Analysis and Design of Current Control Schemes for LCL-Type Grid-Connected Inverter Based on a General Mathematical Model

Pan, Donghua; Ruan, Xinbo; Wang, Xuehua; Yu, Hui; Xing, Zhongwei

doi:10.1109/tpel.2016.2602219

Cited by 114 publications

(60 citation statements)

References 44 publications

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“…In practice, the LCL filter usually suffers from resonance problems, which result in system instability. In order to deal with the problem, active damping controllers have been used [21].…”

Section: Introductionmentioning

confidence: 99%

Impact of phase-locked loop on stability of active damped LCL-filter-based grid-connected inverters with capacitor voltage feedback

Guo

Liu

Wang

2017

J. Mod. Power Syst. Clean Energy

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Active damped LCL-filter-based inverters have been widely used for grid-connected distributed generation (DG) systems. In weak grids, however, the phase-locked loop (PLL) dynamics may detrimentally affect the stability of grid-connected inverters due to interaction between the PLL and the controller. In order to solve the problem, the impact of PLL dynamics on small-signal stability is investigated for the active damped LCL-filtered grid-connected inverters with capacitor voltage feedback. The system closed-loop transfer function is established based on the Norton equivalent model by taking the PLL dynamics into account. Using an established model, the system stability boundary is identified from the viewpoint of PLL bandwidth and current regulator gain. The accuracy of the ranges of stability for the PLL bandwidth and current regulator gain is verified by both simulation and experimental results.

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“…In practice, the LCL filter usually suffers from resonance problems, which result in system instability. In order to deal with the problem, active damping controllers have been used [21].…”

Section: Introductionmentioning

confidence: 99%

Impact of phase-locked loop on stability of active damped LCL-filter-based grid-connected inverters with capacitor voltage feedback

Guo

Liu

Wang

2017

J. Mod. Power Syst. Clean Energy

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“…However, even in a stiff grid where (6) can be perfectly met, there is still a serious stability challenge faced by the grid current. In [30], this stability issue is discussed for λ = 1. To complete the work, the situation of a random λ is further analyzed as follows.…”

Section: A System Description and Modelingmentioning

confidence: 99%

“…However, the reduction of control order relies on an exact knowledge of the grid inductance, which means it is sensitive to the grid impedance variation. Moreover, recent research in [30] shows that even if the control order can be reduced, an implicit resonance hazard still exists in both the inverter current and the grid current, and it will lead to the critically stable operations of these two currents. An extra active damping, e.g., the capacitor current active damping [31], can be introduced as an inner loop to solve these problems.…”

Section: Introductionmentioning

confidence: 99%

“…Depending on the grid configuration, L g may vary in a wide range, which thus calls for a robust control scheme in order to stabilize the system. Such a robust operation is usually performed by controlling either the inverter current i L1 or the grid current i L2 with an extra active damping [30], i.e., a dual-loop strategy. Here, it is evaluated based on a single-loop scheme, which commands the weighted average value of i L1 and i L2 .…”

Section: Introductionmentioning

confidence: 99%

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A Highly Robust Single-Loop Current Control Scheme for Grid-Connected Inverter With an Improved LCCL Filter Configuration

Pan

Ruan

Xiongfei

et al. 2018

IEEE Trans. Power Electron.

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Abstract-Single-loop current control is an attractive scheme for the LCL-type grid-connected inverter due to its simplicity and low cost. However, conventional single-loop control schemes, which command either the inverter current or the grid current, are subject to the specific resonance frequency regions. The weighted average current control, which splits the filter capacitor into two parts (in form of an LCCL filter) and commands the current flowing between these two parts, is independent of the resonance frequency, but on the other hand, it is limited by the poor sensitivity to the grid impedance variation and weak stability in the grid current. These limitations are comprehensively explained in this paper and then addressed by identifying that the single-loop weighted average current control is equivalent to the dual-loop grid current control with an inherent capacitor current active damping. By tuning the capacitor split proportion as a second degree of freedom, an optimal damping performance that is robust to the grid impedance variation can be naturally achieved using only the inherent damping. Thus, no extra damping is required, and the single-loop structure with only one current sensing turns to be adequate. Moreover, for convenience of practical implementation, an improved LCCL filter configuration is proposed to allow the use of two equal nominal capacitances for the split capacitors. Finally, experiments are performed to verify the effectiveness of the proposed method.

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“…However, the control parameter design method of the HRF-based v+i c control strategy is not comprehensive in [34] since it neglects the impact of control delay, which is mainly brought by the computation and pulse width modulated (PWM) delays [35]. It has been reported that the control delay cannot be ignored because it reduces the system phase margin and influences the system minimum phase properties [36], [37]. In [38], a systematic parameter design with control delay consideration for v+i c control strategy is proposed, but the voltage loop applies the PR controller in the stationary frame instead of SRF-PI controller.…”

mentioning

confidence: 99%

Optimal Performance Design Guideline of Hybrid Reference Frame Based Dual-Loop Control Strategy for Stand-Alone Single-Phase Inverters

Han

Jiang

Coelho

et al. 2018

IEEE Trans. Energy Convers.

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Abstract-The dual-loop control strategy in hybrid reference frame (HRF) for single-phase voltage source inverters (VSIs) in islanded operation mode is studied, which applies a capacitor voltage shaping loop in the synchronous reference frame (SRF) and a capacitor current shaping loop in the stationary reference frame (HRF-based v+i c control strategy). This strategy is able to achieve the purpose of active damping, fast dynamic response and zero reference tracking error. However, due to the inherent characteristics of SRF-based voltage loop and the digital control delay, the performance of the system is degraded and the control parameter design of HRF-based v+i c control strategy shows great difficulties. To overcome these shortcomings, in this paper, a systematic parameter design guideline for HRF-based v+i c control strategy is proposed to ensure the system stability and optimize the performance of the system under control delay condition. The mathematic model of the HRF-based v+i c control strategy is established with the consideration of control delay in this paper. Based on this model, a satisfactory region of the system stability indexes can be obtained by stability specifications of the system and the optimal control parameters can be calculated according to the stability indexes selected from the satisfactory region. By using this method, the system stability and robustness can be guaranteed. Finally, the experimental results are presented to validate the effectiveness of the presented optimal control parameter design methodologies.Index Terms-Control delay, single-phase inverter, hybrid reference frame, islanded mode, parameter design guideline. NOMENCLATURE Abbreviations HRFHybrid reference frame. VSI Voltage source inverter.

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Analysis and Design of Current Control Schemes for LCL-Type Grid-Connected Inverter Based on a General Mathematical Model

Cited by 114 publications

References 44 publications

Impact of phase-locked loop on stability of active damped LCL-filter-based grid-connected inverters with capacitor voltage feedback

Impact of phase-locked loop on stability of active damped LCL-filter-based grid-connected inverters with capacitor voltage feedback

A Highly Robust Single-Loop Current Control Scheme for Grid-Connected Inverter With an Improved LCCL Filter Configuration

Optimal Performance Design Guideline of Hybrid Reference Frame Based Dual-Loop Control Strategy for Stand-Alone Single-Phase Inverters

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