scholarly journals Multiloop current control for an inductive–capacitive–inductive‐filtered grid‐connected inverter with frequency‐adaptive capability under distorted grid environment

2019 ◽  
Vol 12 (6) ◽  
pp. 1521-1531 ◽  
Author(s):  
Seung‐Jin Yoon ◽  
Kyeong‐Hwa Kim
Keyword(s):  
Current Control ◽  
Grid Environment ◽  
Distorted Grid ◽  
Adaptive Capability ◽  
Grid Connected Inverter

scholarly journals Current control of grid-connected inverter using integral sliding mode control and resonant compensation

2019 ◽  
Vol 10 (2) ◽  
pp. 1022
Author(s):  
Seung-Jin Yoon ◽  
Thanh Van Nguyen ◽  
Kyeong-Hwa Kim
Keyword(s):  
Sliding Mode Control ◽  
Sliding Mode ◽  
Voltage Control ◽  
Current Control ◽  
Control Loop ◽  
Integral Sliding Mode Control ◽  
Integral Sliding Mode ◽  
Distorted Grid ◽  
Capacitor Voltage ◽  
Grid Connected Inverter

<p>To eliminate the adverse effect from parameter variations as well as distorted grid conditions, a current control scheme of an LCL-filtered grid-connected inverter using a discrete integral sliding mode control (ISMC) and resonant compensation is presented. The proposed scheme is constructed based on the cascaded multiloop structure, in which three control loops are composed of grid-side current control, capacitor voltage control, and inverter-side current control. An active damping to suppress the resonance caused by LCL filter can be effectively realized by means of the inverter-side feedback control loop. Furthermore, the seamless transfer operation between the grid-connected mode and islanded mode is achieved by the capacitor voltage control loop. To retain a high tracking performance and robustness of the ISMC as well as an excellent harmonic compensation capability of the resonant control (RC) scheme at the same time, two control methods are combined in the proposed current controller. As a result, the proposed scheme yields a high quality of the injected grid currents and fast dynamic response even under distorted grid conditions. Furthermore, to reduce the number of sensors, a discrete-time reduced-order state observer is introduced. Simulation and experimental results are presented to demonstrate the effectiveness of the proposed scheme.</p>

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.

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.

scholarly journals A Decoupled Hybrid Current Control for Improving the Performance of 60° DPWM-Based Three-Phase Grid-Connected Inverter

IEEE Access ◽  
2020 ◽  
Vol 8 ◽  
pp. 876-888
Author(s):  
Yuanbin He ◽  
Bangchao Wang ◽  
Xiaogao Xie ◽  
Lei Shen ◽  
Pingliang Zeng
Keyword(s):  
Current Control ◽  
Three Phase ◽  
Grid Connected Inverter

scholarly journals Resonance Instability of Photovoltaic E-Bike Charging Stations: Control Parameters Analysis, Modeling and Experiment

2019 ◽  
Vol 9 (2) ◽  
pp. 252 ◽  
Author(s):  
Ziqian Zhang ◽  
Cihan Gercek ◽  
Herwig Renner ◽  
Angèle Reinders ◽  
Lothar Fickert
Keyword(s):  
Major Effect ◽  
Current Control ◽  
Current Loop ◽  
Control Methods ◽  
Control Parameters ◽  
Charging System ◽  
Grid Connected Inverter ◽  
The Time Domain ◽  
Charging Stations ◽  
And Control

This article presents an in-situ comparative analysis and power quality tests of a newly developed photovoltaic charging system for e-bikes. The various control methods of the inverter are modeled and a single-phase grid-connected inverter is tested under different conditions. Models are constituted for two current control methods; the proportional resonance and the synchronous rotating frames. In order to determine the influence of the control parameters, the system is analyzed analytically in the time domain as well as in the frequency domain by simulation. The tests indicated the resonance instability of the photovoltaic inverter. The passivity impedance-based stability criterion is applied in order to analyze the phenomenon of resonance instability. In conclusion, the phase-locked loop (PLL) bandwidth and control parameters of the current loop have a major effect on the output admittance of the inverter, which should be adjusted to make the system stable.

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