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 An Integrated Design Approach for LCL-Type Inverter to Improve Its Adaptation in Weak Grid

Energies ◽  
2019 ◽  
Vol 12 (13) ◽  
pp. 2637
Author(s):  
Zheng ◽  
Liu ◽  
Liu ◽  
Li ◽  
Dai ◽  
...  
Keyword(s):  
Design Method ◽  
Robustness Analysis ◽  
Integrated Design ◽  
System Stability ◽  
Lcl Filter ◽  
Weak Grid ◽  
Grid Impedance ◽  
Integrated Design Approach ◽  
Simulation And Experiment ◽  
Grid Connected Inverter

To improve the robustness of grid-connected inverter against grid impedance in a weak grid an integrated design method of LCL-filter parameters and controller parameters is proposed. In the method the inherent relation of LCL-filter parameters and controller parameters is taken into consideration to realize their optimized match. A parameter normalization scheme is also developed to facilitate the system stability and robustness analysis. Based on the method all normalization parameters can be designed succinctly according to the required stability and robustness. Additionally, the LCL parameter and controller parameter can be achieved immediately by restoring normalization parameters. The proposed design method can guarantee the inverter stability and robustness simultaneously without needing any compensation network, additional hardware, or the complicated iterative computations which cannot be avoided for the conventional inverter design method. Simulation and experiment results have validated the superiority of the proposed inverter design method.

scholarly journals Stability Assessment of Current Controller with Harmonic Compensator for LCL-Filtered Grid-Connected Inverter under Distorted Weak Grid

2020 ◽  
Vol 11 (1) ◽  
pp. 212
Author(s):  
Seung-Jin Yoon ◽  
Thuy Vi Tran ◽  
Kyeong-Hwa Kim
Keyword(s):  
Closed Loop ◽  
Current Control ◽  
System Stability ◽  
Stability Assessment ◽  
Weak Grid ◽  
Current Controller ◽  
Distorted Grid ◽  
Grid Impedance ◽  
Grid Connected Inverter ◽  
The Stability

An assessment of the stability and performance of current controllers with harmonic compensators is presented for an inductive-capacitive-inductive (LCL)-filtered grid-connected inverter under distorted weak grid conditions. By using two typical current control schemes which are the direct current controller with the capacitor current-based active damping and integral-resonant state feedback current controller, the closed-loop system stability and current control performance are investigated in the presence of both uncertain grid impedance and distorted grid. Even though the controller stability has been investigated under weak grid in several studies, the stability assessment of the entire current control scheme, including the harmonic resonant controllers, still needs a further comprehensive investigation. The system stability is analyzed by obtaining the movement of the closed-loop poles in the discrete-time domain when the grid impedance varies. To fully study the impact of distorted weak grid condition on the LCL filters, three LCL filter parameter sets giving the resonance frequency in different frequency bands are chosen for the purpose of evaluating the system robustness and grid-injected current quality. In order to support the presented theoretical analyses, comprehensive simulation and experimental results based on 32-bit DSP TMS320F28335 to control 2 kVA grid-connected inverter are presented in terms of grid current quality and control stability in the environment of both uncertain grid impedance and distorted grid.

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 An Optimized Parameter Design Method for Passivity-Based Control in a LCL-Filtered Grid-Connected Inverter

IEEE Access ◽  
2020 ◽  
Vol 8 ◽  
pp. 189878-189890
Author(s):  
Faban Zheng ◽  
Weimin Wu ◽  
Bolin Chen ◽  
Eftichios Koutroulis
Keyword(s):  
Design Method ◽  
Parameter Design ◽  
Passivity Based Control ◽  
Grid Connected Inverter

LCL Filter with Active Damping using PI and SSI Regulators in Synchronous Rotating Reference Frame Current Controller for DSTATCOM

2013 ◽  
Vol 14 (4) ◽  
pp. 309-326
Author(s):  
Nagesh Geddada ◽  
Mahesh Kumar Mishra
Keyword(s):  
Steady State ◽  
Dynamic Load ◽  
Distribution System ◽  
Voltage Drop ◽  
Active Damping ◽  
Voltage Source ◽  
Lcl Filter ◽  
Load Compensation ◽  
Current Controller ◽  
Load Conditions

Abstract This article proposes a distribution static compensator (DSTATCOM) with interface LCL (inductor-capacitor-inductor) filter for load compensation in three-phase four-wire distribution system. DSTATCOM, consisting of voltage source inverter (VSI), is connected in parallel to the load and injects currents corresponding to load reactive, harmonic powers. But this injected current consists of unnecessary high-frequency switching ripple generated by VSI. This LCL filter has superior switching ripple attenuation capability compared to L filter. Moreover, this can be achieved with small value of overall LCL filter inductance than L filter. Thus providing high slew rate for output current to track the desired reference current closely, reducing voltage drop across it, as well as cost and size of filter. However, one major concern with LCL filter is its resonating frequency (determined from its L, C, L values), which can create high-resonance oscillating currents and results in improper load compensation. Therefore, in this study, proper design of LCL filter with high switching ripple attenuation and a current controller with proportional integral (PI) plus harmonic compensation (HC) regulators along with active damping feature of LCL filter in synchronous rotating reference (dq0) frame are presented. HC regulator minimizes the steady-state error in the non-sinusoidal filter currents (fundamental and harmonic) which are tracked by the VSI. Active damping feature (obtained by capacitor current feedback control of LCL filter) is used to overcome resonance oscillations and provides proper control, operation of DSTATCOM under steady-state and dynamic load conditions. Stability studies for designed LCL filter and current controller using Bode and root locus plots are also performed and presented. Extensive simulation study, to understand the compensation performance of LCL filter DSTATCOM with two types of current controllers (PI and PI plus HC) under steady-state and dynamic load conditions, is carried out in PSCAD simulator and the corresponding results along with THDs of various parameters are presented.

scholarly journals Adjusting output impedance using a PI controller to improve the stability of a single phase inverter under weak grid

2016 ◽  
Vol 1 (4) ◽  
pp. 50
Author(s):  
Jiao Jiao ◽  
R. Mark Nelms
Keyword(s):  
Single Phase ◽  
Pi Controller ◽  
Output Impedance ◽  
Weak Grid ◽  
Harmonic Reduction ◽  
Grid Impedance ◽  
Single Phase Inverter ◽  
Grid Connected Inverter ◽  
The Stability ◽  
Lc Filter

Explored in this paper is the grid impedance effect on the stability of a single-phase grid connected inverter with an LC filter based on an analysis of the inverter output impedance. For a single-phase grid connected inverter, a PI controller is often used to regulate the current injected into the grid. However, the control performance can be influenced when the inverter is connected to a weak grid. Also, the utility grid has background harmonic noise, which can make the injected current distorted. Therefore, analysis of the output impedance of a single-phase grid connected inverter is important for the robustness and stability of the system. By modeling the output impedance of inverter, it can be determined that the proportional gain and integral gain of the controller have an effect on the output impedance. Analytical results show that by adjusting the PI controller parameters, the ability for harmonic reduction and stability of the system can be improved. Simulation and experiments using a 1 kW single-phase grid connected inverter verify the effectiveness of the theoretical analysis.

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