scholarly journals Equivalent Grid Impedance Estimation Method Using Negative Sequence Current Injection in Three-Phase Grid-connected Inverter

2015 ◽  
Vol 20 (6) ◽  
pp. 526-533
Author(s):  
Chan-Sol Park ◽  
Seung-Ho Song ◽  
Ji-Hoon Im
Keyword(s):  
Estimation Method ◽  
Current Injection ◽  
Negative Sequence ◽  
Three Phase ◽  
Grid Impedance ◽  
Grid Connected Inverter ◽  
Negative Sequence Current

scholarly journals Turn-to-Turn Fault Diagnosis on Three-Phase Power Transformer Using Hybrid Detection Algorithm

2021 ◽  
Vol 11 (6) ◽  
pp. 2608
Author(s):  
Chien-Hsun Liu ◽  
Willybrordus H. P. Muda ◽  
Cheng-Chien Kuo
Keyword(s):  
Fuzzy System ◽  
Power Transformer ◽  
Detection Algorithm ◽  
Current Response ◽  
Negative Sequence ◽  
Three Phase ◽  
Hybrid Detection ◽  
Incipient Faults ◽  
Increase In Accuracy ◽  
Negative Sequence Current

A power transformer (PT) in power generation or transmission is critical to maintaining electrical continuity. Fault detection on a PT is needed, especially of incipient faults, which are often caused by a turn-to-turn fault (TTF) before it develops into a more severe fault. We use a hybrid algorithm between conventional and modern techniques to detect a developing fault in a PT. The current response signals from a negative sequence current directional algorithm, extended park vector algorithm (EPVA), differential negative sequence current, and EPVA-fuzzy system are combined to distinguish the possibility of a TTF. The subalgorithms are combined using a hybrid detection algorithm to distinguish the faults. The model is a 10 MVA, three-phase PT with Δ-Y configuration 150/300 kV, simulated using MATLAB Simulink software. The results show that by combining the subalgorithms, several limitations are distinguished within the TTF with a slight increase in accuracy.

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.

Study of Low Voltage Ride through in Photovoltaic Grid-Tied Inverter Based on Unsymmetrical Grid Voltage Fall

2014 ◽  
Vol 986-987 ◽  
pp. 1277-1281
Author(s):  
Tian Fa Liao ◽  
Yang Chun ◽  
Wen Si ◽  
Chang Wen Dong ◽  
Jia Xiang Xue
Keyword(s):  
Power Output ◽  
Low Voltage ◽  
Hardware Platform ◽  
Negative Sequence ◽  
Grid Voltage ◽  
Low Voltage Ride Through ◽  
Current Controller ◽  
Three Phase ◽  
Overall Efficiency ◽  
Negative Sequence Current

In this paper, 10KW three-phase three-level photovoltaic grid-tied inverter is applied as hardware platform. Considering the insufficiency of PV arrays power output and low overall efficiency due to grid voltage falls asymmetrically, P-R current controller is used to provide unsymmetrical positive and negative sequence current to the grid so that low voltage ride through (LVPT) in photovoltaic inverter can be achieved. Through the implement of experiments, it is well proved that the requirement of LVPT when the grid voltage falls asymmetrically can be met by applying the solution proposed in this paper.

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