Principle and fundamental characteristics of thyristor-controlled negative-sequence current source for balancing three-phase currents

1977 ◽  
Vol 97 (2) ◽  
pp. 86-93
Author(s):  
Tadashi Fukao ◽  
Koki Matsuse ◽  
Masahiko Ishihara ◽  
Shota Miyairi
Keyword(s):  
Current Source ◽  
Negative Sequence ◽  
Three Phase ◽  
Negative Sequence Current

A Study on DG Control Strategy and Grid Protection

2014 ◽  
Vol 521 ◽  
pp. 204-212
Author(s):  
Xin Chao Wang ◽  
Chen Xin Yang
Keyword(s):  
Load Capacity ◽  
Short Circuit ◽  
Current Source ◽  
Islanding Detection ◽  
Test Results ◽  
Total Load ◽  
Line Voltage ◽  
Negative Sequence ◽  
Three Phase ◽  
Negative Sequence Current

DG integration reduces the selectivity and sensitivity of grid relay protection. A new control algorithm is proposed. It shows that the negative sequence current will not be affected by DG when the DG is designed as a symmetric three-phase current source. In this case, the negative sequence characteristic can be utilized for grid protection during short-circuit faults. If DGs maximum power capacity is restricted to be lower than total load capacity, DG terminal line-voltage and the negative sequence voltage can be used as the criteria for islanding detection. Then it is possible to cutoff DG in order to fulfill the reclosing requirement. A complicated simulation system is designed using PSCAD/EMTDC program. Different short-circuit faults are simulated to verify the proposals. The test results confirm well with the conclusions.

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 A Comprehensive VSM Control Strategy Designed for Unbalanced Grids

Energies ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 1169 ◽  
Author(s):  
Huiyu Miao ◽  
Fei Mei ◽  
Yun Yang ◽  
Hongfei Chen ◽  
Jianyong Zheng
Keyword(s):  
Control Strategy ◽  
Current Source ◽  
Synchronous Machine ◽  
Normal Operation ◽  
Complex Coefficient ◽  
Negative Sequence ◽  
Grid Voltage ◽  
Power Oscillations ◽  
Negative Sequence Current ◽  
Virtual Synchronous Machine

A virtual synchronous machine (VSM) is a converter which, compared to other types of converters, has more friendly interactions with the power grid because it is able to simulate the external characteristics of a synchronous machine, which can provide virtual inertia and damping. When the grid voltage is unbalanced, there will be negative sequence current and power oscillations. There will also be double-frequency ripples on the DC bus, which affect the normal operation of the DC power source or load. In order to solve these problems, a comprehensive control strategy is proposed in this paper. The principle of a VSM operated as a current source converter, also called VISMA, is used in the design. A complex coefficient filter is applied to separate the positive and negative sequence components of the grid voltage. By analyzing the reasons of power oscillations under unbalanced voltage, the electrical simulation part of the VSM is improved to achieve several objectives: to suppress negative sequence current and DC voltage ripples. Additionally, the rated voltage in the reactive control part is adaptively adjusted to stabilize the system. The validity of the proposed control strategy is verified by simulation and experiment.

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.

scholarly journals Induction Motor Stator Interturn Short Circuit Fault Detection in Accordance with Line Current Sequence Components Using Artificial Neural Network

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
Gayatridevi Rajamany ◽  
Sekar Srinivasan ◽  
Krishnan Rajamany ◽  
Ramesh K. Natarajan
Keyword(s):  
Neural Network ◽  
Fault Detection ◽  
Induction Motor ◽  
Short Circuit ◽  
Positive Sequence ◽  
Negative Sequence ◽  
Three Phase ◽  
Sequence Components ◽  
Negative Sequence Current ◽  
Short Circuit Fault

The intention of fault detection is to detect the fault at the beginning stage and shut off the machine immediately to avoid motor failure due to the large fault current. In this work, an online fault diagnosis of stator interturn fault of a three-phase induction motor based on the concept of symmetrical components is presented. A mathematical model of an induction motor with turn fault is developed to interpret machine performance under fault. A Simulink model of a three-phase induction motor with stator interturn fault is created for extraction of sequence components of current and voltage. The negative sequence current can provide a decisive and rapid monitoring technique to detect stator interturn short circuit fault of the induction motor. The per unit change in negative sequence current with positive sequence current is the main fault indicator which is imported to neural network architecture. The output of the feedforward backpropagation neural network classifies the short circuit fault level of stator winding.

scholarly journals A Robust Vector Current Controller with Negative-Sequence Current Capability for Grid-Connected Inverters

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4549
Author(s):  
Houshang Karimi ◽  
Aboutaleb Haddadi ◽  
Masoud Karimi-Ghartemani ◽  
Mahdieh Sadabadi
Keyword(s):  
Vector Current ◽  
State Feedback Control ◽  
Islanding Detection ◽  
Parameter Uncertainties ◽  
Negative Sequence ◽  
Double Frequency ◽  
Current Controller ◽  
Three Phase ◽  
Grid Connected Converters ◽  
Negative Sequence Current

This paper presents a vector current controller (in the synchronous reference, or the dq, frame) with negative-sequence current injection capability for three-phase grid-connected converters. This capability is desired for the operation of the converter during unbalanced conditions and also for a certain type of islanding detection. The proposed controller first determines the double-frequency current references and then uses a sixth-order two-input two-output proportional-integral-resonance (PIR) structure, which is optimally designed. Compared with the existing similar approaches, the proposed controller has a simpler structure and more robust performance, e.g., against system parameter uncertainties and weak grid conditions. The proposed controller is developed for converters with both the L-type and LCL-type filters. For the LCL-type converter, a suboptimal partial state feedback control is also proposed to achieve robust stability and active damping of resonance poles without requiring additional sensors. Detailed experimental results are presented to illustrate the properties and performances of the proposed controller.

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