltaic Grid-Connected Power Generation system

2021 ◽  
Vol 233 ◽  
pp. 01080
Author(s):  
Xu Hao Hao ◽  
Wang Fang ◽  
Liang Zhi Cheng
Keyword(s):  
Power Generation ◽  
Real Time ◽  
Power Grid ◽  
Droop Control ◽  
Generation System ◽  
Time Simulation ◽  
Grid Impedance ◽  
Power Generation System ◽  
Impedance Extraction ◽  
Grid Connected Inverter

When the power grid impedance mutates, the output power of the grid-connected photovoltaic power generation system controlled by drooping will become very unstable. To solve this problem, an improved droop control algorithm based on network impedance detection is proposed. Taking photovoltaic grid-connected power generation system as the research object, the influence of power grid impedance on traditional droop control is firstly expounded by introducing power grid impedance value into traditional droop control. Then the method of real-time network impedance extraction is introduced. Furthermore, according to the bandwidth and phase angle constraints of the equivalent output impedance phase frequency characteristics of the photovoltaic grid-connected inverter, the controller parameters are updated in real time to achieve the purpose of adaptive network impedance mutation. Finally, the proposed method is tested and verified by real-time simulation in the loop respectively. The results show that the proposed method is correct.

scholarly journals Coupling Influence on the dq Impedance Stability Analysis for the Three-Phase Grid-Connected Inverter

Energies ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3676
Author(s):  
Chuanyue Li ◽  
Taoufik Qoria ◽  
Frederic Colas ◽  
Jun Liang ◽  
Wenlong Ming ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Nyquist Plot ◽  
Current Control ◽  
Impedance Ratio ◽  
Three Phase ◽  
Grid Impedance ◽  
Nyquist Criterion ◽  
Grid Connected Inverter ◽  
The Stability ◽  
The Right

The dq impedance stability analysis for a grid-connected current-control inverter is based on the impedance ratio matrix. However, the coupled matrix brings difficulties in deriving its eigenvalues for the analysis based on the general Nyquist criterion. If the couplings are ignored for simplification, unacceptable errors will be present in the analysis. In this paper, the influence of the couplings on the dq impedance stability analysis is studied. To take the couplings into account simply, the determinant-based impedance stability analysis is used. The mechanism between the determinant of the impedance-ratio matrix and the inverter stability is unveiled. Compared to the eigenvalues-based analysis, only one determinant rather than two eigenvalue s-function is required for the stability analysis. One Nyquist plot or pole map can be applied to the determinant to check the right-half-plane poles. The accuracy of the determinant-based stability analysis is also checked by comparing with the state-space stability analysis method. For the stability analysis, the coupling influence on the current control, the phase-locked loop, and the grid impedance are studied. The errors can be 10% in the stability analysis if the couplings are ignored.

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