scholarly journals Coupling Influence on the dq Impedance Stability Analysis for the Three-Phase Grid-Connected Inverter

Energies ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3676
Author(s):  
Chuanyue Li ◽  
Taoufik Qoria ◽  
Frederic Colas ◽  
Jun Liang ◽  
Wenlong Ming ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Nyquist Plot ◽  
Current Control ◽  
Impedance Ratio ◽  
Three Phase ◽  
Grid Impedance ◽  
Nyquist Criterion ◽  
Grid Connected Inverter ◽  
The Stability ◽  
The Right

The dq impedance stability analysis for a grid-connected current-control inverter is based on the impedance ratio matrix. However, the coupled matrix brings difficulties in deriving its eigenvalues for the analysis based on the general Nyquist criterion. If the couplings are ignored for simplification, unacceptable errors will be present in the analysis. In this paper, the influence of the couplings on the dq impedance stability analysis is studied. To take the couplings into account simply, the determinant-based impedance stability analysis is used. The mechanism between the determinant of the impedance-ratio matrix and the inverter stability is unveiled. Compared to the eigenvalues-based analysis, only one determinant rather than two eigenvalue s-function is required for the stability analysis. One Nyquist plot or pole map can be applied to the determinant to check the right-half-plane poles. The accuracy of the determinant-based stability analysis is also checked by comparing with the state-space stability analysis method. For the stability analysis, the coupling influence on the current control, the phase-locked loop, and the grid impedance are studied. The errors can be 10% in the stability analysis if the couplings are ignored.

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 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

New Perspectives on Stability Analysis of Three-Phase Grid-Connected Inverter Considering System Couplings

2020 ◽  
Vol 35 (3) ◽  
pp. 1967-1978
Author(s):  
Jingrong Yu ◽  
Xianfu Lin ◽  
Dongran Song ◽  
Ruoxue Yu ◽  
Jian Yang ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Three Phase ◽  
Grid Connected Inverter

Divided DQ Small-Signal Model: A New Perspective for the Stability Analysis of Three-Phase Grid-Tied Inverters

2019 ◽  
Vol 66 (8) ◽  
pp. 6493-6504 ◽  
Author(s):  
Zhikang Shuai ◽  
Yang Li ◽  
Weimin Wu ◽  
Chunming Tu ◽  
An Luo ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Small Signal ◽  
Signal Model ◽  
Small Signal Model ◽  
Three Phase ◽  
New Perspective ◽  
The Stability

scholarly journals Stability Analysis of Centerless Grinding with Loss of Contact Nonlinearity

2019 ◽  
Vol 224 ◽  
pp. 05007
Author(s):  
Marco Leonesio ◽  
Giacomo Bianchi ◽  
Hossein Safarzadeh
Keyword(s):  
Stability Analysis ◽  
Process Model ◽  
Relevant Literature ◽  
Operation Time ◽  
Integer Number ◽  
Integral Number ◽  
Nyquist Criterion ◽  
Delayed System ◽  
Centerless Grinding ◽  
The Stability

The paper presents a novel geometrical stability analysis of centerless grinding that takes into account the nonlinearity associated to wheel-workpiece detachment during lobes formation. Even though the rounding mechanism in centerless grinding has been studied since more than fifty years, stability analysis has been carried out applying stability criteria for linear systems (e.g., Nyquist) on a process model that neglects actual removal “clipping” due to wheel-workpiece detachment. This model limitation is usually overcome by considering only an integer number of lobes, supporting the restriction by the claim that a non-integral number of waves is less likely to build up since the waviness must be constantly removed and replaced by a succeeding wave, which is constantly moving around the workpiece. In this work, the nonlinearity entailed by removal clipping is explicitly taken into account and, by harmonic linearization, represented by a double input describing function (DIDF). Applying the Nyquist criterion on the resulting equivalent delayed system, the paramount instability associated to a quasi-integer number of lobes emerges naturally, without requiring additional assumptions. Moreover, it is shown that the nonlinearity due to wheel-workpiece detachment does not produce a limit cycle in a reasonable operation time. The results delivered by the proposed approach are verified by numeric simulations and positively compared to the relevant literature. The proposed formulation can be easily extended to consider also machine structure dynamics, thus increasing, even in this case, the accuracy of the stability analysis provided by the standard approach.

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