scholarly journals Performance Improvement of a Grid-Connected Inverter under Distorted Grid Voltage Using a Harmonic Extractor

Electronics ◽  
2019 ◽  
Vol 8 (9) ◽  
pp. 1038
Author(s):  
Sungjoon Cho ◽  
Ho-Sung Kang ◽  
Kyo-Beum Lee ◽  
Ji-Yoon Yoo
Keyword(s):  
Control Strategy ◽  
High Harmonic ◽  
Harmonic Signal ◽  
Current Control ◽  
Grid Voltage ◽  
Current Controller ◽  
Synchronous Reference Frame ◽  
Distorted Grid ◽  
Harmonic Components ◽  
Grid Connected Inverter

This paper introduces an improved current control strategy for a grid-connected inverter system operating under distorted grid voltage conditions. Although existing current controllers for grid-connected inverters have proportional integral gains with suitable bandwidth, low-order harmonic components can be generated by distorted grid voltages. The proposed improved current controller is established in a synchronous reference frame that rotates at harmonic frequency. The input signals for the harmonic current controller should contain only the specific harmonic components requiring suppression. Therefore, the proposed current controller uses a harmonic extractor to distinguish current signals from fundamental and specific harmonic components. The harmonic extractor retains only the relevant harmonic components for individual current controllers with high harmonic signal ratios. This paper introduces two different strategies to extract specific harmonic components for the current controller. The proposed control strategy does not require any additional hardware filter circuits and can be implemented easily by designing a suitable digital filter. When using the proposed method, grid current quality is significantly improved compared to conventional methods that do not include harmonic extractors. The effectiveness of the proposed method is verified through simulations and practical experiments.

Control for Grid Connected Inverter under Unbalanced Grid Voltage Based on PI-QR Controller

2014 ◽  
Vol 716-717 ◽  
pp. 1648-1653
Author(s):  
Jia Jin Pan ◽  
Yan Cheng Liu ◽  
Chuan Wang ◽  
Qin Jin Zhang
Keyword(s):  
Reference Frame ◽  
Control Strategy ◽  
Control Model ◽  
Grid Voltage ◽  
Synchronous Reference Frame ◽  
Distorted Grid ◽  
Control Scheme ◽  
Grid Connected Inverter ◽  
Typical Model ◽  
Unbalanced Grid

Control strategy under unbalanced and distorted grid voltage is one of the most significant tasks for grid-connected inverter (GCI). In order to guarantee that the grid current meets the related IEEE Std.929-2000, a new control scheme was presented. Firstly, the typical model of GCI was presented. Secondly, the GCI control model based on PI-QR controller in synchronous reference frame (SRF) was built. Finally, the system’s simulation was conducted under distorted and unbalanced grid voltage. The results demonstrate the effectiveness of the presented control strategy.

scholarly journals Grid Voltage Estimation Based on Integral Resonant Current Controller for LCL-Filtered Grid-Connected Inverter without AC Voltage Sensors

Electronics ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 2051
Author(s):  
Thuy Vi Tran ◽  
Kyeong-Hwa Kim
Keyword(s):  
Phase Angle ◽  
Sensorless Control ◽  
State Observer ◽  
Current Control ◽  
Grid Voltage ◽  
Current Controller ◽  
Start Up ◽  
Control Scheme ◽  
Full State ◽  
Grid Connected Inverter

A high reliability of a grid-connected inverter (GCI) system at reasonable cost is a critical requirement for maximizing renewable energy potential in the electrical energy market. Several grid voltage sensorless control approaches have been investigated not only to eliminate the vulnerability of faulty sensors but also to further reduce the GCI commercial price. In this paper, a frequency adaptive integral-resonant full-state feedback current control scheme with the facilitation of a full-state observer is adopted for a grid-connected inductive–capacitive–inductive (LCL) filtered inverter without sensing the grid voltages. The proposed scheme actively damps the filter resonance and ensures the robustness of the inverter system against unexpected severe grid conditions with low cost and simplified hardware construction. The synchronization of the inverter with the main grid is accomplished by the proposed current controller-based grid voltage estimator, in which the grid frequency and phase angle can be detected effectively. In addition, the actual grid voltages are precisely regenerated to ensure the stable performance of the full-state observer. A safe start-up procedure is also presented for the grid voltage sensorless control of the LCL-filtered inverter to avoid a critical overcurrent and long settling time during the start-up instant, offering a stable and reliable inverter system operation with low computational burden. The effectiveness and feasibility of the proposed voltage sensorless current control scheme are validated by the simulation and experimental results under non-ideal grid conditions such as the harmonic distortion, grid frequency variation, and sudden grid phase angle jump.

scholarly journals An Improved Droop Control Strategy for Grid-Connected Inverter Applied in Grid Voltage Inter-Harmonics and Fundamental Frequency Fluctuation

Electronics ◽  
2021 ◽  
Vol 10 (15) ◽  
pp. 1827
Author(s):  
Wanwan Xu ◽  
Bin Wang ◽  
Jiang Liu ◽  
Da Li
Keyword(s):  
Fundamental Frequency ◽  
Control Strategy ◽  
Negative Impact ◽  
Low Complexity ◽  
Frequency Fluctuation ◽  
Droop Control ◽  
Grid Voltage ◽  
Frequency Detection ◽  
Distorted Grid ◽  
Grid Connected Inverter

This paper presents a current suppression method based on a droop control strategy under distorted grid voltage with inter-harmonics and fundamental frequency fluctuation. In this proposed strategy, the current incomplete derivation controller is employed to decrease the negative impact caused by harmonic and inter-harmonic grid voltage. This method provides a good dynamic response and has low complexity against the inter-harmonics with unfixed fundamental frequency. Based on a mathematical model of the grid-connected inverter, we designed novel instantaneous frequency detection and feed-forward methods to suppress the grid fundamental frequency fluctuation impacts. Then the main parameters were analyzed. The simulation and experimental results verified the feasibility and effectiveness of the proposed method.

ANFIS Controller Design of DFIG under Distorted Grid Voltage Situations

2019 ◽  
Vol 12 (5) ◽  
pp. 445-452
Author(s):  
Hossein Komijani
Keyword(s):  
Controller Design ◽  
Control Strategies ◽  
Grid Voltage ◽  
Pi Regulator ◽  
Component Decomposition ◽  
Current Controller ◽  
Distorted Grid ◽  
Seventh Order ◽  
Harmonic Components ◽  
Doubly Fed

Background: Modeling and controlling of Doubly Fed Induction Generator (DFIG) are presented in this paper. The DFIG is considered in the positive synchronous reference framework under Distorted Grid Voltage Situations (DGVS). The DFIG electromagnetic torque, active and reactive powers of the instantaneous stator are discussed under the condition of harmonically DGVS. Methods: Four alternative control strategies are implemented on DFIG system to enhance the responses under DGVS. A novel rotor current controller based on adaptive neuro-fuzzy interface system (ANFIS) is developed. The main, fifth and seventh order harmonic components of rotor current are straightly adjusted by ANFIS controller without using any sequential component decomposition techniques at six times the grid frequency. The simulation results of implementing the presented control strategies on a two megawatt wind turbine driven DFIG system validate the feasibility and the robustness of the control scheme. Results: The results are compared with the compound controller consisting of a proportional integral (PI) regulator and a harmonic resonant (R) compensator. Conclusion: This comparison indicates the notable removal of torque and DFIG power oscillations either under DGVS.

scholarly journals An improved synchronous reference frame current control strategy for a photovoltaic grid-connected inverter under unbalanced and nonlinear load conditions

PLoS ONE ◽  
2017 ◽  
Vol 12 (2) ◽  
pp. e0164856 ◽  
Author(s):  
Amirreza Naderipour ◽  
Abdullah Asuhaimi Mohd Zin ◽  
Mohd Hafiz Bin Habibuddin ◽  
Mohammad Reza Miveh ◽  
Josep M. Guerrero
Keyword(s):  
Reference Frame ◽  
Control Strategy ◽  
Current Control ◽  
Nonlinear Load ◽  
Synchronous Reference Frame ◽  
Grid Connected Inverter ◽  
Load Conditions

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.

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