scholarly journals An Improved Current Control Strategy for a Grid-Connected Inverter under Distorted Grid Conditions

Energies ◽  
2016 ◽  
Vol 9 (3) ◽  
pp. 190 ◽  
Author(s):  
Ngoc Lai ◽  
Kyeong-Hwa Kim
Keyword(s):  
Control Strategy ◽  
Current Control ◽  
Distorted Grid ◽  
Grid Connected Inverter

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.

Direct current control strategy of LCL‐type converter for harmonic suppression under distorted grid condition

2020 ◽  
Vol 13 (17) ◽  
pp. 3922-3930
Author(s):  
Qi Wang ◽  
Wenping Qin ◽  
Wei Dai ◽  
Xiaoqing Han ◽  
Lei Wang ◽  
...  
Keyword(s):  
Direct Current ◽  
Control Strategy ◽  
Current Control ◽  
Harmonic Suppression ◽  
Distorted Grid ◽  
Direct Current Control

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 Weighted average current method for active damping control based on grid voltage feed-forward

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Shengqing Li ◽  
Xinluo Li ◽  
Xiaobao Lee
Keyword(s):  
Control Strategy ◽  
Weighted Average ◽  
Stability Margin ◽  
Current Control ◽  
Power Network ◽  
Weak Current ◽  
Damping Control ◽  
Average Current ◽  
Grid Connected Inverter ◽  
The Stability

AbstractIn the weak current network environment, the existence of power network impedance will reduce the current control stability margin of LCL grid connected inverter, the stability margin will gradually deteriorate as the inductive component of the power network impedance increases, leading to system instability. In this paper, an improved weighted average current control strategy is proposed, which is based on the active damping control of the voltage feedforward of the charged network. In the new control strategy, with the zero-pole cancellation method, a new weighting coefficient related only to the parameters of LCL filter is obtained, which reduces the order of the system, suppresses the influence of power network impedance, and improves the stabilization of the system, getting better inverter output current quality. Then the influence of power network impedance on the control system of grid connected inverter is analyzed, and the feed-forward control of grid voltage is improved to improve the stability of inverter in weak current network. The Bode diagram analysis and MATLAB simulation results proved that the proposed control strategy is feasible.

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.

Research on Control Strategy for the Three-Phase Grid-Connected Inverter

2012 ◽  
Vol 614-615 ◽  
pp. 1578-1582
Author(s):  
Chun Qing Qi ◽  
Yi Ruan ◽  
Feng Wen Cao
Keyword(s):  
Control Strategy ◽  
Reactive Power ◽  
Response Speed ◽  
Current Control ◽  
Loop Control ◽  
Closed Loop Control System ◽  
Three Phase ◽  
Control Scheme ◽  
Loop Control System ◽  
Grid Connected Inverter

This paper proposes a control strategy，based on the grid voltage oriented vector control (VOC), which makes three-phase inverter control the active and reactive power of grid-connected inverter under the premise of the direct current control. This paper analyzes the principle of three phase photovoltaic grid connected inverter and describes the control structure of the inverter. The control strategy can overcome the deficiencies of the indirect current control scheme. This paper designs the current closed-loop control system, which not only improve the system dynamic response speed and output current waveform quality, while also reduce its sensitivity to parameter changes to improve the robustness of the system. The simulation results show the validity of control strategy proposed.

scholarly journals Improved Operation Strategy with Alternative Control Targets for Voltage Source Converter under Harmonically Distorted Grid Considering Inter-Harmonics

Energies ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1236 ◽  
Author(s):  
Bo Pang ◽  
Heng Nian
Keyword(s):  
Control Strategy ◽  
Control Method ◽  
Control Object ◽  
Current Control ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Pass Filter ◽  
Control Gain ◽  
Distorted Grid ◽  
The Stability

This paper proposed an improved control method for grid-connected voltage source converter (VSC), when the grid voltage consisted of the integer harmonics and inter-harmonics. Control object of the proposed control can be alternated to achieve the sinusoidal current or smooth output power, which enhances the operation adaption of VSC under the harmonically distorted grid. On the basis of a PI regulator in the fundamental current control loop, the novel control strategy was proposed with a supplementary controller which consisted of a prepositive high-pass filter and a modified proportional-derivative controller. In the proposed control, the inter-harmonics could be suppressed without detecting frequency, while the traditional resonator was effective in the premise of knowing the harmonics frequency. Also, the influence of control gain on the steady performance and the stability of VSC was analyzed, and the influences on the fundamental control caused by the proposed controller were also analyzed to verify the practicability of the proposed control strategy. Finally, the effectiveness of the proposed strategy was verified by the experiments.

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